Primate Mating Systems PDF

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Primate Mating Systems: All behaviors adapt to enhance reproduction rates Patterns of courtship, mate choice, and parental care vary greatly within primate order: because of male vs male or because of female preference Strategy: to describe the behavior of animals. A conscious plan of action. The evolution of reproductive strategies: Primate females provide lots of care for their offspring, but males do so in only a few species.  The amount of time/effort/resources that females and males invest into their offspring has profound consequences for the evolution of virtually every aspect of their social behavior. Males do not care for their offspring: 1. They can easily access resources to acquire many additional mates 2. When caring for offspring would not appreciably increase the offspring's fitness *if time, energy and resources were unlimited, then individuals would benefit from devoting to caring for offspring! But this is obviously not true. Unequal parental investments: 1. Acquiring additional mates is relatively easy, so gains are achieved by investing in mating efforts 2. The fitness of offspring raised by only one parent is high! So payoff for investing in parenting effort is relatively low

In other animals, it's possible for males to head on taking care of offspring: male seahorses carry them in their pouch BUT in primates, this is not possible because females lactate and males do not. Reproductive strategies of females: Primate pregnancies are prolonged because of their large brain size and slow tissue development. Primates also have an extended period of dependency after birth Each mother is incredibly committed to the welfare of each offspring because the time/energy needed for one offspring is constraining! Females can only rear a relatively small number of surviving infants in her lifetime. *a females reproductive success depends on her ability to obtain enough resources to support herself and her offspring. Sources of variation reproductive performance Very young and very old females do not reproduce as successfully as middle-aged females.  Young females usually have a higher % chance of waiting a whole year before reproducing again. o Lack experience o Struggle to maintain their nutrition and their infant  Longevity is a major source of variation for female fitness o Longevity increases lifetime reproductive success!

 High-ranking females tend to reproduce more successfully o Offspring may even develop faster o Female dominant hierarchies can regulate access to resources better  Trade-off though, because low ranking females can also compensate by feeding on the periphery of the group. Where they are less likely to compete with other females. BUT this also makes them more vulnerable to predators.  Quality of social bonds also infuence female reproductive success. o Always preserving time for socializing, through grooming, sitting near or interacting with others Reproductive trade-offs: Females make trade-off between the number of offspring they produce and the quality of care they can provide.  Mothers must decide how much to invest in current offspring because that can take away from the next  Mothers spend more time with infants and gradually try and make their offspring more independent o Infants need more energy when they grow older, for transportation and larger quantity of food o Mothers must wean their kids off their milk or else they can't conceive another infant

during lactation Sexual selection and male mating strategies: Sexual selection leads to adaptations that allow males to compete more effectively with other males for access to females.  Characteristics that increase male success in competition for mates  Has a greater effect on behavior and morphology than other forms of natural selection bc male reproductive success varies much more than females Two types of sexual selection: 1. Intersexual selection results from female choice 2. Intrasexual selection results from competition between males Intrasexual selection in primates Competition favors large bodies, large canine teeth, and other weapons that enhance male competitive ability  Intrasexual selection plays a great deal in sexual dimorphism (difference between male/female size) o one-male and multi-female groups  Bachelor males: outcast males that exert pressure on resident males  More competition when females out number males o Multi-male and multi-female groups

 Females mate with several mates so within the given estrous period, sexual selection favors increased sperm production  Estrus: the period of time where females are receptive to mating during this portion of her reproductive cycle when fertilization is possible  Males with more sperm have a higher chance of impregnating females Males with larger testes! Male reproductive tactics: Male-male competition is lower in pair-bonded species Investing males Pair-bonding is typically associated with high levels of paternal investments...