Student Resources

Chapter 1: Introduction to Primate Studies


Primates as Study Subjects

Descriptive Studies

  • Anthropocentric Perspectives
  • Comparative Biology
  • Early Classification Schemes
    • Activity Patterns
    • Diets
    • Habitat Use and Ranging
    • Group Size
    • Social and Reproductive Units
  • Field and Captive Studies
  • BOX 1.1 Clues from Captivity

Evolutionary Models and Problem-Oriented Studies

  • Sociobiology and Behavioral Ecology
  • BOX 1.2 Word Watching and Ethics
  • Testing Predictions about Behavioral Adaptations

Long-Term Field Studies and Individual Variation

  • Comparisons among Species
  • Other Units of Comparisons
  • Niche Construction and Phenotypic Plasticity

Conservation Applications

  • BOX 1.3 Techniques for Tracking Primates Take Off


This introductory chapter reviews the brief history of primate behavioral ecology, beginning with the different motives that led scientists to study primates and the ways in which different disciplinary approaches have contributed to the field. Basic categories of primate behavior and ecology are introduced, including the ways in which primates are described and the interrelationships that exist among basic social and ecological variables. There are more “key words” in this chapter than in any other. Many of the terms introduced in this chapter will be used throughout the book. This chapter also introduces the concepts of individual, group, population, and species variation and their respective strengths and limitations in comparative models. The importance of primate behavioral ecology to the conservation of primates is emphasized, setting the stage for more focused discussions in later chapters.

Each of the three Boxes highlights a different component of primate behavioral ecology that may resonate more or less with different people.

Box 1.1 describes how captive and field studies can inform one another and extend our understanding of primates. It focuses on reproductive suppression in marmosets and tamarins, featuring Dr. Charles Snowdon’s pioneering research group. This research shows that work with captive primates can provide important insights that have direct implications for their well-being and conservation in addition to their theoretical value.

Box 1.2 calls attention to the implications of describing features of primates and their interactions with humans using terms that carry culturally laden and usually negative meanings. While some terminology has been revised as a result of these kinds of considerations, other terms have not. It is very rare now to use words like “harems” to describe the one-male, multi-female social or breeding groups of primates. We are changing words like “crop-raiding” to “crop-foraging” because the latter describes what primates do when they look for and consume foods they encounter in their environments. Changes to other terms, like “Old World primates” and “New World primates” are being discussed, and although this edition of Primate Behavioral Ecology retains the traditional terms, some people have made the shift to referring to primates by the continents on which they occur, e.g., the primates of Africa and Asia, and the primates (or monkeys) of the Americas, respectively. The words we use have ethical implications because they shape how we think about the subjects we are describing.

Box 1.3 highlights the use of drones in particular and other remote sensing tools in general to monitor primates and their habitats. The applications of these technological advances to primate research and conservation are clearly important, especially when they provide a way of gaining information about unhabituated animals and the status of primates and habitats in remote areas. It is important to consider not only how cool drones and equipment like arboreal cameras are, but also the trade-offs involved between what is often known as “boots-on-ground” and new methods of remote observation. What are the strengths and limits of each? Which is more invasive and why?


Key Words and Terms

activity budget





phylogeny (phylogenetic level)

affiliative bond





polygamy (see polygynandry)



polygynandry (polygynandrous)




behavioral adaptation



behavioral ecology

home range

population density


inclusive fitness

predator sensitivity

captive setting

indicator species







referential model

comparative genomics

interspecific variation

reproductive strategy

day range, daily path length

intraspecific variation

reproductive success


life history strategy



life history trait



local tradition

social strategy

ecological or evolutionary trap





socionomic sex ratio




energy maximizer


strategic model

energy minimizer

multilevel social organization (multi-level society)



natal group

study group


niche construction

systematic method

evolutionary theory




nutrient balancing


feeding strategy

ontogeny (ontogenetic level)









phenotypic plasticity




Study Guide

Introductory textbook chapters are usually assigned to coincide with the first few lectures, so it is always useful to identify how your professor’s perspective may differ from the perspective I take in my textbook. You will want to know whether there will be other reading assignments and whether the sequence of the chapters assigned in your class follows or differs from their sequence in the textbook. There are many different ways to approach the subject primate behavioral ecology. The main guiding principles for organizing the material can be summarized as follows:

  1. Primate behavioral ecology is a comparative endeavor. That means we are always looking for patterns in primate behavior while also paying attention to the exceptions, which help us to evaluate our underlying theories and hypotheses. This is how science advances.
  2. Primate behavioral flexibility is becoming the rule, not the exception. This may be because we are learning more about primates living under different ecological and demographic conditions as primate habitats and populations change in response to anthropogenic activities.
  3. Everything we can learn about primate behavior and ecology can play a role in our ability to conserve primates. This is why there is often a sense of urgency in our research.

The conservation status of primates today is a good starting point, especially in terms of the diversity of species under different types and levels of threats. Contemporary concerns include climate change scenarios and what these will mean for primate habitats, and therefore the primates themselves. Increasingly we have also seen the impact of zoonotic diseases. Think about how different components of primate behavioral ecology can help to inform conservation efforts. If you can come up with one or more examples, the relevance of the subject matter will be more apparent. In the book I use a lot of examples from studies of the most common and familiar primates, such as baboons, macaques, or chimpanzees, which were originally studied largely because of the insights they can provide into humans. But then I discuss how comparisons of the behavior of these species with one another and with other species has contributed to our comparative perspectives.

Table 1.1 shows the basic taxonomic groups. A downloadable version is available here.

Table 1.2 provides a basis for explaining the comparative method and for developing ways of asking testable questions about the underlying causes of behavioral similarities and differences in different species. You can do this while thinking about Tinbergen’s classic four levels of inquiry (functional, phylogenetic, proximate, and ontogenetic) on the one hand, and in terms of ecological, demographic, and phylogenetic influences on the other hand. There is tension between ecological and evolutionary deterministic or positivist models versus considerations of epigenetic processes and phenotypic plasticity, which in most cases we talk about from the perspective of behavioral flexibility. Primates alter their social (and physical) environments through their own behaviors. This is the basis for the concept of niche construction.

Figure 1.18 is a new addition to this edition of the textbook. The link to the journal article where it was first published and described is provided in the Supplementary Resources tab.

Thinking about the different kinds of questions primate behavioral ecologists ask creates an opportunity to consider the most appropriate study conditions (e.g., field, provisioned, captive, etc.) for particular kinds of questions, and how data from different sources can be mutually informative. There are trade-offs in terms of the questions each kind of approach is best suited to answer.

Study Questions

  1. Explain two advantages and two disadvantages for using primates as model species to test theories of behavioral ecology.
  2. Savanna baboons differ from muriquis, chimpanzees, and mountain gorillas in a variety of ways. Choose two of these primates, and list two ways in which they differ from savanna baboons.
  3. Draw the graph that depicts Optimal Group Size when predation and food competition are considered. Label all axes and lines and discuss how the compromises between increased protection from predators and reduced feeding success are thought to affect optimal group sizes in primates.
  4. Tinbergen described four levels of explanation of why certain behaviors occur. Select one of the following examples of primate behavior and describe how each of the four levels could be used to explain it.
    1. Pygmy marmosets display their genitals when they encounter neighboring groups at the edge of their territories.
    2. Male chimpanzees participate in cooperative hunting expeditions more often than females.
  5. Consider the trade-offs between the kinds of research that can be conducted on captive and wild primates, and present one type of question that might be most appropriate to each. Be sure to specify the conditions of your captive and wild subjects.
  6. Explain the differences between social organization, social system, reproductive system, and parenting system.
  7. Discuss how the degree of dietary and habitat specialization affects a species’ vulnerability to human disturbances.
  8. Define phenotypic plasticity and explain its importance for behavioral adaptations, particularly in environments that are undergoing rapid changes.

Supplementary Resources

Babies Are Cute!

If you are interested in the energetic costs of carrying twins for a primate, check out this amazing video of newborn pygmy marmosets (Web video 1.1).

Web video 1.1 These two sibling pygmy marmosets (Cebuella pygmaea) were born only a day before this video was recorded in Puyo, Ecuador. They fiercely wrap their tiny tails around their mother’s body while she is feeding on gum. Video by I. Duch-Latorre.


There is a lot more on drones. These things are amazing.

Drones and Muriquis:

I wrote the new Box 1.3 about Dr. Fabiano R. de Melo’s pioneering applications of drones to muriqui research because I was completely entranced on the occasions I have been able to accompany him on some of his aerial surveys.

image of a man flying a drone

Figure 1.1 Dr. Fabiano R. de Melo flying his drone during a search for muriquis at São Francisco Xavier, São Paulo Brazil.

This silent video shows you even more about what the drone’s camera sees and how the software processes the images of muriquis:

Drone Downed by a Chimpanzee:

This video clip shows the novel behavior of chimpanzees at the Arnhem Zoo. While the chimpanzees were being filmed by a camera mounted on a drone, one chimpanzee grabbed a stick and used it to attack and bring the drone down. The article that describes the event is Open Access and can be found at Chimpanzee attacks drone (van Hooff and Lukkenaar, 2015; it is definitely worth reading before you skip straight to the Video in the Supplementary Material here.

Drones for Conservation Monitoring:

One of the pioneers in the use of drones for primate conservation is Dr. Serge Wich. You can watch his TedX talk about using drones to save orangutans and their habitat here.

Chapter 2: Traits, Trends, and Taxonomy


Distinguishing Traits

  • Allometric Scaling of Brain and Body Size
    • Effects of Diet
    • Life Histories and Their Social Consequences
    • Sexual Dimorphism
  • Other Morphological Traits
    • Stereoscopic Vision
    • Distinguishing Features of the Hands and Feet
    • The Collarbone and Arm Mobility
    • Teeth


  • Taxonomic Considerations
  • Major Taxonomic Groups
    • Strepsirrhines
    • Haplorhines
      • New World Monkeys
      • Old World Monkeys
      • BOX 2.1 Fundamentals of Food Processing
      • Apes
  • Cladistic Analysis

Phylogenetic Analyses of Behavior

  • Evidence Related to Diet
  • Evidence Related to Ranging Patterns
  • Evidence Related to Mating Systems
  • Evidence Related to Dispersal Patterns




The first section of this chapter outlines the basic ways in which primates differ from other mammals, beginning with their large brains relative to body size. A closer look at the importance of the neocortex is provided in this link to Web Box 2.1The energetics of body size and their effects on diets, life histories, and sexual dimorphism are discussed. Eyes, hands, feet, shoulder mobility, and teeth are described. To see how animals with different kinds of color vision see fruit, leaves, and predators, check out the Supplementary Resources to this chapter.

The second section of this chapter reviews current classification schemes. Each of the major taxonomic groups and some of their defining anatomical and behavioral features are introduced. Updated classifications, following those listed in Table 1.1 are provided in Figures 2.9a and 2.9b.

The third part explains how traits are used to understand the evolutionary relationships among species. Examples illustrate how understanding patterns in the diets, sexual dimorphism, and dispersal of living species can provide insights into those of extinct species.

Box 2.1 describes the food processing functions of cheek pouches in cercopithecines. This box features research conducted by Dr. Joanna Lambert on different primates in Kibale National Park, Uganda. The relevance of primates in seed dispersal will come up again in Chapter 11.


Key Words and Terms



precision grip

allometric scaling, allometry





prehensile tail




basal metabolic rate, BMR

isometric scaling

primitive trait


Jarman/Bell principle

Prosimii, prosimian





last common ancestor (LCA)



masseter muscle



mitochondrial DNA, mtDNA

sacculated stomach

cheek pouch


sexual dimorphism


molecular clock

sexual monomorphism

cladistic analysis


stereoscopic vision







convergent evolution



dental formula



derived trait

opposable thumb



parallel evolution

taxonomic classification



taxonomic inflation



temporalis muscle



trichromatic vision



Study Guide

Review the major trends that characterize the primate order and taxonomy. It is helpful to think about the major systems, and to remember that not all traits are found in all primates. The exceptions can be confusing, or they can make the subject more interesting. I focus a lot on the implications of the large relative brains of primates and their relatively slow life histories because both of these have social correlates and consequences.


Traits and Trends


  • Increased brain-to-body size (relative brain size)


Sensory system

  • Vision enhanced, stereoscopic depth perception; some with trichromatic (color) vision


Generalized diet & teeth

  • Reduction in the number of teeth (dental formulas)

Limbs & locomotion

  • Increased mobility of digits; some have opposable thumb & big toe
  • Clavicle well developed
  • Nails replace claws

Life history

  • Extended, slow maturation, long life spans


  • Social complexity

For each of these traits, think about the selective pressures that may have made the traits adaptive for early primates. What does having stereoscopic vision enable you (and other primates) to do better?

