Adder

Adders are typically active during the day, when they hunt mainly for small mammals, including voles, shrews and mice. Lizards, young birds and frogs may also be taken (8). In warm conditions, adders actively hunt their prey, but they often use a 'sit and wait' technique. The adder strikes prey animals with its fangs to inject venom, it then releases the prey and follows the scent trail it leaves behind. Upon finding the dying or already dead animal, the adder begins to swallow it head first (3). Adders emerge from hibernation in March, with males emerging before females (3). For the first few weeks after emergence, they are fairly inactive and spend much of their time basking (8). After the males shed their skin in April they become more active and begin to search for mates by following scent trails. Females shed their skin a month later than males, and both sexes shed again later on in summer. Adders do not feed until after they have mated, and so during the time before mating, males and females live off fat reserves that they built up during the previous year (3). Upon discovering a receptive female, a male begins a courtship display in which he flicks his tongue over the female's body. The male and female may vibrate their tails briefly and bouts of body quivering may ensue. If the courtship is a success, copulation takes place, after which the pair may remain together for two hours or so. If another male approaches a pair at any point, the first male will defend the female aggressively, and a fight may result (3). These fights are known as 'the dance of the adders' as the males partly raise their bodies off the ground and may become entwined, often repeatedly falling to the ground and rising up again. More than two males may be involved in such a contest (4). Female adders reproduce once every two years and are 'viviparous'; they give birth to live young which are initially encased in a membrane (7). Towards the end of August or early September, the female will return to the site of hibernation, and give birth to 3-18 young. After giving birth they must feed intensively in order to build up sufficient reserves for hibernation (3). The young adders do not feed until the following year, but live off a yolk sac and fat reserves that they are born with. They reach sexual maturity at 3-4 years of age (3). Adders usually enter their hibernacula in September or October (3). Hibernacula are often the abandoned burrows of small mammals typically located on high, dry ground (8). A single hibernation site can contain around 100 adders (9). Although adders are poisonous, they are not aggressive and rarely bite humans or domestic animals, preferring to retreat into thick vegetation instead. Most adder bite incidents result when they are picked up or trodden upon, and in most cases they are not serious. The elderly, the very young or people in ill health are at most risk (3).

Although this species isn't threatened with extinction in Britain at present, the long-term survival of all our native amphibians and reptiles remains in the balance (3). Interest in reptiles and amphibians has increased massively in the last 30 years and there are now conservation charities dedicated to these fascinating and often overlooked species, such as the Herpetological Conservation Trust (5). The ecology and habits of the adder are well understood, and effective monitoring is in place. This will enable the status of the population to be tracked carefully, so that any future decline will be apparent and informed conservation action can take place. Although not classified as a priority species under the UK Biodiversity Action Plan (UK BAP), the adder is featured in a number of Local Biodiversity Action Plans. An important proposed action is to educate the public about this species to dispel the fears and prejudice surrounding it and reduce its deliberate persecution (5).

The adder is Britain's only venomous snake and is, as a result, a much-maligned species with a wealth of folklore surrounding it (4). Despite the public perception of this snake, however, it is a shy, timid and non-aggressive species (5). This stocky snake is easily identified by the dark zigzag line passing along the back bordered by rows of spots. A dark mark which takes the form of an 'X', 'V' or 'H' is located on the rear of the angular head and the pupil is vertical (3). Males are greyish, whitish, pale yellow or cream in colour with very dark contrasting markings, whereas females are typically a brownish or reddish colour with brown markings (2). Females also tend to be longer and wider than males, and have shorter tails. Male and female juveniles are reddish in colour (3). In all cases, the belly is grey, greyish-brown or bluish, and the throat is dirty yellow or white. Completely black (melanistic) adders arise quite frequently (3).

Found in a range of habitats including open heathland, woodland and moors. It requires sunny glades or slopes where it can bask and dense cover in which to take shelter (7).

In Britain the adder has a rather patchy distribution. It is more numerous in southern England than the north, is not common in the Midlands, but is fairly numerous in west Wales and southwest England. It is widespread in Scotland but is absent from the Outer Hebrides, the Central Lowlands and the Northern Isles (3). The adder has the widest global distribution of all terrestrial snakes; it is found from Scandinavia to central France, reaching as far east as the Pacific coast of Russia, and is the only snake to occur in the Arctic Circle (3). It is not, however, found in Ireland (6).

It is illegal to kill, injure, harm or sell adders under the Wildlife and Countryside Act, 1981 (3).

There is evidence that there was a decline in adder numbers in Britain in the 1960s and 1970s, which was most marked in southern England. In Europe the population has decreased by 25% in the last 25 years, and the species has an unfavourable conservation status (8). Habitat loss is proposed as the major threat facing the species. The open habitats it needs, including heathland, have been lost as a result of scrub encroachment, development, agriculture and afforestation. Remaining habitats are fragmented, causing isolation and problems with movement. A further threat is the persecution of this fascinating species by humans. Despite the legal protection afforded the adder by the Wildlife and Countryside Act, deliberate killings unfortunately still take place (8).