The real reason Ireland doesn’t have snakes

The real reason there are no snakes in Ireland

By KR Callaway edited by Andrea Thompson

When revelers gather in the streets of Dublin for Ireland’s annual National St. Patrick’s Day Parade, one green-clad group won’t be there: snakes.

Saint Patrick, a fifth-century missionary from Roman Britain, is primarily known for spreading Christianity in Ireland. However, his other claim to folklore fame comes from his supposed role as an exterminator – he is said to have chased all the snakes out of Ireland with an ornate shepherd’s crook known as a crozier.

A haven for those with ophidiophobia, Ireland has zero native snake species. However, this snake-free status predates Saint Patrick. In fact, the fossil record suggests that the island has never hosted wild snakes—or many other reptiles, for that matter.

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“We really only have two reptiles,” says Collie Ennis, science officer at the Herpetological Society of Ireland and biodiversity officer at Trinity College Dublin. “We have one native land reptile – that’s the common lizard…. We also have an introduced reptile in Ireland called the slow worm, and it’s a type of legless lizard.”

Most scientists agree that the last ice age, which ended about 11,700 years ago, is the reason for Ireland’s lack of reptile diversity. When the ice age of the epoch retreated and temperatures warmed enough for the ectotherms, Ireland had broken away from the European continent and was inaccessible to roaming reptiles.

Even today, Ireland is simply too cold for most snakes. Because reptiles cannot heat internally as mammals can, they tend to prefer warm temperatures between 70 and 100 degrees Fahrenheit (21 and 38 degrees Celsius) and can be rendered immobile or perish from long periods of cold. Ireland’s native lizard (Zootoca vivipara) and the introduced slow worm (Anguis fragilis) is both much hardier and able to go dormant through the winter.

Geographical isolation and cold temperatures have actually prevented snakes from populating the wilds of many islands; New Zealand, Iceland and Greenland are all also snake-free.

Still, being naturally snake-free doesn’t mean there isn’t a single snake slithering around Ireland. Dublin Zoo and the National Reptile Zoo in Kilkenny are both home to several snake species and see many thousands of visitors each year. And among Ireland’s pet owners, snakes are becoming an increasingly popular choice.

“In my lifetime we went from where the only time you’d see a snake in Ireland would be in the actual zoo … to lots of people of all ages keeping them as pets,” says Ennis. “I think they’re one of the favorite animals we have in the country at the moment, so there’s a huge interest in reptiles.”

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