Top scientists in Ireland have discovered that the venomous noble false widow spider, which can be found in Irish homes, is now capable of feeding on bats that are hundreds of times its weight.
A team of scientists from the Ryan Institute in the National University of Ireland Galway who conduct research into the species recorded the incident which happened in England.
The extraordinary discovery was made by wildlife artist Ben Waddams at his home in north Shropshire. On two consecutive days, bats living in the attic were found entangled on the spider’s web below the entrance to the roost.
The first bat, a young pup, was completely immobilised with its limbs pinned tightly to the torso with silk. It was slightly shrivelled and discoloured from the spider feeding off the remains.
A second, much larger adult bat, was also captured and entangled in the web but as it was still alive, the bat was rescued from the web and released.
This is the first time that a false widow spider has been recorded preying on a bat, or a mammal, anywhere in the world - and one that is much larger than the spider's own size.
The important discovery, which was published in a study in the international journal Ecosphere, presents another example of the invasive impact the false widow spider is threatening to have on native wildlife species.
Three years ago in Ireland, the noble false widow was also reported feeding on a protected species of native viviparous lizard.
False widow spiders, or Steatoda nobilis, normally feed on house flies and small insects by paralysing their prey with their sting, a fast-acting neurotoxic venom.
They originate from Madeira and the Canary Islands and were first discovered in Ireland in 1999 and have become one of the most common urban spiders. Experts have said it could become one of the most invasive spiders in the world.
Despite their tiny size, one venomous bite from a false widow can cause a range of mild to severe symptoms and in some cases can even send their human victims to hospital.
They are tiny, one-centimetre-long chocolate brown spiders with a large bulbous body and a smattering of cream on top, sometimes in the shape of a skull.
Over the past five years, the team led by Dr Michel Dugon in NUI Galway’s Ryan Institute, have been studying a wide range of characteristics specific to the species including its venom, symptoms after envenomation, ecology and behaviour.
Dr Dugon said: “We have been working on the Noble False Widow for the past five years, and have learnt a great deal about this species - yet, we are still surprised by its ability to adapt to new environments and make the most of the resources available. It is a truly remarkable species.”
Dr John Dunbar, lead author of the study of the interesting case, 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 Britain, 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.”
The team of scientists are encouraging members of the public to email them at falsewidow@nuigalway.ie to report sightings of the Noble False Widow spider.
