Male black widows scare off rivals by destroying female’s webs

Male black widow spiders get a little destructive during their courtship rituals, tearing down a large portion of their mate’s webs and wrapping it up in their own silk – and most surprising of all, the females don’t appear to mind, according to a recently-published study.

Writing in the journal Animal Behaviour, researchers from Simon Fraser University in Canada explained that the behavior helps deter rivals by making the female’s web less attractive to them, and that the females appear to appreciate being protected from harassment from those males.

Benefits for the males…

In fact, lead author Catherine Scott and her colleagues said that the female black widows view this destructive behavior, allowing her to focus on parenting her offspring. The study marks the first time that the destruction of the female’s web by male spiders has been observed in the wild as a technique used by males to fend off competition.

Scott, an MSc student at the university, said that she was not certain how this unusual behavior began, but told redOrbit via email that the reasons behind it were “pretty clear” – it’s because male black widows that engage in web reduction were more likely to be successful because they faced less competition, “and thus were able to pass on more of their genes.”

“If you’re a male black widow, your only goal in life is to find a female to mate with and father as many of her offspring as possible,” Scott added. “If you can prevent other males from finding her and interrupting your courtship, you will improve your chances of successfully mating.”

…and for the females, as well.

So why do females tolerate this behavior, allowing males to destroy the web that they rely upon to capture prey, keep her safe from predators and attract mates? The reason is that she benefits as well. Scott explains, the web of a well-fed virgin female spider makes her extremely attractive to males, and will remain so for several days, even if she doesn’t add additional silk pheromone.

By destroying her web and making it unattractive, a male spider might actually be doing his mate “a favor” by allowing her to “build a new one without attractive pheromones” after she has found a mate and no longer needs to attract males. Since web destruction makes her seem less attractive to male spiders, it allows her to rebuild her web and produce egg sacs without being bothered.

Scott also passed along one last interesting note about black widow spiders – contrary to popular believe, females do not always cannibalize males after mating. In fact, she explained that, “sexual cannibalism is very rare in western black widows.”


Follow redOrbit on Twitter, Facebook, Google+, Instagram and Pinterest.