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Chapter 7
Primate Behavior
Observing Primates
(a) Rhesus macaques spend much of their time on
the ground and are easier to observe than (b) blackand-white colobus.
Terms
Behavior – Anything organisms do that involves
action in response to internal or external stimuli.
Free-ranging – Pertaining to non-captive animals
living in their natural habitat.
Social Structure – The composition, size, and sex
ratio of a group of animals.
Behavioral Ecology - An approach that focuses on
the relationship between behaviors, the natural
environment, and biological traits of the species.
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.
Factors That Influence Social
Structure
Basal Metabolic Rate (BMR) and Diet
– Smaller animals generally have a higher BMR
than larger ones.
– Consequently, smaller primates require an
energy-rich diet high in protein, fats, and
carbohydrates.
• Metabolism – The chemical processes within cells
that break down nutrients and release energy for the
body to use.
Factors That Influence Social
Structure
Distribution of Resources
– Leaves can be abundant and will support large
groups of animals.
– Fruits and nuts occur in clumps. These can be
efficiently exploited by smaller groups of
animals.
Distribution of Resources
This male mountain
gorilla has only to reach
out to find something to
eat.
Factors That Influence Social
Structure
Predation
– Primates are vulnerable to many types of predators
– Where predation pressure is high, large communities
are advantageous.
Factors That Influence Social
Structure
Relationships with Other, Nonpredatory
Species
Factors That Influence Social
Structure
Dispersal
– Members of one
sex leave the
group in which
they were born
when they
become sexually
mature.
Factors That Influence Social
Structure
Life Histories
– Life history traits are characteristics or
developmental stages that typify members of a
species and influence reproductive rates.
Factors That Influence Social
Structure
Factors That Influence Social
Structure
Activity Patterns
– Nocturnal species tend to forage for food alone or in
groups of two or three and many use concealment to
avoid predators.
Factors That Influence Social
Structure – Human Activity
Matrilines
Groupings of females who are all descendants of
one female
Matrilines also include dependent male offspring.
Types of Nonhuman Primate
Social Groups
One male-multifemale.
Multimale-multifemale
Monogamous pair
Polyandry
Solitary
Philopatric
Sympatric
Living in the same area.
Kibale Forest, Uganda
Primate Social Strategies
Primate Social Behavior:
Dominance
Many primate societies are organized into
dominance hierarchies.
These impose order by establishing parameters of
individual behavior.
Breeding and Suppressed Males
Fully mature, breeding male orangutan with welldeveloped cheek pads (a) compared to a suppressed
adult male without cheek pads (b).
Factors that Influence
Dominance Status
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–
–
–
–
–
–
Sex
Age
Aggression
Time in the group
Intelligence
Motivation
Mother’s social position
One young male savanna
baboon mounts another as an
expression of dominance.
Primate Social Behavior:
Communication
An adolescent male
savanna baboon threatens
with a characteristic
“yawn” that shows the
canine teeth.
Note that the eyes are
closed briefly to expose
light, cream colored
eyelids.
This has been termed the
“eyelid flash.”
Displays
Sequences of repetitious behaviors that
serve to communicate emotional states.
Nonhuman primate displays are most
frequently associated with reproductive or
agonistic behavior.
Chimpanzee Facial Expressions
Primate Social Behavior:
Aggression
Conflict within a group frequently develops out of
competition for resources, including mating
partners and food items.
Primate Social Behavior
Affiliative Behaviors
Common affiliative behaviors include
reconciliation, consolation, and simple amicable
interactions between friends and relatives.
Patterns of Reproduction
In most primate societies, sexual behavior is
tied to the female’s reproductive cycle.
Reproductive Strategies
Behavioral patterns that contribute to
individual reproductive success.
K –selected
Sexual Selection
Infanticide As A Reproductive
Strategy?
Hanuman langurs live in
groups of one adult male,
several females, and
offspring.
Males without mates form
groups and occasionally
attack a reproductive male
and drive him from his
group.
Sometimes the new male
kills some or all of the
group’s infants.
Chacma Baboons
When chacma baboon
males migrate into a
new group, they
“deliberately single out
females with young
infants and hunt them
down”.
Mothers, Fathers and Infants
The basic social unit among primates is the female
and her infants.
(a) Sykes monkey. (b) Patas monkey.
Primate mothers with young.
(c) Mongoose lemur. (d) Orangutan. (e) Chimpanzee.
Infant Macaque Clinging to
Cloth Mother
Misunderstanding Primates
This unfortunate advertising display is a good
example of how humans misunderstand and
misrepresent our closest relatives.