Lions, wolves, and fish are most commonly known to hunt in groups to increase the success of hunting their prey down, especially if it is too large to be taken care of by a single animal. A new study shows that a species of social spiders called Anelosimus eximus also hunt in packs using specialized web vibrations.
MailOnline reported that this spider species is native to South America and lives in large non-sticky webs. These spiders can suddenly swarm over an insect that has fallen into their web by using a two-pronged attack that involves staying still to perceive the vibrations from their web and coordinate their movements.
64. Anelosimus eximius, social weaver from South America.
— Stag Do(e) (@doeantlers) March 26, 2020
Theridiids are cool by themselves but when they team up, they're unstoppable. These well-studied spiders are nature documentary darlings: they're photogenic and they work together to take down prey many times their size. pic.twitter.com/2DYtRuLadX
Social Spiders Display Synchronize Attack
Social spiders live together in large colonies and cooperate to hunt for food. More so, they share parental duties and rarely stray from their colony. Out of the 50,000 known spider species, only 20 have developed a sense of cooperation that founded their permanent social life.
Among these social spiders is the A. eximus that hunt in packs to catch insects, like moths and grasshoppers. Their colonies can house several thousands of spiders of all ages and co-exist peacefully in towering webs that could reach up to several cubic meters.
In the study, titled "A Variable Refractory Period Increases Collective Performance in Noisy Environments," published in the Proceedings of the National Academy of Sciences, scientists wrote that these spiders use vibrations from their webs to choreograph a synchronized swarming process.
Study lead author Raphaël Jeanson, a researcher at the French National Centre for Scientific Research, Paris (CNRS), pointed out that these coordinated movements are done without a leadership role. Instead, each one coordinates its attack after receiving the same information from web vibrations.
According to Live Science, the colony attacks by swarming on their prey includes closing in on their struggling victim and standing still to help them time their approach so all of them could strike at once. Researchers found that the attack is directed almost entirely by web vibrations as they conducted field observations and used computer simulations.
"When the prey falls in the web, this triggers the movement of the spiders," Jeanson told Live Science. "But after a while, they all stop for a few milliseconds before they start moving again."
Social Spiders Look After Others' Babies
Evolutionary biologist Lena Grinsted, a senior lecturer at the University of Portsmouth in the UK, said that the findings seem to raise some intriguing questions. She wonders whether each spider is inclined toward synchronicity or some are naturally freeloaders or cheaters, National Geographic reported.
She added that the study defies the stereotypes that people have on spiders, especially because A. eximus, has shown an unusual way of allowing other spiders and insects to hang out in their webs. They are so sociable that they also take care of other spiders' young, not only their own. For her, it is cute to see how the baby spiders would crawl up and drink from the mouths of the females to feed.
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