These Spiders Hunt in Packs With Thousands of Creatures Weaving Giant Webs

A species of "social" spider hunts in packs among webs woven by thousands of creatures, scientists have found.

Scientists with the University of Toulouse and the French National Center for Scientific Research (CNRS) published their findings in the Proceedings of the National Academy of Sciences (PNAS). Findings showed incredible synchronicity between a species of social spider while hunting.

There are around 50,000 known species of spider on Earth, but only 20 of those are known to be "social" animals that survive and live communally.

Among them are the Anelosimus eximius, a spider found in French Guyana that lives in large colonies of massive webs home to thousands of spiders of all ages. Previous research on the species published in the journal Behavioural Ecology and Sociobiology showed how Anelosimus eximius' cooperative behavior helps them catch an "unusually high number of large insects."

The latest paper took our understanding of the spiders to new heights. Researchers examined their giant webs, which can stretch for several cubic yards, to observe the spiders' hunting method.

They found that Anelosimus eximius hunt in packs. When prey entered their web, the spiders coordinated their attack, with scientists observing them alternating their individual movements to hunt as one larger and more effective force.

Stock image of an Anelosimus eximius web
Stock image of an Anelosimus eximius web. The "social" spiders hunt in packs and synchronize their movements with one another. twigymuleford/Getty Images

"People generally believe that spiders are solitary, intolerant and aggressive, but our study shows that they can coordinate their activities to collectively catch prey—sometimes up to hundreds of times larger than the size of a spider—that would not be accessible to isolated individuals," co-author Raphael Jenson of the Université Paul Sabatier in Toulouse told Newsweek.

"Cooperation in collective hunting has been documented in several vertebrate species such as lions. However, I do not think that the existence of synchronization in the approach to a prey has been described in any other animal."

Jenson said that the paper deepened our generally limited understanding of arachnids compared to other social invertebrates, which have received more attention historically. He said that the Anelosimus eximius showed hunting behaviors not seen in other predators, described in the paper as "synchronicity."

"There is no leader to coordinate the hunt: each spider integrates information via vibrations that propagate across the web," he said. "This allows the spiders to adapt efficiently and flexibly to any change that occur during the hunt ... Our study contributes to our understanding of the principles that govern coordination in animal groups. This is particularly important in spiders, which are still poorly studied compared to other more iconic and charismatic social species such as ants or bees."