杏吧原创

Britain has only three native snakes but a fourth species, the 2-metre-long Aesculapian snake, is breeding in the wild in at least two places 鈥� by exploiting the warmth of buildings and compost heaps.

at Bournemouth University in the UK and his colleagues have been tracking these newcomers to understand how they are surviving in this non-native habitat.

鈥淭he use of buildings for shelter and vegetation piles for egg laying appear to be important to their success in a temperate climate,鈥� say the researchers in a paper about their work. 鈥淲e observed Aesculapian snakes actively seeking and returning to use inhabited buildings and鈥� climbing large structures to access the attics and wall cavities of houses.鈥�

These snakes (Zamenis longissimus) are native to warmer parts of Europe. They are excellent climbers and feed on small animals such as rats, killing them by constricting, as boas do. They aren鈥檛 venomous and pose no threat to people.

Fossils show they were present in Britain at times before around 300,000 years ago, but they never recolonised it after being wiped out during a glacial period. In theory, they still shouldn鈥檛 be able to thrive here, as despite global warming, the climate in Britain isn鈥檛 as warm as in their normal range.

Yet Aescupalian snakes that have escaped from captivity are now breeding in the wild around the Welsh Mountain Zoo in Colwyn Bay in north Wales and around London Zoo in Regent鈥檚 Park ().

Major鈥檚 team implanted tracking devices in 21 snakes in the Colwyn Bay area in 2021 and 2022. This showed that buildings and gardens were the preferred habitat of almost all the males. Females preferred woodland, but laid their eggs in compost heaps.

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鈥淭his attraction towards anthropogenic features is unusual behaviour compared with native snake species in the UK that often avoid built up urban areas,鈥� write the researchers, who declined to discuss their work.

, an independent researcher in the Czech Republic, says that this preference for human structures is key to their survival in an unfavourable climate. He and colleagues have seen , in areas also beyond their normal climatic range.

Of the 21 snakes tracked by Major鈥檚 team, three were killed by traffic and another three by predators, with one tracking device ending up in a buzzard鈥檚 nest. Two of the snakes killed by traffic were females with eggs, which suggests they were seeking out places to lay them.