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College of the Sequoias
Primate Mating: Males
Selection shapes parenting strategies of males and females.
● Parental investment is costly
● Parents must make trade offs between current and future offspring.
● Strategies depend on details of reproductive biology.
● Mammalian females are obligated to invest in offspring.
● Mammalian males have more options.
Males will invest when benefits derived from extra matings are less than benefits derived form
● Expect males to invest when finding additional makes is difficult, or fitness of
offspring raised by one parent is low.
● Difficult to find more mates when females widely spaced and when females mate
● Fitness of offspring raised by one parent is low when infants are quite large, litter size
is > 1, and in high infant mortality contexts.
Pair-bonded species: solicitous mates and committed fathers
● Males invest in offspring (carry infants, share food).
● Males guard females vs. rivals
● Closely bonded to mate.
● Marmosets, Titi monkeys, gibbons, siamangs.
Multi-male groups: competitive males, distant fathers.
● Males compete for dominance rank
● Male dominance rank is function of size & strength
● Rank order changes frequently
● High ranking males monopolize conceiving females.
● Baboon males are twice as large as females- sexual dimorphism.
● In multi-male groups, some males may provide low cost care
o Tolerant of juveniles
o Support juveniles in aggressive interactions
o Some evidence that males selectively help their own offspring.
One-male groups: competition is intensified.
● Males compete for access to groups of females
● Outsiders exert constant pressure on resident males
● Tenure of resident male often short
Male-male competition leads to sexual dimorphism