Invasive snakes breeding in the wild in at least three UK regions crawl up walls and into attics to survive, researchers said.
Aesculapian snakes, which can grow to over 7ft long, originally escaped from captivity, but are now surviving on their own using warm corners made by humans.
Researchers tracked 13 males and eight females between 2021 and 2022 to find out how they were surviving in a climate previously thought to be too cold for them.
They found out they relied on ‘human habitats’ – such as your house.
Researchers said in their paper: ‘We observed Aesculapian snakes actively seeking and returning to use inhabited buildings and… climbing large structures to access the attics and wall cavities of houses.’
This is ‘unusual behaviour’ compared to native snakes in the UK, the team led by Tom Major said.
The areas where there are known to be populations of the large snakes are around London Zoo in Regent’s Park (although the zoo says they are not responsible), near Bridgend in South Wales, and around Colwyn Bay in North Wales.
The populations have lived here for some years, but it’s only now that researchers have shed more light on what their lifestyles involve.
And we have to say, we we not expecting to have to worry about getting a bonus scaly flatmate.
Using radio trackers to snakes in the Colwyn Bay population, researchers monitored where the snakes went and how they spent their time, with updates twice a day.
The results found that male snakes showed a ‘distinct preference’ for buildings, while female snakes preferred woodland.
‘For snakes, anthropogenic structures such as buildings and culverts provide shelter, thermoregulatory opportunities and egg-laying sites,’ the paper said.
‘Snakes frequently took shelter in human features of the habitat, and compost heaps, vegetation piles, and buildings represented long-term shelter for female snakes.
‘This attraction towards anthropogenic features is unusual behaviour compared with native snake species in the UK that often avoid built up urban areas.’
Aesculapian snakes are non-venomous and don’t pose a threat to humans
Of all the 21 tracked snakes, five died during the study and one died shortly afterwards. Three were killed by cars, one was preyed on by a buzzard and found in its nest, one was cannibalised by a male snake, and one was killed by a mammal thought to be a stoat, badger or cat.
During the study, five of the males were seen sheltering in two different buildings each, while three males used three different buildings.
On one occasion, researchers discovered eggs inside the compost heap of a residential home.
Aesculapian snakes had not been seen here for around 300,000 years after they were wiped out in an Ice Age.
They were first reintroduced to the UK after their long absence following an escape from the Welsh Mountain Zoo in the 1970s.
Since then, the rat-eating snakes have occasionally been spotted, with a dog walker finding one along the Regent’s Canal towpath last year.
They kill their prey using constriction, like boas, are not venomous and do not pose a threat to humans.
Ranging from France to Iran, they are one of mainland Europe’s largest native snakes.