Relative brain size is easiest to understand from figures. Try drawing the relationship between brain and body to be sure you understand the differences between isometric and allometric relationships, and then what it means to be “off” the line, deviating in one or another direction. Articulating what the figure shows can be a useful way to process the concept. After that, it is easy to extend the graph to illustrate the effects of body and brain size on diets and life history parameters. Life history traits lead nicely into how the extended juvenile periods and long life spans of most primates contribute to the development of their complex communication, social organizations, and social relationships. Although cognitive abilities are covered in greater detail in Chapter 10, they are also relevant here because they are part of what distinguishes primates from many other mammals.

Be sure you know what level of taxonomic knowledge will be expected in your course. Table 1.1 (in Chapter 1) includes some of the common names of familiar primates, shown to the level of the genus, whereas Figure 2.9a and 2.9b may be easier to conceptualize. The full list of all known taxa (as of this writing) is in the Appendix to the book.

Situating the taxonomic names of species that are frequently discussed in your class is a good way to start. Can you identify each of the major taxonomic groups to which humans belong, as shown in Figure 2.9a?

Once you have a grasp of taxonomy, try working through some examples of how homologies and homoplasies can help to interpret evolutionary relationships among primates. Think about an obvious example, such as bipedality in humans versus knuckle-walking in chimpanzees, bonobos, and gorillas, and then carrying it out to increasingly distant last common ancestors to identify the last common ancestor that had each trait. Of course, in many cases we don’t know the ancestor, which illustrates the value of the fossil record. Brachiation in gibbons and suspensory locomotion in New World spider monkeys and muriquis also demonstrates parallel evolution.

You may already be familiar with this material from other classes. In that case, you can leap directly into thinking about why understanding the phylogenetic signal of traits is relevant to the behavioral ecology of living primates. Think about how these can tell us about adaptions to particular ecological conditions, versus traits that are inherited from common ancestors.

The last section of this Chapter takes a very cursory look at what we can and can’t say about the phylogenetic patterning of some key behavioral traits. Some instructors may opt to skip over this section of the chapter, but I left it in the book because I think it is important to remember that many traits we observe today may be part of the evolutionary history of a species that may or may not have adaptive explanations.

I like to ask my students to think about the different rationales that could be made for prioritizing the conservation of different taxa on the basis of different criteria. For example, should chimpanzees get special conservation status because of their close phylogenetic relationships to humans? Should the aye-aye, the sole living representative of its family, be prioritized over any one of the 33 species of titi monkeys? How would you fill in the blanks for each of these conceivable criteria:

  • Most unique species, based on Ecological distinctiveness? Based on Endemic species?
  • Special evolutionary meaning?
  • Longest evolutionary history?

Of course, we hope we never have to make these kinds of choices!

Study Questions

  1. List five traits that tend to distinguish primates from other mammals.
  2. List three life history traits.
  3. Describe three different locomotor systems found in apes.
  4. Draw the phylogenetic relationships of the hominoids and indicate the position of last common ancestor between humans and apes.
  5. Name one nonhuman primate found in each of the following areas today: Madagascar, Japan, Indonesia, Brazil, India, Africa.
  6. Two primate species inhabit the same tropical forest, where logging operations have severely disturbed the habitat. There is no evidence that either species has been hunted, but in just a few years, the population size of one species declines. You know that one was a large, folivorous primate, and the other a smaller-bodied frugivore. Using your knowledge of body size energetics and life histories, explain which of the two species is most vulnerable to the kind of population crash described. (This may also be appropriate, with modifications, for Chapter 11.)
  7. Primate dispersal systems have a strong phylogenetic signal, meaning that closely related taxa tend to have similar dispersal systems to one another. What are the consequences and correlates of sex-biased dispersal and bi-sexual dispersal for primate social systems?


Supplementary Resources

Color Vision

This Open Access article by Carvalho et al., 2017 on The Genetic and Evolutionary Drives behind Primate Color Vision (Frontiers in Ecology and Evolution, 26 April 2017) explains the different types and evolutionary routes of the mutations that led to color vision in some, but not all primates.

Figure 5, Examples of evolutionary drives that might have influenced the evolution of primate color vision, ( is reproduced with Open Access permission below. As stated in the published Figure legend, “Original pictures (left column) and simulations of dichromatic (middle column) and monochromatic (right column) vision are shown.” It is clear why trichromatic vision would be advantageous to animals that rely on visual cues to identify ripe fruits (and immature leaves), attractive mates, and dangerous predators.

A bunch of different colored animal  Description automatically generated

Lemur Facial Color Variation

There are so many different lemurs it can be hard to keep track. Check out some of their facial characteristics at this Open Access article by Rakotonirina et al. (2017) Evolution of facial color pattern complexity in lemurs. Here is a preview, with permission:

From: Evolution of facial color pattern complexity in lemurs

Figure 1

Examples of facial color patterns diversity in lemurs. Presented are (left to right): nocturnal species including Microcebus murinus, Cheirogaleus medius, Mirza coquereli, Avahi laniger, Lepilemur dorsalis, Daubentonia madagascariensis, cathemeral species: Eulemur macaco, Hapalemur griseus, Varecia variegata, Eulemur collaris, Eulemur coronatus, Eulemur rufifrons; diurnal species: Propithecus coquereli, Indri indri, Lemur catta. (All photographs taken by M. Markolf).

Rights and permissions

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More about the Amazing Aye-Aye

As you’ll see in this article, the highly specialized fingers of the aye-aye are not very good for grasping. But they may have evolved a solution, via an extra “pseudo thumb.” As my former TA A.J. Hardie wrote: “Pretty cool stuff!”

Add 'Pseudo Thumb' to the Aye Aye Lemur's Bizarre Anatomy. (Links to an external site.)

Here is a short video that really shows them at their best:

The Demon Primate/World's Weirdest

What Does Suspensory Locomotion Look Like?

Check out this video, taken by Irene Duch-Latorre during a field study in Ecuador. More videos to come from other suspensory primates.

Website video 2.1 Brown-headed spider monkeys (Ateles fusciceps fusciceps) crossing a dirt road that passes through their home range in a forest fragment in Manabí, Ecuador. Video by I. Duch-Latorre, courtesy of Proyecto Washu.

Chapter 3: Primates Past to Present


Evolutionary History

Primate Diversity in the Past

  • Primate Origins
  • Biogeography and Barriers
  • Miocene Monkeys and Apes
  • Pliocene Highlights
  • Pleistocene Glaciations
  • Holocene
  • Anthropocene

Interpreting Diversity Today

  • Intraspecific Variation
  • Local Population Variability
    • The Status of Hybrids
    • BOX 3.1 Hybrid Baboons
    • The Status of “New” Species
    • BOX 3.2 Lucky Lemurs
  • Implications for Primate Behavioral Ecology



This brief chapter traces the evolutionary history of the primate order from the oldest fossil finds to recent discoveries of new species. The rationale for including primate evolutionary history in a book about primate behavioral ecology is because of its relevance to the extinction risks affecting so many primates today. In the first sections of the chapter, hypotheses about the original primate radiation (e.g., arboreal, visual predation, and evolution of angiosperms) are presented.

The major evolutionary events of the Cenozoic epochs are then briefly described, along with continental drift and global climate changes that affected the biogeographic distributions and adaptive radiations of primates in the past.

The third section of the chapter focuses on contemporary primate diversity, including population and intraspecific variation. The biology and conservation issues pertaining to hybrids and newly identified species are discussed, along with the implications of species diversity for comparative models in primate behavioral ecology.

For those who are interested in learning more about the Mosaic Nature of Human Evolution, some background can be obtained from Web Box 3.1.This box explains how different anatomical systems (e.g., locomotion, dental, and brain size) evolve at different rates, often making it difficult to draw species boundaries.

Box 3.1 features the hybrid baboons studied in Ethiopia’s Awash Valley, focusing on the long-term research by Dr. Clifford Jolly and Dr. Jane Phillips-Conroy. The box includes a great map showing the current distributions of living baboon species and the major hybrid zones, and a side table summarizing comparative traits.

Box 3.2 recounts the discovery and rediscovery of lemurs in the 1980s, featuring the long-term work of Dr. Patricia Wright. Many new species of primates have since been discovered, including a new species of orangutan that is also now one of the 25 most endangered primates in the world.


Key Words and Terms


intraspecific (Chapter 1)

adaptive radiation



mosaic nature of human evolution


neutral mutation



continental drift

plate tectonics

ecological niche






evolutionary significant unit


genetic drift


hominid (Chapter 2)




interspecific (Chapter 1)



Study Guide

This chapter focuses on the evolutionary history of primates and reviews information about species and hybrids. You may be familiar with this material from other courses, but you may not have previously thought about the relevance of primate evolutionary history to the ways we compare the behavior of different species or the extinction risks of different species.

A good way to organize the evolutionary history of primates is to think about what is going on in time and space. This is because the parts of primate evolutionary history most relevant to behavioral ecology and conservation are the parts that pertain to species biodiversity. The spatial variables of this include geographic, ecological, reproductive, and behavioral isolation of species. The temporal variables include rates of evolution, generation lengths, strength of selection pressures relative to genetic drift. You will notice that some of these variables are also ones that affect primate extinction risks, as well as their ability to adapt to current conditions.

The biogeographic distribution of extant primates is very restricted compared to the past. What processes were involved in getting living primates to get where they are, and when did these occur? Today, nonhuman primates are mostly restricted to low altitudes between the Tropic of Cancer and the Tropic of Capricorn. This distribution is generally attributed to the basic effects of rainfall on the seasonality, productivity, and diversity of the plants on which primates rely. This provides a link with some of the topics covered in Chapters 1 and 2 pertaining to the energetic needs of primates, and sets the stage for thinking about how the distribution of ancestral primates shifted with changing global climate trends.

Review the major events during the Cenozoic, focusing on the emergence and locations of each of the major taxonomic groups. Each of the epochs is associated with a major evolutionary event, as shown in the following simplification of evolutionary history:

A screenshot of a cell phone  Description automatically generated

Thus, the Eocene is associated with the initial strepsirrhine radiations and possibly the origin of the first haplorhines. These Eocene primates include adapiforms, omomyiforms, and Eosimias. The Oligocene is associated with the early anthropoid radiations, known mainly from the Fayum of Egypt, the early Miocene is known for the high diversity of hominoids, while the mid–late Miocene is when Old World monkeys diversified. There is contrasting evidence about whether monkeys replaced or succeeded hominoid diversity, which provides a good way to think about the difference between competition for existing niches versus the adaptive radiations that can occur when niche vacancies arise. Hominids appear in the late Miocene and are established by the Pliocene.

I think it is really interesting to spend a few minutes thinking about human evolution in the same context as that of other primates. There was a hominin radiation similar to the radiations of other primates, but in our case the result was the survival of only a single species, our own.

The Anthropocene has been recently defined as beginning with the nuclear bomb tests of the 1950s. It is alarming to think how much we humans have negatively impacted other primates since then.

Primate evolution was greatly impacted by ecological and geological events during the Cenozoic. For example, the tropical climate of North America and Europe during the Eocene changed with continental drift. Hypotheses for how lemurs reached Madagascar and the origins of platyrrhines in South America are similarly illustrative of the different location of continents and different levels of the sea—and to what degree it created a barrier. To see a floating island, check out the video link posted on the Supplemental Resources tab for this chapter.

Are you persuaded that ancestral platyrrhines rafted from Africa? How much of their subsequent evolution can be explained by parallel evolution with the catarrhines?

Ecology is a key component of each major evolutionary event. For example, the diversity of Fayum anthropoids includes a wide range of body sizes and probable dietary differences. Other examples include the ecological specializations of colobines and cercopithecines, and how these may have influenced or coincided with their geographic distributions, and the ways in which increasing seasonality might have diminished the diversity of apes in the Miocene.

The discussion of species is a fascinating one. Some people think it is crazy that primatologists can’t yet say how many species there are. This is because they don’t understand that taxonomy is a moving target; we are still learning how to categorize diversity.

How do primates that live in marginal habitats survive? There are many examples of primates living in tropical habitats that have been altered by human activities. Think about some of the specific examples to illustrate the diversity of primate responses to different kinds of threats.

Factors such as species geographic distribution, habitat loss, and population size and trends are used to identify the conservation status of species. This is another case where the definition of a species matters, and how variation is classified.

Study Questions

  1. Beginning with the Eocene, list each of the geological epochs and the major primate evolutionary radiation associated with them.
  2. Explain what is meant by the Mosaic Nature of Evolution.
  3. Discuss why hybrids, such as the baboons in the Awash Valley of Ethiopia, challenge the traditional biological definition of a species.
  4. List and discuss two criteria that are used in classifying the status of threatened primates.
  5. Discuss the effects of continental drift and climatic changes on the biogeographic distribution of primates during their evolutionary history.
  6. Discuss the role of taxonomy in conservation.
  7. Dozens of new species of primates have been discovered by scientists during the past three decades. Most of the new species discovered have been callitrichids and prosimians, which are relatively small compared to most other monkeys and apes. Using your knowledge of the allometric relationship between body size and life history traits, explain why isolated populations of small primates may evolve more rapidly than those of large primates that occur sympatrically.
  8. How do predictions about the effects of contemporary global climate change on primate biodiversity differ from the effects of environmental changes that contributed to the adaptive radiations in primate evolutionary history?

