CHAPTER 7 Primate Behavior What is Meant By Behavior? • Anything organisms do that involves action in response to internal or external stimuli. • The response of an individual, group, or species to its environment. • Such responses may or may not be deliberate and they aren't necessarily the results of conscious decision making. Ecological Perspective • Pertains to relationships between organisms and all aspects of their environment • Temperature • Predators • Vegetation • Availability of food and water • Types of food • Disease organisms • Parasites Behavioral Ecology Focuses on the relationship between behaviors, natural environment, and biological traits of the species. Based on the assumption that animals, plants, and microorganisms evolved together. Behaviors have evolved through the operation of natural selection, or Some behaviors are influenced by genes and are subject to natural selection the same way physical characteristics are. The Evolution of Behavior Behavior constitutes a phenotype  Individuals whose behavioral phenotypes increase reproductive fitness pass on their genes at a faster rate. Genes do not code for specific behaviors, but they do code for biological factors that impact behavior, i.e. hormone levels, intelligence Species vary in their limits and potentials for learning and behavioral flexibility, set by genetic factors. Natural selection acts on genetic factors shaped by ecological, the same as it does physical characteristics Social Structure • The composition, size, and sex ratio of a group of animals. • The social structure of a species is, in part, the result of natural selection in a specific habitat, and it guides individual interactions and social relationships. Why Are Primates Social? • Group living exposes animals to competition with other group members, so why not live alone? • Costs of competition are offset by the benefits of predator defense provided by associating with others. • Group living evolved as an adaptive response to a number of ecological variables. Some Factors That Influence Social Structure • Body Size • Larger animals are better able to retain heat and their overall energy requirements are less than for smaller animals • This means they need fewer calories per unit of body weight. Some Factors That Influence Social Structure • Metabolism • The chemical processes within cells that break down nutrients and release energy for the body to use. • Basal Metabolic Rate (BMR) and Diet • Smaller animals generally have a higher BMR than larger ones. • This means smaller primates require an energy-rich diet high in protein, fats, and carbohydrates (fruit, and insects). Some Factors That Influence Social Structure • BMR and Diet • Nutritional needs have evolved along with BMR and body size • Benefits are considered in terms of energy (calories) obtained from food .

1. CHAPTER 7
Primate Behavior
What is Meant By Behavior?
• Anything organisms do that involves action in response to
internal or external stimuli.
• The response of an individual, group, or species to its
environment.
• Such responses may or may not be deliberate and they
aren't necessarily the results of conscious decision
making.
Ecological Perspective
• Pertains to relationships between organisms and
all aspects of their environment
• Temperature
• Predators

2. • Vegetation
• Availability of food and water
• Types of food
• Disease organisms
• Parasites
Behavioral Ecology
natural environment, and biological traits of the
species.
umption that animals, plants, and
microorganisms evolved together.
natural selection, or
subject to natural selection the same way physical
characteristics are.

3. The Evolution of Behavior
reproductive fitness pass on their genes at a faster
rate.
code for biological factors that impact behavior, i.e.
hormone levels, intelligence
and behavioral flexibility, set by genetic factors.
ecological, the same as it does physical
characteristics
Social Structure
• The composition, size, and sex ratio of a group of
animals.
• The social structure of a species is, in part, the

4. result of natural selection in a specific habitat, and
it guides individual interactions and social
relationships.
Why Are Primates Social?
• Group living exposes animals to competition with other group
members, so why not live alone?
• Costs of competition are offset by the benefits of predator
defense provided by associating with others.
• Group living evolved as an adaptive response to a number of
ecological variables.
Some Factors That Influence Social Structure
• Body Size
• Larger animals are better able to retain heat and their overall
energy
requirements are less than for smaller animals
• This means they need fewer calories per unit of body weight.

