# Adder (*Vipera berus*) > The adder (Vipera berus) is Britain's only venomous snake, a stocky viper of heathland, moorland, woodland edges, and dunes across Europe and into Asia. It grows to about 60 to 90 cm and roughly 100 g, and is recognised by the dark zigzag stripe down its back. It slithers out to bask and hunt small mammals, lizards, and frogs. Its bite is venomous but rarely fatal, and adders live 10 to 15 years. - **Category:** Reptile - **Conservation status (IUCN):** Least Concern - **Range:** Heathland, moorland, and woodland across Europe and into East Asia, reaching within the Arctic Circle; the UK's only native venomous snake. - **Canonical page:** https://globalanimalguide.org/animals/adder/ - **Last reviewed:** 2026-07-16 ## Scientific classification - **Kingdom:** Animalia - **Phylum:** Chordata - **Class:** Reptilia - **Order:** Squamata - **Family:** Viperidae - **Genus:** Vipera ## Facts at a glance | Attribute | Value | | --- | --- | | Scientific name | Vipera berus | | Diet | Carnivore (small mammals, lizards, frogs) | | Habitat | Heathland, moorland, woodland edges, dunes | | Lifespan | 10–15 years | | Length | 60–90 cm (24–35 in) | | Venom | Venomous; bites rarely fatal to humans | | Conservation status | Least Concern (IUCN) | ## Appearance and identification The adder is a short, thick-set snake, usually 60 to 90 cm long and about 100 g, with a distinctive dark zigzag stripe running the length of its back. Colours range from silvery-grey in many males to reddish-brown in females, and some individuals are entirely black. A V or X marking often shows on the head, and the eyes have vertical, cat-like pupils typical of vipers. This bold dorsal pattern makes the adder one of Britain's most recognisable reptiles. ## Venom and its bite As a true viper, the adder has hinged fangs that fold back against the roof of the mouth and swing forward to inject venom in a rapid strike. The venom is designed to subdue small prey and is only mildly dangerous to humans; bites cause pain and swelling but are very rarely fatal. Most bites occur when a snake is trodden on or handled, and it will always try to escape first. Anyone bitten should seek medical advice, as reactions can occasionally be severe. ## Diet and hunting The adder is a carnivore that preys on small mammals such as voles and mice, along with lizards, frogs, and nestling birds. It hunts by ambush, striking prey with a venomous bite and then following the scent trail until the animal succumbs. After swallowing prey whole it may rest for days to digest. Young adders take smaller fare, including insects and slow-worms, until they are large enough for bigger prey. ## Habitat and behaviour Adders favour open, sunny habitats including heathland, moorland, woodland edges, and coastal dunes across much of Europe and into Asia. Being cold-blooded, they rely on the sun and are often seen basking on banks or paths in spring to warm up. They are shy and secretive, quick to slither away into cover at the first sign of disturbance. Over winter they hibernate communally in sheltered spots, emerging around March to bask and breed. ## Reproduction and lifespan Adders mate in spring, when males perform a swaying "dance" as they wrestle rivals for access to females. Females give birth to live young in late summer, producing a litter of roughly three to twenty, rather than laying eggs. This ability to incubate young inside the body helps the species breed successfully in cool northern climates. Adders can live 10 to 15 years, though females often breed only every two or three years. ## Conservation status Globally the adder is listed as Least Concern by the IUCN, but in Britain many local populations are declining and fragmented. Loss and disturbance of heathland, intensive land use, and the isolation of small colonies are the main pressures. In the UK the species is legally protected against being killed or injured. Sympathetic habitat management and the linking of isolated sites are key to reversing local declines. ## Frequently asked questions ### How dangerous is an adder bite? An adder bite is venomous but rarely dangerous; it causes pain and swelling and is very seldom fatal to a healthy adult. Anyone bitten should still seek medical advice, as some people react more strongly and children and pets are more vulnerable. ### How do you identify an adder? Look for a short, stocky snake 60 to 90 cm long with a dark zigzag stripe running down its back and vertical, cat-like pupils. Males are often silvery-grey and females reddish-brown, and a V or X mark frequently appears on the head. ### What do adders eat? Adders are carnivores that hunt small mammals such as voles and mice, as well as lizards, frogs, and nestling birds. They ambush prey with a venomous bite and then track it down before swallowing it whole. ### Where do adders live? They inhabit heathland, moorland, woodland edges, and coastal dunes across Europe and into Asia. As Britain's only venomous snake, the adder is often found basking in open, sunny spots in spring. ### Do adders lay eggs? No. Adders give birth to live young, with a female producing a litter of around three to twenty in late summer. Incubating the young inside the body helps them breed in cool northern climates. ### How long do adders live? Adders can live 10 to 15 years in the wild. Females often breed only once every two or three years, so populations recover slowly from losses. ## Sources - [IUCN Red List — Vipera berus.](https://www.iucnredlist.org/search?query=Vipera%20berus&searchType=species) - [Animal Diversity Web — Vipera berus. University of Michigan Museum of Zoology.](https://animaldiversity.org/accounts/Vipera_berus/) - [Wikipedia — Adder.](https://en.wikipedia.org/wiki/Adder) --- Source: Global Animal Guide (https://globalanimalguide.org/animals/adder/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.