Supplementary Resources

Review of Primate Traits and Evolution

Here is a PBS video that offers a nice review of general primate characteristics and looks at some potential primate ancestors, like the plesiadapiforms and the evolution of modern species:

PBS: Your Place in the Primate Family Tree

Also, for more on the evolution of Anthropoids, including a great figure of their evolutionary relationships, see Open Access article by Williams et al., 2010.

Does Rafting Really Happen?

There is lots of evidence. Check out this video of big floating landmasses with trees in Panama (to show how rafting might have occurred):

The Anthropocene

  • Who decides when the Anthropocene began?

Answer: These people:

  • What do orangutans do in the Anthropocene?

Answer: Use their tremendous behavioral flexibility:

Spehar et al., 2018


Climate Change Today

Thinking about the impact of climate change on primate evolution helps to put today’s climate change concerns into perspective. There are many important articles covering the impact of climate change on primates today. Here are just a few of the Open Access ones:

The link to this paper is also provided for other chapters; it is where we find the statistics that 60 percent of the world’s primates are threatened with extinction and 75 percent of the world’s primates have declining population sizes:

Extreme weather events like cyclones and droughts impact primates in different parts of the world to different degrees. This paper shows where the impacts are expected to be greatest:

This paper assesses how primates may be affected by predicted changes in local weather patterns that occur as a result of climate change:

Here are some amazing figures and links. Check out this NASA time series of climate change from 1884 to 2019.


Chapter 4: Evolution and Social Behavior


Natural Selection

  • Sources of Genetic Variation
    • Variation among Individuals
      • Mutations
      • Mechanisms of Inheritance
      • Sexual Reproduction and Mating Patterns
      • BOX 4.1 MHC Genes and Mate Choice
    • Variation within and between Populations
      • Random Genetic Drift
      • Gene Flow and Dispersal
  • Genetic versus Environmental Influences
    • Testing Evolutionary Hypotheses for Behavior
      • Problems with Comparing Fitness among Primates
      • Identifying Optimal Traits
      • Generational Time Lags and Changing Environments
    • Evaluating the Role of Ecological Pressures

Kin Selection and Reciprocal Altruism

  • Altruism and the Challenge of Group Selection
  • Selfish Benefits of Helping Kin
  • BOX 4.2 Multilevel Selection
    • Hamilton’s Rule
    • Evidence for Kin Selection among Primates
    • Evaluating the Evidence for Kin Selection
  • Benefits of Helping Nonkin
    • Conditions for the Evolution of Reciprocity
    • Evidence for Reciprocity among Primates
    • Evaluating the Evidence for Reciprocity

Individual Strategies and Social Organizations

  • Conflict and Cooperation among Same-Sexed Individuals
  • Conflicts between the Sexes



This chapter establishes the framework for behavioral evolution, beginning with the sources of variation that are necessary for evolution to act. The initial section on genetics is included because genetics are important to understanding so much about behavior and the risks of extinction.

Natural selection, kin selection, group selection, and reciprocal altruism are explained in sequence. There is critical evaluation of evidence for the flexibility in primate responses to environmental pressures. Evidence and critiques of claims for nepotistic behavior and reciprocity among primates are equally emphasized. How the behavior of individuals can affect their social organization is discussed.

Box 4.1 describes MHC genes and mate choice as examples of the benefits of avoiding close inbreeding. Primate studies and recent human studies have been updated with new empirical findings.

Box 4.2 discusses current views about multilevel selection and its role in shaping group cooperation.



Key Words and Terms



multilevel selection

alloparental care (also Chapter 9)

gene flow



genetic drift

natural selection

agonism, agonistic (Chapter 1)

genotype (Chapter 1)

negative assortative mating


group selection

neutral mutation

behavioral syndrome

Hamilton’s rule




phenotype (Chapter 1)

coalition rank


phenotypic matching

codominant alleles



cooperative breeding (also Chapter 5)

inbreeding depression

positive assortative mating

costs and benefits


Prisoner’s Dilemma

degree of relatedness

inclusive fitness (Chapter 1)

recessive allele



reciprocal altruism (reciprocity)

dominant allele



epigenetic inheritance

kin recognition

relatedness threshold for altruism


kin selection


extended evolutionary synthesis

lactational amenorrhea


evolutionary stable strategy, ESS


triadic awareness


major histocompatibility complex, MHC

viability, viable

founder population



game theory

Mendelian genetics



Study Guide

This is probably the most theoretically dense chapter in the book because it reviews basic genetics and evolutionary theory and then focuses on the evolution of behavior, from natural selection, to kin and group selection, to reciprocal altruism. You may already be familiar with the introductory genetics material, but you may not have previously thought about how the same basic genetics can explain why small, isolated populations of primates are at risk of extinction. It may help to visual these dynamics with the Extinction Vortex, which shows the impact of loss of genetic variation in small, isolated populations.

A close up of a map  Description automatically generated

The evolution of behavior by natural selection begins with Darwin’s perceptions about morphological variation relative to diets. He only had access to phenotypic variation but we know that phenotypes are a product of genotype and environment interactions. It is really important to understand the sources of genetic variation (mutations, recombination, and gene flow) because these are important both to evolution and extinction risks. Natural selection can act on the variation in a behavioral trait if the variation corresponds with differential survival and reproductive success among individuals. But, it is important to remember that behaviors are complex traits, undoubtedly influenced by a combination of genes and environmental interactions, as well as epigenetic effects whose mechanisms are just beginning to be understood. The extended evolutionary synthesis provides a framework for thinking about some of these other influences on phenotypic evolution. The different forms of selection—directional selection, stabilizing selection, and disruptive selection—illustrate the role of particular environmental pressures, the effects on population variation over time, and the idea that natural selection is a process whose product can change over time.

It is often hard to think about the currency with which fitness is measured (i.e., survival and genetic contribution to future generations) because really, who thinks about these things when we are making decisions about our lives and friends and mates?

The concept of optimality is about the trade-offs or compromises between different costs and benefits. The classic compromise between reducing risks from predators and increasing competition over food on group size is one example to keep in mind when you think about how changes in predation pressure or access to food could shift the optimum group size in one direction or another, assuming that the primates have choices. Comparing the behavioral differences found across populations of the same species or among individuals in the same populations can illustrate how local ecological and demographic conditions and individual differences in access to resources affect behavior. Behavioral responses can be presented as compromises, with individuals as actors whose behaviors have been influenced by natural selection but may also be highly flexible. The difference between adaptations shaped by natural selection and flexible responses to diverse opportunities is an important distinction to make. It is important to distinguish what types of evolutionary hypotheses can be tested.

Plot out the costs and benefits to males and females of alternative behavior strategies. The infanticide scenario provided in the text is one such example. It is important to be critical in evaluating whether the behaviors we observe in some species (in this case, infanticide) are “adaptive” in an evolutionary sense (they seem to be, at least under some social and demographic conditions). It is difficult to evaluate how recent environmental changes have altered primate behavior from what it was selected for in the past. Genetic findings that support or challenge adaptive scenarios can be a stimulating way to identify where new discoveries about primate behavior can still be made. In the infanticide example, what kind of genetic data would help to test the adaptive explanations?

Most discussions of group and kin selection begin with the paradox of seemingly altruistic behaviors, including reproductive restraint. There are specific conditions necessary for group selection to act, but it is hard to decouple these in primates because most primates live in groups, where opportunities for reciprocity occur, and many primates live in groups with kin, where opportunities for nepotism exist. Box 4.2 on multilevel selection gives more context to contemporary perspectives on group-level cooperation.

Be sure you can distinguish among:

  • Nepotism--> Preferential treatment of kin.
  • Altruism--> Benefit another at cost to one’s self.
  • Mutualism--> Mutual benefits from cooperation.

The basis for understanding kin selection is that relatives share genes. I would encourage you to calculate the degree of relatedness between different sets of relatives, using your own extended families as your basis. However, it is also important to remember that what we mean by kin when we talk about primates and other animals is different from what we mean when we talk about kin (and kinship) in humans. Humans recognize nonrelatives as kin (e.g., step-parents, mothers-in-law) that primates do not.

It is also helpful to work out Hamilton’s rule for yourself by adding values to the example of callitrichid brothers provided in the book. For example, if two brothers can each sire two offspring by themselves, from a subordinate brother’s point of view, how many more offspring would his dominant brother need to sire to make it beneficial for the subordinate brother to forego reproduction and instead help his brother? In the process of working out this example, consider the probability of both males reproducing, dispersal costs in different habitats, and the benefits of assistance to offspring survival. You will want to be able to describe the conditions necessary for kin selection to act, including the role of kin recognition, difficulties of distinguishing between nepotism and mutualism, and the challenge of measuring inclusive fitness in primates.

Kin selection naturally leads into discussions of dispersal patterns in primates, because dispersal patterns affect what kind of kin, if any, are likely to end up in groups. Cooperation among nonkin is difficult to distinguish from mutually beneficial behavior, or reciprocal altruism, which involves time lags and thus the ability to keep track of past relationships. There are many specific examples for cooperation, such as coalitions and mate guarding, alarm calls, and game theories such as the Prisoner’s Dilemma. To illustrate the latter, I give a demonstration of cooperative behavior (which I modified from a survey published in Discover decades ago) whereby the students are told they can request a grade of “A” or “B” in the course, and that they will receive the grade they request unless more than 5 percent of them request an “A,” in which case they will all receive a “C.” They cannot consult one another, but should write their request down on a scrap of paper and turn it in. If time and class size permit, I tally the results on the spot. This exercise helps to reinforce the idea that one’s own optimal behavior can be dependent on how other individuals behave. There are flaws in the grade exercise, because you know that there are no real “costs,” in terms of your actual grades in the course. It is interesting to consider whether you would change your behavior in a subsequent interaction after learning what others are likely to do. It is also interesting to think about how your behavior might change toward particular individuals if you knew what their choices had been.

Study Questions

  1. Discuss at least three difficulties with determining when behaviors are adaptive.
  2. What is the equation for Hamilton’s rule? Explain what each of the variables refers to, and describe what the equation predicts about when an individual should help his or her kin.
  3. Two females in a muriqui group have each given birth to 6 offspring. One of these “mega-moms,” BS, has given birth to 5 daughters and 1 son. Her oldest daughter, BR, has a daughter of her own. The other mega-mom, NY, has given birth to 2 daughters and 4 sons. Using this information, answer the following questions:
    1. Which individuals represent BS’s inclusive fitness?
    2. What is the difference between BS’s and NY’s inclusive fitness to date?
    3. What would be the difference between BS’s and NY’s current inclusive fitness if two of NY’s sons had fathered 1 offspring each?
  4. Mantled howler monkey troops can consist of both unrelated females and unrelated males because both sexes disperse from their natal groups. Describe the kind of evidence that would be needed to support an argument that group selection occurs in these primates.
  5. The risks of extinction are greater in small, isolated populations of primates (and other organisms) than in large, continuous population. Provide two reasons why this is the case.
  6. During your field study of wild Japanese macaques, you observe a fight between two females [A and B] at a food source. A third female [C] runs to the assistance of female A, and joins her in threatening female B. Using your knowledge of evolutionary theory, briefly explain the conditions that could account for female C’s behavior under Kin Selection, Reciprocal Altruism, and Mutualism. Be sure to consider the fitness costs and benefits to both actor (female C) and recipient (female A), and any other necessary conditions that might apply in your answers.
  7. There are many possible reasons why the behavior we observe in nonhuman primates appears to be inconsistent with our predictions based on evolutionary theory. One reason may be that our theories about behavioral evolution are wrong, or need to be further refined. Another reason may be that the conditions under which we are observing the behaviors differ from those under which the behaviors evolved. Select a primate and briefly discuss how captive conditions are known, or might be predicted, to affect any aspect of that species’ social behavior compared to wild conspecifics.
  8. What are the spatial and temporal (space and time) conditions necessary for cooperative behavior to evolve under Kin Selection and Reciprocal Altruism? Are there any necessary conditions for one that are not necessary for the other?
  9. Does it matter if animals don’t “know” who their kin are or how closely related they are to different group members? How does kin recognition in primates and other animals differ from our understanding of kin recognition in humans?

Supplementary Resources

Extended Evolutionary Synthesis (ESS)

For further reading on the ESS (and the source for Figure 4.3 in the textbook), here is a link to the open access online article:

This article forms a good basis for our ways of thinking about additional mechanisms and concepts of evolution.

