For an Orangutan, does age matter?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The male Sumatran Orangutans, Pongo pygmaeus abelli, are able to delay puberty for up to ten years in order to compete for mates with the full-grown adult males [1]. This is unique only to the Sumatran orangutans, while the Bornean orangutans are unable to display this behaviour [2].

What are the differences between a subadult male from a fully grown one? The fully grown adult male has flanged cheeks as well as a throat sack in order to make loud calls to attract mates [3]. However, do not be deceived by the fact that they have not undergone puberty. These males have sexual desires and they are able to impregnate the females [4]. The dominant adult males have the fertile females at his disposal while the subadult males have to coerce the females into copulation, and they face resistance from the adult females [5]. Coercion is used as the females will tend to pick the dominant adult males. Whether the orangutan was able to remain as a subadult male depends on the level of androgen produced and the level of stress in the environment that it was subjected to [6].

Would all non-dominant males be subadults? No, there are non-dominant males who would have to wait till they are picked by the females as they were easily spotted by the dominant males who would prevent forced copulation from occurring [5]. These non-dominant adults and subadult males are not unwanted by any means. There would be females who are left unguarded by the dominant males and the opportunity would arise for these other males [3].

The strategy of delaying puberty confers advantages to the male orangutans. The unflanged subadult males are more agile and this allows them to roam and search for females to copulate within a short amount of time without risking detection [3]. In this way, they are able to prevent serious injuries from happening to them. Hence, this strategy changes our perception of what it means to grow up and growing up slowly may present advantages for the Sumatran orangutans. What human beings understand about them is still little and more has to be researched on to gain a fuller understanding of this behaviour.

 

References

1. Orangutans Can Delay Puberty for Up to 10 Years to Be More Attractive by Christine Hsu. Medical Daily, 21 May 2012. URL: http://www.medicaldaily.com/articles/9968/20120521/orangutans-reproduction-evolution-primates.htm (accessed on 4 Apr 2013)
2. Sumatran orangutans have mystery ability to hold back puberty for 10 years-until they are strong enough to challenge the dominant males by Eddie Wrenin. The Daily Mail, 21 May 2012. URL: http://www.dailymail.co.uk/sciencetech/article-2147501/Sumatran-orangutans-mystery-ability-hold-puberty-10-years–strong-challenge-dominant-males.html (accessed on 4 Apr 2013)
3. Atmoko, S.S.U, Setia, T.M., Goossens, B., James, S.S., Knot, C.D., Morrogh-Bernard, H.C., van Schaik, C.P. and van Noordwijk, 2008. Orangutan mating behavior and strategies. In S.A. Wich, S.S.U. Atmoko, T.M. Setia and C.P. van Schaik (ed), Orangutans: Geographic Variation in Behavioral Ecology and Conservation. URL: http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199213276.001.0001/acprof-9780199213276-chapter-16?rskey=J1VBNm&result=1&q=force (accessed 04 Apr 2013)
4. Why Some Orangutans Never Want to Grow Up by Erin Wayman. Smithsonian.com, 14 May 2012. URL: http://blogs.smithsonianmag.com/hominids/2012/05/why-some-orangutans-never-want-to-grow-up/ (accessed on 4 Apr 2013)
5. Singleton, I. and van Schaik, C.P., 2002. The Social Organisation of a Population of Sumatran Orang-Utans. Folia Primatol, 73, pp. 1-20
6. Thompson, M.E., Zhou, A. and Knott, C.D., 2012. Low Testosterone Correlates with Delayed Development in Male Orangutans. PLoS ONE, 7(10), URL: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047282 (accessed on 4 Apr 2013)