Snake-eating spiders live on every continent except Antarctica

It may come as a surprise to learn that some spiders eat snakes, and a study from the University of Basel has now revealed that this unusual predation strategy can be found on every continent except Antarctica. The researchers analyzed over 300 reports of snake-eating spiders.

The study revealed that spiders from 11 different families are able to catch and eat snakes. “That so many different groups of spiders sometimes eat snakes is a completely novel finding,” said study co-author Dr. Martin Nyffeler. 

Overall, 80 percent of the incidents studied were observed in the United States and Australia. By contrast, this feeding behavior has rarely been observed in Europe.

According to the researchers, snake-eating spiders have never been reported in Switzerland, and one possible explanation is that the native colubrids and vipers are too big and heavy – even when freshly hatched.

The researchers found that about half of the reported snake-eating spiders were black widows of the family Theridiidae. These spiders have powerful, paralyzing venom that targets vertebrate nervous systems. In addition, black widows build webs with extremely tough silk that allows them to capture larger prey.

The analysis also revealed that spiders can subdue snakes from seven different families, about 30 percent of which are venomous themselves.  

Furthermore, the observed spiders can outcompete snakes that are up to 30 times their size. The snakes caught by spiders ranged from six centimeters to one meter, with an average length of 26 centimeters. The experts report that most of the snakes caught were very young, freshly hatched animals. 

Many snake-eating spiders have venom that is also deadly to humans, attacking the nervous system in similar ways. Ultimately, observations of snake predation may provide new insight the mechanisms by which spider neurotoxins affect vertebrate nervous systems.

“While the effect of black widow venom on snake nervous systems is already well researched, this kind of knowledge is largely lacking for other groups of spiders,” said Dr. Nyffeler.

“A great deal more research is therefore needed to find out what components of venoms that specifically target vertebrate nervous systems are responsible for allowing spiders to paralyze and kill much larger snakes with a venomous bite.”

The study is published in the Journal of Arachnology.

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By Chrissy Sexton, Earth.com Staff Writer