Primate Mating Systems and Sexual Selection

What primates are solitary (noyau)

Orangutangs and Lorises (

What primates are pair-bonded (monogamy)

Gibbons, owl monkeys, and tarsiers

What primates are uni-female/ multi-male (polyandry)

Tamarins (cooperative breeding)

What primates are uni-male/ multi-female (polygyny)

Langurs (fares leaf monkey), mountain gorillas, and hamadryas baboons (non-resident males may form bachelor groups)

What primates are multi-male/ multi-female (polygyandry)

Vervets, macaques (special case: fission-fusion; sometimes all together but most time in sub groups- spider monkeys and chimpanzees)

Define strategy in adaptation

Set of behaviours occurring in a specific functional context

Strategies are products of

Selection (not conscious plans)

What is reproductive success

Number of offspring surviving to reproductive age

Strategies may be different for

Males and females and in different group compositions

Primate females always

Provide lots of care for their young

Why do primate males rarely provide care for their young

Because of physiology do not need to

Infants survival in mammals depends on what two factors

Carrying offspring to term and nursing them until they can forage independently

What is paternity uncertainty

Do not know which offspring are theirs (males)

Often better strategy for male primates to use their resources to

Access additional females

Male primates will be less involved when

Attracting additional mates is relatively low and when fitness of offspring raised by one parent is high

When benefits of investment outweigh costs of seeking new mates

Males will provide more care (tamarins, owl monkeys - females can’t provide enough care)

Dominance hierarchy rank is positively correlated with

Reproductive success

In macaques what two factors influence RS

Rank and group size

In Hanuman langurs what two factors influence RS

Rank and age

In chimpanzees: mother’s rank influences

Survival to weaning in offspring (hence RS)

Best data from socializing influencing RS comes from

Baboons (Females who form friendships with low or mid ranking males- all males are dominant to females)

What is sexual selection

Special form of natural selection: traits increase success in competition for mates

Sexual selection was proposed by

Darwin

Features with no obvious survival functions are

Secondary sexual characteristics (peacock plumage and deer antlers)

Sexual selection affects

One sex more strongly. the one whose access to mates is limited

What is intrasexual selection

Competition within the sex (es), usually stronger among males and common in primates

What is intersexual selection

Mate choice, usually stronger in female, common in birds

What do females want in a mate

Defend resources, infanticide protection and show good genetic quality

Intersexual selection does not

Operate in primates (may occur via matings with multiple males and possibly cryptic female choice (female sperm storage)

What is the most basic form of male-male competition

Fighting

SD is highest in

Uni-male multi-female groups

Testicle size is biggest highest in

Multimale/multi female groups (sperm compeition)

In multi-male/multi-female groups what forms among the males

Dominance hierarchies (determines access to estrous females)

In pair-bonded groups RS success depends on

Finding mates, defending territory, and rearing durviving offspring

What is mate guarding in pair bonded primates

Male grooms female a lot to keep her happy and close to him

Infanticide is

An adaptive strategy for males (after group takeovers, male kill dependent offspring)

After infanticide

Females return to estrus allowing infanticide male to reproduce more quickly (before they are ousted)

Infanticide is costly for females therefore:

Expect counter-strategies such as false estrus, female coalitions, spontaneous abortions, and male friendships

Infanticide counterstrategies in langurs

Concealed ovulation, sexually receptive with multiple males, terminate pregnancy after takeover (spontaneous abortion), and social supports/ friendships to try to avoid infanticide