Britain’s largest wild snake is “thriving” in the part of North Wales they have colonised, a study has concluded. Around 240 Aesculapian snakes have been identified as living in Conwy, centred on Colwyn Bay. Despite weather challenges, the reptiles have proven to be “adaptable generalists”, capable of coexisting with humans. Researchers found they were “unafraid” to move into homes and live in “close proximity” to people. Being excellent climbers, they are known to have scaled the walls of local houses to hibernate in attics and roof spaces. Larger males have a strong preference for buildings, while females favoured woodland areas, although some move into homes and sheds too. Dr Tom Major, who led a two-year-long study at Bangor University, said the snakes saw buildings as “warm and safe retreats”. During the study he received messages from scared residents worried about home invasions – but he reassured them the cold-blooded predators are shy and harmless to humans. Most people, he said, considered it a “privilege” to have wild animals living alongside them. Aesculapian snakes established the world's most northerly population in the 1970s when several escaped from a failed enclosure at the Welsh Mountain Zoo. Since then, many Colwyn Bay residents have become fond and protective of their reptilian neighbours. Dr Major said the population appeared constrained from further expansion by human-made barriers such as roads. But the fact they had survived, despite originating from warmer countries, showed how exotic reptiles may in future establish in cooler climates by living among people. Join the North Wales Live Whatsapp community now “Aesculapian snakes are a novel addition to our fauna, being larger than any of our native snake species,” he said. “Using buildings for shelter is a valuable strategy for an animal that faces a cool climate and numerous threats including domestic cats and a variety of native predators such as stoats and buzzards. Whether they will persist in Wales is uncertain, as the population is hemmed in by roads and housing developments, but for the time being they seem to be thriving.” The snakes were once native to the UK but they went extinct some 300,000 years ago. Today, they range from France to Iran, and are capable of growing to 6ft – though those in North Wales tend to be smaller, up to 5ft, due to limited food supplies. They are not venomous and instead constrict their prey, mainly birds, eggs and small mammals. For the Bangor University study, 21 adult snakes – 13 males and eight females – were implanted with radio transmitters in 2021-2022. All were caught by hand, including two by keepers at the Mountain Zoo. It was a laborious process: each snake found took an average of eight hours to find. Male snakes, being larger, had slightly larger home ranges than females, averaging 29ha – equivalent to 29 rugby pitches. Females averaged 23ha. Some were found warming themselves in garden compost heaps, where females often laid eggs. A huge dung pile at the Mountain Zoo, 33ft across, is a known egg-laying site, as is a nearby pile of wood chippings. All faced threats numerous threats, not least from traffic. During the two-year study, three of the eight tracked females died, two of them on roads, both carrying eggs. A transmitter belonging to the third was found inside a male – it’s thought she was a victim of cannibalism. Three males died too – one was killed by a car at the Mountain Zoo. Another was found with a broken neck, partly eaten, probably having been predated by a stoat, badger or domestic cat. No trace of the third was located – but its transmitter was found more than 100ft up a tree. It was near a nest built by a buzzard, assumed to be the guilty party. Building culverts under roads is likely to improve survival rates. But if population expansion is possible, it’s like to be slow - North Wales is seen as the northern limit of current viability, unless the climate continues to warm. The study concluded: “The use of buildings for shelter and vegetation piles for egg laying appear to be important to their success in a temperate climate that is further north than any remaining native populations. However, simply being successful in an area is not evidence to suggest the area contains ideal conditions. “The broad range of habitats selected by individual snakes in this study suggest that Aesculapian snakes are adaptable generalists, capable of using mixed habitat and unafraid of using buildings and other features in close proximity to humans.” Sign up for the North Wales Live newsletter sent twice daily to your inbox Find out what's happening near you