Home-Wrecking Spiders Keep Their Mates Close

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New research published last week describes how black widow spiders destroy their mate’s nests to deter rival males.

Female black widow spiders don’t just use their webs to catch food, they also lace them with pheromones to attract a mate. But once a male black widow has found his perfect partner, he is very possessive. So much so that he deliberately damages her carefully spun web to try and make it less attractive to other potential males.

A new study published in Animal Behaviour tested male’s preferences for damaged and pristine webs. Dr Scott and her team at Simon Fraser University, Canada, found that damaged webs were three times less attractive to new males. The exact type of damage was also important – webs artificially damaged by the researchers remained equally attractive to males.

“One whiff of the pheromone can tell a male about the age, mating history and even hunger level of the female. These complex chemical messages are just one part of the spiders’ communication system, and web reduction is a fascinating behaviour that allows a male to interfere with a female’s message.” – Catherine Scott (Simon Fraser University, Canada)

This suggests that males black widows carefully remove the pheromone-laced part of the web, leaving the remaining silk intact. This delicate behaviour therefore enables black widow males to guard their mate but may also help the female by reducing unwanted attention from rival males. Whether you view it as selfish jealousy, or a chivalrous gesture may be a glass half full / half empty kind of dilemma.

“By reducing the web, the male is not only reducing his chances of competing with other males, he might also be doing the female a favour. Web reduction may be giving her the opportunity to rebuild her web without pheromones and get on with reproduction, rather than wasting time and energy chasing away a parade of redundant male suitors.” – Catherine Scott

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