Primate Mating Systems & Sexual Selection Flashcards
Primate Mating Systems
- solitary or “noyau”
- pair-bonded (monogamy)
- uni-female/multi-male (polyandry)
- uni-male/multi female (polygyny)
- multi-male/multi-female (polygynandry)
Strategy
= set of behaviors occurring in specific functional context
- strategies are products of selection, not conscious plans
Reproductive Success (RS)
number of offspring surviving to reproductive age
Why Females Invest More
- must carry offspring to term
- must nurse them until they can forage independently
- extra time + energy per infant
- extended pregnancy
Why Males Invest Less
- time, energy, resources limited
- paternity uncertain
- use their resources to access additional females
Males Will Be Less Involved:
1) when attracting additional mates is relatively easy
2) when fitness of offspring raised by one parent is high
Gendered Causes of Variation in RS
Females: securing resources (food)
Males: securing mates
Female Reproductive Strategies
- depends on the ability to obtain enough resources (food) for her and her offspring
- rank is positively correlated with RS
- socializing positively influence RS
- females produce few offspring, invest heavily in each, raise them without males
Female Dominance Hierarchies
high ranking females gain access to more/better quality food
Male Reproductive Strategies
- males less constrained by food, rarely invest in offspring, potentially mate with many females
- access to mates
Sexual Selection
- special category of natural selection
- accounts for features with no obvious survival function
- helps explain traits that seem maladaptive in terms of natural selection
Sexual Selection Favors + Affects
favors phenotypes that increase success in competition for mates
affects one sex more strongly, the one whose access to mates is limited
Intrasexual Selection
- competition within the sexes
- usually stronger among males
- common in primates
Intersexual Selection
- mate choice
- usually stronger in females
Intersexual Selection: What Do Females Want?
- females have high parental investment
- also reproduce slowly
- should mate with “quality” mates
Females Can Choose Males That:
- will increase their fitness (defend resources, infanticide protection)
- show good “genetic quality” (will produce more fit offspring)
Intrasexual Selection in Males
- most basic form of male-male competition is to fight/drive other males away
- winners have advantage in mating opportunities
- favors traits that enable males to be effective fighters
- increases body and canine size
- leads to sexual dimorphism
SD should be most pronounced in groups where males compete most
= single male-multi-female
Reproductive Strategies: Single-Male Groups
male tries to establish residence in an unrelated group of females, then restricts access to other males
Reproductive Strategies: Multi-Male Groups
- less direct competition over access to females
- sperm competition
- dominance hierarchies
Reproductive Strategies: Pair-Bonded Groups
- males don’t compete for access to females
- RS depends on finding mates, defending territory, rearing surviving offspring
- mate guarding
