A model for the evolution of developmental arrest in male orangutans
Version of Record online: 3 MAY 2012
Copyright © 2012 Wiley Periodicals, Inc.
American Journal of Physical Anthropology
Volume 149, Issue 1, pages 18–25, September 2012
How to Cite
Pradhan, G. R., van Noordwijk, M. A. and van Schaik, C. (2012), A model for the evolution of developmental arrest in male orangutans. Am. J. Phys. Anthropol., 149: 18–25. doi: 10.1002/ajpa.22079
- Issue online: 17 AUG 2012
- Version of Record online: 3 MAY 2012
- Manuscript Accepted: 26 MAR 2012
- Manuscript Received: 9 MAY 2011
- development of flanges;
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. Am J Phys Anthropol 2012. © 2012 Wiley Periodicals, Inc.