Kin Selection vs. Multilevel Selection

For a review of the differences, history, and points of controversy, the following article by Kramer and Meunier (2016) may be useful:

Chapter 5: Evolution and Sex


Sexual Selection

Sexual Dimorphism

  • Phylogenetic Constraints
  • Ecological Constraints

Mating Patterns

  • Mating Patterns When Females Are Solitary
    • The Case of Monogamy
    • An Extreme Form of Polygyny
    • BOX 5.1 Gibbon Games and Tarsier Tactics
    • Polyandry
    • Ambivalent Polygynandry
  • Mating Patterns When Females Live in Groups
    • Single-Male Female Groups
    • Multi-Male Female Groups
    • Extra-Group Copulations
    • Seasonal versus Aseasonal Breeders
    • The Influence of Males on Females

Female Mating Strategies

  • Sperm and Fertilization
  • Food and Safety from Predators
  • Allies against Aggression
  • Parental Investment
  • Good Genes
  • Sexual Signals
    • Female Choice and the Unpredictability of Ovulation
    • Sexual Swellings and the Female Dilemma

Male Rank and Reproductive Success


This chapter is essentially about the sexual dynamics of primate societies. It introduces sexual selection and the morphological and behavioral indicators of levels of intrasexual competition. The biological differences between male and female reproductive potential and the consequences of these differences for the greater potential variance in male reproductive success and greater choosiness of females are discussed. Sexual dimorphism in canine and body size, and sperm competition, as measured by relative testes size, are considered. The alternative reproductive strategies available to males when females are solitary or gregarious are reviewed, along with the effects of female mate choice. The status of male floaters is presented, and the concept of female power is introduced (though mentioned earlier in Box 1.2) and its components of female dominance and female leverage are explained.

The distinctions between who lives together, who mates together, and who reproduces together reinforce topics raised in Chapter 1.

Box 5.1 describes the variability in grouping and mating patterns of gibbons and tarsiers to illustrate both the difference between social and reproductive units and the degree to which grouping and mating patterns can vary within a single species. New insights from comparative and genetic studies are integrated with past findings on gibbons by Dr. Ulrich Reichard and other scientists, and the tarsier studies of Dr. Sharon Gursky, are featured.


Key Words and Terms


mating effort

arrested development



nuclear family


operational sex ratio, OSR


paternity certainty

cooperative breeding (also Chapter 4)

polygyny threshold

core area

priority of access

developmental arrest


dominance hierarchy


estrous, estrus

rank reversal

extra-pair copulation


extra-pair fertilization

reproductive potential

female choice

reproductive seasonality

female dominance

reproductive skew

female leverage

reproductive synchrony

female power



secondary sexual characteristic

graded signal

sex skin

honest advertisement

sexual selection

interbirth interval

sperm competition

intrasexual competition

variance in reproductive success

mate guarding


Study Guide

The material presented in this chapter can be broken down into two main themes: the first covers sexual selection and the second behavioral strategies. It is key to have a firm grasp on the concept that sexual selection acts on traits that affect the variance in reproductive success among both males and females. Sexual dimorphism in body size, physical appearance, and behavior can be explained as the outcome of intrasexual competition.

Review the biological differences between the reproductive potentials of males and females so that male–male competition for fertilizations and female choice are put into perspective. The greater investment of females in reproduction begins with their larger gametes, through gestation and the energetic demands of lactation, during which times males are biologically free to seek reproductive opportunities elsewhere. Reproductive mistakes are more costly for females, leading to predictions of greater choosiness by females about their mates. Here, however, it is important to consider that, despite much research effort, it is still difficult to evaluate what, if any, traits female primates choose in their mates, and to what degree their mating patterns reflect efforts to ensure fertilization versus selectivity about mates. There may also be differences between reproductive versus social partners and it is important to think about why this might vary across species, in different populations of the same species, or over the lifetime of an individual.

Explaining sexual dimorphism in terms of mating systems is tricky because many polygynandrous primates are sexually monomorphic, and some of the socially pair-bonded primates (e.g., gibbons), which are sexually monomorphic, nonetheless mate with multiple partners and are therefore not reproductively monogamous (as shown in Box 5.1).

It is important, therefore, to distinguish between mating systems and the errors of inferring mating systems from the composition of social groups. This is continuous with the Kappeler framework presented in Chapter 1, Figure 1.18.

Review each of the major mating systems (monogamy, polyandry, polygyny, and polygynandry), with examples and explanations of each. In the latter case, emphasize how reproductive skew among males and among females varies with different types of mating systems.

A useful formula for thinking about the factors that influence levels of competition among males is as follows:

  • What is the socionomic sex ratio in the group and population (because dispersal between groups in the population will influence group composition)?
  • What is the spatial distribution of females (do females live in a cohesive group that can be monopolized or are they spread out either alone or with other females)?
  • What is the temporal distribution of fertile females, in terms of:
    • Seasonal versus aseasonal sexual receptivity?
    • Synchronous versus asynchronous estrus?
    • Birth intervals (because during gestation and lactation most nonhuman female primates are not ovulating)?

Consider the different levels of male paternity certainty and male investment in infant care and defense of females or resources that attract females. You may want to refer back to the infanticide material here.

Consider each of the different mating patterns from both the female and the male’s point of view.

Draw out the polygyny threshold on your own, beginning with the first female choosing the male holding the best territory, and so on. This is a good way to make sure you understand the theoretical effects of variation in male resource-holding potential on female mate choices. You should also consider what conditions might make it advantageous for males to cooperate in defending a female or her territory. Gibbons are good examples to consider.

The second major body of information in this chapter revolves around the impact of different mating systems and levels of competition among males over access to females to introduce the idea of reproductive synchrony and how the number of sexually receptive females at any one time can affect levels of male competition. Working through the question of whether males are expected to be more or less competitive when females have short annual breeding seasons (e.g., lemurs or Costa Rican squirrel monkeys) versus long or no breeding seasons is instructive because arguments can be made for both cases. This is also a good opportunity to think about the impact of interbirth intervals on the potential risks (to females) and gains (to males) of infanticide.

I also think it is worthwhile to consider alternatives to sexual selection, such as the ecological constraints on levels of sexual dimorphism in body size, or the effects of demography and how dispersal patterns can influence levels of male–male competition within groups. Not only does this tie back into earlier material about dietary and locomotor differences between males and females in highly dimorphic species, but it also sets the stage for future discussions of the importance about food to females.

Study Questions

  1. List three traits that might make particular male primates more attractive to females as mates.
  2. Discuss the possible costs and benefits of concealed ovulation versus the visible advertisement of ovulation through sex skins from both the female and male perspective.
  3. In many human cultures, men are more likely to divorce wives who commit infidelities than women are to divorce their husbands for the same offense. Using your knowledge of evolutionary biology, provide an explanation for this tendency and discuss the conditions under which you might expect men and women to react similarly to a spouse’s infidelity.
  4. Describe the ways in which levels of sexual dimorphism (including sexual monomorphism) can affect male–female and female–female relationships.
  5. Draw the graph that depicts the polygyny threshold, being sure to label both axes. In two or three sentences, describe what evolutionary principle(s) it depicts.
  6. Explain the distinctions between graded signals and honest advertisements as they apply to sexual swellings.
  7. What is the female dilemma, and what are some of the strategies female primates employ to overcome it?
  8. Discuss how mating patterns affect the genetic composition of primate populations, and therefore influence the viability of populations.
  9. Female gibbons are found in both single- and multi-male groups. Describe the conditions that favor single versus multi-male groups, and consider the costs and benefits to the female as well as the males in both types.
  10. Explain the patterns of variation in sexual dimorphism and relative testes size with levels of male–male competition (mating systems).

Supplementary Resources

Trade-offs in Male Traits

Below are links to a video and an article summarizing a great study about howler monkeys that ties in with a lot of the material from this chapter. In particular, this study is a useful tool for helping us think about how reproductive strategies are related to biology and evolution.

Calls vs. balls: An evolutionary trade-off

Here is a summary of a scientific article (link below) published in Science Magazine: Big testicles mean a softer voice, at least in howler monkeys (Links to an external site.)

Full scientific article, open access via Current Biology: Evolutionary Trade-Off between Vocal Tract and Testes Dimensions in Howler Monkeys (Links to an external site.)

Discussion/Thought Questions (provided by my former TA, A.J. Hardie)

  1. What is the evolutionary trade-off presented in this study? What is the explanation for that trade-off proposed by the authors of this study?
  2. How do you think group size, operational sex ratio (number of reproductive males versus number of reproductive females), and population density might impact male–male competition in howler monkeys?
  3. How would you integrate female choice into the study presented here? What characteristics might a female howler monkey look for in a potential mate?

Chapter 6: Food and Foraging


Food Quality and Nutrient Balancing

  • Energy and Nutrients
  • Digestibility and Edibility
    • Physical Deterrents
    • Chemical Deterrents
    • BOX 6.1 Forest Pharmacy
  • Body Size Energetics and Turnover Rates
  • Reproductive Energetics

The Spatial Distribution of Food

  • Patch Size and Defensibility
  • BOX 6.2 Position is Everything
  • Effects of Patch Density on Ranging Patterns

The Temporal Availability of Food Resources

  • Behavioral Adjustments to Food Seasonality
  • Reproductive Seasonality
  • BOX 6.3 The Power of Food

Interpreting Diets and Their Behavioral Correlates

  • Evaluating “Critical Functions”
  • Effects of Altered Habitats



This chapter reviews the basic features of primate diets. The ways in which food quality, distribution, and availability affect behavior and reproduction are discussed. The differences between scramble and contest competition, and the conditions under which females cooperate to defend food resources are introduced. The perspective is one of how food and energetic constraints affect primate behavior and evolution, especially for females with high reproductive costs. Methodological issues are included, such as the differences in characterizing diets by food type versus nutrient content and the difference between characterizing primate diets based on what they eat most of the time versus during critical periods of preferred food scarcity is questioned. Methods of monitoring habitats are also mentioned. The effects of altered habitats on primate diets, behavior, and microbiomes are also reviewed.

Box 6.1 summarizes recent research on medicinal plant use by primates, illustrating that foods can be eaten for purposes other than their nutritional content, featuring an updated review of some of Dr. Michael Huffman’s work with chimpanzees and other primates.

Box 6.2 discusses the importance of positional behavior, particularly as it relates to feeding sites and positions within food patches and to behavioral thermoregulation, including basking and huddling, which are integrally related to energetics.

Box 6.3, on the Power of Food, features Dr. Cheryl Knott’s findings on the relationship between diet, urinary C-peptide, ketones, and reproduction in orangutans, and Dr. Patricia Wright’s model of energy frugality for explaining the unusual ways in which lemurs have adapted to the unpredictable ecology of Madagascar.


Key Words and Terms


growth diet


high-quality diet

behavioral thermoregulation




contest competition

low-quality diet

critical function

mast fruiting


microbiota (microbiome)



fallback foods

nutritional geometry

feeding party

positional behavior

food availability


food distribution

scramble (competition)

food patch

secondary compound

food quality

subsistence food



foraging efficiency


geometric framework

urinary C-peptide




Study Guide

The material covered in this chapter can be divided into two main themes. The first focuses on primate foods, including: i) how body size and energetics affect nutritional needs and results in dietary differences among species; ii) how primate diets and foraging are measured; and iii) the trade-offs between seeking patchy, high-quality foods versus exploiting abundant, lower-quality foods. Characteristics of plants, including nutrient and mineral content, and physical and chemical deterrents, should be reviewed. How primates perceive foods is an interesting way to begin, and the paper by Dominy et al. (2001), The Sensory Ecology of Primate Food Perception, which is cited in the textbook, is worth consulting for background.

The Jarman/Bell principle and anatomical specializations for different types of diets (e.g., teeth and masticatory apparatus, digestive system), which were introduced in the second chapter of the textbook, might be helpful to review here as well. The effects of selection pressures on morphological specializations for “critical functions” illustrate some of the difficulties of measuring primate diets and inferring diets based on morphology. The effects of altered habitats on primate diets and microbiomes illustrate some of the differences in extinction risks among species. You can test your thinking on these topics by considering the effects of climate change on primate diets and the consequences for the primates if key food sources for different species become scarce.

The second major theme focuses on the behavioral consequences of different kinds of diets. For example, for a given group weight, day range length and home range size tend to increase with the proportion of fruit in the diet. Think about how different primates respond to seasonality in their preferred foods, which can be either by shifting their diets or grouping or ranging behavior. Review the effects of ecology on female reproductive seasonality, remembering the importance of operational sex ratios to levels of competition among males (Chapter 5). This is also a good time to consider Wrangham’s model of female-bonded primates, which distinguishes what kinds of food distributions (including patch sizes) make it advantageous for females to cooperate for intergroup defense or avoid one another to reduce intragroup competition. Comparing intra- and intergroup scramble and contest competition will also prepare you for the next pair of chapters, and tie in with previous material addressing the compromise between predation risks and feeding competition.

It is interesting to consider the question of the effects of habitat fragmentation on primate diets and intra- versus intergroup feeding competition. Working through this question is one way of connecting the behavioral and ecological sides of the problem to a contemporary problem that increasing numbers of primates face. It is also interesting to think about whether the diets and feeding strategies (and corresponding social organizations) we observe in primates today reflect their evolutionary adaptations versus facultative responses to current ecological conditions.

