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To survive post-coital cannibalism, male orb-weaving spiders catapult away

Researchers hypothesize the catapulting mechanism evolved to helps the male spiders survive female’s after-sex craving for protein.

(CN) — Immediately after mating, male orb-weaving spiders catapult away — not because they’re trying to keep things casual, but to avoid being eaten by the mother of their future children. Research published in the journal Cell on Monday described the hydrologic mechanism allowing male spiders a quick get away.

“When we studied sexual selection of the communal web spider, we found that mating is always ended by a catapulting,” explained Shichange Zhang, a behavioral ecologist at Hubei University in Wuhan, China, via email.

In nature, sexual cannibalism is most commonly found in insects and spiders, including the notorious black widow, which gets its name from females ritually eating males after mating. For male orb-weavers, catapulting is therefore a necessary adaptation to survive knocking boots with their eight-legged lover.

Each spider must slowly build up and store energy in preparation for the launch. Similar tactics are seen throughout the animal kingdom to aid in the speedy capture of prey capture or avoidance of a predator.

The male orb-weaver is able to move nearly three feet in a single second with powerful hydraulic pressure built up in the joint on his first pair of legs. Researchers found males needed their first set of legs to successfully mount and mate, but could perform the same ritual missing middle pairs of legs.

Using a high-resolution camera, researchers studied the mating ritual of 155 communal orb-weaving spiders, Philoponella prominens. After mating, 97% of the male spiders catapulted themselves away from the female and survived. Only three males failed to launch in time, each of which was then captured, killed and consumed by the mother-to-be.

"These results clearly indicate that the catapulting behavior is an obligatory component of the male mating repertoire and a strategy to avoid post-mating sexual cannibalism attempts,” researchers concluded.

Most female spiders can easily lure in a new mate, leaving few downsides to consuming whatever quick protein they can catch — even if that means eating a recent lover. Researchers therefore concluded that the catapulting behavior is a necessary adaptation to survive the female’s sexual cannibalism.

Besides giving rationale into the nuances of animal mating behavior, Zhang said understanding the mechanism may inform the development of robots.

“Studying how the hydraulic pressure drives the movement may help us to apply it in the production of robots," Zhang said.

Grants from the National Natural Science Foundation of China, the Ministry of Education AcRF grants from Singapore, and the Slovenian Research Agency supported this international study.

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