Graphical summary

Primate Social Behavior 1

Anthropology 2200

Primate Behavior

Why do we care? • Primate behavioral ecology • Social behavior

• Types of social groups

Stress, Social Hierarchy, and Baboons • Robert Sapolsky

• Neurobiologist at Stanford • Studies Olive Baboons

• East Africa • 30 + years

• Takes blood samples • Tests levels of cortisol and epinephrine

• Neurotransmitters that trigger brain activity • Found that higher stress levels were present in

lower ranking individuals • Whitehall UK government study found the same in

humans • Study went further when aggressive dominant

male baboons died of TB • Changed culture in affected baboon troop

Social change in baboons

The Beginning: Louis Leakey • Discovered human ancestors

• Olduvai Gorge, E. Africa • Can we use modern great apes to understand

human behavior?

• Sent three untrained women to study ape behavior: • Jane Goodall • Diane Fossey • Birute Galdikas

Jane Goodall

• Studied Chimpanzees at Gombe National Park (20 years)

• Noted similarities between chimps and humans:

• Emotions • Intelligence • Family and social behavior • Aggression • Tool use

• Termite fishing • Dispelled “man the tool maker” • https://www.janegoodall.org/

Dian Fossey

• Studied Gorillas in Rwanda (18 Years) • Demonstrated that Gorillas were not as

fierce as people assumed • Helped save Mountain Gorillas from

extinction • Social relations, feeding behavior,

infanticide, vocalization • Murdered in 1985 - Unsolved

Birute Galdikas

Primate Behavioral Ecology • Understanding the ecological

and evolutionary reasons for primate behavior

Social Behavior

Group living: Residential Patterns • One aspect of social behavior • Group living is a balance between

competition for resources and the benefits associated with social behavior

• In general, primates are highly social • Exceptions = some nocturnal

prosimians and Orangutans

Group Living: Residential Patterns

Advantages Disadvantages ● Protection from predators ● Competition for resources ● Locating and protecting resources

● Opportunity for violence

● Access to mates ● Competition for mates ● Long-term bonds (e.g. child rearing, learning)

● Increased spread of disease

Constant struggle between competition and cooperation

Group living: Residential Patterns • Residential patterns related to reproductive

success • Evolutionarily, the goal is to have offspring. • Females

• Limited by access to resources • Males

• Limited by access to females

Its all about the babies!

So …

Types of Social Groups: Residence Patterns

One-male, multifemale (polygynous)

One-female, multimale (polyandrous)

Multimale, multifemale

All-male

One-male, one-female (monogamous)

Solitary

One-male, multifemale

• Polygyny • Most common type of social group • One male, multiple females, and

their immature offspring

• Sexual dimorphism • Ensures reproductive rights to

females • Females select males • Leave if not suitable

One-male, multifemale

• Females stay in their natal (birth) group

• Males leave the group as juveniles – before reproductive maturity

• Females = close social network • Allomothering in some cases • Males marginalized

One-male, multifemale

• Infanticide common • The killing of nursing

young • Foreign male drives

out dominant male • Females try to protect

young • Males larger, kill young • Females resume

ovulation • New baby belongs to

new male • Old male’s genetic

contribution reduced

Male Gorilla interaction with infants

One-male, multifemale

Langur

Howler monkey

Gelada baboon?

Gorilla

One-female, multimale

• Polyandry • One female, multiple males, and

their immature offspring

• Most rare type of social group • Female reproduction

consumes more time and energy

• Need only a few males • Only NWM – Callitrichidae

One-female, multimale

• Communal breeding • Males help with parenting • These groups raise twins

• Small primates • Die often due to predators • More offspring =

reproductive strategy • Increase reproductive output

Common Marmoset – Babies on Father Emperor tamarin

One-female, multimale

Multimale, multifemale • Large troops – OWM, NWM,

Chimpanzees/Bonobos

• Males, females, and their offspring • Promiscuous mating • Male competition relatively low • Sexual dimorphism = Low • Advantages:

• Protection from predators • More effective food acquisition • Lots of genetic variability

Chimpanzee family

Multimale, multifemale

• Dominance relationships (male and female)

• Determined by: • Sex • Age • Aggression • Intelligence • Mother’s position • Time in group

Macaque

Multimale, multifemale

• Impose a degree of order • Reduction of violence

• Dominant individuals = greater reproductive success • Access to food • Access to females

• Complicated and flexible rather than simple and linear • “Know your role” • Learned socially

Multimale, multifemale

• “Common” chimpanzee (fission- fusion)

All-male • Temporary all-male groups formed

before joining groups that include M/F • Commonly exist together with

multimale, multifemale groups

• “Bachelor” groups • Exist together with one-male,

multifemale groups • Consist of males who are not

able to obtain females • May attack one-male groups

and attempt to evict the resident male from his females (infanticide)

Baboon

One-male, one-female • Monogamy • Male knows his offspring

• Invests more time in supporting his own offspring

• Protection/food acquisition • Less sexual dimorphism than other

types of social systems • Lower degree of competition

• Uncommon • Gibbons, Siamangs, Night

monkey, some Marmosets, some Prosimians

One-male, one-female

• Males and females share defense of the territory

• Social interactions limited (small groups)

• Infants will engage in solitary play unless siblings are present

• Parents play with the infants

• Gibbons: aggregate at territorial borders

• Infants from different families play

• Best understood as female reproductive strategy

Pygmy Marmoset: a monogamous Callitrichidae

One-male, one-female GibbonSiamang

Gibbons in the wild

Solitary

• Noyau • One male range encompasses several female ranges • Individuals forage separately and socialize for

reproduction • Less successful males = more solitary

• Orangutans, some prosimians • Marked sexual dimorphism

• Large territory = increased male reproductive success

Solitary

Orangutan

Many Nocturnal prosimians

Aye-aye

Mouse lemur

• Males = 2x females • Large canines • Large cheek pads • Very loud calls

Watch from 5:30 until 10:00

Factors influencing the type of residence pattern

• Food distribution • Type of food • Seasonality

Fruit

Leaves

Insects

Factors influencing the type of residence pattern • Food is abundant = large groups

• Multimale-multifemale • One male-multifemale • Leaves • Fruits

• Food in small clumps = small groups • Monogamous pairs • One female-two males

• Food is very limited = individuals • Solitary • Insects

Factors influencing the type of residence pattern

• Predation • If predation = high • And body size = small • Large group may help fend off

predators • Large bodied primates are not

preyed on as often • Nocturnal species not preyed

on as often • Solitary tend to be

large/nocturnal

Humans

• What residential pattern do humans have?