Study Questions

  1. List two anatomical specializations that distinguish folivores from frugivores.
  2. Discuss three factors that must be considered in characterizing primate diets.
  3. Describe the different kinds of behavioral trade-offs that primates can make when preferred, high-quality foods are seasonally scarce. Include specific examples in your answer.
  4. Using your knowledge of the Jarman/Bell principle and reproductive energetics, explain how and why male and female diets may differ.
  5. Peruvian squirrel monkeys exhibit male-biased dispersal and high rates of aggressive competition over food, whereas Costa Rican squirrel monkeys exhibit female-biased dispersal and very low rates of feeding competition. Describe the differences in their feeding ecologies that could predict these divergent behavioral patterns.
  6. List two of the possible ways in which primates can adjust their behavior in response to seasonal shortages in the availability of their preferred foods and provide an example of a primate that responds in each way.
  7. List three of the ways in which a female’s nutritional condition can affect her reproductive success.
  8. Briefly explain the different between contest competition and scramble competition and discuss the ways in which the distribution of different types of foods interact with group size to affect levels of these kinds of competition in primate groups.


Supplementary Resources

Are these Primates Self-Medicating?

After you read Box 6.1 on zoopharmacognosy, check out these amazing clips:

If you like dirt … here is a great Open Access review on geophagy, with a video byte embedded:

Adaptation to the Cold

Living in extreme climates is a challenge for most primates because of lack of food. But a few have figured out ways to make a living in the cold. Here is a video that shows you one of them:

Some Other Real-life Videos (from Researchers) of Primates Finding and Eating Food

Web Video 6.1: This is one of my favorite videos from one of the camera traps we use at my field site. It was taken in January 2020, and shows a mother black-horned capuchin monkey (Sapajus nigritus) with an infant on her back, selecting among the mangos available on the ground. No one was near when this video was made (Video from Karen B. Strier/Projeto Muriqui de Caratinga).

Web Video 6.2: Adult female Ecuadorian mantled howler (Alouatta palliata aequatorialis) feeding on young Cecropia leaves, with her infant holding tight, in Manabí, Ecuador. Video by I. Duch-Latorre, courtesy of Proyecto Washu.

Web Videos 6.3a–c: The ripe fruits of the palm tree Attalea colenda are highly regarded as a food resource by the brown-headed spider monkey (Ateles fusciceps fusciceps) in Manabí, Ecuador. Fruits from Attalea colenda are hard-to-process and require unusual strength to access the fleshy mesocarp, but that has never discouraged brown-headed spider monkeys from getting the prize. Video by I. Duch-Latorre.

Web Video 6.4: Northern sportive lemur (Lepilemur septentrionalis) infant feeds on Vahimavo leaves (Cephalocroton leucocephala) with its mother at Montagne des Français, Madagascar. Most sportive lemur mothers park their infants in tree tangles or holes for security while they forage, however this infant is old enough to be out on its own foraging alongside its mother. After a few months of independently feeding, this infant will be completely weaned from its mother and must find a new range to call home. Sportive lemurs are solitary or pair-bonded, meaning that females often have territorial ranges that only overlap with males. Video by Mary P. Dinsmore.

Web Video 6.5: A northern sportive lemur female (Lepilemur septentrionalis) bites bark on a tree trunk in Montagne des Français, Madagascar in order to “tap” it for gum. Individuals may lick up sap or gum from their “taps” immediately or return days later as it accumulates. While sportive lemurs primarily rely upon leaves or other types of foliage for their diet, they will supplement that with fruits, gum, or flowers when available. Video by Mary P. Dinsmore.

Web Video 6.6: Herd feeding (video): Geladas (Theropithecus gelada) feeding on grasses in the Guassa Community Conservation Area, Ethiopia. Geladas are the only graminivorous primates in the world. Video by Jacob B. Kraus.

Web Video 6.7: Brown howler monkeys (Alouatta guariba) drinking water from a tree cavity at the RPPN Feliciano Miguel Abdala, Caratinga, Brazil. Video by A.J. Hardie.

Web Video 6.8: Black-horned capuchin monkey (Sapajus nigritus) banging stick on a tree. This monkey is cracking open the dead wood to gain access to insects at the RPPN Feliciano Miguel Abdala, Caratinga, Brazil. Video by A.J. Hardie.

Comparing Diets

The following two figures compare different populations of the same or closely related primates. The percentage of fruit reported in the diets of spider monkeys (blue bars), howler monkeys (orange bars), and muriquis (purple bars).

The point of the first figure was to illustrate that although the absolute proportion of fruit in the muriquis’ diet at my field site resembles that of howler monkeys elsewhere, relative to the sympatric howler monkeys in this more seasonal habitat, muriquis are as frugivorous as spider monkeys relative to sympatric howler monkeys in less seasonal forests. You can access the abstract to the publication where this figures appear here Strier, 1992: Atelinae adaptations

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The second figure shows a more extensive comparison of other sympatric communities of Atelidae primates. It illustrates the role of seasonality in lowering the degree of frugivory across these taxa.

Chapter 7: Female Strategies


Ecology of Female Relationships

  • Types of Relationships
  • Within- and Between-Group Competition

Social Dynamics in Female Groups

  • Matrilocal Societies
  • BOX 7.1 Mysterious Matrilines and Market Theory
    • Rank Inheritance
      • Relations among Females
      • Relations with Males
    • Age-Related Rank
      • Relations among Females
      • Relations with Males
    • Life without Kin
      • Gaining Group Membership
      • Autonomous Interests
        • Aggregations around Males
        • Avoidance of Males
        • Managing Males

Population Consequences of Female Strategies

  • Habitat Disturbance, Fragmentation, and Saturation
    • Effects on Philopatric Females
    • Effects on Groups of Unrelated Females
  • Reproductive Implications
  • Manipulating Sex Ratios



This chapter expands on the ways in which female relationships reflect different levels of within- and between-group competitive regimes, reinforcing previous discussions of primate extended life histories and high reproductive investment compared to other mammals. Female bonding, and scramble and contest competition, are explained in greater detail, building on the basics provided in Chapter 6. Differences in female power and female dispersal are related to differences in their competitive regimes, including the effects of group size on levels of intra-group feeding competition. The ecological conditions under which females disperse from, or remain in, their natal groups, and maintain egalitarian versus hierarchical relationships with one another are described.

Each of the major categories of female groups is described with examples, beginning with matrilocal societies. Rank inheritance in savanna baboons and Japanese macaques, and age-related rank in other female-bonded species are discussed. How females in these species maintain their relationships by postconflict reconciliation, how they trade grooming and support for other resources, and interact with males are described with examples from current research. The conditions that lead to female dispersal, and the challenges confronted by dispersing females, are considered next. Distinctions are made among females that are attracted to males (e.g., mountain gorillas and howler monkeys), avoid males (e.g., chimpanzees and orangutans), or manage males through their strong relationships with one another (e.g., bonobos).

The final section of this chapter focuses on the interactions between female strategies and their populations. The effects of habitat alterations on female relationships under different competitive and dispersal regimes, and the reproductive implications of female group size and population densities, which are affected by habitat alterations, are described. Hypotheses for female manipulation of infant sex ratios under different ecological conditions are reviewed.

This last section is included in the main text of the book for two reasons. First, it would be pretty amazing if we could predict under what conditions females would produce male or female offspring. When studies support the evolutionary theories they get published, but we also know that as sample sizes increase, oftentimes what look like significant effects disappear. We still don’t have a firm answer to the question of whether birth sex allocation is adaptive. A second reason to include this is that infant sex ratios can have profound impact on levels of intrasexual competition once the infants mature, and on population growth rates, which impact the ability of small populations to recover in size.

Box 7.1 discusses the difficulties of recognizing the kinship structures of primate societies during relatively short studies. It includes a discussion of biological market theory, and the insights that long-term studies can provide into the dynamics of female social relationships and interactions.


Key Words and Terms

basic rank

local resource enhancement

biological market


dependent rank

postconflict resolution

displacement activities



resource-defense polygyny

female-defense polygyny

social network analyses

local resource competition




Study Guide

You may want to review Wrangham’s model of female-bonded primates so that the theoretical and empirical extensions to his model in this chapter make sense. Simply put, though, the main point of these refinements is to distinguish the variant forms that female-bonding can take. In Wrangham’s original model, female relationships were strongly hierarchical and differentiated. In Sterck et al.’s extension, females sometimes remain in their natal groups but with relaxed hierarchies. It may seem like these and other kinds of refinements are exceptions to the general rule. But that is not quite the case because the refinements capture behavioral variation that, in this case, can be organized around the relative strength of within- versus between-group competition over food. If you can work your way through the consequences of different competitive regimes, the resulting behavioral categories will be easy to track.

A good example of subtle differences in female social relationships is the difference in female macaque dominance styles, as described by de Waal and Luttrell (1989) in their comparison of captive stump-tail and rhesus macaques. This comparison also provides a way to review the importance of temperament, as well as the actual behavioral interactions (e.g., grooming, threats, agonistic aid, and reconciliation) that females (and males) use to negotiate their relationships. You can test your thinking by comparing other closely related species, such as female chimpanzees and bonobos. What are the main similarities and differences in their respective female–female and female–male relationships and what might account for these differences?

Review the advantages of high rank to female primates using specific examples, including the reproductive suppression of subordinates in some callitrichids, and the effects of extreme food scarcity on mortality in wild primates such as toque macaques or the Amboseli vervet monkeys. Go through the ways in which female baboons and macaques inherit their mothers’ ranks, and discuss the ways in which the size of female matrilines and the number of matrilines in female-bonded groups affect their inter-matriline and intergroup relationships. I think it is important that matrilineal societies arise from matrilocality, and that it is the overlap in generations that permits multiple generations of females to interact. This helps to anticipate subsequent discussions of life histories later in this chapter and in Chapter 9 that can be tied in with Box 9.1 on Menopause.

Remember that not all female primates resemble savanna baboons or macaques, even though these well-studied primates are used in many of the examples. Be sure you have a good grasp of the social dynamics of female prosimians, including the different ways in which they hold power over males. Colobines, howler monkeys, and the apes all have different female dynamics. A comparison of the relationships between female rank in matrilineal baboons and macaques versus among unrelated female spider monkeys that disperse from their natal group will reinforce some of the differences between female-bonded and nonbonded hierarchical societies, but it is also important to think about examples in which female relationships are weak, as predicted by their more abundantly occurring food resources. This is also a good opportunity to recall prior examples of primates, such as in lemurs and bonobos, in which females hold power over males. Distinguishing between whether females are individually dominant over males, or rely on alliances with one another, can help integrate previous discussions on the importance of diet and sexual selection in understanding behavior, and set the stage for upcoming discussions of male primate strategies in Chapter 8.

Additional topics that fit neatly with this material include the effects of habitat disturbances and alterations on female diets, levels of feeding competition, and reproductive rates. The difficulties of evaluating female lifetime reproductive success against different social strategies are also appropriate to review. As mentioned in the Chapter Overview, it is worthwhile to think about why sex ratios at birth matter. Think about their impact on group and population size and composition, intra- and intersexual competition, and the ability of populations to grow.

Study Questions

  1. List three of the ways in which being a high-ranking female can result in higher reproductive success compared to low-ranking females.
  2. Explain the two main ecological conditions that select for the occurrence of female-bonded primate groups.
  3. In some baboon and macaque societies, subordinate females may give birth to more sons than daughters. Explain this tendency using your knowledge of evolutionary and ecological theories. What are the consequences of skewed sex ratios?
  4. Define the different forms of female power over males, and discuss the conditions under which female–female alliances might be selected.
  5. Describe the major differences observed in the social relationships of female chimpanzees and female bonobos and explain the effects of these relationships on their male counterparts.
  6. Discuss two ways in which habitat fragmentation can affect female behavior patterns, using specific examples.
  7. Consider the ways in which changing ecological conditions might alter the ways in which female primates interact with one another, and ultimately their social organizations.
  8. Discuss the biological market theory and how its assumptions compare to those underlying kin selection, reciprocal altruism, and mate choice in structuring primate social interactions.

Supplementary Resources

Female Power Distinctions

It used to be common to refer to lemurs and a few other primates as being “female dominant,” but as University of Texas-Austin anthropology professor Rebecca Lewis has shown, there are different ways of achieving female power. I mention her insights in Box 1.2 of this book, but I think it is worth saying a bit more about this distinction. Lewis writes about these ideas in some recent publications, including the Open Access paper here: Lewis, 2020: Female Power: A new framework for understanding "female dominance" in lemurs. I usually don’t change a major term or meaning unless it has been in use for a while and I know it is going to stick. But in this case, I really think it should stick, so I am going to start using it myself, and hope that others do as well. Here is why:

I know that when I have talked about female muriquis being codominant with males over the past few decades, what I really meant was that females were not submissive to males in a general way. Females can keep eating at food sources or drinking without being displaced by a male, and females can reject a male’s mating advances without being harassed. In the former case, the male waits patiently until the female is finished and moves off. In the second case, it is usually the female who moves off but the male doesn’t follow or else he hangs back as if he wants to be near in case she changes her mind later. Both of these examples are different from a case where a female threatens a male and wins in a direct agonistic context over food or another resource.

