Male giant rhinoceros beetles sport giant horns that can reach two-thirds their entire body length. A new study, published in Proceedings of the Royal Society B: Biological Sciences, found that despite their large size, the horns have little impact on flight efficiency.
The beetles use their huge horns to fight against other males over feeding sites on trees. However there is more at stake than access to food, as males who can take and hold the best feeding sites will have access to females who come to feed on said sites. This is a well documented phenomena called sexual selection, where competition for mates drives evolution of increasingly exaggerated body features in males.
Scientists have long believed that sexual selection leads to cumbersome features that have little use outside of their ability to attract a mate. For example, the male peacock's large and gaudy tale results from sexual selection. While it puts the males at risk of higher predation, that risk is offset by greater access to mates.
However, in giant rhinoceros beetles, it appears that sexual selection has very little cost. The horns might be long, but they are very light weight. They have a very small effect on drag during flight, only increasing the effort required for flight by about 3 percent.
The study is significant because it cast doubts on the traditional notion that sexually selected traits are costly and have a negative impact on fitness.
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