Spiders Caught Hunting in Giant Synchronized Swarms, And Now We Know How

Pack hunting spiders can be found in places other than nightmares. 20 of the 50,000 known spider species live in colonies.

One species of spider lives in colonies of up to 1,000 individuals that work together to build webs.

Spiders can take down larger prey than they could if they hunted alone because they coordinate their attacks. It was a mystery how these spiders carry out such coordinated attacks.

A new study found that the spiders use vibrations in their mega-web to swarm.

Raphael Jeanson, a researcher at the Research Center on Animal Cognition (CRCA) at the University of Toulouse in France and senior author on a new study about the social arachnids, said that there is no leadership role among these spiders.

Each individual in the spider colony gets the same information.

Photos of spiders are incredible.

As the colony attacks, the spiders close in on their prey and stand still. The spiders can time their approach so that all of them strike at the same time.

Jeanson's team used both field observations and computer simulations to learn that the attack is almost entirely directed by the shared web.

Jeanson told Live Science that when the prey falls in the web, the spiders stop moving.

A colony of A. eximius was located in French Guyana. Credit goes to Raphaël Jeanson/CNRS.

The researchers showed that hunting behavior was triggered by the struggling of helpless prey, when they tried to lure the spiders with a dead fly. That did not explain the colony's coordinated movements.

Scientists needed a computer model. The models showed that the spider colony's vibrations enabled the predator to coordinate their attack.

The spiders started walking when they heard the prey's sound. The sound of a trapped meal was muddied by the steps of hundreds of spiders that descended on the insect.

Jeanson said it was a bit like when you are in a room with people talking. Every step a spider takes makes noise. They have to stop moving so they can listen for the prey, to make sure they are in the right direction.

The quieter the prey is, the harder it is for the spiders to coordinate their stop-and-go movements.

When the researchers vibrated the web and then removed the lure, the colony responded by moving toward the prey, but then every spider had to stop moving for telltale signs.

The scientists found that if the prey was vibrating more intensely, the colony would be less synchronized.

The study was published in the journal on March 7.

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The article was published by Live Science. The original article can be found here.