Why Do Male Adders Dance? The Spring Combat Ritual Explained

What is the dance of the adders?

The dance of the adders is a ritual fight between two male common European adders (Vipera berus). It usually starts when a male guarding a female meets a rival. The two snakes move side by side, flicking their tongues, then raise the front third or so of their bodies off the ground.

Face to face, they sway, lean into each other and wind their necks and bodies together. Each male tries to press the other’s head and forebody down to the ground. When one is pinned, the snakes separate, rise again and start over. The movements are fast and flowing, which is why observers have long described it as dancing.

For centuries, people assumed the dancers were a male and female courting. Closer observation showed that both snakes are males, and that the “dance” is a contest of strength, not romance.

Why do male adders fight?

The fight decides which male gets to mate. In spring, males far outnumber receptive females at many sites, partly because females in many populations breed only every second or third year. A male who finds a female will stay with her, sometimes for days, and drive off any rival that follows her scent trail.

The dance lets males settle these disputes without injuring each other. Adders have strong venom and long fangs, and a real fight with bites could hurt or kill both males. A pushing contest, by contrast, tests size, strength and stamina, and the loser can leave unhurt to look for another female.

Studies of adders in Sweden have found that larger males tend to win these bouts. Another long-observed pattern is that the male already guarding a female very often wins against an intruder, perhaps because he is more motivated to keep his position.

Females, meanwhile, often mate with several males in the same season. Swedish research found that females mating with more than one male tended to produce more surviving young, which may explain why they do not simply stay with the first winner.

When and where can you see adders dance?

In Britain, the dance usually happens from about late March to early May. The timing follows a fixed order:

1. Males emerge from hibernation first, often in February or March, and bask near their winter dens for several weeks.
2. They shed their skin for the first time of the year, usually in April. Only then do they become fully active and start searching for females.
3. Females emerge a few weeks later, and males follow their scent trails, sometimes for hundreds of meters a day.
4. Rival males meet and dance, and mating follows, usually in April or May.

Farther north, in Scandinavia, the season is later and shorter, and mating is mostly in May. In some places, adders have also been seen mating in summer or early fall, but spring is the main season.

The dance takes place close to hibernation sites and spring basking areas, on heaths, moors and woodland edges. Lowland heathland in southern England, such as the New Forest and the Dorset and Surrey heaths, is among the best places to see it. You will need patience, a warm, still day and binoculars. See Where do adders live? for typical habitats.

Watch only from a path and keep well back. Adders are protected in Britain, and disturbing them at this stage wastes the energy they need for breeding. Never try to separate or handle fighting snakes; if someone is bitten, call 999 (UK), 112 (EU) or 911 (US) and seek emergency medical help immediately.

What happens after the dance?

The winning male stays with the female and courts her. Courtship involves the male lying alongside her, flicking his tongue along her back and making quivering movements of his body and tail. After mating, the pair often stays together for a day or two while the male guards her from rivals.

The female carries the developing young inside her body through the summer. Adders do not lay eggs; they give birth to 3–20 live young, usually in August or September. A female may then skip the following year’s breeding season to rebuild her fat reserves. For more on adder life cycles, see our article Do all snakes lay eggs?

Do other snakes do the same?

Male combat dances are widespread among snakes. Many vipers, including rattlesnakes in North America, perform similar contests, as do mambas, rat snakes and many other species. In each case, males wrestle without biting, and the stronger snake wins access to females.

Not all snakes fight this way. In many species, such as garter snakes, males compete by racing and scrambling to reach a female, sometimes in large “mating balls”, rather than by one-on-one wrestling.

Myths and facts about the adder dance

• Myth: the dance is a male and female courting. Fact: both dancers are males competing for a female.
• Myth: dancing adders are dangerous and attack anyone nearby. Fact: they are focused on each other and usually flee if disturbed, though they should always be left alone.
• Myth: the dance ends in a deadly bite. Fact: there is no record of males biting during these bouts.