An alien species of snake has started breeding in the countryside again after being introduced to the UK half a century ago. Researchers in North Wales believe the Aesculapian ratsnake – which can grow up to 6ft long – has a stable population in the Colwyn Bay area.
However, the snakes, more commonly found in southern Mediterranean and Balkan countries, are thought to be struggling with the climate in Wales, according to Tom Major, a PhD student at Bangor University who studies the snake. non-venomous for five years. They are reluctant to cross roads, limit their range, and have difficulty catching prey – usually rodents up to the size of a rat.
“We found a snake yesterday that was born around September 2018 and weighed eight grams in 2019,” Tom said. “Three years later, it weighed 15 grams – about the same as an HP pencil, reports North WalesLive.
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“Even taking into account six months of hibernation each year, and the cooler climate, it’s an extraordinarily slow growth rate. This suggests he may have only eaten once or twice in the past three years.
The Aesculapian Ratsnake arrived in Conwy in the mid-1960s when Robert Jackson, founder of the Welsh Mountain Zoo, imported reptiles from Italy. In the early 1970s, baby snakes were found in the zoo grounds and were first thought to be grass snakes due to their yellow markings.
Later confirmed as Aesculapian snakes, they had already begun to breed and spread – very slowly – beyond the zoo. Some conservationists hailed their arrival as a ‘returning’ species – they were once native to Britain before the last Ice Age and are not considered a pest.
In 2010, a second, smaller population was found to live on rats along Regent’s Canal near London Zoo. Just two years ago a third population was reported in Bridgend, although confirmation has proven elusive.
The Colwyn Bay colony is believed to be the largest in the UK – Tom estimates there are around 70 adults and 120 juveniles. In southern Europe, Aesculapians can reach two meters in length, making them one of the largest snakes on the continent.
Although they are the longest snakes in Britain, in colder North Wales where there is more rain, Tom suspects they are unlikely to exceed 1.5 meters . The discovery might worry some people, but Tom says there is no cause for alarm.
“On the mainland, the snake co-exists with all other species, including the animals you find here like badgers, stoats and domestic cats,” he said. “For a naturally balanced ecosystem, diversity is generally a good thing. It is used to living alongside humans and there is little to no evidence that it causes harm.
Despite this, the snake is a management priority species for Wales. The Colwyn Bay population has been monitored since 2004 so that “rapid response can be taken if necessary”, the North Wales Wildlife Trust said.
Tom, whose research is sponsored by the Welsh Mountain Zoo, began with field investigations. Last year he began radio tracking nine snakes and will repeat the exercise this summer.
“We learned that they have a limited range, moving up to 500m per day, and are often limited by things like roads,” he said. “They spend long periods of time hiding in hay bales and in the walls of buildings.”
Generally, they do not avoid humans. They can be found in gardens and sheds, although they prefer old stone walls, abandoned buildings and ruins. Often they lay their eggs in garden compost heaps and revisit the same safe places to seek refuge.
And because they feed on small rodents such as rats, the snakes tend to stay near areas where populations are high – usually where people live.