Female rhinoceros beetles probably find this beetle a stud. (Photo : Wikimedia Commons)
There might be more to size than simply the slogan from the 1998 Godzilla flick, "Size Does Matter." It might have something to do with health and reproductive capabilities. Scientists have uncovered a link between the size of a male rhinoceros beetle's horn and its health.
The correlation is simple, the bigger the horn, the better fit the beetle is, the more handsome and attractive he is to females of his species. The horns are used in battles between the rhinoceros beetles where they furiously try to fling one another into submission.
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The study was carried out by a team of scientists led by Douglas Emlem from the University of Montana and the report was published in the online journal Science.
"Our research explains how these enormous traits get to be so enormous," said Emlen. "People have known for 100 years that the best males produce the biggest structures, but nobody has really understood how. Our work looks under the hood to explain why so many sexually selected structures get so massive."
The beetle's horns, it turns out, are sensitive to nutrition signal such as insulin levels and illness.
If you have a lot of food, you have a lot of insulin," said co-author of the paper Laura Corley Lavine, a Washington State University entomologist. "You respond to that by making a really giant, exaggerated horn. Then the female can tell she wants to mate with you because you are truthfully advertising your condition."
The team tested this by cutting off insulin and recording the growth of the horns. The results were smaller horns, and less fit rhinoceros beetles.
The implication is obvious. Unlike humans, which tend to have concepts like love drive mating (sometimes), most of the rest of nature mates based off impressive mating displays where the male flaunts some kind of appendage or dukes it out with a fellow males. This is all for the female spectators' benefit, so that they can choose which one is the healthiest and most dominant - essentially, which male has the best genes.
Watch these two rhinoceros beetles fight it out: