Reptiles on the waterways

Specialist Tony Jones discusses the cold-blooded creatures you might be lucky enough to see on the network

Native reptile species
In almost two decades of boating, I can count on the fingers of one hand the times I have seen reptiles in the wild on the waterways. I’m always on the lookout and I’d love to catch a glimpse of them more often, but reptiles are reclusive so sightings will remain a rare treat.

There are six species of reptile native to the UK but two of these, the smooth snake and the sand lizard, are extremely rare. Those of us who spend time on the waterways are far more likely to see the other four species, with the grass snake being the most often spotted.

If you have seen a snake in or near the water it is almost certainly a grass snake. They’re Britain’s largest and most common species and because their diet almost entirely comprises frogs, toads and newts, they’re routinely found near water sources. They’re easily identified by their distinctive cream or yellow-coloured collar behind the head.

Grass snake and adder — Grass snake (left) and adder (right) with its distinctive zig-zag pattern.

Adders are almost as common but are usually found in much different habitats, specifically dry heathlands, moorlands and open woodlands. This means adders are less likely to be sunning themselves next to the cut but their habitats often nestle closely beside canals and rivers, so seeing them there is not unknown. Adders are mildly venomous but only likely to pose a small risk.

Adder markings are more variable than those of the grass snake. They can be grey, brown or even cream-coloured with a messy zig-zag marking running down their back. There’s also a melanistic variant that’s entirely black, a literal black adder. Given the adder’s variance, if you want to identify a snake you’ve spotted then looking for the grass snake’s collar is probably the best strategy. If it has a collar then it’s a grass snake for sure, and if it doesn’t have a collar it’s probably an adder.

However, if you’ve spotted a snake that doesn’t match either of these descriptions then it’s probably not a snake at all. The UK is home to a legless lizard called a slow worm which is also very common. They are usually silvery-grey, brown or cream, but the feature that defines it as a lizard is its eyelids. There is no such thing as a snake with eyelids, so if a snake blinks or winks at you, then it’s actually a legless lizard – in this case, a slow worm. You’ll rarely see them out and about though as they’re more at home digging around in thick mulch and leaf litter.

The final often-seen reptile is the common lizard, although these are not so frequently spotted as the slow worm, adder or grass snake. Again, identification is a simple process of elimination. If you see a lizard with legs in the UK then it’s probably a common lizard. However, there is also a remote possibility that it could be an interloper.

Non-native reptile species in the UK
Boaters are perhaps more likely than most to spot reptiles in the UK, but this isn’t always a good thing. We have several non-native reptile species that have made a home here in the UK, some of which have taken up residence in or near the waterways.

The turtles you’ll see most of are those known as sliders or terrapins from the Trachemys family – either red-eared sliders or yellow-belly sliders. These are hardy animals hailing from North America that can reach around the size of a dinner plate, although there have been specimens that have grown much larger. You’ll usually find them basking on logs or embankments during the hot days of summer. They came to this country as babies, around the size of a 50p piece, via the pet trade during the 1990s and 2000s. Having been sold to unsuspecting pet-keepers they then grew quickly, needed large enclosures and expensive equipment and emitted vile-smelling faeces. No wonder some of them ended up being released. Sadly, when governments finally banned the sale of Trachemys turtles the trade switched to importing another species, which grows even larger and is potentially even more likely to be discarded by their owner.

Spotting reptiles
If you want to spot snakes and lizards in the UK then early mornings during the early months of spring are the best times to search. Look for patches of sunshine near the waterside for grass snakes, and alongside paths and on drier heathland for adders. Common lizards are much harder to find as they are fast and flighty and likely long gone by the time you get near. Slow worms are rarely found basking as this fossorial species likes to dig, but they’ll often turn up in compost heaps and piles of decaying mulch or leaf litter.

This is an abridged version of the article which appears in "On The Cut" in Waterways World January 2024