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Abstract ObjectivesChimpanzees (Pan troglodytes) are notable for exhibiting high levels of male‐to‐female aggression. Much of this aggression from adult males serves sexually coercive functions. Despite being smaller and lower‐ranking than adult males, adolescent males also engage in regular aggression against adult females. Here, we test whether the primary function of this aggression is sexual coercion, as in adult males, or, alternatively, whether adolescent males use aggression to establish social dominance over females. Materials and MethodsWe analyzed 1771 copulations and 1812 instances of male‐initiated aggression between adolescent males (aged nine through 14 years) and adult females across 21 years of observation of the Kanyawara chimpanzee community in Kibale National Park, Uganda. ResultsOur test of the sexual coercion hypothesis revealed that adolescent males did not selectively target cycling females for aggression, nor did aggression against cycling females predict rates of copulation with those females. Our test of the social dominance hypothesis showed that males succeeded in dominating all adult females before, or soon after, dominating their first adult male. Additionally, we found that adolescent males dominated females approximately in the order of the females' own ranks, from the bottom to the top of the female hierarchy. DiscussionOur data illustrate that the establishment of social dominance was more important than sexual coercion in explaining patterns of adolescent male aggression toward females. In comparison, evidence for sexual coercion was clear and compelling in adult males. These findings highlight that the primary function of male‐to‐female aggression differs between adolescent and adult males.
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Infanticide and Sexual Conflict in Cetaceans
Abstract Infanticide by adult males is a striking example of sexual conflict; males can increase their reproductive success by killing an unrelated infant and accelerating the mother’s return to breeding condition. Reports of infanticide in cetaceans have quadrupled in the past decade, and infanticide has now been documented in six species of toothed whale, including multiple populations of common bottlenose dolphins (Tursiops truncatus). Evidence of infanticide in these species is consistent with the sexual selection hypothesis; perpetrators are predominantly adult males and targets are neonates. Toothed whales have long lactation periods that suppress estrus, making infanticide potentially adaptive for adult males. However, it remains unclear if infanticidal males are likely to sire the mother’s subsequent offspring. Here, we provide an overview of infanticide in cetaceans, evaluate the evidence for the sexual selection hypothesis, and propose a framework to predict infanticide risk in this clade. Toothed whales do not typically have dominance hierarchies, stable social groups, or monopolizable mating opportunities, all hallmarks of infanticide risk in terrestrial species. Instead, we hypothesize that infanticide risk in toothed whales is modulated by encounter rates with unfamiliar males.
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- PAR ID:
- 10630164
- Publisher / Repository:
- Springer International Publishing
- Date Published:
- ISBN:
- 978-3-031-35650-6
- Page Range / eLocation ID:
- 199 to 224
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Book Chapter:
- https://doi.org/10.1007/978-3-031-35651-3_10
