Uncovering the speedy secrets of the ground spider

An international team of scientists including Czech biologist Milan Řezáč of the Crop Research Institute has just published surprising findings about the ground spider in The Journal of Experimental Biology.

Photo: archive of Milan Řezáč

The team uncovered how the spider, which does not spin a web, captures prey using sticky silk. The moves are too quick to spot by the naked eye.

I began by asking Michal Řezáč about the species.

“We studied spiders from the gnaphosidae family which are spiders that live on the ground and are nocturnal. So during the day, you can find them under stones for example. We wanted to know how they capture prey because we noticed they had a very unusual spinning apparatus and we wanted to document their hunting behaviour.”

Is it fair to say that their method of hunting was something of a mystery? How had it been documented in the past?

“Their method of capturing prey had been described but not very well. We wanted to change that. We wanted to use videos and to better analyse the material the material they use. A very detailed study had not been done yet.”

Spiders have different kinds of hunting techniques I imagine, from using a spun web to camouflage. What is the technique here as you uncovered it?

Photo: archive of Milan Řezáč

“That’s right. A capturing web is the way for some spiders but more and more spiders no longer use those webs anymore but simply jump on their prey. In this case, the ground spiders don’t attack their prey directly because that would be too dangerous but rather immobilize it. Immobilizing the prey is very crucial to prevent injury. Prey they try to capture are other spiders, even larger ones than themselves, and ants. These spiders usually live in dry habitat, which is why they are known as skálovky in Czech, something like ‘rocky’ spider.”

I read that the process is too fast to see by the naked eye, is it fair to describe the method as 'fast and furious'?

“Yes, definitely! It is too fast. You can’t tell what is going on just by the naked eye, so that was the importance of getting footage close-up which could be slowed down. When you slow the film down, you see that first the spider fixes the fibres to the ground and then begins to run around the prey.

“Then it runs around and attaches each leg of the prey with these very sticky and tough silk fibres, which are coated with glue. In evolutionary terms, the method is very widespread so it is a successful strategy.”