The Ecology of the UK’s Snakes

David Beeson, April 2022

A 9-month-old adder in the New Forest. It does not eat until it is over 18-months-old. Size: about a pencil length and width.

I’ve always been a fan of the underdog. If some creature is being ‘got at’ then I’m prepared to put in some effort to attempt to right-the-wrong. That was how it was when I started working with the Mammal Society and then the Otter Trust to stop the hunting of the animal with dogs, the use of traps by waterkeepers and to reverse the trend to extinction that was happening in the 1970s. Human aggression, water pollution and a total disregard of the environment was where I started. And it worked! I set up a nationwide Otter Conference in 1976 and that helped push the survival of the otter in the correct direction.

Male adder, basking in the New Forest gloom. We saw a similar male out and about the same day.
Female sand (green) lizard in the New Forest – suitable food for the adder. Snakes lack eyelids, but lizards have them.

Now, snakes need some support. Their numbers are declining, and their habitat often so divided that genetic flow is impossible, and inbreeding depression a possibility. I did watch adders a few years back and have carried out some very basic research, and the creatures are unaggressive when left alone. Only considerable human or dog aggression causes them to respond negatively. So, if you go out looking for and at snakes you can proceed without fear of being bitten.

The UK has three snake species: the Adder (Viper), Grass Snake and Smooth Snake. All are said to be declining and the smooth snake is already rare. The frequent heathland fires are a negative influence too.

The snakes have their own niches, which largely fail to overlap. The smooth snake are heathland specialists, grass snakes are wetland creatures and the adder a grassland and wood pasture animal over much of its range. Yes, that is an simplification and I have seen adders on heathland at Pullborough Brooks and a grass snake in my, edge of woodland, grassy garden … but it is a fair reflection.  

Why the decline? Well, many reasons.

Firstly, people seem to dislike them. A colleague at work played golf and happily said he killed any snakes he saw with a golf club. No reason really. He was not threatened or, worse, attacked. Just fancied killing them.

Two, their habitat has been lost to farming, golf courses or housing / industry.

Three, dogs, whose numbers seem to increase exponentially, disturb the animals and inhibit hunting and mating.

Four, men with guns. A friend was filming adders for the BBC and all the animals he captured had shotgun pellets embedded in them. The lead shot would, of course, kill them immediately or poison them over a short time.

Five, pheasants (Asian birds) and chickens eat young reptiles and soon eliminate them. The Netherlands bans pheasants to preserve their reptiles. If the UK stopped pheasant rearing the snakes would fair much better. An RSPB reserve in west Wales had a healthy snake population until a pheasant shoot started – the snakes are now all gone.

A male and female adder. My mini-research was to photograph the heads of adders (all slightly different) to start a database.

The Adder or Viper.

Vipera berus, the adder is one of our three native snake species. It is most often seen on heaths and grassy coastal areas. Undisturbed grassy areas are great locations. However, its secretive nature and camouflaged markings mean it often goes unnoticed. Whilst it has a large range across the UK, recent declines, especially in central England, mean it is of major conservation concern. The adder is the UK’s only venomous snake. Though potentially serious, adder bites to humans or dogs are very rarely fatal. There are only around ten recorded cases of death from adder bite in the last 100 years, and most bites occur when the snake has been disturbed or deliberately antagonised.’ ARC.

The animal is found across England, Wales and Scotland but you will need to work hard to find them in many locations. In my own area, north-west Hampshire they have been hugely impacted by pheasant breeding. Even gamekeepers tell me that their snakes have vanished. I would struggle to find one within 20 miles, although I know of many locations where they have been previously. However, Martin Down NNR is a good location.

The distinct black and white colour of the typical male can be much darker – the black adder. The females are usually slightly larger and have an olive / brown / copper complexion.

Female adder in the New Forest.

Adders are not easy to see in the wild as they merge well with their background, are often coiled to conserve warmth and seldom are seen moving. The animals coil and uncoil, round their body or flatten it depending on the weather conditions. I have read reports of their climbing bushes to gain the early or late sunlight, yet I have never witnessed that.

I have seen adders as early as February 14th in the New Forest, and some reports indicate they can be active all winter in mild locations.


I associate male adders in combat / dancing at the same time as the early purple orchids are in flower – April or May. Why? Well, I was lying down photographing said orchid when an adder pair started their combat dance alongside me! I have lived to tell the tale.  

The dance is a combat of strength with the animals loosely intertwined and moving. They are then oblivious of all around them. The winner will hold that key territory and will mate with the local female.

Female adders breed annually in warm locations and less frequently in colder areas. Their eggs are incubated internally, and you are seen from late summer. The babies are worm-like and vulnerable to avian predation.

Lifespan is said to be up to ten years.

My filming friend was lying down in his home adder pit when a female evaded his cycle clips – employed to stop access to his trousers. The female spent several hours basking on his bum but inside his trousers!

Prey animals are poisoned by injection and then followed until they are immobile and then swallowed whole. Mice, voles and lizards are suitable foods. Hunting may occur at night.

The venom of young adders is stronger than that of adults.

Where to look? Undisturbed grassland fringes and especially grassy areas near heathland. Purbeck is an excellent location.

When to look? When you can see a shadow there will be active snakes. However, they are best viewed early April or May and in the early morning.

How to look? Walk very slowly. They will not hear quiet conversation yet will feel footfall if it is heavy.

Snakes, including adders, are important parts of the ecosystem. Unless actively disturbed they avoid humans and dogs.

Grass snakes have a yellow collar just behind the head. They have no eyelids and are ‘cold blooded’ – that is their temperature is not internally controlled. So, it can be above or below the surrounding temperature.

The Grass Snake, Natrix helvetica

The UK’s longest snake at nearly a metre.  

Grass snakes are found throughout England and Wales and are most likely seen in wet locations. Around Andover the River Test is a good location and especially the Longstock Water Gardens (John Lewis). There are also reports of these animals from Stoke and along the A303. The Salisbury Water Meadows was a good site and I have spotted them swimming in the River Avon.  

Feeding primarily on fish and amphibians, grass snakes can occasionally venture into garden ponds in the summer months, particularly in rural or semi-rural parts of the south. They are not to be feared.

Grass snakes are non-venomous and are extremely timid, moving off quickly when disturbed. If cornered they can feign death, and if handled frequently, produce a foul-smelling excretion. This excretion happened to me as I saved a large animal from my polecat’s attention. My hand and clothes stank for a week, but I soon released the grass snake unharmed.

Female grass snake with a clutch of leathery eggs.

Grass snakes are Britain’s only egg-laying snake. Females lay eggs in June or July, normally in rotting vegetation (including garden compost heaps) which acts as an incubator. The eggs hatch into miniature versions of the adults in the late summer months.

All snakes are protected by law. Observe them and leave them alone.

Smooth snake

The Smooth Snake, Coronella austriaca

I have not seen one actively in the wild. It is a rare animal and a heathland specialist. They also are infrequent baskers, so attempting to spot one is an unrewarding task!

Smooth snakes usually emerge from hibernation in April-early May. They are non-venomous and feed mainly on common lizards, slow-worms and small mammals (especially shrews and nestling rodents), which are captured and constricted in the coils of its body. Live young, which look very similar to the adults, are born in September. Smooth snakes are long-lived and females tend not to breed every year. The smooth snake is a secretive animal and when it basks in the sun it does so entwined amongst the stems of heather plants, where it is superbly camouflaged.

As with all UK snakes, the best location to view them is at The Reptile Centre in the New Forest. There you should see all the types in their large outdoor enclosures.


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