There are three species of snake in Sweden: the adder, the grass snake and the smooth snake. Only the adder is dangerous to humans, although the others can also bite.
The adder can live further north than any other snake, and is found in almost all of Sweden, except up in the mountains above the tree line.
Zigzag pattern and vertical pupils
The adder has a large, triangular head, and its tail is much narrower than its body. Males are usually grey with a black zigzag pattern along the back. Females are often brown or yellowish, with a darker zigzag pattern. There are also completely black adders that resemble grass snakes, but grass snakes almost always have a yellow patch on each cheek.
About the adderScientific name:
Usually up to around 65 centimetresSexual maturity:
The male reaches sexual maturity at 3½–4 years, and the female at 4–6 yearsBreeding season:
April–MayNumber of young:
Small rodents, but can also eat lizards, frogs and young birdsDistribution in Sweden:
The whole country
Another way to distinguish between adders and grass snakes is to look at their eyes. If the pupil is round, it is a grass snake, if it is narrow and vertical, it is an adder.
Body temperature follows the air temperature
Snakes are poikilothermic (commonly referred to as ‘cold-blooded’), meaning that their body temperature follows the air temperature. Dark bodies mean that they can be more easily warmed by the sun. Adult adders usually grow up to 65 centimetres long, but the longest adder recorded in Sweden was just over a metre long. In the spring, they spend three or four weeks basking in the sun and maintaining a high body temperature. The males then shed their skins, after which the breeding season begins.
Eats small rodents and lizards
Adders play an important role in nature, eating creatures including voles and mice. Their diet consists mainly of small rodents, but they can also eat lizards, frogs and young birds.
Smells with its tongue
A snake moves its forked tongue continuously to pick up scents from the air and water. The snake’s sense of smell is located in the roof of its mouth. Different levels of odour particles on the two tips of the tongue tell the snake where food and danger are.
Hibernates all winter
Adders can be found in different types of habitats, such as mossy ground, the edges of forests, road verges, and the edges of meadows and fields. They avoid dense forest, as they need a lot of sunlight.
Adders hibernate throughout the winter beneath the frost, in holes in the ground or in among rubble. A large number of snakes can hibernate in the same place, with up to a hundred snakes gathering in some places. They emerge in the spring, warm themselves up in the sun and shed their skins. Snakes shed their skin in order to grow. You can sometimes find the dry, empty skin on the ground around its hibernation site.
Eggs hatch inside the female’s body
After hibernating, they mate and then move on to their hunting grounds, which may be several kilometres away from their hibernation site. A pregnant female does not travel very far. Her eggs are warmed and hatched inside her body, and in August she gives birth to a dozen or so young, called snakelets.
Most likely to spot adders in the spring
The adder is the first Swedish snake to appear in the spring, and you are most likely to spot an adder in the spring sunshine when they have just emerged from their hibernation. Look for rocky, sunny southern slopes where the snow thaws early. Gravel ridges and boulder fields with large rocks and many holes make for good hibernation sites. If you are lucky, you may see many snakes basking in a small area. Later in the summer, adders are harder to find. They then move on to beaches and wetter ground. Adders are good swimmers, slithering at high speed along the surface of the water.
A protected species
All snakes are protected in Sweden. In the past, however, it was common to kill adders. School classes would go out to kill snakes on outdoor activity days! Today, however, we think differently. If you find a snake on your property, you have the right to catch it and release it a few kilometres away. Snakes have a fear of open spaces, so if you don’t want snakes on your property, keep the grass short and leave open space around the house.
The adder is classified as ‘Least Concern’ on the Swedish Species Information Centre’s red list.
THE VENOMOUS SNAKE
The adder has two fangs in its upper jaw. In each fang, there is a channel to a venom gland. The venom is used to stun or kill its prey: frogs, lizards, mice, voles, young birds and other small creatures. The snake has a keen sense of smell, and will slither deep into a vole’s burrow until it finds the vole. Then it strikes, and the vole scurries away for a while until it dies. The snake smells its way towards the vole and eats it whole. Snake venom also contains enzymes – chemical substances that help break down the vole in the snake’s gut.
The snake can also defend itself by biting. It does this if we accidentally step on it or knock it with our hand. However, the adder never slithers towards a human to attack. Rather, it slithers away or lies completely still to avoid being seen. There is a myth that young adders are more venomous than adult snakes, but this is not true – small snakes are less venomous than large ones.
Being bitten by an adder is very painful. It is said to feel like being hit hard on the thumb with a hammer. You should always seek medical assistance if you are bitten by an adder, even though it is extremely rare for an adder bite to be dangerous enough to be fatal. Around 200 people seek medical assistance for adder bites every year. In many cases, the snake has bitten without injecting any venom. Someone in Sweden dies from an adder bite roughly once every eight years.
The Swedish Poisons Information Centre can always answer questions in the event of an incident – call 08-331 231 or 112 around the clock.