Female Tarantulas Cannibalize Mates Because They Can

If there’s one thing that keeps spiders from moving up the list of favorite pets, it’s that annoying habit many females have of consuming their male mates after sex. If that’s not intimidating enough, a new study found that some of the females don’t even wait to consummate before chomping away.

As reported recently in the journal Ethology, researchers from the Experimental Station of Arid Zones (EEZA) in Spain sought to find out how and why female tarantulas cannibalized their dating pool. They fed 80 virgin female Iberian tarantulas (Lycosa hispanica) as many beetles as they wanted and noted which dined docilely and which preferred to aggressively gorge.

The virgins were then let loose among male tarantulas and their mating and eating habits were observed. The first surprise was that the well-fed aggressive females were more likely to consume males even if they weren’t hungry, while the less aggressive, more hungry females didn’t always cannibalize their mates.

Another surprising discovery had to do with selectivity. The researchers found that the passive females mated with strong, healthy males while killing and eating the weaker ones. The aggressive females mated and killed indiscriminately without regard to a male’s suitability as a sperm donor or post-coital dinner, often dining without having sex at all.

These results show that the well-fed females, who had the energy reserves to selectively mate with genetically superior males, instead squandered this advantage. On the other hand, the weaker females chose to mate rather than eat and may not have built up a sufficient nutritional storehouse to feed their offspring.

Jordi Moya Laraño, who directed the study, gave this summary.

We reached the conclusion that there are aggressive genetics which vary among females and make them act aggressively both when they feed off prey and when they approach a male in courting. Others are docile in both contexts, highlighting the existence of different personalities.

One more warning to male tarantulas – the females probably lie about their age too.

http://www.youtube.com/watch?v=5k0Dpcv58kc