A number of explanations have been proposed for the occurrence of sex ratio bias in primates, including the Trivers-Willard hypothesis on differential investment, local resource competition or enhancement as a result of sex-biased dispersal, dominance-related advantages conferred on one sex but not the other, and the fragile male hypothesis. However, none of these theories was thought to be applicable to monogamous primate species. Here, we examine data on zoo-housed populations of three hylobatid species to test the null hypothesis of equal sex ratio. We analyzed over 40 years of demographic data on Nomascus leucogenys, Hylobates lar and Symphalangus syndactylus. We identified a strong male-biased birth sex ratio in N. leucogenys. Male infant mortality was consistently higher than female infant mortality for N. leucogenys, but this difference was not significant. We found that prime-age N. leucogenys females (aged 13–20) produced significantly more male offspring than female offspring, and young S. syndactylus females (<13 years) produced significantly more female offspring. Recent field evidence of more flexible mating systems in H. lar and S. syndactylus may also be occurring in N. leucogenys. However, N. leucogenys has not been well studied in the wild. Ecological differences among species may further contribute to these observed patterns.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.