Male Brown Widows Prefer Sexual Partners That Are More Likely to Cannibalize Them

Image: Matthew Fields/Wikimedia Commons

Male brown widow spiders seem to have a death wish: they prefer mating partners that are more likely to cannibalize them, an unusual study recently revealed.

When given the choice, males gravitate towards older, less fertile females who are 50 percent more likely than younger females to eat them after mating. What’s even more baffling is that there doesn’t appear to be any clear advantage to being devoured, since older females are less likely to bear offspring.

For the study, published in the journal Animal Behavior, brown widow spiders of each sex were collected from central and southern Israel by research teams from three universities. The spiders were then situated in a way that gave the males a choice to approach either the immature (sub-adult) or mature females for mating.

“We originally thought the males would prefer the sub-adult females, as they are more fertile and far less likely to cannibalize them, but we were surprised to discover that was not the case,” said the researchers.

Image: Roy Niswanger/Flickr

Sexual cannibalism is used by some species as a way of nourishing the mother and improving the odds of reproductive success; however, male brown widow spiders are significantly smaller than their female counterparts and likely provide minimal nutritional value.

The spiders’ unusual preferences have left researchers scratching their heads.

“Males don’t seem to be behaving in their own self-interest and suffer a twofold cost—fewer offspring and no opportunity to mate with another female. Thus, we lack an adaptive explanation for male preference for mature older females.”

The researchers hypothesize that the older females may be pumping out copious amounts of pheromones to rope in the unsuspecting males. This idea has yet to be tested, however.

Perhaps this species just likes to live dangerously.