While Britain has three species of native snake (adder, grass and smooth snakes as well as a wild colony of non-native Aesculapian snakes in London's Regent's Park), Ireland has none, despite being only 12 miles distant from Britain at its nearest point between County Antrim and Scotland's Mull of Kintyre.
There are two main theories to explain this absence. The first is that, according to legend and to fervent believers even today, St Patrick cast out the snakes during his successful mission to convert Ireland to Christianity in the fifth century.
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The story, first written down in the 12th century, credits Patrick with driving all the snakes into the sea after they attacked him while he was fasting. Curiously, a Roman writer had noted that there were no snakes in Ireland (Hibernia) 200 years before Patrick.
Secondly, according to science, snakes have never existed in Ireland. They could not have survived anywhere in the British Isles during the last Ice Age 10,000 years ago as it was too cold. But as the ice retreated, many animal and plant species crossed into Britain. Alas for the snakes, rising sea levels prevented them from making the final step of colonising Ireland.
