Sexual behavior and reproductive strategies Notes PDF

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Sexual behavior and reproductive strategies Female has high investment in offspring and male has low investment in offspring Bateman’s principle- looked at flies and who they mated with and found that number of males females mate with doesn’t increase reproductive success where as males have a linear relationship. Not necessarily true with primates because it is a guard against infanticide  A males reproductive success benefts more from extensive mating o Sexual selection should act more strongly on males, leading to more elaborate behavior and structures  Variance among females in mating success is low, whereas variance among males is high Looked at differences in different human societies- those with land or cattle are more paternal and so males do better Variance in reproductive success explains which sex is subject to stronger sexual selection- can be equal in monogamous species Mechanisms of sexual selection  Pre copulatory- all things leading to acquiring mates  Post copulatory- events that occue during and afer mating o Male-male sperm competition o Sperm plugs

o Female choice  Cryptic choice- occurs inside the female reproductive tract Trade of between mate guarding and sperm competition Bonobos have large testes and lots of sex and those whose females only mate with one male have slower sperm Mating systems  When species live in pairs, tend to be pretty similar in size  Single males are much larger but have smaller testes  Multi males are larger but have by far the largest testis Vagina kills many, many sperm to get only the best and invitro fertilization tends to bypass these evolutionary systems Intersexual When female choice is stronger than male-male competition  Seasonal breeders  Frequent prolonged estrous cycles- many females available at the same time  Monogamous groups What does the choosy sex want?  Good genes o High fertility

o Healthy offspring- immunofunction o Successful offspring- strength, dominance  Parental investment o Defend territory/resources/partner/offspring o Provide resoruces o Not coercive Runaway process- coevolution of male ornaments and female choice, what female wants vs what is optimal for NS Sexual conflict- coevolutionary arms race between male and female competition In ducks, tend to be more males than females and males have coercive sex organs while females have multiple chambers Life history theory- trade-offs between/within reproduction, maintenance and growth  Reproduction- quantity or quality- mating vs parenting- current vs future o Testosterone and the tradeoff between mating and parenting – challenge  Did in birds- high levels when getng territory and that goes down once mating and having children  See this in humans too when they have children  Also found amount of testosterone correlates to amount of caregiving and guys who do more caregiving get more pleasure from seeing their infant

 Maintenance  Sleeping  Feeding  Vigilance  Growth  Other organs  Muscle  Brain Parental investment- mother offspring conflict  Mother benefts from switching to next infant while current infant benefts from continued investment  Regression age when infants try to seem needier than they are  Parent and offspring closely related but genetic interests don’t always overlap o C < B*r o R is relatedness o B is RS of current o C is RS of future...