Chapter 6: Primate Mating Systems

Chapter Outline

1. Mating Systems Are Adaptive

1. Primate behavior is strategic in that it occurs in a specific functional context. Examples include mating, foraging, and parenting.

2. Evolution of Reproductive Strategies

1. Selection pressures influence the amount and pattern of parental investment.
2. Mammalian anatomy requires primate females to invest in their offspring.

3. Female Reproductive Strategies

1. Female primates are heavily invested in their offspring, which are slow to develop because of their large brain size.
2. Females need access to good nutrition for reproductive success.
3. Female fertility declines in old age.
4. High-ranking females produce more offspring than low-ranking females because of access to necessary resources.
• A dominance hierarchy or a dominance matrix can be used to describe competitive encounters among members of a primate species.
5. Social bonds have an effect on reproductive success.
6. Reproductive trade-offs
• If a mother invests effort in one offspring, she has less effort to invest in others.
• Mothers can change their behavior, distancing themselves from their offspring and allowing them to become independent.
• Many primate mothers must wean their infants before they can conceive additional offspring.

4. Male Mating Strategies

1. Sexual Selection
• Increases male success in competition for mates.
• Can have a greater effect on behavior and morphology than other forms of natural selection.
• Can be much stronger when females choose males than when males choose females.
2. Intrasexual Selection
• Favors traits that enhance fitness in male–male competition.
• Enables males who win competitions to have higher reproductive success.
• Favors larger body size and larger teeth.
• Leads to the evolution of sexual dimorphism.

5. Male Reproductive Strategies

1. Investing males
• Are often pair-bonded.
• Sometimes engage in mate guarding.
• Enhance female fertility.
2. Male–Male Competition
• Males compete to establish residence in groups of females.
• Conflict arises over group membership and access to females.
• Competition is often mediated through dominance relationships.
3. Infanticide
• Has been documented in about 40 primate species.
• Appears to be part of sexual selection, as males achieve reproductive benefits.
• Is associated with changes in male residence or status.
• Occurs so the mother can become fertile again.
• Males do not kill their own infants.
• Females have evolved responses to infanticidal threats.

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