TO KNOW FOR EXAM:Taxonomy down to and including family (subfamily for

OW monkeys and apes) level for extant primates (fill in the blanks)

Evolutionary trendsCharacteristics of each of the extant groups of primates, e.g.

apes do not have tailsOverview of the evolutionary history of the primates, e.g.

what was happening during the Eocene, what were names of important groups, where are their fossils found, and what group(s) is derived from them

Locomotor categories and species examplesSocial organizations and species examplesTerms, e.g. rite mirabile, tapetum lucidum,

sympatric/allopatric…

PRIMATE SOCIAL

ORGANIZATION

‘Most primates spend their life in a social group. Primate social groups are often complex and permanent and group members perform most of their activities within the confines of their group. They depend on the group for survival in terms of protection from predators, conspecifics, and/or other group members, as well as for finding resources and mates. Group life does not come without its share of constraints, primarily competition for resources. Group size and structure vary from species to species but within a species, are somewhat stable, i.e. one type of social structure is seen in each species and group size remains stable over time under natural conditions via emigration, predation, and group fission.’ (Berman)

How a group is organized…and classified Numbers of particular aged-sexed

individualsImmigration and emigration

Mating system Patterns of interactions between

members Dominance hierarchy

Strier: Primate social organization “reflects the compromises between female and male strategies to gain access to mates, food, and other resources that they and their offspring need to survive. These compromises are constrained by life history and physiology, and vary with ecological and demographic conditions”

TYPES OF SOCIAL

STRUCTURES

I. Where the nature of the diet warrants females foraging solitarily:

Dispersed polygyny Male monopolizes a couple of females or acts as

satellite

Territorial pair Cooperate in home range defense and be (almost)

assured of paternity

Community: “resource defense polygyny” Males cooperate and defend home range containing

females

Solitary foragers / dispersed polygynyorang, galago, potto, loris, nocturnal lemurs

Group composition Male-biased dispersal

Female relatives may associate, sleep together Dispersed polygyny Evolutionary/ecological significance More social than thought :

Orangs: adolescents, fruit trees Galago sisters Mouse lemur sleep groups

Communication – scent, vocal

Monogamous or territoreal pairsindri, night monkey, gibbon, siamang

Group composition Territorial

Spacing mechanism: duet

Emigration Couples are stable but

EPC’s Monomorphic Evolutionary / ecological

significance Male caretaking

Community / Fission-fusionchimps, bonobos, spiders, muriquis

Group composition Emigration Evolutionary / ecological

significance Resource-defense

polygyny Female chimps & muriquis

mate promiscuously – confuse paternity

Sperm competition Avoids conflict with kin

II. Where the nature of the diet allows females to forage together:

Where resources are defensible → females cooperate (female-bonded) in resource defense and groups are larger and multi-male

Where resources are not defensible or worth defending → females do not cooperate and groups tend to be smaller Monopolizable → 1-male Hamadryas and gelada

• Multi-tiered SO

One-male groups / harem

all non-savanna baboons, patas, some colobines, lowland gorillas

Hamadryas

Langurs and leaf monkeysPatasMandrill

Gelada

Group composition Misleading Emigration Evolutionary / ecological significance

Nature of resources → small groups → monopolizable Infanticide Complex social organization in open living baboons

• Resource-poor dangerous environments Hamadryas: 1-male units → clans (2-4 units + bachelors) → band (several

clans ~60) → troop (multiple bands) → several troops come together on sleeping cliffs

Geladas: 1-male units + bachelors→ bands →herd (↑600)

Age-graded multi-maleMountain gorilla (red howler, hanuman langur)

Mountain gorillas

Group composition Emigration Female mountain gorillas

attracted to >1 male

Multi-male/multi-femalemacaques, savanna baboons, capuchins, squirrel

monkey, vervets…

Mine!

Group composition Usually –♀-philopatric

Emigration Solitary, all-male bands,

other group Exceptions

Squirrel monkeys CR ♀’s SA ♂’s

Howlers Ecological significance Fission

PolyandryTamarins and

Marmosets

Where polyandry reported: Group composition

Two adult males Both may be reproductively mature Usually only one sires offspring

1 breeding female Chemical suppression

Possibly mature offspring Immature offspring

Mean number offspring: twins

Helpers Males Siblings

Inclusive fitness Emigration Evolutionary /

ecological significance