Primate Social Behavior

Primate Social Behavior Are Chimps Like Us?

Why Study Primate Behavior?
Sociobiology: Do genes govern our behavior?
Ant society as genetically determined
“ Instincts” among nonprimate mammals
Humans are guided by culture
Product of learning
Involves language, lacking in all other species
Can nonhuman primate behavior give us a clue to our own?

Primatology: Basic Concepts
Ethology : Study of any animal’s behavior
Primatology: Study of nonhuman primates; subfield of ethology
Field Research: To avoid influencing primate behavior
Provisioning: Providing food to primates to shorten time in field
Drawback: Provisioning does influence primate behavior

Social Groups
Primates form social groups
Primate behavior is the most complex among nonhuman animals
Why groups?
Defense of resources
Defense against predators—safety in numbers
Social control: dominance hierarchies
Group cohesion: grooming
Protection and raising of young: mother-infant bonds

Types of Social Groups
Fusion-fission society: Groups come and go; chimpanzees ( Pan troglodytes)
Harems (gorillas): one male, several females
A few other, related males
Multimale (baboons): several males and females
Male dominance hierarchies are rigid

Mother and Infant Bonds
Mother-infant bonds are strong among all primates (monkey and apes)
Top: baboon mother pulls leg of reluctant infant
Bottom: Chimp infants have long period of dependency

Social Behavior: Grooming
All primates groom
One combs fur of another
Pick out dried skin, parasites
Main function: interaction to maintain social bonds
All primates but prosimians use fingers
We haven’t lost the grooming habit

Social Behavior: Territoriality
Home range : area of cyclical migration
Core area: smaller unit which is the primary area of activity
Chimps defend their core area against other troops
These chimps are on patrol for that purpose
Baboons are more tolerant of baboons from other troops

Social Behavior: Communication
Gibbon calls (like this one) are closed
Danger: high-pitched shouts
Assembling: clatters and clicks
Chimps have some aspects of language
Kanzi—bonobo capable of making requests by pressing computer keys with symbols
Chimpanzees—able to use American Sign Language
Spoken language does not exist among nonhuman primates

Social Behavior: Dominance Hierarchies
Dominance hierarchies: system of rank among nonhuman primates
Here, the alpha chimp touches the back of the lower ranked one (top)
Bonobo dominance behavior centers on females (bottom)
Sons’ hierarchy depends on that of their mothers

Communication: Threats
Calls of greeting or threats when two troops meet
Threat gestures
Baboons: baring canines (top)
Chimpanzees
Slack jaw: sign of anger
Chimpanzee : Displays, screams (bottom), tearing vegetation
Reactions of target individuals :
Grimacing; crouching; presenting rear end

Communication: Reconciliation
Embracing
Extending hand for reassurance (top)
Grooming (to curry favor)
Even kissing

Sexual Behavior: Individual
Estrus: cyclical female receptivity
Swelling of sexual skin among monkeys and some apes (such as this hamadryas baboon)
Receptivity longer among bonobos and humans
Sexual positioning in copulation
Most primates: male copulates with female from rear
Bonobos and human: frontal (ventro-ventral) copulation, as between this couple

Sexual Behavior: Partners
Gibbons form lifetime monogamous pairs (top)
Other species:
Harems among baboons and gorillas (such as these two females, bottom)
Multiple male-female sexuality among chimpanzees and especially bonobos
“ Homosexual” behavior found among bonobos

Phases of Growth
Newborns: cling to mother’s stomach
Up to a year: start riding mother’s back
Juveniles form play groups, a good way to learn basic skills
Juveniles may also show empathy, as with this distressed adult
Imitative behavior gradually integrates subadults into the troop

Foraging and Sharing
Prosimians: insects and plant foods
Most anthropoids: roots, fruits, seeds—some species eat meat of small animals
Gorillas: strict vegetarians
Chimpanzees: often cooperate in stalking, killing prey, and sharing the meat
Bonobos: Share food of all kinds

Yes, Chimps do eat meat
Chimps feeding on red colobus monkey
About 10% of these monkeys are killed by chimps in the Gombe reserve

Tool Making and Tool Use
Chimpanzees at Gombe are famous for termite fishing with twigs
They also use leaves as sponge
May be culturally derived:
Chimps in West Africa crack nuts but don’t fish for termites

Tool Making and Use: Other species:
Bonobos make rain hats from leaves
Orangutans also use tools
Gorillas and gibbons do not make or use tools—so far as we know!

Agonistic Behavior and Warfare
Agonistic behavior characteristic of all species
mostly over mating females
competing for dominance
Primates were once thought incapable of killing their own kind.

Conflict: Comparing Chimps and Bonobos
Chimpanzees
Warfare actually was observed between one troop and a breakaway group.
Cannibalism observed and reported
Bonobos
Philosophy: “Make love, not war”
Frequent sexual contact between sexes and within one sex

Primate Behavior and Fossil Hominid Behavior
Inferring the past
Similarities between nonhuman primate and human behavior
Tool making before the Paleolithic
Interaction without language: kinesics and paralanguage
When did language become necessary?

Interpreting the evidence
Nature of prehominid and early hominid society
Child rearing techniques
Was hierarchy inevitable?
Was warfare inevitable? Bonobos versus chimps

Primate Social Behavior

by PaulVMcDowell

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