When I asked Dr. Lewis (she lets me call her Becca) to check my brief definitions of her terms for the glossary of my book, she replied with such a helpful example that I asked her permission to quote her. This is what she explained:

“ … ‘maintenance’ … refers to the means of power – how power is exercised – rather than the base (source) of power. So a female lemur may have leverage because she is only in estrus for 1 day/year (in other words, she has resource-based power) but she may be aggressive towards a male to get what she wants. That aggression (or actual use of force) is the ‘how’ not the ‘why’. So the asymmetry in the ability is why the power arises.”

She clarified the definitions, which are shown this way in the glossary, as follows:

  • female dominance The social condition under which female power occurs because females have a greater physical capability to use force in contests against males; see female power.
  • female leverage The social condition under which female power occurs because females have an intrinsic resource that males need; see female power.

Implications of Dispersal for … Everything

The phylogenetic distribution of dispersal patterns is also shown in the textbook (in black and white) in Chapter 2, Figure 2.30. The added boxes on the right show how dispersal affects life histories, opportunities to interact with same-sexed kin, mating and reproductive options, and whether or not female social relationships involve close matrilineal kin or not.

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What Does Grooming Really Look Like?

Check out this video sequence of pygmy marmosets grooming:

  • Web Videos 7.1a–b Pygmy marmosets (Cebuella pygmaea) spend a considerable amount of time engaged in allogrooming, as shown in this video recorded in Puyo, Ecuador. Video by I. Duch-Latorre.

Chapter 8: Male Strategies


Ecology of Male Relationships

  • Types of Relationships
  • BOX 8.1 Using and Misusing Infants
  • Within- and Between-Group Competition

Social Dynamics among Males

  • Patrilocal Societies
    • Rank Acquisition and Coalitions
      • Relationships among Males
      • Relationships with Females
    • Maternal Rank Inheritance
    • Ranks in Age-Graded Groups
      • Relationships among Males
      • Relationships with Females
  • When Males Disperse
    • Hierarchical Relationships
    • Gaining Group Membership
    • BOX 8.2 Beyond the Group
    • Unattached Males
  • Males in Pair-Bonded Societies

Population Dynamics

  • Genetic and Demographic Correlates
  • Male Life Histories



This chapter is deliberately organized to mirror the previous chapter on female strategies (Chapter 7) in its structure and coverage of male strategies. It focuses on the ecology of male relationships and the ways in which male–male competition is manifested, as introduced during the coverage of sexual selection in Chapter 5. Distinctions are made between male affiliations and associations, and between intra- and intergroup competition among males over access to mates. Male social dynamics in different kinds of societies are covered, beginning with comparisons of male relationships in patrilocal societies. Male dominance over females in chimpanzees is contrasted with the egalitarian relationships between males and females of bonobos and muriquis. Competition for rank among male chimpanzees and the maternal support male bonobos receive from their mothers are compared. Male relationships in age-graded societies, which may or may not be patrilocal, are described. Male social dynamics when they disperse from their natal groups are considered. The challenges of gaining group membership, the benefits of transferring in cohorts or into groups where familiar males reside, and the consequences of surplus males, are presented.

The population consequences of male strategies focus on the genetic implications of male dispersal, the monopolization of fertilizations by individuals or groups of related males, and extra-group copulations. The effects of habitat fragmentation on intergroup conflicts among males and dispersal options are emphasized.

Box 8.1 discusses the ways in which males use and misuse infants by carrying them during their agonistic interactions.

Box 8.2 reviews the evidence for male social networks that extend beyond their immediate groups. The topic can apply to females, as well.



There are no flashcards for this chapter

No New Key Words and Terms


Study Guide

Begin with a review of the primary resource over which males compete and the different levels at which males can compete with one another for maximum fitness. These can be thought of along the same space and time dimensions we have previously used, and include: i) competing for access to females, which may or may not require associating with females in groups; ii) competing for access to ovulating females within these groups; iii) achieving successful fertilizations; and iv) protecting their reproductive interests via mate guarding and the infants they may have sired. Note that in some respects these four steps also parallel some of the different ways of thinking about primate social complexity mentioned in Chapter 1 (i.e., social, mating, reproductive, and infant care systems). How do different female spatial distributions and the temporal distribution of ovulating females affect male options? Once you have a clear map of these relationships, the rest follows logically from the more theoretical perspective of mating systems in Chapter 5. By now, you will have a better understanding of why females and female reproduction are distributed in such different ways. Here you can concentrate on how males implement their reproductive and social strategies.

Male access to female groups is linked to whether or not males disperse, and whether dispersing males can join extant groups or must establish new groups. From here we can categorize male grouping patterns and the degree to which males influence or respond to female grouping patterns. Follow with what males do once they are in groups with females, being sure to notice how dynamics differ when females join philopatric males versus when males join up with females. Integrating male and female strategies is a good way to check your understanding of how different social situations lead to differences in the ways that males interact with one another and with females.

Review the overt, ritualized forms of aggression, the difference between male competition for rank (including their use of coalitions) and how well (or poorly) male rank predicts priority of access to females, and more subtle forms of competition, such as sperm competition and friendships with nonreproductive females. I find it useful to think through a cost/benefit analysis, such as whether a male should participate in an aggressive contest based on the probability of obtaining access to a contested resource through aggressive versus nonaggressive strategies, the fitness benefits of the resource, and the fitness costs to the male and his relatives. This helps to illustrate how asymmetries in male competitive abilities can lead to different “optimal” strategies for different males. As these competitive abilities change during a male’s lifetime or under different ecological and demographic conditions, the “optimal” strategies of males are also expected to shift.

Male resource-holding potential and the ability of females to choose among males can be introduced here. Specific examples include Hausfater’s (1975) discussion of male rank and mating success in yellow baboons, Tutin’s (1979) early work on different mating strategies of dominant and subordinate male chimpanzees, and experimental studies, such as those conducted by Bachmann and Kummer (1980) on female choice in captive hamadryas baboons. It is important to review the difficulties of estimating male reproductive success based on observed mating success. These are classic sources that influenced primatology in its formative years. They set the stage for the predictions that have since been tested by genetic studies of red howler monkeys, long-tailed macaques, yellow baboons, bonobos, and chimpanzees at multiple sites. In all cases, the higher reproductive success of dominant males is consistent with predictions, although there are big differences in the degree of this variance, or reproductive skew. The importance of variance in alpha male tenure durations on male lifetime reproductive success cannot be ignored.

Why do levels of male reproductive skew vary so much across primates, as shown in Figure 8.3 and reproduced here?

Think about the effects of food provisioning, group size, and sex ratios on the affiliative behavior of male macaques (Hill, 1999), or the behavioral differences seen in male Costa Rican, Peruvian, and Surinam squirrel monkeys (Boinski, 1999) to get some clear examples of how ecological and demographic conditions can predict behavioral differences among populations of the same or closely related species. Understanding this variation is important for interpreting the effects of altered habitats on male behavior. We know that females can influence male group membership and male–male relationships, but a good exercise is to compare female influence on males in closely related primates, such as mountain gorillas–chimpanzees–bonobos, or howler monkeys–woolly monkeys–spider monkeys–muriquis. The differences between males that invest in their relationships with females (e.g., gibbons) versus males that receive attention from females (e.g., mountain baboons) is also effective in distinguishing subtle differences in primate social dynamics.

Finally, I always like to connect behavioral ecology with conservation. We know that the number of reproductive females is more important to population growth than the number of males. Nonetheless, high male reproductive skew (with male reproductive monopolies) versus low male reproductive skew (with lots of males siring offspring) can have a tremendous impact on the genetic composition of groups and populations. Do some mating systems represent greater risks than others in small populations of primates?

Study Questions

  1. Describe two alternatives to aggressive competition employed by male primates and briefly explain the conditions under which nonaggressive competition may evolve.
  2. Long-term studies of recognized individuals indicate that males engage in different reproductive strategies at different times in their lives. Some researchers emphasize the “friendships” that young males establish with females in the groups the males are trying to join. Others emphasize the value of heterosexual friendships to older, more mature males. Briefly evaluate each of these explanations, considering how similar behavioral interactions might reflect the different competitive abilities of young versus mature males.
  3. Explain two difficulties with using male mating success as an indicator of male reproductive success.
  4. Demographic conditions can explain why different males in the same populations follow strikingly different social pathways. Select one primate, and describe the demographic conditions associated with alternative male strategies.
  5. Compare the social strategies of a male chimpanzee and a male bonobo.
  6. Explain why in some primates, males initiate grooming interactions with females whereas in other primates, females invest more in their relationships with males. Provide examples for each case.
  7. Explain why secondary dispersal is more common for males than for females.
  8. List three factors that can affect levels of paternal care by male primates.
  9. Think about the kind of data that would be necessary for distinguishing between the agonistic buffering versus protection hypotheses for male baboons carrying infants during agonistic interactions as describe in Box 8.1. Specifically, for each hypothesis, indicate how you would predict an infant and the infant’s mother to behave (e.g., calm or distressed) when the infant is carried by different kinds of males (familiar versus unfamiliar) during a fight with another male (familiar versus unfamiliar).

Supplementary Resources

What Is the Deal with Alpha Males?

Here is a link to a fantastic TedMed talk by Dr. Frans de Waal, called the Surprising science of alpha males.

You may want to challenge yourself to know about how we can use our knowledge of the emotional and cognitive complexity of primates to help protect them in the wild and manage them in captivity, or are these topics unrelated.

Chapter 9: Developmental Stages through the Life Span


Fertilization to Birth


  • Maternal Care
  • Paternal Care
  • Alloparental Care

Weaning Conflict

  • BOX 9.1 Menopause

Juvenile Challenges

  • Staying Alive
    • Age, Size, and Sex
    • Experience
  • Social Skills
    • Long-Term Bonds
    • Sex-Biased Dispersal


Adulthood and Aging

  • BOX 9.2 The Legacy of Life Histories

Population Consequences of Life Histories

  • Life History Flexibility and Constraints
  • Demography and Conservation



The first section of this chapter pursues the theme of development from the perspective of when male and female primate strategies begin to diverge. Primary and secondary sex ratios are discussed, as well as the slow rates of development of primates. Infancy is covered both in terms of broad taxonomic comparisons, and in terms of maternal, paternal, and alloparental care. Different mothering styles consistent with female rank and age are described. Weaning is presented from the perspective of parent–offspring conflict, which is highly variable both across different species and among mothers in the same social groups. Locomotor independence as a second form of parent–offspring conflict is considered.

The next section of the chapter focuses on juveniles, whose major challenge seems to be staying alive until puberty. Ecological and social considerations, including play, are briefly outlined.

Puberty and Adulthood and Aging complete the developmental stages covered. The chapter closes with a discussion of the costs of dispersal and the population consequences of sex differences in mortality.

Box 9.1 presents the grandmother hypothesis, and its implications for the long life spans of and overlapping generations of primates.

Box 9.2 focuses on the history of the Amboseli Baboon Project and some of the questions about life histories that it has been so uniquely able to address because of the longevity of the study and the relatively short lives of the baboons, compared to many other monkeys and apes.



Key Words and Terms

alloparental care (also Chapter 4)



parent–offspring conflict


primary sex ratio

capital breeders


grandmother hypothesis





reproductive life span

income breeders

secondary sex ratio





Study Guide

Development is a fascinating topic that can be covered at many different levels depending on the detail with which life history trade-offs are discussed. This chapter begins with a review of major life history parameters (e.g., gestation and interbirth intervals, reproductive lifespan, etc.) and the general correspondence between life histories and body size, building on previously acquired knowledge, especially from Chapter 2.

Make sure you remember the difference between precocial and altricial primates. Consider the fact that in humans, postnatal brain development extends for another 9–12 months; if our extended brain development occurred in utero, like it does in other primates, it would make human gestation nearly 24 months long (which would be untenable in terms of the biomechanics of our bipedal locomotion with our current pelvic morphology).

Male and female differences begin early on with sex determination by sperm, and despite hypothetical patterns in the sex of infants mothers produce under different ecological and social conditions (discussed in Chapter 7), the precise mechanisms of infant sex determination are still poorly understood.

Review the energetic costs of motherhood, particularly during late lactation, and consider how maternal and offspring interests come into conflict during weaning. Parent–offspring conflict provides a way to reinforce previous material on kin selection and differential access to siblings as social partners or competitors in different kinds of primate societies. Parent–offspring conflict is usually discussed in terms of weaning but locomotor independence tends to lag behind feeding independence and creates another type of parent–offspring conflict.

