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A model for the evolution of developmental arrest in male orangutans


Pradhan, Gauri R; van Noordwijk, Maria A; van Schaik, Carel (2012). A model for the evolution of developmental arrest in male orangutans. American Journal of Physical Anthropology, 149(1):18-25.

Abstract

Male Sumatran orangutans (Pongo abelii) may delay for many years the acquisition of the full array of secondary sexual traits, including their characteristic cheek flanges. Such flexible developmental arrest is unique among male primates. Among male Bornean orangutans (Pongo pygmaeus) such long delays appear less common. Here, we develop a simple model to identify the conditions under which developmental arrest can be adaptive. We show that the baseline strategy (i.e., males are not susceptible to arrest) cannot be invaded by the flexible strategy (i.e., males can arrest their development when the conditions are unfavorable) when the potential for high-ranking unflanged or flanged males to monopolize sexual access to females is low. In contrast, at high monopolization potential, the flexible strategy is the evolutionarily stable strategy. We also derive the proportion of flanged males in the population for each combination of monopolization values. This model concurs with field data that found a different monopolization potential between Bornean and Sumatran flanged males and a lower proportion of flanged males in the population in Sumatran orangutans. Pronounced developmental arrest is linked to very low adult mortality, which explains why it is so limited in its taxonomic distribution.

Abstract

Male Sumatran orangutans (Pongo abelii) may delay for many years the acquisition of the full array of secondary sexual traits, including their characteristic cheek flanges. Such flexible developmental arrest is unique among male primates. Among male Bornean orangutans (Pongo pygmaeus) such long delays appear less common. Here, we develop a simple model to identify the conditions under which developmental arrest can be adaptive. We show that the baseline strategy (i.e., males are not susceptible to arrest) cannot be invaded by the flexible strategy (i.e., males can arrest their development when the conditions are unfavorable) when the potential for high-ranking unflanged or flanged males to monopolize sexual access to females is low. In contrast, at high monopolization potential, the flexible strategy is the evolutionarily stable strategy. We also derive the proportion of flanged males in the population for each combination of monopolization values. This model concurs with field data that found a different monopolization potential between Bornean and Sumatran flanged males and a lower proportion of flanged males in the population in Sumatran orangutans. Pronounced developmental arrest is linked to very low adult mortality, which explains why it is so limited in its taxonomic distribution.

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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:2012
Deposited On:22 Jan 2013 13:21
Last Modified:02 Aug 2017 19:10
Publisher:Wiley-Blackwell
ISSN:0002-9483
Publisher DOI:https://doi.org/10.1002/ajpa.22079
PubMed ID:22552966

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