Invasive Spider Discovered Preying On Bats In Man's Home

A man has discovered a noble false widow spider preying on bats in his home in England. It is said to be the first reported case of a spider in the Theridiidae family preying on a bat.

Wildlife artist Ben Waddams of Loppington Shropshire had been monitoring the "growing colony" of pipistrelle bats in his attic, authors noted in their paper describing the discovery. He was also aware that he was sharing his home with a noble false widow spider (Steatoda nobilis), which is an invasive species, according to the National University of Ireland (NUI) Galway.

In the Spring of 2021, Waddams found a small bat pup dead on the spider's web. It was reportedly wrapped in silk and had signs that it had been preyed upon.

"There were a lot of bats up there," Waddams told BBC News. "I started checking every morning every evening, just to check what was going on, and then one morning I found a dead pup in this false widow spider's web."

The following morning, another pipistrelle bat was found to be entangled in the same web. This time, it was an adult that was still alive, and Waddams was able to rescue and release it.

Experts from NUI Galway saw the photos Waddams posted on social media and contacted him. In February, the team, including Waddams, published their findings in Ecosphere, where they noted the many firsts that were marked by the discovery.

"To our knowledge, this is the first recorded case of a Theridiidae spider preying on a bat globally, the first case of a Theridiidae spider preying on a vertebrate in Britain, and the first global case of a Steatoda preying on a mammal," the researchers wrote.

The team then titled its work "Webslinger vs. Dark Knight: First record of a false widow spider Steatoda nobilis preying on a pipistrelle bat in Britain."

Invasive vs. protected species

As mentioned, the noble false widow spider is an invasive species. It first came to England in 1879. More recently, the species has spread to Scotland, Wales and Ireland. It has also reached Europe, East Asia and North and South America.

The Pipistrelle bat, on the other hand, is protected under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017, BBC News noted.

"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," Aiste Vitkauskaite of NUI Galway, one of the paper's authors, said in the university's news release.

According to the authors, the impact of the invasive spider on native species hasn't been "fully assessed." As such, observations such as the one Waddams witnessed are critical to understanding the species impact.

"With increasing human encroachment into natural habitats, urban habitats are regarded as crucial refugia for many species," the researchers wrote. "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."

Members of the public are encouraged to report sightings of the noble false widow spider by sending an email to falsewidow@nuigalway.ie.