Organize the different types of infant care, which include maternal, paternal, and alloparental, including sibling involvement, aunting behavior, and cooperative breeding systems, that can have either or both adult male and female helpers. Then, consider the various challenges and opportunities that come with the prolonged juvenile periods of primates. It can be amusing to think about your own experience with the bystander effect and infant-rearing practices.

I always think of the transition to independent feeding and moving as the first (or first two) biggest hurdles in primate development. The next comes at puberty, which is also around the time that one or both sexes usually disperse from their natal groups. Dispersal has impacts on development and life histories that merit some thought.

Life history trade-offs between maturation, reproduction, and longevity have implications for primate behavioral ecology and social evolution. Consider the discussion of menopause and the grandmother hypothesis in human evolution for an example of these kinds of trade-offs. Life histories also have implications for the growth and viability of small populations of endangered species. Being able to explain these different kinds of trade-offs will help to cement the concepts with others encountered so far.

Study Questions

  1. Discuss the costs and benefits of allomothering behavior and describe the conditions under which the frequency of allomaternal behavior varies across different primates.
  2. Discuss two explanations for why male primates differ in the degree to which they participate in parental care.
  3. List three differences that distinguish precocial (P) and altricial (A) infants, being sure to indicate if you are describing (P) or (A) characteristics.
  4. Draw the graph depicting parent–offspring conflict. Label both the X-axis and the Y-axis, all curves, and where PI is optimized from the parent’s and offspring’s perspective. Indicate the area of conflict and briefly explain the basis of the conflict.
  5. Explain the ways in which life history traits may affect population growth and the viability of small populations.
  6. Discuss the life history trade-offs between reproduction and longevity in primates.
  7. Consider why primates might be especially responsive to bystander effects and discuss both the advantages and disadvantages to adjustments in
  8. What are the social conditions necessary for grandmothers to help their grandoffspring? Think about these in terms of their access to one another in time and space and evaluate the conditions under which grandmothers should prioritize their own offspring or their offsprings’ offspring.


Supplementary Resources

Paternal Care

Read about the influence of prolactin, and then watch Dr. Toni Ziegler, the scientist featured, while she demonstrates one component of her research on the role of prolactin and male experience in the behavior of male marmosets. The part featuring Toni’s work is just a few minutes long, and begins at around the 8:10 minute mark in the show, Fatherhood ....

More Amazing Babies

This young pygmy marmoset is just figuring things out:

  • Website Video 9.1: Juvenile pygmy marmoset (Cebuella pygmaea) engages in self-grooming and self-exploration in Puyo, Ecuador. Video by I. Duch-Latorre.                                                                                                                               

And then there are these Baby snub-nosed monkeys!

Chapter 10: Communication and Cognition


Components of Communication Systems

Modes of Primate Communication

  • Tactile Communication
  • Visual Communication
  • Olfactory and Gustatory Communication
  • Vocal Communication
    • Species Recognition
    • Within- and Between-Group Distinctions
      • Long-Distance Calls
      • Close-Range Calls
    • Ontogeny
    • Intentional or Involuntary Information Sharing


  • Learning and Imitation
  • Ecological Intelligence
    • Spatial Memory
    • Tool Use
  • Social Intelligence
    • Alliances
    • Tactical Deception
    • Social Traditions

Implications for the Ethical Treatment of Captive and Wild Primates

  • BOX 10.1 Rehabilitation, Reintroduction, and Sanctuary



This chapter reviews the major features in primate communication and cognition. Descriptions of the four primary modes of primate communication are provided, as well as the evolutionary contexts under which communication systems evolved. Scent, gesturing, and multi-modal signaling provide a broader background into non-vocal primate communication. Advances in our understanding of primate cognition are also introduced here, including questions about how primates develop their cognitive abilities.

Evolutionary models focused on ecological and social selection pressures are discussed with examples of tool use and tactical deception. Behavioral traditions and what these reveal about intraspecific behavioral variation are described and discussed in the context of both cognition and conservation.

The ethical treatment of primates is considered from the perspective of their cognitive abilities.

Box 10.1 discusses the rehabilitation of retired laboratory research subjects, such as chimpanzees, and reintroduction projects for endangered species, focusing on the golden lion tamarins and including updated survey data about the status of the population today.


Key Words and Terms



cultural primatology


cultural tradition



sound spectrogram


tactical deception



Machiavellian intelligence

theory of mind





multi-modal signaling




Study Guide

The material in this chapter can be divided into two main themes, corresponding to the title, Communication and Cognition. It is helpful to contextualize these topics in terms of the long infancy and juvenile periods that provide extensive opportunities for learning in a social context. Communication plays a key role in reproduction, from being able to recognize the appropriate species to mate choice, and in maintaining social relationships and social spacing mechanisms. It may help to think of timing relative to developmental phases when the acquisition of communication skills and perceptive abilities are necessary. Mechanisms for learning, and the costs and benefits of reliance on learning versus innate abilities, should be considered.

You will want to be familiar with each of the modes of communication and the spatial distances at which each can be perceived. Sensory systems are needed to receive signals, which may limit which modes of communication can be employed at different times. Multi-modal signaling may occur across multiple temporal and spatial scales, so think about the conditions under which these signals might be favored.

Learning and the acquisition of novel behaviors set the stage for examining the advances in our understanding of primate cognition. Because so much of the evolutionary theory covered earlier involves predictions and assumptions about the outcome of selection, insights into primate cognition provide additional perspectives into the evidence for decision-making by primates in different contexts. Both tool use and tactical deception are obvious examples of cognitive skills that are difficult to explain without invoking some degree of flexibility and responsiveness to ecological and social opportunities.

The ecological models of cognition reinforce earlier material on the relationships between relative brain size, energetics, and food distributions. Similarly, the social models of cognition (including kin recognition studies) provide continuity with material about the challenges and compromises of a gregarious lifestyle. It is interesting to think about evidence from other animals, including the differences in maze-learning, or spatial abilities demonstrated in male versus female voles that are polygynous as opposed to monogamous in the wild, to link social and ecological selection pressures that appear to affect individual performances on experimental tasks.

Population-wide differences in chimpanzee tool use extend earlier considerations about the influences of local ecological and demographic conditions on intraspecific behavioral variation. It is important to understand that the different definitions of culture applied to the traditions of primates such as chimpanzees (and those of whales and dolphins) differ from the definitions of culture usually applied by cultural anthropologists to humans.

Think about the challenges involved in studying primate communication and primate cognitive abilities, including the possibilities of captive and experimental field studies compared to strictly observational work. Field playback experiments have been used with great success to address a wide variety of questions in primate behavioral ecology, and have been integrated as examples of creative methodological advances here. Check out Dr. Tetsuro Matsuzawa’s work with the chimpanzee, “Ai,” which shows her enthusiastic participation in various cognitive tasks. It is a nice example of a captive study in which the chimpanzees are not only well treated, but clearly seem to “enjoy” their assignments.

A separate but related focus in this chapter pertains to the ethics and responsibilities that come with the use of primates in biomedical and other kinds of invasive research. Primates have played important roles in the space program, basic biomedical research, and drug and vaccine testing, and there are much more stringent governmental controls over the use and treatment of primates today than there were in the past. Concern and action about ethical considerations involving primates as research subjects have increased with our growing understanding of their cognitive abilities. These are among the most important applications of advances in our understanding of primate cognition.

Study Questions

  1. Describe the different contexts in which each of the four modes of primate communication are used and consider the conditions under which multi-modal signaling might be selected.
  2. Contrast what is known about the different cognitive abilities of monkeys and apes, using specific examples for each.
  3. Explain the rationales behind ecological and social models of the evolution of primate cognitive abilities.
  4. Field playback experiments have been used in a variety of ways to understand primate communication and cognitive abilities.
    1. Describe two such studies on different primate species, and discuss the major findings from each.
    2. Now, consider the ethical concerns, and how research has (or should have) reduced any risks to the primates.
  5. Briefly discuss the risks of reintroductions and translocation projects for endangered primates, and evaluate the conditions under which such risks might be justified.
  6. Define what is meant by the “theory of mind” and explain its importance to primate social behavior.


Supplementary Resources


Remember the capuchin monkey smelling fruit?

Web Video 6.1: This is one of my favorite videos from one of the camera traps we use at my field site. It was taken in January 2020, and shows a mother black-horned capuchin monkey (Sapajus nigritus) with an infant on her back, selecting among the mangos available on the ground. No one was near when this video was made (Video from Karen B. Strier/Projeto Muriqui de Caratinga).

If you want to read more, check out this Open Access article, Nevo et al. 2018-Fruit scent as signal to primate

How Do People Study Primate Vocal Communication?

This brief video, Studying Primate Communication, explains methods of research on vocalizations of primates.

How Do People Study Primate Gesture Communication?

Check out this website from Dr. Catherine Hobaiter’s lab, which shows the The Great Ape Dictionary and has a video from the field!

Comparisons of gestures between bonobos and chimpanzees found that the gestures overlapped by 90 percent (Graham et al., 2018).

Howler Monkey Vocalization

Web Video 10.1: Adult male Ecuadorian mantled howler howls to advertise his presence to a nearby neighboring group in Manabí, Ecuador. Video by I. Duch-Latorre.

Web Video 10.1: Adult male Ecuadorian mantled howler howls to advertise his presence to a nearby neighboring group in Manabí, Ecuador. Video by I. Duch-Latorre.

Visual and Social Tolerance

Check out this Open Access article about the relationship of tolerance toward eye contact: Harrod et al., 2020: Social tolerance and eye contact


Remember the peaceful baboon culture? Here is a follow up on the Peaceful baboons

These chimpanzees are smart, especially this young male, whose mother, named Ai, showed the world how good a chimpanzee’s memory is, at least for some things: Ai's son is smart!

In his Ted talk on Moral behavior in animals, Dr. Frans de Waal shows that primates have morality, too.


This is a video about a the sanctuary, Safe Haven for Chimps, created for former laboratory chimpanzees.

Here is another really interesting story, about a rescue operation after Hurricane Maria’s devastating damage to Puerto Rico, where the famous Cayo Santiago Primate colony, known as Monkey Island, is located.

2017 article from The Atlantic about the macaques: Rescuing Puerto Rico's Monkey Island (Links to an external site.)

A brief video showing the initial damage and the status of the monkeys:

Rescuing Monkey Island

2018 video (4:44min) from NOVA about studying this population of monkeys after the hurricane: Puerto Rico Moves Forward: Macaque Monkeys Adapt After Hurricane Maria

2019 article from the New York Times Magazine about research with the macaques in the aftermath of Hurricane Maria: Primal Fear: Can Monkeys Help Unlock the Secrets of Trauma? (Links to an external site.)


Chapter 11: Community Ecology


Primate Communities

  • BOX 11.1 Ethnoprimatology
  • Niche Divergence
  • Polyspecific Associations
    • Foraging Benefits
    • Predator Protection

Predator–Prey Interactions

  • BOX 11.2 Predatory Perspectives
  • Primates as Predators
  • Primates as Prey

Primates, Parasites, and Microbiota

  • Social Transmission
  • Environmental Disruption

Primate–Plant Interactions

  • Pollination
  • Seed Dispersal and Seed Predation

Conservation of Communities

  • Specialists, Generalists, and Social Responses
  • Preserving Diversity



This chapter extends the focus on primates from individuals and species comparisons to the place of primates in their ecological communities. It begins with primate–human interactions in an extended box on ethnoprimatology. The chapter then discusses niche divergence and the costs and benefits of polyspecific (multi-species) associations in terms of the two major themes that affect primate grouping patterns, predators and food. The next three sections examine (i) primates as predators and prey; (ii) their parasites and microbiomes, including the impact of anthropogenic disturbance and diets, and (iii) their roles as pollinators and seed dispersers. Although there is only very limited evidence for coevolutionary relationships between primates and plants, there is strong evidence that frugivorous primates play vital roles in dispersing seeds, and thus maintaining the forest foods upon which they depend.

The last section of this chapter discusses the conservation of communities. It includes discussion of recent analyses of the impact of habitat disturbances on different kinds of primates, and the differences in the ability of niche specialists and generalists to respond to environmental changes. This discussion sets the stage for the more explicit considerations of primate conservation that are covered in the final chapter of the textbook.

Box 11.1 reviews ethnoprimatology and its importance in understanding human–primate interactions.

Box 11.2 is an updated consideration of predation by, and especially of, primates. In the previous edition, this box focused on chimpanzee hunting. The role of predators as top-down regulators of community dynamics is discussed.


Key Words and Terms




mixed-species association (see polyspecific association)

citizen science

niche divergence




polyspecific association (see mixed species association)

empty forest syndrome

species richness




zoonotic diseases



Study Guide

The material in this chapter shifts the perspective that we have taken so far. Instead of focusing on individuals, groups, populations, and comparisons across species, in this chapter the topics are related to the relationships when different species of primates and other organisms inhabit the same communities. The material presented in Box 11.1 is important because it is the only part of the book where human–primate interactions and their long history in communities is considered. Ethnoprimatology is a field of study with many connections to other areas of the biological and social sciences.

