Post on 17-May-2015
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