GALWAY, Ireland — Even in nature, bigger isn’t always better. Astounding research has documented the first ever instance of a noble false widow spider actually catching and eating a bat. Moreover, the specific variety of Pipistrelle bat seen in the spider’s web is considered a protected species in the United Kingdom, providing further evidence that false widow spiders are impacting various native species populations.
This is the first time a member of this spider family (Theridiidae) has been recorded eating a bat anywhere on Earth, or any vertebrate in Britain for that matter. Moreover, this study also marks the first time ever any species of false widow spider has been recorded preying on and eating a mammal.
Where did this spider’s big feast take place? Wildlife artist Ben Waddam’s home in north Shropshire, England. For two days in a row Mr. Waddam found bats living in his attic caught in the spider’s web. The first bat was only a baby, and completely immobilized due to its limbs being pinned tightly to its torso by the silk. The bat was dead, discolored, and shriveled from the spider slowly feeding off the remains.
The second bat was a much larger adult, and ultimately rescued by Mr. Waddam before the spider could begin eating.
Noble false widow spiders pose serious threat
Per the Wildlife and Countryside Act of 1981 and the Conservation of Habitats and Species Regulations passed in 2017, Pipistrelle bats are a protected species in Britain. And, while these observations may seem like a rare, isolated incident, it isn’t the first time noble false widow spiders have been known to catch and eat much larger prey. There were reports three years ago of such a spider eating a protected species of native lizard in Ireland.
The noble false widow spider (Steatoda nobilis) originates from the Canary Islands and Madeira. Today, many scientists believe it may become one of the world’s most invasive species of spider. First detected in England way back in 1879, noble false widow spider numbers have increased dramatically in recent decades across the United Kingdom (Scotland, Wales) and Ireland. Beyond those areas, these spiders have also spread virtually all over the world, from Europe and East Asia to both North and South America.
Regarding potential threats to humans, the severity of a noble false widow spider bite can vary quite a bit. Some bites produce only mild symptoms while other cases are much more severe. Very little, up until now, had been confirmed about its impact on native species.
‘Truly remarkable species’
Meanwhile, over the past five years a team of scientists led by Dr. Michel Dugon in NUI Galway’s Ryan Institute have been analyzing the species in great detail. They’re studying the spider across a variety of considerations including its venom, ecology, typical behavior, and usual symptoms seen in animals/humans following envenomation.
“We have been working on the noble false widow for the past five years, and have learnt a great deal about this species – yet, we are still surprised by its ability to adapt to new environments and make the most of the resources available. It is a truly remarkable species.” Dr. Dugon, senior study author and Head of the Venom Systems Lab, Ryan Institute, NUI Galway, explains in a statement.
“In more exotic parts of the world, scientists have been documenting such predation events by spiders on small vertebrates for many years, but we are only beginning to realize just how common these events occur. Now that this alien species has become well established in Ireland and Britain, we are witnessing such fascinating events on our very own doorstep,” adds lead study author Dr. John Dunbar, Irish Research Council Post-Doctoral fellow, Venom Systems Lab, Ryan Institute, NUI Galway.
“Even other, much smaller, species of false widows are known to capture and feed on snakes and lizards. This study presents yet another example of the invasive impact by the Noble false widow spider on native species. We know they are much more competitive than native spiders, and this further confirms their impact on prey species,” he continues.
These spiders have a fast-acting neurotoxic venom that is actually quite similar to that of true black widows. This venom is capable of paralyzing mammal muscles, which is what allows the spiders to slowly eat large prey (small mammals and lizards).
“False widow spiders, just as their close relatives’ black widow spiders, have extraordinary prey capture techniques and remarkably potent venom which allows them to capture small vertebrate prey many times larger than the spider itself with surprising ease,” concludes Aiste Vitkauskaite, researcher at the Venom Systems Lab, Ryan Institute, NUI Galway. “In the last three years alone, we have observed two occasions of the alien noble false widow capturing and feeding on protected species of vertebrate animals in Ireland and Britain. As the noble false widow continues to expand its range and increase populations across Ireland and Britain, we should expect to observe similar predation events on small vertebrate animals by this spider, including protected species.”
The study is published in Ecosphere.