With hairy legs, scraggly facial hair and eight eyes, the wolf spider is one scary beast. The spry hunters don't use a web to catch prey, but run it down instead. And creepiest of all: sometimes they eat their own eggs.In the natural selection game, where the ultimate goal is to produce as many fit offspring as possible, killing your babies generally doesn't make sense. Yet "filial cannibalism" occurs in species across the animal kingdom, from damselfish to house finches to bank voles. So, since the behavior persists, ecologists have tried to pin down the environmental and social conditions in which it might be evolutionarily advantageous.
In the past, scientists had hypothesized that eating eggs may be the only way for parents to survive in times of food scarcity. (If the parents die, after all, the eggs wouldn't have a chance, anyway.) But this theory was questioned when researchers observed some fish species that continued to snack on their eggs even when food was abundant.
Turns out other factors make filial cannibalism pay off in the long run, according to computer models made by zoologist Hope Klug, of the University of Florida and Oxford ecologist Michael Bonsall. The pair published their results in the December issue of The American Naturalist.
First off, if parents eat only the eggs that take the longest to hatch, then the egg-hatch rate will increase over many generations. In other words, cannibalism might be a way to weed out the young that will need the most care. And if parents spend less time on each kid, then they can use the extra energy to produce more.
More perplexing, the researchers also found that when adults eat some of their young, they become more attractive to potential mates, thus further increasing their reproductive rates. Sexy, huh?