A rare woodland sighting
Sightings of the shy and silent adder are rare, but more likely when they emerge from hibernation in early spring
On a fine day in Dorset, a solitary bee moves from bloom to gleaming bloom of a gorse bush in full flower. Its low drone underpins the birdsong ringing from the trees. A sandy trail leads through the mixed varieties of heather in this precious area of lowland heath. It is the perfect day for a walk and the sunshine, now beaming for approximately 12 hours a day, warms the skin. On a pale rock beside the path, an animal lazily absorbs the heat, its long body looped into a comfortable coil. Adders are very sensitive to vibrations in the ground and often slip off to a safe hiding place before they can be seen. To spot one on a walk is rare. This is a precious opportunity to observe one of only three snakes native to Britain, firsthand.
Identifying adders
The adder, Vipera berus, lives throughout much of England, Wales and Scotland, and is the only snake found north of the border. There are no snake species in Ireland. Its habitats include heathland, moorland and the edges of woodland. In recent years, they have begun to disappear from many central English counties, due to habitat loss. Numbers are hard to gauge, but the latest estimate is that there are
approximately 130,000 adders in the UK at the start of the breeding season, in April or May. Spotting one of these timid reptiles is a rare treat, but as they come out of hibernation in spring, there is a higher chance of an encounter. This is particularly so on sunnier mornings, when they may venture into the open to bask. The only venomous snake in Britain, adders are relatively small and stocky. Any encountered in March will almost certainly be male, as the females sleep for a full six months, awakening approximately four weeks later. Males range in length from 16-22in (40-55cm), while the females are slightly larger, at 20-27½in (50-70cm). Males are usually brighter, showing a greater contrast between light and dark, with dark brownish-black markings against a pale background. The females show brown markings against a duller brown background. However, they are notoriously variable and can appear in many shades of grey, rufous and brown. A few are melanistic, meaning they appear almost completely black. Usually though, the thick body, dark pattern along the back and noticeable inverted V-shape near the top of the head, make it easy identify the adder. Both sexes have a distinctively red eye with a vertical slit for a pupil.
Courtship and reproduction
Soon after emerging from hibernation, the adder dance begins. This is a striking sight. Both participants are male and each has shed its old skin to reveal a shining new garb of buffs and browns. When the two meet, they simultaneously rise from the
“Or is the adder better than the eel, Because his painted skin contents the eye?” William Shakespeare, The Taming of the Shrew
ground, swaying their heads and upper bodies rhythmically to and fro. Each pushes its head against the other, attempting to throw it off balance. They may chase one another across the ground at speed, covering a wide area. This goes on until one, often the intruder, slinks off, beaten and exhausted. Scientists once assumed that this ‘dance’ was a courtship display between males and females. However, it is now known to be a contest: one male defending its territory and the other trying to oust the incumbent. When female adders begin to emerge in April, they leave trails of scent behind them. This allows the males to track them, and they can often cover up to half a mile to catch up with their potential mate. Once the male has found a female, he slithers alongside her, trying to follow her every move. All the while, he flicks both his tail and his long, V-shaped tongue across her body until she is won over, and they mate. After coupling, he guards her for a few days to ensure that another male does not supplant him, then goes his own way. Adders are ovoviviparous, which means that the young grow inside an egg-like sac within the body of their mother and are nourished by a yolk. As soon as she ejects this sac from her body, the baby adders break it open and emerge, without any intervening incubation period. The newborn snakes are nearly 7in (17cm) long and often brick red in colour, sporting the same pattern as their parents. Female adders give birth between midsummer and late autumn, usually in August or September. They have an average of 10 young, sometimes as few as three or as many as 20. Once born, the youngsters must fend for themselves, though some stay close to their mother for a few days. Young adders often go straight into hibernation, usually in an abandoned burrow, without eating first. When they emerge the following spring, despite their relatively small size, they are able to catch, kill and eat prey as large as lizards. They will also take baby birds, frogs and spiders.
Reaching maturity
Unlike human skin, a snake’s skin does not grow as the animal does. Instead, a new layer of skin forms beneath the current one, which then peels away, leaving a shell, along and any parasites that may have been attached. Young adders shed their skin as many as three or four times a year. Before it happens, they change their appearance considerably, becoming duller in colour, with the eyes also turning milky as the scales are sloughed off. The old skin starts to break around the head or mouth area before peeling away from the body. When fully grown, adders usually shed their skin once a year, after hibernation. Once they have reached full size, adders prey mainly on small mammals, such as voles and mice, and the eggs and chicks of ground-nesting birds. They hunt by striking rapidly at their victim and holding it tight as they inject a lethal dose of venom from the sharp, hollow fangs on their upper jaw. The bones of its flexible, hinged jaws are able to move independently of one another, so the snake can feed on much larger prey than it could otherwise swallow. Their flexible ribs and strong stomach fluids help them to rapidly digest food, quickly becoming mobile again. However, once a snake has eaten, it may not feed again for days or even weeks. Adders are poikilothermic, or cold-blooded, and so need external warmth to heat themselves up before they can be active. On sunny mornings and evenings, they will often bask in the sunshine to warm their bodies. Even during the hibernation period from October to early spring, adders may be seen basking on warmer, sunny days, before going back to sleep when the temperature drops again. In March or April, they emerge, and the dance begins again, to create a new cycle of life. On an early spring walk, a fortunate few may have the privilege of seeing it.
“The world’s great age begins anew, The golden years return, The earth doth like a snake renew Her winter weeds outworn” Percy Bysshe Shelley, ‘Hellas’