Abstract
The local resource enhancement (LRE) model predicts that in cooperatively breeding species, sex ratios will be biased in favor of the more helpful sex. In this study, we assess the assumptions underlying the LRE model in a population of cooperatively breeding wild dogs (Lycaon pictus) in Northern Botswana monitored over a 15-year period. In this population, litter size and pup survival to 1 year are strongly affected by pack size and the breeding female’s age, but adult males have a stronger and more linear effect on females’ reproductive performance than do adult females. This asymmetry in the benefits derived from male and female helpers is reflected in male-biased sex ratios in litters at the time pups emerge from the den. Sex ratio biases are most pronounced in the litters of the youngest mothers who live in significantly smaller packs than older females. The presence of potential rivals for the dominant female’s position depresses pup production at the time of emergence, suggesting that competition among females for breeding positions may also contribute to the selective forces affecting birth sex ratios.
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Acknowledgments
This work was supported by Frankfurt Zoological Society—Help for Threatened Wildlife, grants from Conservation International, National Geographic Society, Woodland Park Zoo, Zoological Society of Philadelphia, and the Moore Family Foundation. We are grateful to Botswana’s Ministry of Environment, Wildlife and Tourism and Department of National Parks for permission to conduct wildlife research in Botswana. We are also grateful for helpful comments on earlier drafts of this manuscript from Markus Gusset and Stuart West, and thank Michael Somers for providing us with access to unpublished work.
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Communicated by A. Schulte-Hostedde
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McNutt, J.W., Silk, J.B. Pup production, sex ratios, and survivorship in African wild dogs, Lycaon pictus . Behav Ecol Sociobiol 62, 1061–1067 (2008). https://doi.org/10.1007/s00265-007-0533-9
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DOI: https://doi.org/10.1007/s00265-007-0533-9