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Evolutionary Stable Strategies in Orangutan Reproduction

The idea of evolution stable strategies has arisen in discussions why certain traits of animals survive in nature. The main idea concerning this concept is that one strategy is not only a Nash equilibrium , but performing the strategy also gives the animal the greatest chance of surviving in the wild. This means, in the context of a dove and hawk, that in a dove dominated world if the best option for the bird is still to be a dove then that is a evolutionary stable strategy. If we apply this concept to other areas it can explain why certain traits can survive whereas others do not. On the most basic level, a mother can choose a father based on a trait that will give her offspring the highest chance of surviving and reproducing. However, the female does not optimize for her possible female offspring but rather her male offspring since there are more challenges in being a male animal. In this article the author explores what traits in male orangutans do females look for to decide who will be her reproductive partner.

In the wild female orangutans choose to mate with the dominant male orangutan in the area. The dominant male orangutan usually has cheek pads (among other traits) whereas other male orangutans do not. The question the researchers asked is why is this trait present in dominant males when the presence of cheek pads do not inherently help their survival (i.e. these pads do not make them stronger, or faster) or reproductive abilities. The researchers found out an interesting idea after testing the paternity of orangutan offspring over the span of a decade. The cheek pads not only signal to females that the orangutan is the dominant male, but it is a trait that is more attractive to them. This means that females will then choose that male to reproduce with passing on his dominant genes, whereas the other males will struggle to reproduce without the cheek pads. The researchers concluded that this therefore is a evolutionary stable strategy. In other words in a world of orangutans with cheek pads it is still in a orangutans best interest to have cheek pads.


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November 2015