Protected pipistrelle bats have been captured and fed on by a noble false widow spider, the first time the behaviour has been seen.
The arachnids are thought to have been accidentally introduced to the UK from the Canary Islands about 100 years ago and have been spreading ever since.
While most spiders feed on small insects, bats are at risk from the false widow because they have a potent venom which allows them to catch vertebrates much larger than the spider itself. Experts have said this spider could become one of the world’s most invasive.
Scientists from the National University of Ireland Galway, who have been studying the spider, have published the extraordinary images of the spider feeding on pipistrelle bats in Shropshire, England.
The study, published in the journal Ecosphere, warns that this spider is continuing to threaten native species.
This is the first time a member of the false widow family of spiders has been recorded preying on a bat anywhere in the world. A noble false widow has, however, been seen preying on a lizard in Ireland.
Wildlife artist Ben Waddams alerted scientists after bats living in his north Shropshire attic were found entangled in the spider web on two consecutive days.
One, a young pup, was found dead after the spider completely immobilised it, pinning its limbs tightly to the torso with silk. Its body was shrivelled and discoloured from the spider feeding off the remains. A second adult bat was found entangled but alive, and was released safe and well.
Dr John Dunbar, Irish Research Council post-doctoral fellow, Venom Systems Lab, Ryan Institute, NUI Galway 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 commonly 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 spider on native species. We know they are much more competitive than native spiders, and this further confirms their impact on prey species.”
As well as being a potential danger to native wildlife, the false widow is known for its bite, and has caused mild to severe symptoms in those humans it has bitten.
Pipistrelle bats, which are protected in the UK, declined sharply in the 20th century, with numbers falling 70% between 1978 and 1993, but conservation efforts have recently led to a small recovery.
The noble false widow spider was first reported in southern England in 1879 and has increased its range and population density in recent decades, spreading northwards towards Scotland and westward through Wales and Ireland. In that time the species has also spread globally from across Europe, east Asia, North America, and South America.
