Sexual coercion by male chimpanzees shows that female choice may be more apparent than real

Martin N Muller,Melissa Emery Thompson,Sonya M Kahlenberg,Richard W Wrangham

doi:10.1007/s00265-010-1093-y

Abstract

The extent to which active female mating preferences influence male reproductive success in mammals is unclear, particularly for promiscuously breeding species like chimpanzees (Pan troglodytes). Previous studies from multiple long-term study sites have shown that female chimpanzees mate more restrictively around ovulation, and this has been taken as evidence for female choice. However, none of these studies rigorously evaluated the alternative hypothesis that restrictive mating results not from unconstrained choice, but in response to coercive mate guarding, in which males use punishment and intimidation to reduce female promiscuity and promote their own mating interests. Nor did they consider evidence for the potential genetic or phenotypic benefits that females might be choosing. Using 11 years of data from the Kanyawara community in Kibale National Park, Uganda, we previously demonstrated that males achieve elevated mating success with those females toward whom they direct high levels of aggression. Here we extend those findings to show that even female copulatory approaches, which have previously been attributed to female choice, are correlated with male aggression. Specifically, individual females at our site initiated periovulatory copulations most frequently with the males who were most aggressive toward them throughout their cycles. Those males showed high rates of aggression toward females throughout estrus, despite achieving high copulation rates, demonstrating a continuing conflict of interest over the exclusivity of mating access. Because sexual coercion is potentially widespread in primates and other mammals, our results stress the importance of considering the influence of male aggression in studies of female choice.

Highlights

Females in a broad range of species, especially birds, are known to choose mates that offer genetic or phenotypic benefits (Andersson 1994, Hill 2006, Mays et al 2008).Female choice is less well understood in mammals (Clutton-Brock & McAuliffe 2009).Because most mammals are polygynous and rarely provide paternal care, male-male competition for access to females is relatively intense
Because sexual coercion is potentially widespread in primates and other mammals, we conclude that male aggression must be taken into account before mating preferences can be inferred from female behaviour
Males that are successful at mating tend to be high quality, which reduces the benefits of active female choice (Clutton-Brock & McAuliffe 2009)

Summary

Introduction

Females in a broad range of species, especially birds, are known to choose mates that offer genetic or phenotypic benefits (Andersson 1994, Hill 2006, Mays et al 2008).Female choice is less well understood in mammals (Clutton-Brock & McAuliffe 2009).Because most mammals are polygynous and rarely provide paternal care, male-male competition for access to females is relatively intense. Females in a broad range of species, especially birds, are known to choose mates that offer genetic or phenotypic benefits (Andersson 1994, Hill 2006, Mays et al 2008). Female choice is less well understood in mammals (Clutton-Brock & McAuliffe 2009). Because most mammals are polygynous and rarely provide paternal care, male-male competition for access to females is relatively intense. Males that are successful at mating tend to be high quality, which reduces the benefits of active female choice (Clutton-Brock & McAuliffe 2009). Intense male mating competition can select for both armaments and large body size, which males of some species employ to constrain female mating behavior Primates present additional difficulties for the assessment of female choice

Methods

Results

Conclusion