During the mating season - late April - males wrestle for supremacy in a kind of dance, twining round each other and trying to force opponents' heads down. Once they have mated successfully, they move off to new sites, looking for further conquests. Females breed every other year: those that are now pregnant will find a good site where they can bask in the sun until they give birth in August. They abandon their babies as soon as they are born, and the young snakes - about five inches long, and thin as pencils - are left to fend for themselves, feeding on spiders, grass-hoppers and juvenile lizards.
Adders are not normally aggressive, but if threatened they go into a defensive coil and do not hesitate to attack.
In the New Forest alone some 20 or 30 people are bitten every year. Although rarely fatal, the venom can cause severe swelling: anyone who does get bitten should go straight to hospital for remedial injections.