Wednesday 22 January 2020

Alien venomous spider putting Ireland's only native lizard in danger

The false widow spider
The false widow spider
The viviparous

Payu Tiwari

The future of Ireland’s only native lizard is in murky waters after a specimen was found to have been eaten by an alien venomous spider.

The native lizard, also known as viviparous, is found across all 32 counties in Ireland and is a protected species under the Wildlife Act 1976. A juvenile specimen of this lizard was found killed by an invasive spider at a house in Killiney, Co Dublin last year.

The lizard was found trapped in the web of the false widow spider, and the spider was eating it.  It was the first recorded instance of the native lizard falling prey to the alien spider in Ireland, and the research was published in the Proceedings of the Royal Irish Academy journal yesterday.

The false widow spider was first found in Ireland 20 years ago, in Bray, Co Wicklow. The spider is described as being cold, tolerant, with a high reproductive rate and an exceptional longevity.

The viviparous
The viviparous

A female can live up to seven years and produce one egg sac with 200 eggs every two weeks for four months of the year. Common species in Ireland usually live for one or two years and produce 30-50 eggs a year.

The spider also possesses a fast acting neurotoxic venom, which can be fatal for small reptiles, and can result in a few days of pain and discomfort for human beings.

The spider is multiplying across the country at a rapid rate: by 2017, it was found in 17 countries, and is said to be spreading fast in urban and suburban habitats throughout the country.

The False Widow spider is said to be “remarkably adaptive species,” that prey on beetles, hymenopterans, spiders and occasionally feed on small reptiles.

John Dunbar, lead author of the study and PhD researcher at the Venom Systems Laboratory in NUI Galway, said: “While Black Widows are known to prey on small reptiles, there are only two previous accounts from other species of False Widow spiders preying on a lizard in Iran and on a snake in Bulgaria. Surprisingly, this is the first time the False Widow spider that is currently colonising Ireland has been documented preying on vertebrates.

“In addition to its venom possessing a powerful vertebrate specific neurotoxin, it can produce very strong silk which gives it a real advantage over our native spiders in entangling large prey.”

Co-authors Collie Collie Ennis and Rob Gandola from the Herpetological Society of Ireland, have warned about the increasing possibility of the false widow coming in contact with the native wildlife and have asked people to be alert.

They said: “We are right in the middle of the lizard birthing season and this is when most lizard sightings are made and when juveniles are likely to turn up in gardens. Female lizards give birth to between 6-11 babies that are jet black and about 40mm long.

It’s the juveniles that disperse to new areas but given their tiny size you can see how this is a dangerous endeavour. We’d ask people who are lucky enough to have lizards near or on their property to keep a watch out and report any sightings of False Widows predating on lizards. It would be really helpful to get an idea of how frequent these interactions occur and even the size classes involved, it may not only be young lizards that fall prey.”

The false widow spider species is causing a detrimental effect on local species in Ireland because of their competitiveness and fast breeding nature. The False Widow lives for five to seven years whereas most other spider and bug species in Ireland only lives for a maximum of one year.

In Ireland,  False Widow spiders live close to buildings and houses inhabited by people. Dublin, Cork and Wexford have the highest number of False Widows to date.

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