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Malevolent or Just Misunderstood?
- Madeleine H
- Apr 26, 2020
- 6 min read
As the UK's only venomous reptile, the Adder is often wrongly perceived as dangerous. However, this is one of the many misconceptions that surround this shy reptile.
The adder (Vipera berus) belongs to the viper family and is one of the three species of snake found the UK. This small stocky snake inhabits woodland, heathland, and moorland. Its shy and secretive nature, and its excellent camouflage, means this species is rarely seen. Adders live up to 15 years old. Their main predators include birds of prey, such as buzzards, and crows. Despite widely distributed across the UK, the adder is currently facing declines in central England, making the conservation of this species a high priority.
Where to Find Them:
Adders are distributed all across England, from the south coast to the far north in Scotland, and is the most northernly distributed member of the viper family. Its range even extends to the Arctic Circle in Scandinavia! However, adders are not present in the Isles of Scilly, the Channel Islands, the Isle of Man, Ireland and Northern Ireland.
How to Identify Them:
Adders grow between 60 - 80cm in length and have a stocky build. Their heads are large and the snout is typically raised to form a low ridge. Adders can easily be identified by the dark zig-zag stripe along their backs. Rows of dark spots can be seen along their sides. Adders are also easily distinguished by their red eyes and slit pupils. Colouration can vary from grey-white in males to brown or copper in females. Colouration in juveniles also varies from copper, light brown and reddish with dark markings. Melanistic (black) colour variations also occur in some areas, giving the adder it's alternative name, the "black adder". These melanistic individuals are typically female!
Adder Diet:
Adders use their venom to immobilise prey. Their dietary composition is dependent on the availability of prey; however, they mostly predate upon small mammals. They have also been known to eat lizards, nesting ground birds, and amphibians, such as frogs, newts, and salamanders. Juveniles predate upon juvenile mammals, small lizards, frogs, and invertebrates, such as worms and spiders. At 30cm in length, juveniles begin eating similar diets to adults.
Adder Lifestyle and Reproduction:
Adders are mostly diurnal, however in some regions they can be seen at dusk during warmer summer months. This terrestrial species has also been known to climb steep embankments and low bushes to bask and hunt. Like other reptiles, the adder is ectothermic, meaning it is dependent on external heat sources, such as the sun, to maintain its body temperature.
Adder hibernate during the winter months, from October to March, in abandoned mammal burrows. Despite their solitary nature, many adders will actually hibernate together. Adders will return to the same hibernation site each year. Juvenile adders are also known to return to the place they were born to hibernate.
Adders mate at the end of April and beginning of May. Adders have also been observed matting in June and early October, however it isn't known whether autumnal mating yield any offspring. Female Adders breed once every two years; however, this can sometimes be limited to once every three years if seasons are short and the climate is not suitable.
Adders have a very good sense of smell, which the males use to locate females during breeding season. Males can travel hundreds of meters a day to find a mate. Adder courtship involves a side-by-side "flowing", tongue flicking along the back, and lashing of the tail. Mating pairs will stay together for a couple days after mating. Males engage in combat to compete for females, which often entails similar "flowing" movements as courtship, before progressing into a "dance". During this dance, males will rise vertically and sway, whilst attempting to push their competitor to the ground. These dance battles continue until one of the males gives up. Typically, the defending male is so aroused by courtship, he won't give up his mate and consequently rarely loses.
Unlike most snake species, the adder is viviparous, meaning it gives birth to live young. Female adders typically give birth between August and September; however, they have also been known to give birth as early as July and as late as early October. Clutches have between 3 -20 juveniles. Juveniles are born still in their amniotic sac, which they must break themselves. Sometimes, this can happen whilst they are still inside the female. Juveniles are between 14 and 23 cm in length at birth and shed their skins for the first time a couple days after being born. Juvenile adders are also born with fully functioning venom and fangs. Female adders do not care for their offspring; however, the young are known to spend their first several days of life close to their mother.
