Ireland used to be a perfect place for someone with a snake phobia to live or visit. There were no snakes, absolutely none, anywhere on the island. Legend attributed this absence to St. Patrick, who was said to have driven all of Ireland’s snakes into the sea.

The St. Patrick legend is one way of explaining what the Irish had observed as true, but biogeography offers another. When the last ice age ended, Ireland was still connected to Britain by a land bridge, and the whole landmass was still connected to Europe. As the ice melted, the sea level rose, first submerging the land bridge to Ireland and only later the land bridge where the English Channel now is. By the time snakes had slithered their way northward from Europe into Britain, Ireland was already an island. Hence, Britain has wild native snakes and Ireland doesn’t.

The legend of St. Patrick was actually helpful to Ireland’s ecology because it kept imported snakes off the island for a long time. As recently as 1831, for instance, a man who wanted to test the effectiveness of St. Patrick’s ban released six English snakes into his garden only to have them eliminated by his neighbors. The locals were so horrified to see snakes defying St. Patrick’s ban that they killed them on sight and offered rewards for any they might have missed.

But Ireland might yet be invaded by snakes. In 1989 a pet shop owner in Limerick started promoting snakes as “guard dogs” and began selling various imported species — including pythons — to city dwellers. In short order two of these “guard snakes” escaped and three were stolen. Then, in 1991, the Secretary of the Herpetological Society of Ireland, hatched 15 snakes in his living room. These snakes, announced as the first ever to be born in Ireland, brought this enthusiast’s personal snake population to 40.

The current Chairman of the Herpetological Society of Ireland assures me that no one today is keeping “guard snakes.” And he also tells me that whatever snakes there are in Ireland are bred only under controlled circumstances. But it’s still alarming to think what these imported snakes might do to Ireland’s snake-free ecology should they escape from their owners’ tanks.

If Ireland’s cold climate didn’t do them in, the Irish might begin to wish for another St. Patrick — if not another ice age — to help them start all over again.