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Infanticide and reproductive restraint in a polygynous social mammal


Henzi, S P; Clarke, P M R; van Schaik, C P; Pradhan, G R; Barrett, L (2010). Infanticide and reproductive restraint in a polygynous social mammal. Proceedings of the National Academy of Sciences of the United States of America (PNAS), 107(5):2130-2135.

Abstract

Alpha male chacma baboons experience uncontested access
to individual estrus females. Consequently, alpha male paternity certainty is high and underpins significant levels of infanticide by immigrant males that, in turn,
has selected for male defense of infants. There is also, however, a high probability that alpha males will be absent during the period when their own offspring are vulnerable, suggesting selection for additional countermeasures.
We use data from a long-term study to test the prediction that alpha male chacma baboons cede reproductive opportunities to subordinate males and that this leads to the presence of other fathers that can serve as a buffer against infanticidal attack. We found that subordinate males obtained significantly more conceptive opportunities than predicted by priority of access alone, and that this occurred because alpha males did not consort all receptive periods. There was no evidence that this was due to
energetic constraint, large male cohorts, alpha male inexperience, or the competitive strength of queuing subordinates. The number of males who benefited from concession and the length of time that they were resident relative to those who did not benefit in this way greatly reduced the probability that infants of alpha males would face immigrant males without a surrogate father whose own offspring were vulnerable. The absence of such males
was associated with observed infanticide as well as, unexpectedly, an increased likelihood of takeover when alpha males with vulnerable infants were present.

Abstract

Alpha male chacma baboons experience uncontested access
to individual estrus females. Consequently, alpha male paternity certainty is high and underpins significant levels of infanticide by immigrant males that, in turn,
has selected for male defense of infants. There is also, however, a high probability that alpha males will be absent during the period when their own offspring are vulnerable, suggesting selection for additional countermeasures.
We use data from a long-term study to test the prediction that alpha male chacma baboons cede reproductive opportunities to subordinate males and that this leads to the presence of other fathers that can serve as a buffer against infanticidal attack. We found that subordinate males obtained significantly more conceptive opportunities than predicted by priority of access alone, and that this occurred because alpha males did not consort all receptive periods. There was no evidence that this was due to
energetic constraint, large male cohorts, alpha male inexperience, or the competitive strength of queuing subordinates. The number of males who benefited from concession and the length of time that they were resident relative to those who did not benefit in this way greatly reduced the probability that infants of alpha males would face immigrant males without a surrogate father whose own offspring were vulnerable. The absence of such males
was associated with observed infanticide as well as, unexpectedly, an increased likelihood of takeover when alpha males with vulnerable infants were present.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Anthropology
Dewey Decimal Classification:300 Social sciences, sociology & anthropology
Language:English
Date:2010
Deposited On:08 Jan 2011 11:34
Last Modified:07 Dec 2017 04:32
Publisher:National Academy of Sciences
ISSN:0027-8424
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1073/pnas.0913294107
PubMed ID:20080652

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