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False Widow Spider Spotted Killing And Eating Bats For The First Time

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Rachael Funnell

Social Editor and Staff Writer

clockMar 2 2022, 14:36 UTC
false widow kills and eats bats

The unexpected observation played out in the United Kingdom, where false widows are invasive. Image credit: Dunbar et al. 2022, Ecosphere. CC BY 4.0

The black widow’s deadly bite is feared among arachnophobes, a reputation that’s rubbed off somewhat unfairly on the noble false widow (Steatoda nobilis) whose bite isn’t actually all that venomous to humans but can transfer antibiotic resistant bacteria leading to serious infections. However, these spiders have recently proven that they still pack quite a punch as one was spotted catching, killing, and eating a mammal for the first time.

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The ambitious arachnid’s unconventional meal was spotted in a web outside an attic in Shropshire, Britain, where one dead juvenile bat and a still-alive adult bat were found trapped in a web. The researchers behind the novel observation also believe it to be the first reported case of a tangle-web spider (Theridiidae family) killing a bat globally, and the first vertebrate killed by such a spider in Britain.

In their paper “Webslinger vs. Dark Knight First record of a false widow spider Steatoda nobilis preying on a pipistrelle bat in Britain,” published in Ecosphere, they describe how the noble false widow spider has expanded its range globally, including parts of Europe.

There are currently 66 invasive species listed in the Europe Union, none of which are spiders, but following their discovery the researchers suggest that noble false widows could be contenders for the list. Why? Because it appears they could well be eating protected species.

The exact species of the bats caught up in the drama isn’t known for certain, but they’re expected to have either been common pipistrelles or soprano pipistrelles based on their size. Both are protected under the Wildlife and Countryside Act, 1981, and the Conservation of Habitats and Species Regulations, 2017.

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The observation was made possible thanks to a roost of bats that had – in an example of scientific serendipity – taken up residence in one of the study author’s attics in north Shropshire. They were joined in spring, 2021, by a large false widow spider who built a web on the corner of an external chimney breast.

By summer, the spider had ensnared a small bat pup that was dead, silk-wrapped, and slightly shriveled from being fed on. The capture happened overnight and the dead pup was eventually dropped from the web, but 24 hours later an adult bat was found in the same predicament.

The author stepped in to disentangle the still-alive (and still protected – under human law, anyway) pipistrelle from the web and returned to the roost.

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“The predation event on a bat reported here is the second case of predation by S. nobilis on a protected vertebrate species,” concluded the study authors. “Although published accounts of spiders preying on vertebrates seem relatively rare… the true occurrence of such events may be much higher than anticipated.”

“As S. nobilis continues to expand its range and increase its population density wherever it occurs outside of its native range, we should expect more species to fall prey to this spider, including rare, threatened, or protected species. S. nobilis warrants close monitoring to assess its full impact on native organisms and its possible classification as an invasive species where it is most abundant.”


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