It is important to emphasize that sympatric species can compete for food and other resources, but usually not for mates (although reviewing prior discussions on hybrids may be appropriate here). The behavior of mixed-species, or polyspecific, associations that form in response to increased foraging efficiency or predators therefore differ from larger groups of conspecifics in which dietary overlap and competition for mates will be greater.

The first topic is polyspecific associations. These are not restricted to mixed species of primates; there are many other birds and mammals that form these with primates as well. Examine the criteria used to define these associations, and the various types that have been identified. The concept of ecological niches is important here, and it can be related back to earlier material on the adaptive radiations that have occurred over the course of primate evolutionary history when new ecological niches opened up. Dietary differences are just one of the components of niche separation; there is also activity cycle, habitat preferences, and strata use. Species differ in their vulnerability to different kinds of predators, and between food and predators; it is straightforward to review the costs and benefits of polyspecific associations. Remember that direct, contest competition, and indirect, scramble competition can occur between species just as they occur within the same species. Be sure you can give specific examples of each type of polyspecific association, including those that are essentially permanent (e.g., tamarins), as well as those that are transient or opportunistic. The classical types of polyspecific associations described from Manu National Park, Peru, by John Terborgh make good examples. Field experiments involving playback recordings from Täi and Kibale provide examples of how one can evaluate predictions about mixed-species associations.

A second theme focuses on predator–prey, parasite and microbiota, and primate–plant interactions. When thinking about primates as predators, be sure to consider the nutritional, reproductive, and social explanations for hunting. When thinking of primates as prey, you can include both the impact of predation on primate populations and the abilities of different species to recover from severe predation, which ties in with life histories from Chapter 9, and the behavioral mechanisms primates use to reduce their vulnerability to predators, which ties in with both polyspecific associations and the size of conspecific social groups. Box 11.2 on chimpanzee predation on red colobus monkeys also raises important questions about the degree to which predation pressures can select for behavioral adaptations in prey and in terms of the impacts of predators (or the loss of predators) on populations of prey species.

Coverage of parasite and microbiota includes the perspective that both are part of naturally occurring communities with and within primates. There are great differences in the risks of parasite infections and in the microbiome communities of primates depending on where they live, how much anthropogenic disturbance there is, and how this affects their diets. Seasonality affects the life cycle of the parasites, while population density and social patterns affect the levels of social transmission.

Primate interactions with plants must begin with a clear understanding of coevolution and the criteria of mutual dependence by which it is measured. Primates share the plants they eat, pollinate, and disperse with other animals, from insects including dung beetles, to birds, bats, and other frugivorous mammals. They contribute to forest regeneration through seed dispersal, as the figure on defaunation of forests without primates and other animals shows. Can you list the characteristics of plants that stimulate or deter primates from exploiting them? There are strong connections here with previous material on primate dietary adaptations (Chapter 6) and with primate scent and visual abilities (Chapter 10), including color vision (Chapter 2).

The effects of habitat alterations on different species of primates within a community are of increasing concern. Here is where concepts of “generalists” and “specialists” come up. Be sure you understand the respective competitive abilities of each of these categories, and the principle of competitive exclusion. It will seem obvious that habitat alterations affect different primates to different degrees. Can you describe or predict which species are most likely to be negatively impacted by which kinds of disturbances? How do these impacts affect the primate communities? This brings us back to biodiversity hotspots, and the ways in which species’ richness, diversity, and endemism contribute to identifying conservation priorities.

Study Questions

  1. Describe two factors that reduce the risk of infectious parasite transmissions among primates.
  2. List three ways in which sympatric species of primates can avoid direct competition with one another over food.
  3. Discuss the social and environmental causes of variation in parasite transmission over time and among individuals.
  4. Explain the major difficulty in identifying coevolutionary relationships between primates and plants.
  5. Discuss the relationship between projected primate extinctions and the impact of their extinctions on the ecosystems these primates inhabit.
  6. Select at least two primates that are known to form polyspecific associations with one another. Explain which species is/are responsible for maintaining the association, and the costs and benefits of the association to each species.
  7. Define the criteria used to identify ecological hotspots and discuss the role of hotspots in primate conservation.
  8. How do primate ranging patterns and passage rates affect the survival of seeds they disperse? Be sure to consider the trade-offs (costs and benefits) from the plant’s perspective in your answer.
  9. List two of the hypotheses advanced for why male chimpanzees share the meat they hunt, and provide a brief description of the kind of data one would need to test each hypothesis.
  10. Describe the behavioral adaptations primates are thought to have evolved to protect themselves from predation.
  11. Explain the advantages and disadvantages that generalist and specialist primates will have as climate change affects their habitats.


Supplementary Resources

Chimpanzee Hunting Red Colobus

Here are two videos with amazing footage of chimpanzee hunts—beware, though, the first is very graphic.

Chimps hunt and eat a monkey

Chimpanzees hunting monkeys

Mixed-Species Associations

This video, from Dr. Hannah Buchannan-Smith and the Living Links facility in Edinburgh, shows how researchers can use behavioral observations to improve the conditions of two primate species housed together:

Living together: capuchin and squirrel monkeys

Impacts of Primates on Seed Dispersal

Here is a link to the Open Access article, Quantifying the impacts of defaunation on natural forest regeneration in a global meta-analysis. (Links to an external site.) which is the source of Figure 11.12, shown here again as well:

A close up of a map  Description automatically generated


  • There is disagreement about whether the best way to protect primates is to focus on individual species or entire ecosystems. But when conservationists mapped the distribution of endemic species, they fell into a small number of biodiversity hotspots. You can read more about these on Conservation International’s website here (Links to an external site.).
  • A good question to think about is: How can we balance protecting hotspots with protecting species that may occur in other areas but are equally threatened?

Chapter 12: Conservation


Threats to Primates

  • Habitat Loss and Disturbances
  • Climate Change
  • Hunting Pressures
  • Disease
  • BOX 12.1 Disease Demons

Conservation Policies

  • Economic Incentives
  • Increasing Public Awareness
  • Nongovernmental Organizations
  • BOX 12.2 The Primates’ People

Noninvasive Research

  • Diet and Habitat Change
  • Reproductive Biology and Stress
  • From Paternity to Population Genetics
  • BOX 12.3 From Methods to Practice

The Next Millennium



This final chapter of the textbook covers practical aspects of primate conservation, including the main risks to primates today. These include habitat loss and fragmentation, and hunting. Some primate species are more affected than others. Each of these topics is considered with examples from around the globe, with Box 12.1 focusing on zoonotic diseases. There are practical solutions, such as establishing corridors or bridges to connect populations isolated in different fragments and prohibiting (and enforcing prohibitions) on hunting and live capture of primates, and promoting eco-tourism as a way to bring funding to conservation as well as education about primates. The challenges of developing and implementing effective conservation policies are reviewed, focusing on the importance of generating economic incentives, education, and strategies employed by many nongovernmental organizations. Box 12.2 features the contributions of Dr. Russell Mittermeier and the importance of collaborations among conservationists, nongovernmental organizations, and researchers.

The chapter also discusses the vital role of research. Noninvasive methods ranging from stable isotope analyses of hair samples, to fecal steroid assays, to hair and fecal genetic studies, have become part of the field primatologist’s basic tool kit over the past 20 years. New advances, particularly in remote observation of primates and their habitats with drones and sophisticated cameras, are discussed in the context of the new kinds of questions that can now be addressed to increase our understanding of primates and advance our conservation aims. The book closes with the grim economic realities that limit conservation efforts and the urgent challenges to primatologists of the twenty-first century. Box 12.3 features the next generation of primatologists and some of the resources they can draw on in their pursuit of primates.



Key Words and Terms


edge effects




nongovernmental organizations, NGOs


sustainable forest management

ecosystem services



Study Guide

The topic of primate conservation is extensive. That is one reason why conservation issues are integrated throughout the 11 prior chapters of this book. The many applications of behavioral ecology to conservation are exciting, and the exercise of explicitly articulating the connections between basic science and conservation can be an effective way of reviewing the entire content of the course.

Try to outline the major sources of threats to primates on a global and regional scale and then think about some of the main human activities that are responsible for these threats. Disease and climate change are probably at the forefront of most of our minds nowadays, but it is important to remember that the driving forces over the past century that have brought more than half of extant primate species to be threatened with extinction were more conventional ones, like habitat loss and hunting pressures. Remember that humans have altered habitats and ecosystems throughout the world (as described in Chapters 3 and 11), and that the impact of humans is directly related to both subsistence needs as human population increases, and to economic gains that are often associated with multinational corporate greed. Often, the local human communities that live in proximity to primates are also negatively impacted by anthropogenic activities beyond their control. Distinguishing between these different causes and impacts can help you to identify what kinds of conservation efforts are more likely to work, where they might work, and with which species they could have the best chances.

Some particularly effective examples of conservation dilemmas include the controversy of sustainable development projects. Think about the oil palm agro-industrial activities in Indonesia, and the challenges to the conservation of entire ecosystems versus particular species these create. Nonetheless, primates and other appealing megafauna continue to be effective as flagship species that can generate concern and action on behavior of the other animals and plants in their ecological communities.

The use of noninvasive research methods and new remote sensing methods of observing primates and their habitats play a synergistic role in being able to address and advance basic research questions in behavioral ecology that can help inform conservation. Consider, for example, how insights into primate reproductive biology and genetics can contribute to both behavioral ecology and conservation concerns. Having now gained a combination of knowledge about primates and the practical relevance of this knowledge to conservation concerns, you are ready to move forward, whether it is to specialize in a particular area of research, or focus on conservation, or simply to pay more attention to news that negatively impacts the other primates of the world.

The chapter includes boxes featuring people and resources that may be helpful in figuring out where to learn more and what you can do next. The Appendix to this website includes some useful links, and the content in Box 12.3 provides references to other resources. I hope that after mastering the basics of Primate Behavioral Ecology, you will have gained a greater appreciation for the other primates that are part of our natural world that will stay with you wherever you go.

Study Questions

  1. List three of the major threats to primates today.
  2. Discuss the ecological and demographic factors that affect the viability of primate populations in small, isolated forest fragments. Include specific examples of primates in your answer.
  3. For each of the following conservation initiatives, explain the rationale behind them and some of the obstacles that can undermine their effectiveness:
    1. Sustainable forest management
    2. Eco-tourism
    3. Captive breeding.
  4. Select one example of noninvasive research methods and describe how results from such studies can contribute to both advances in our understanding of primate behavioral ecology and conservation efforts on behalf of endangered species.
  5. Conservation biologists disagree over whether the best way to protect endangered species is by setting aside a single large (= SL) area that contains suitable habitat versus several small (= SS) areas that contain suitable habitat but are not connected to one another. (a) Using your knowledge of evolutionary ecology and conservation biology, discuss the arguments for and against each of these positions for primates in general. (b) Then, using your knowledge of primate behavioral ecology, discuss how characteristics such as body size, reproductive rates, and degree of ecological specialization might influence the effectiveness of one type of approach over the other. Be sure to give examples of particular primates in your answer.

Supplementary Resources

More on Amazon Deforestation

  • This is another figure from the same Mongabay story as the one reproduced in the textbook. Take a look at the entire story, and look around at the site; there is a lot of good coverage on primates and conservation at this Open Access journal.

A screenshot of a cell phone  Description automatically generated

From: Butler, R. A. 2020. Amazon Destruction. Published on Mongabay, at reproduced under creative commons license, Attribution-No Derivatives 4.0 International (CC BY-ND 4.0), Date accessed (and copied): 29 April 2020.

  • Here is a link to a story about a recent journal article that asks the question: How much space does Nature need?

  • I previously included a link to this key paper by Alejandro Estrada and colleagues (2017); here it is again:

Impending extinction crisis of the world's primates: Why primates matter (Links to an external site.)

Video about Primates in Peril in four countries

Arboreal Bridges

  • This link describes a project to build an arboreal Bridge for the Tamarins to move between their forest fragments.
  • And here is a video of a black-horned capuchin monkey resting and then walking on a powerline at my field site. Video by A.J. Hardie.

Wildlife Markets

Check out this essay about COVID-19 and other zoonotic diseases and human consumption of wildlife at Global Wildlife Conservation's website.

Pet Trade

Here is a link to a video about the pet trade involving pygmy marmosets in Ecuador, Requiem for the forest--saving pygmy marmosets. It was made by Dr. Stella de la Torre and her colleagues. It is a poignant reminder of how vulnerable primates are, and how all of us can make a difference to help to save them.


Useful Links

Appendix: Useful Links to Resources on Primate Conservation and Primate Research Opportunities



Primate Specialist Group, IUCN (includes tabs with links to the Red List of threatened species and other resources)

IUCN Red List of threatened species

International Primatological Society (IPS)

Affiliate page of IPS—has links to other national and regional primate societies

International Primatological Society facebook (open)

Primate Information Net

Primate jobs!categories/primate-job