Introduction and Identification
The Common Adder (Vipera berus) is a member of the Viperinae family and is Britain’s only venomous reptile. They are relatively short and fat compared with our other common snake, the grass snake (Natrix helvetica), growing up to around 70cm. Adders are very distinctive thanks to the bold zigzag pattern along their dorsal side. Males are usually grey with a black zigzag, while females are usually brown with a darker brown zigzag. However, adders come in a range of colours and shades and entirely black (melanistic) adders are not uncommon. Juveniles are usually brick red. Unlike other native snakes in Britain they have vertical pupils; a distinguishing feature of adders.
Habitat
Adders can be found in a range of habitats. They are commonly associated with open heathlands and commons, as well as moors and chalk downs. Adders are also found in open woodland or woodland rides where sunlight is able to penetrate the canopy, enabling adders to bask. South facing road and railway embankments are also good places to spot adders.
Distribution
Absent from Ireland, this species is widespread across mainland Britain except for some areas of the Midlands, Merseyside and greater London. Adders can live at altitudes of up to 1000m in upland areas of Scotland. Some of the best places to see adders are the heathlands in the south of England.
Feeding
Adders have a variable diet of voles, most commonly field vole (Microtus agrestis), mice, eggs, amphibians and even lizards. As adders are venomous, to catch their prey they first bite the victim, injecting venom into the prey. The snake then follows its prey’s scent trail, tackling it after the venom has taken effect. However, the venom is relatively mild and a mouse can still travel some distance before it collapses.
What Do Adders Get Up to Throughout the Year?
October to March: Adders are most likely to be seen basking in the sun outside their hibernation sites in autumn and spring, either side of their main hibernation period from October to March. During this time, they stay inactive underground, often hibernating in groups within disused animal burrows. As the animals are inactive while hibernating, they are vulnerable and have been known to be eaten by rodents!
February to March: After surviving their winter underground, adders often spend their first few weeks above ground in groups. Males will shed their skin ready for the breeding season and mating will occur approximately one month after emerging from hibernation.
On warm days, males will wrestle each other in order to win access to females by attempting to drive away the smaller male. This display is called the ‘dance of the adders’ where the males can cover large distances at great speed. Often the adders will raise themselves off the ground in an attempt to overpower each other.
April to September: By now the communal gatherings of adders will have dispersed. Adders spend the summer months living alone. Pregnant females will spend these five months fasting for reasons which are not properly understood.
September: The female adder usually reproduces once every two years. Pregnant females give birth to about 10 young, usually using the female’s previous hibernation site. Adders are viviparous which means they don’t lay eggs but instead give birth to live young. Juveniles are approximately 16cm and survive on the yolk sac and fat reserves they were born with, not feeding on live prey until the following year. Females feed continuously to gain sufficient reserves for hibernation.
September to October: During the autumn, adult snakes follow scent trails left by other adders to find their way back to their hibernation sites. Hibernation sites are usually used by many snakes over several years. Young adders tend to hibernate in the area where they were born. Their survival depends partly on the severity of the weather in the following winter but also on their ability to find sufficient prey in the months leading up to hibernation.
Are Adders Dangerous?
Adders are not aggressive animals by nature. They are shy and cryptic and will usually move away if approached by humans. In most cases, they feel the vibrations of an approaching threat and quickly disappear. Adders very rarely bite people, and if they do it is only ever in self-defence or after being provoked. Usually, this is because a foolish human has decided that they know best and have tried to pick up the terrified adder! Although not life-threatening, a bite from an adder can be serious. Medical attention should be sought immediately in the unlikely event you are bitten. Although not lethal to humans, adder venom is powerful enough to kill a dog. Dogs should always be kept on a lead in areas where adders could be present.
Population Trends
The absence of adders in much of the Midlands in England and their overall population decline is thought to be largely due to increased human disturbance, habitat loss, habitat fragmentation and persecution through public misunderstanding of the species. The release of game birds such as pheasants is thought to negatively impact reptile populations.
In light of their decreasing populations, adders are protected under the wildlife and countryside act (1981). Thanks to an increasing body of knowledge of the species (and other reptiles) through the work of conservation and local wildlife groups, adders are increasingly better understood as a species which can ultimately help us work with the wildlife and protect their populations.
Take a look at the video below for more information on adders!
Back to our Reptile Species Guides
Grass Snake Smooth Snake Slow Worm Sand Lizard Common Lizard
Our ecologists have extensive experience in surveying and designing mitigation for reptiles and can advise you on survey methodology, legal protection, mitigation options and the timing of development works.
For more information about the Ecology Services, we can offer, call us on 029 2065 0331 or contact us on info@acerecology.co.uk.