5. Some Factors That Influence Social Structure
• Metabolism
• The chemical processes within cells that break down nutrients
and release
energy for the body to use.
• Basal Metabolic Rate (BMR) and Diet
• Smaller animals generally have a higher BMR than larger
ones.
• This means smaller primates require an energy-rich diet high
in protein,
fats, and carbohydrates (fruit, and insects).
Some Factors That Influence Social Structure
• BMR and Diet
• Nutritional needs have evolved along with BMR and body size
• Benefits are considered in terms of energy (calories) obtained
from food
versus costs (energy expended) of obtaining and digesting them.
• Larger primates consume large amounts of lower quality foods

6. Some Factors That Influence Social Structure
• Distribution of Resources
• Leaves are abundant, dense, and support large groups of
animals. (gorillas)
• Insects are widely scattered, causing animals to feed on
them alone or in small groups of two or three (lorises,
marmosets, tarsiers)
• Fruits and nuts occur in clumps and are most efficiently
exploited by smaller groups of animals; large groups
break up into smaller subunits to feed. (baboons, vervets,
chimpanzees)
• These groups tend to be the most territorial due to the
need and ability to defend limited food supply
Some Factors That Influence Social Structure
• Predation
• Primates are vulnerable to many predators, including snakes,
birds of prey, leopards, wild dogs, lions, and even other
primates.
• Where predation pressure is high, large communities are
advantageous (safety in numbers).

7. Some Factors That Influence Social Structure
• Dispersal
• Upon sexual maturity individuals leave their birth group
• Usually males disperse, but sometimes it is the females
• Dispersal decreases the chances of inbreeding, competition
for mates, and the likelihood of gene survival.
Some Factors That Influence Social Structure
• Life Histories
• Characteristics or developmental stages of a species that have
an impact on reproduction
• i.e. length of gestation, time between pregnancies, period of
infant
dependency and age at weaning, age of sexual maturity, and life
expectancy.
• For example gorillas are not sexually mature until approx. 12,
infant
dependency is 3 to 5 years, even with a 35 year life span a
female will
only produce 3 to 4 offspring in her life
• Unpredictable environments (seasonal food supply) favor
shorter life histories and stable ones (steady resources),
longer lives
• Today, the slow rate of reproduction increases the threat of
extinction for all the great apes.

8. Primate Social Behavior: Dominance
• Many primate societies are organized into dominance
hierarchies that impose order and establish
parameters of individual behavior.
• Higher-ranking animals have greater access to
preferred food items and mating partners than lower
ranking individuals.
• Dominance hierarchies are sometimes called “pecking
orders” that change throughout one’s life and are
learned
Factors that Influence Dominance Status
• Sex
• Age
• Aggression
• Time in the group
• Intelligence
• Motivation

9. • Mother’s social position
Primate Social Behavior: Communication
• Any act that conveys information to another individual.
• Frequently, the result of communication is a change in the
behavior of the recipient.
• Communication may be the result of involuntary
processes or a secondary consequence of an intentional
action.
Communication
• Raised body hair is an example of an autonomic, or
unintentional, response.
• Gestures, facial expressions, scent marking and vocalizations
are examples of deliberate communication.
• Grooming serves to indicate submission or reassurance.
• Displays communicate emotional states.
Primate Communication

10. • The fear grin, seen in all primates, indicates fear and
submission.
• Often misconstrued by humans as a greeting!
• Threat yawns are a warning and are also seen amongst many
primates
Primate Social Behavior: Affiliation and Altruism
• Common affiliative behaviors include reconciliation,
consolation, and interactions between friends and
relatives.
• Hugging, kissing and grooming are used in reconciliation.
• Relationships are crucial to nonhuman primates and the
bonds between individuals can last a lifetime.
• Altruism, behaviors that benefit another while posing risk to
oneself, are common in primate species.
Grooming
• Picking through fur to remove dirt, parasites, and other
materials
that may be present.
• Social grooming is common among primates and reinforces

11. social relationships.
• Grooming is also used to show submission/ appeasement or
reaffirm the pecking order
Primate Social Behavior: Aggressive Interactions
• Are disruptive to the group and are typically avoided or
mitigated before harm is done.
• Conflict within a group frequently develops out of competition
for resources, including mating partners and food items.
• Most intragroup aggression occurs in the form of various
signals and displays within the context of a dominance
hierarchy.
• Most tense situations are resolved through various submissive
and appeasement behaviors.
Serious and Fatal Consequences of Aggression
• Dominant displays or actions are often linked to reproductive
success:

12. • Dominant female macaques can control the food supply of
subordinates
leading to weight loss and poor nutrition, impacting their
chances of
reproductive success
• Competition among males for mates can result in injury and
death
Intergroup Aggression
• Primate groups are associated with a home range where they
remain permanently.
• The home range contains the core area where the best most
reliable food supply is, this is where the group is most often
found.
• Home ranges of different groups may overlap, but core areas
don’t. The core is said to be the groups territory, and it is the
area that is defended against intruders. (sometimes violently)
Reproduction and Reproductive Behaviors
• In most primate societies, sexual behavior is tied to the

