Male Spiders Avoid Cannibalism By Becoming Pedophiles

The animal kingdom is a complicated and confusing place, particularly when it comes to sex. In what may be one of the oddest discoveries of that nature, certain male spiders have been observed essentially becoming pedophiles to avoid being eaten by cannibalistic mates. But it gets weirder: The immature female partners they choose might even benefit from that behavior.

Male redback spiders pivot to young partners because their targets are not as proficient in eating their mates. There are downsides to this behavior, as the male has to rip the exoskeleton that protects the young female’s genitalia in order to mate. Although the genitalia are fully developed, the tearing might cause injury. However, according to a new study in the journal Scientific Reports, the interaction does not affect the female’s longevity or fertility. That means it does not qualify as a “coercive” sexual behavior.

“Immature mating is neutral or beneficial to female fitness,” the study explains.

Among the positives for the immature female is mating sooner in life. This would not necessarily be a good thing in humans, but female redback spiders, venomous members of the widow spider family, live longer when they mate.

“This early mating may be good for female redback spiders because in nature they’re at risk of not finding a mate at all,” lead study author Luciana Baruffaldi said in a statement from the University of Toronto.

Young female redback spiders have sometimes been observed to struggle against their older male mates, but that resistance does not necessarily classify the sexual contact as coercive because in the animal kingdom coercion is defined by the sexual behavior being detrimental to the target.

“There’s no evidence to suggest this behavior is costly to females in terms of survivorship and reproductive output,” Baruffaldi said.

The researchers also found that female redbacks that mated when they were immature do not seek more mates in the future, according to the study, further suggesting the lack of coercion in the encounter.

Although the sexual matchups between the older male redbacks and their young females mates would be horrifying in the context of humans, the researchers warn against looking at it through such a lens.

“When you study evolutionary ecology, there’s a temptation to ascribe human characteristics or judgments on the behaviour being observed,” study co-author Maydianne Andrade said in the university statement. “What we’re seeing could have more than one evolutionary implication, and even if it looks abhorrent to us, the evolutionary consequence can be positive for the animal engaging in that behaviour.”

When the mature male spiders seek out immature female partners, they are avoiding something that sounds both poetic and straight out of a horror movie, to read the University of Toronto’s description: “Males have been observed to actively assist in being cannibalized by doing summersaults to place their abdomen over the adult female’s mouth. In the majority of cases, females will continue to eat the male even while they mate.”