Noble false widow spiders prey upon protected bat species

A research team led by National University of Ireland Galway (NUI Galway) has published the first record of a noble false widow spider feeding on a protected species of Pipistrelle bats in the United Kingdom. It is also the first time for any species of false widow spiders to be recorded preying on mammals, offering new evidence of how these spiders continue to impact native UK species.

The noble false widow is a species of spiders belonging to the family Theridiidae. It was first reported in southern England in 1879 and has significantly increased its range and population density in recent decades, spreading through Scotland, Wales, and Ireland. During the same period, the false widow has also spread globally to Europe, East Asia, North America, and South America. 

These spiders possess a fast-acting neurotoxic venom with a very similar composition to that of true black widows, which can cause neuromuscular paralysis in terrestrial vertebrates. Although their bites are known to cause a range of mild to severe symptoms in people, their impact on native animal species has not yet been systematically documented.

Wildlife artist Ben Waddams has recently found two bats living in the attic of his home in North Stropshire, England, entangled in the spider’s web below the entrance to the roost. While a young bat pup was already dead and completely immobilized with its limbs pinned tightly to the torso with silk, the second, much larger bat, was still alive and was rescued.

“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,” said study lead author Dr. John Dunbar, a postdoctoral fellow at 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.”

“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,” added study co-author Aiste Vitkauskaite, a research assistant at NUI Galway.

“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 the journal Ecosphere.

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By Andrei Ionescu, Earth.com Staff Writer