13. female’s reproductive cycle--estrus.
• Permanent bonding between females and males is not common
among nonhuman primates.
• Male and female Bonobos may mate even when the female is
not in estrus, a behavior that is not typical of chimpanzees.
Reproductive Strategies
• Behavioral patterns that contribute to individual
reproductive success.
• Primates produce only a few young in whom they invest a
tremendous amount of parental care (K–selected)
(contrast r-selected)
• Male competition for mates and mate choice in females
are both examples of sexual selection.
Sexual Selection
• A type of natural selection that operates on one sex,
usually males due to female “selection” of mates.

14. • Long-term, this increases the frequency of traits that
lead to greater success in acquiring mates.
• Sexual selection produces dimorphism with regard to
a number of traits, most noticeably body size.
• This is due to competition, which frequently leads to physical
combat, for
mates
Examples of Sexual Dimorphism
The following traits are characteristics of the males only of
many
of the great apes. Primarily gorillas, chimpanzees, orangutan
• Not bonobos. Why?
• Sagittal crest: Allows for much more surface area for
temporalis
and mastoid muscles which allows for a much more powerful
bite. This is used for combat and defense of territory and
females
• Canine-premolar (CP3) honing process: sharpens the canine
teeth, again needed for male combat and defense
Male gorilla skull (left) and female
(center) CP3 process (right)

15. /
Infanticide: A Reproductive Strategy?
• One way males increase their chances of reproducing
is by killing infants fathered by other males.
• Individuals maximize their reproductive success, no
matter the effect on population or species.
• When an infant dies, its mother resumes cycling and
becomes sexually receptive.
• An infanticidal male avoids waiting up to two to three
years for the infants to be weaned before he can mate
with their mothers.
Hanuman langurs
Mothers, Fathers and Infants
• The basic social unit among all primates is the female and
her infants.
• Except in species in which monogamy or polyandry
occur, males do not participate in rearing offspring.
• The mother-infant relationship is often maintained
throughout life.

16. Primate Maternal Bonding
• Primate infants raised without a mother have been
found to not be able to create necessary social bonds,
to successfully copulate or productively raise their own
young
Primate Cultural Behavior
• Cultural behavior is learned; it is passed from
generation to generation through observation and
instruction.
• Nonhuman primate infants, through observing
their mothers and others, learn about food items,
appropriate behaviors, and how to use and
modify objects to achieve certain ends.
• More complex, chimpanzee culture includes tools
such as termite fishing sticks and leaf sponges.
• Cultural practices are unique to differing groups

17. Examples of Cultural Behavior
• Japanese macaques and sweet potato washing
• Orangutan nest building
• Gorilla depth testing
• Chimpanzee termite fishing, leaf sponges, hunting
“spears,” nut cracking
• Kanzi’s stone tool making
Anthropocentric
• Viewing nonhuman animals in terms of human motives,
and experience and capabilities; emphasizing the
importance of humans over everything else.
• This sets up a hierarchy that says humans are “better” or
the ideal state
Language
• Nonhuman animals haven’t been considered capable of

18. communicating about external events, objects, or other
animals.
• It has been assumed that nonhuman animals use a
closed system of communication, where vocalizations
don’t include references to specific external phenomena.
Language
• Vervet monkeys use specific vocalizations to refer to
particular categories of predators, such as snakes,
birds of prey, and leopards.
Kanzi • Kanzi, a Bonobo, began
using symbols when he
was 21/2 years old and
his younger half-sister
began using symbols at 11
months old.
• Both went to training
sessions with their mother,
but neither had been

19. taught or were involved in
the sessions.
The Biological Continuum
• Human brains are larger than primate brains, but
the neurological processes are functionally the
same.
• The necessity of close bonding with at least one
parent
• Need for physical contact
• Developmental stages and dependence on learning
• Capacity for cruelty, aggression, compassion,
altruism, with humans more adept at cruelty and
compassion and capability to reflect on behavior
Thinking About Humans
• How is social stratification similar to and different from the
dominance hierarchies found in many primate species?
• What patterns characterize human “dispersals”?
• How are primate aggressive behaviors similar to and
different from the violent actions that are present in

20. human societies?