Bat-eating spider has spread through Wales and could pose a threat to other native species say researchers

An invasive species of spider that has spread through Wales has been found to prey on bats.

A new study entitled ‘Webslinger Versus Dark Knight’ published in the journal Ecosphere records that the false widow spider Steatoda nobilis is preying on pipistrelle bats.

The invasive species of spider has spread up through England and then westward through Wales and Ireland over recent decades, scientists said. The first example of one of the spiders praying on a bat was picked up by scientists was discovered just miles from the Welsh border in Shropshire.

The grisly discovery was made after one of the paper’s authors one became aware of a growing colony of bats in the attic of his main residence, a detached house on the edge of a small housing estate.

“One morning during the first week of July 2021, a small bat pup was found dead on the spider’s web, with the wings tucked under the body evidently wrapped with silk, slightly shriveled, and presented with a dark purple coloration toward the posterior end,” the paper says.

“The following morning, an adult bat was discovered entangled in the same web. The specimen was alive, and, in this instance, the bat was rescued and placed on the wall, where it crawled up back toward the roost.”

‘Alien’

The open access paper adds that “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,” the paper adds.

The Steatoda nobilis spider originates from Madeira and the Canary Islands. Meanwhile Pipistrelle bats are in the UK protected under the Wildlife and Countryside Act, 1981, and the Conservation of Habitats and Species Regulations 2017.

Dr John Dunbar, Irish research council post-doctoral fellow at the venom systems lab, and lead author of the study, said: “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 realise just how common these events occur.

“Now that this alien species has become well established in Ireland and the UK, we are witnessing such fascinating events on our very own doorstep.

“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 on native species. We know they are much more competitive than native spiders, and this further confirms their impact on prey species.”