Adder Venom:
As previously mentioned, the adder is the UK's only venomous snake. The adder has hinged fangs which it used to kill its prey. The fangs lie against the roof of the mouth, allowing them to grow quite long. It should be noted though that adders are an unaggressive species, and are actually very timid. When startled, adders will typically disappear into the undergrowth. Most bites from adders occur when the animal is cornered or alarmed. People are most frequently bitten when attempting to handle an adder or when accidently stepping on one. Sometimes adders, typically pregnant females, will make their presence known by loud sustained hissing as a way to deter aggressors. Threatened adders will draw their body into an S-shape, commonly known as the striking position.
Adder Bites and Treatment:
Adder bites are most typically seen in domestic animals, such as dogs, and occasionally livestock. Nevertheless, under 5% of bites to dogs lead to death. Bites from this species are of relatively little danger to humans. In 70% of bites there is very little envenomation, resulting in just local swelling of the bite and pain. It is estimated that in one third of adder bites, no venom is injected. Despite opposing very little danger to humans, people with pre-existing health conditions, small children and the elderly are more likely to have a serious reaction to an adder bite. Nevertheless, the majority of people bitten by adders recover quickly, and it's very rare that a bite would result in death. There have been only 14 deaths from adder bites since 1876. In recent decades, treatment of adder bites has been drastically improved and eight antivenoms are available.
Adders in Your Garden:
Adders have been known to enter gardens if suitable adder habitat is nearby, however they are typically rare in urban areas as gardens do not provide the right habitat type needed for adders. Most adders spotted in gardens are just passing through and don't stay for long. As previously stated, adders oppose little threat to people and seldom bite, so you needn't worry if there is a snake in your garden. Additionally, most adder sightings in gardens are usually grass snakes or slow worms that have been misidentified. If there is an adder in your garden, leave it be and do not attempt to remove it. Occasionally the removal of an adder from a garden is warranted if there is a high risk to vulnerable people. Furthermore, it is very rare for adders to enter houses and only in these cases should a very experienced person carefully remove the animal to a safe place.
PLEASE NOTE: adders are protected by the Wildlife and Countryside Act 1981 meaning it is an offence to deliberately kill, injure, harm and trade them. Additionally, adders are further protected by the Bern Convention.
Adder Population Declines:
The adder is a UK Biodiversity Action Priority Species. Despite ranked as Least Concern on the IUCN Red List of Endangered Species, adder populations are facing widespread declines, and it is estimated that populations will be restricted to just a few areas within the next 20 years. This considerably increases the adder's risk of extinction. A study conducted by the Amphibian and Reptile Group found that 90% of the 260 survey sites supported very small populations of adders, and these small populations were further declining. Most of these small populations contained fewer than 10 individuals, which can lead to inbreeding, resulting in lower genetic and reduced physical fitness of offspring.
The main threats to adder populations are disturbance caused by the public, habitat mismanagement and fragmentation. Loss of hibernation sites also threaten adder populations as individuals return to the same hibernation site each year. Additionally, the management and mowing of grasslands leaves adders more exposed and vulnerable to predators. Aspects of the adder's ecology suggest it is less adaptable to anthropogenic environments than other British snakes, such as the grass snake, and thus require more considerable conservation prioritisation.
Current Conservation Action and How You Can Help:
The Amphibian and Reptile Conservation Trust are strongly working towards the conservation of these amazing animals though habitat management and surveys. The organisation is currently working on mapping adder hibernation sites to guarantee sufficient conservation of these sites. Additionally, ARC Trust are also collaborating with landowners to encourage adder-friendly habitat management, and set up regional projects to improve the connectivity between adder populations.
You can get involved with adder conservation by volunteering with your local wildlife organisation, such as ARC Trust, ARG and the Wildlife Trusts. Many of these organisations host events and volunteering opportunities where you can learn more about British wildlife, including adders! If you see an adder, report your sighting to ARC Trust to improve the dataset on adder distribution! You can also further help adders by taking part in the Amphibian and Reptile Group's citizen science project, "Make the Adder Count" by reporting your adder sightings.
Want to take part in "Make the Adder Count"? Here's the link www.recordpool.org.uk/make-the-adder-count or alternatively, contact Angela Julian at: info@arguk.org.
Want to learn more about adders? Check out this useful booklet made by the Amphibian and Reptile Conservation Trust! https://www.arc-trust.org/Handlers/Download.ashx?IDMF=82f988ea-533b-4cd5-b50d-7305c4865128
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