You may have seen headlines about Aesculapian snakes living wild in parts of the UK, including urban areas. Understandably, the idea of snakes in attics or garden walls can cause a bit of concern, but the truth is, there’s no reason to worry.
Aesculapian snakes are non-venomous and pose no threat to humans. They are slender, harmless reptiles that mainly feed on small rodents like rats and mice, actually helping to control pest populations. Despite their impressive size (they can grow up to two metres long), these snakes are incredibly shy and avoid contact with people.
Not New to Britain — And Not Even New to British History
Aesculapian snakes are not a new arrival. They’ve been living quietly in small populations in the UK for decades (see our blog post last year about UK snakes). Their story dates back to accidental escapes — not from the exotic pet trade, but from a zoo and a scientific research centre in the 1960s and 1970s.
Interestingly, these snakes have a much deeper connection to Britain: the Aesculapian snake was once native to the UK before the last Ice Age. As the climate changed, the species disappeared from Britain naturally, but fossils show it was once part of our ancient ecosystems. In that sense, their modern presence here isn’t so surprising after all.
Because Aesculapian snakes survive in very limited areas and don’t pose any serious ecological threat, authorities have allowed them to remain without large-scale eradication efforts.
The Dangers of Invasive Species
While the Aesculapian snake is not considered a major threat, invasive species can sometimes cause serious problems. A classic example is the grey squirrel, introduced from North America. Grey squirrels have outcompeted the native red squirrel, taking over much of their habitat and food sources. Even more damaging, grey squirrels carry squirrelpox virus, a disease deadly to reds but harmless to themselves, which has accelerated the red squirrel’s decline across the UK.
That said, the situation isn’t entirely black and white. Grey squirrels have also provided unexpected benefits — by enhancing the success of tree planting through seed dispersal, they are estimated to save the UK around £32 million annually in carbon emissions by supporting woodland growth.
Another potential risk comes from reptiles. There have been occasional sightings of Natrix natrix (the European grass snake) in the UK, most likely due to human activity, possibly arriving hidden in imported goods and parcels. If Natrix natrix were to establish itself here, it could outcompete or hybridise with our native Natrix helvetica (the barred grass snake), putting further pressure on our already sensitive native species.
These examples show why careful, science-led management of non-native species is crucial — even small mistakes can have wide-reaching effects on our ecosystems.
How Species Arrive
It’s a common misconception that most non-native species arrive because of irresponsible pet ownership. In reality, there are many pathways through which animals and plants reach new areas.
Some species arrive through human movement, hitching a ride in suitcases, cars, food crates, or parcels, like the mourning gecko or house gecko, which have reputations for turning up in unexpected places. Others are introduced through horticulture, such as the Asian long-horned beetle, which arrived hidden in imported plants and trees.
Sometimes, species naturally expand their range into the UK due to climate change or habitat shifts. The Eurasian spoonbill and little bittern are two bird species that have recolonised Britain naturally, and insects like the small red-eyed damselfly have made their way across Europe without human assistance.
Currently, there are an estimated 2,000 non-native species in the UK, but only around 200 are classified as “of concern”, meaning they have significant ecological, economic, or health impacts. Not every new arrival is harmful, and many live alongside native species without causing major problems (or are even used as a food source).
Not All Introductions Are Negative
It’s important to remember that not all introduced species have a negative impact. Some have even had positive effects, particularly when they’ve filled ecological gaps left by extinct species. A few success stories include:
- Eurasian Beavers: Reintroduced in Scotland, beavers have improved water quality, reduced flooding, and boosted biodiversity by creating wetland habitats that benefit species like otters, amphibians, and kingfishers.
- Tamarix Beetle: Introduced to control the spread of the invasive Tamarix tree (saltcedar), the beetle has been an effective tool in restoring native plant communities in affected areas.
These examples show that, when handled carefully and scientifically, some introductions can actually help restore balance to ecosystems.
However, it’s equally important to warn against unregulated or poorly planned releases. A recent example is the case of lynx reportedly released in Scotland without a proper license or ecological assessment. Such actions can create public fear, cause conflicts with landowners, and threaten the success of legitimate conservation efforts. Responsible, science-driven reintroductions are key to protecting both wildlife and communities.
Other Invasive Animals You Might Not Know About
When we hear the word “invasive species,” many of us think of reptiles and spiders, but the UK has numerous invasive animals that may surprise you:
- Rabbits: Believe it or not, rabbits aren’t native to Britain. They were introduced by the Normans in the 12th century for food and fur. Since then, they’ve become a familiar part of the countryside, but they’ve also caused significant damage to natural habitats.
- Grey squirrels: These were introduced from North America in the 19th century. They have since spread widely, often outcompeting and displacing the native red squirrel.
- American mink: Originally farmed for their fur, mink escaped or were released into the wild. They’ve had devastating impacts on native species like the water vole.
- Signal crayfish: Another North American import, they threaten our native white-clawed crayfish and cause erosion of riverbanks.
- Rose-ringed parakeets: These bright green birds have established large colonies, particularly in London. While beautiful, they can impact local bird populations.
In Summary
The sight of a snake in Britain might seem startling, but the Aesculapian snake is harmless, shy, and not new. Alongside them, species like rabbits and grey squirrels remind us that our wildlife is full of surprises and that sometimes, nature adapts to changes in ways we might never expect.
Understanding the complex impacts of non-native species, both good and bad, helps us make better decisions for the future of our wild places.
