Evolution Update

Evolution Update

Unattractive Males Should Be More Risky than Attractive Males

Christopher Jenness March 7, 2015

Modeling the evolution of risk-taking behaviors in males gives insight into how attractiveness affects behavior.

Across a wide variety of animal species, males will compete with each other to court females. This can range from male crickets chirping a song to a peacock displaying his colorful feathers. By having a louder and prettier song or brighter and more attractive feathers, males can gain a competitive advantage in courting females.

This competition come at a cost though. As a cricket chirps louder, it not only attracts females, it also attracts predators looking to eat crickets. Similarly, brighter feathers should draw the attention of tigers, putting attractive male peacocks at a disadvantage.

Over evolutionary time, it is likely that the advantage for attractive males in courting females and disadvantage of attracting predators would reach an optimal balance. In a recent study published in Evolution, scientists examined this balance. Courting females is a risky behavior for males because they expose themselves to predators, but to what extent does this influence how risky they should be?

Using computer models that vary male attractiveness, risky behavior, and the danger posed by predators during risky behavior, researchers from the University of Bern attempted to figure out how males should behave based on how attractive they are.

In a landmark finding, their models predict that if all males are on the same playing field, the more attractive males should not be risky. Practically speaking, attractive males should not attempt to court females when a danger is present. Because they are attractive and able to court females easily, it is not worth the risk for attractive males to put themselves in danger during the courting process.

Alternatively, less attractive males should be much more risky than attractive males. When no danger is present, less attractive males are at an extreme disadvantage. To gain an upper-hand, the less attractive males should take risks and attract females even when predators are around.

Interestingly, the differences between the optimal strategies for unattractive and attractive males hold true even when the difference between their attractiveness is small.

Although this is a high impact study in evolutionary biology, it will be interesting to see to what extent their modeling holds up in the wild. In direct support of this research, preliminary studies have shown that attractive male crickets are more likely to avoid their mating call when predators are present. However, there is also contradicting evidence. For example, attractive moths are more likely to ignore predatory bats when attempting to attract females. Ultimately, more data on animals in the wild and laboratory are needed, but this model is a large step towards understanding how male attractiveness affects risky behavior.

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