Like six-legged James Deans, some male crickets that live high on the hog also die young. But not before they spread their love around, according to a study that supports a new theory about sexual selection.
Being attractive as a male animal--such as sporting extravagant body parts or displaying exhaustive mating behavior--often comes at a cost that only the fittest individuals can bear. That may be why several studies have found that animals that are good at luring mates also live longer than others. But more recent theories contend that the opposite is sometimes true as well. "High-quality males," as biologists call them, may sometimes invest so much in wooing members of the opposite sex that they use up their energy and die earlier than their inferior counterparts. That hypothesis holds true for the field cricket, or Teleogryllus commodus, say evolutionary biologist John Hunt and his colleagues at the University of New South Wales in Sydney, Australia.
To produce insects of varying "quality", the researchers fed 300 crickets either low-, medium-, or high-protein diets. Baby crickets survived better on higher protein diets, and adult females on such diets lived a couple of weeks longer than normal. But adult males eating lots of protein died several weeks earlier than their poorly-fed peers, the researchers found. The scientists then isolated the male bugs in individual Styrofoam containers and recorded their calls overnight. While low-protein males started calling chicks in earnest at about 25 days of age, those on the protein-rich regimen started at about 15 days, and also put in significantly more effort every night, Hunt's team reports in 23/30 December Nature.
To determine whether the eagerness of the protein-stuffed males would pay off, the researchers replayed the calls to females in the wild, and found that the more frequent the calls, the more females responded. This suggests that, although the well-fed crickets died young, their frantic mating efforts would likely get them considerably more action than the poorly fed males--and probably more offspring.
The results support the theory that success in sex isn't always correlated with a long life, says evolutionary biologist Hanna Kokko of the University of Helsinki, Finland. Sometimes, a male can opt "to be so super sexy that he dies in the process," Kokko says, "but it can still pay off." The work also shows that scientists have to be careful how they set up experiments, keeping in mind, for instance, that diet can determine the outcome, says evolutionary biologist Allen Moore of the University of Manchester, U.K. "The conditions under which you measure sexual selection really matter."
John Hunt's website