Anthropology, Yale University
April 14, 2016 9:00, A 706/707
Chimpanzees (Pan troglodytes) have a complex mating system in which males use multiple tactics to gain copulations. Research on the effects of male rank and male-female aggression on male mating success in chimpanzee communities with relatively few males has shown that male dominance status positively influences mating success and that males often direct aggression at sexually receptive females, behavior that can constrain mate choice and potentially influence paternity probabilities. Multiple studies have shown that high-ranking males have relatively high paternity success.
We investigated relationships among dominance rank, aggression, and mating success in the unusually large Ngogo community, using data collected over seven years during which the community contained > 25 adult males. We constructed linear mixed models, using the lmer package in R, to test the hypothesis that both rank and male/female aggression influence male mating success. The response variable was the relative share of copulations that individual males gained with a given female; predictor variables included male dominance rank, the rate of male/female aggression, male identity; female identity; female parity (nulliparous vs. parous); whether females were periovulatory; and year of data collection. Results showed that male rank and male/female aggression significantly and independently affected male mating success. These effects were stronger during periovulatory periods (POPs), but also held outside of POPs. They did not vary significantly among years. Ngogo data thus reinforce the arguments that success in male status competition influences mating success in chimpanzees and that males also use aggression to females as a mating tactic.
L.S.B. Leakey Foundation, National Geographic Society, US National Science Foundation BCS-0215622 and IOB-0516644, Yale University