![]() ![]() If there was some kind of cost to having big horns, then one of these traits should be affected.īut the team found no evidence of any kind of cost associated with horn size. They also tried to determine whether any trade-offs in these allocations affected beetle survival. In the study, the researchers examined how beetles allocated resources to horns, wings, eyes, forelegs and genitalia and also looked at several measures of immune response. Their results appear in Animal Behaviour. For weaponry in particular, investing in something big and showy isn’t helpful if the male can’t back that up and win a fight.Ī pair of researchers at the University of Montana in Missoula recently tested out these competing theories by studying the Japanese rhinoceros beetle. The other side, though, says that these signals needn’t necessarily be costly to create as long as there’s a penalty for cheating. ![]() The cost of developing those traits is the subject of two competing theories: One side says that weapons and ornaments should be costly to an animal because there would be no reason to pay attention to such a trait if it wasn’t an indicator that the male has the resources or genetics to back up the signal. Wesley Chan/FlickrĮvolutionary theory about sexual selection says that weapons and ornaments most often evolve when they reliably signal a male’s genetic quality. ![]() This view of a male Japanese rhinoceros beetle shows its long, forked horn, which it uses in duels with other guys to get a girl. Sexual selection is often the reason behind things like why male birds have elaborate plumage and why male fiddler crabs have one enormous claw. And that kind of thing is always interesting to evolutionary biologists, going as far back as Charles Darwin, because it belongs to a subset of natural selection called sexual selection. Two males will duke it out, usually in the hopes of gaining access to a female. ![]()
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