Adder (c) Tom Aspinall

The Adder (Vipera berus) is the UK's only venomous snake, and has a striking zig-zag pattern along its back. It is in decline nationally, so we're interested in knowing where its remaining strongholds are. In the Community Science project area, it is thought to be primarily found in the Eastern Moors of the Peak District; but your sightings could help us to fill in gaps in knowledge about where it can be found and the potential impacts of climate change on the species.



Confusion Species

Why We're Interested

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Ecology: Adders usually emerge from hibernation in March or April and mate in April or May. This is the best time to see them as males are conspicuous while they bask (warm up in the sun), look for females to mate with and compete with other males for dominance. After mating the animals disperse, and non-breeding females together with juveniles tend not to be very visible, spending most of their time in deeper vegetation during the summer.

Adders are usually found in heathland, moorland and open woodland (as well as sea cliffs and railway/road embankments). Females incubate their eggs internally and give birth to between 3 and 20 live young in August or September. Adults and young then prepare for hibernation. In November, they follow scent trails back to hibernation sites where they will often spend the winter in groups.

The main prey items of adders are small rodents, frogs, newts and lizards along with ground nesting birds such as skylarks and meadow pipits. Adders kill their prey by biting them and injecting their venom. They wait for their prey to die before swallowing them whole and digesting them. Adders themselves are preyed upon by birds of prey, such as buzzards, and members of the crow family and can be eaten by rodents when in hibernation.

Adders are currently declining in the UK due to human persecution and habitat loss or fragmentation. Improving the size, quality and connectivity of sites that are currently occupied could lead to an increase in population sizes and hence improve resilience as the climate changes.

In Great Britain, adders are protected by law: it is illegal to deliberately kill, injure or sell wild adders.


Adder male and female

  • Male adders (left) can reach up to 60cm in length and females (right) up to 80cm. Both sexes appear rather stocky.
  • Adders have a prominent zig-zag pattern along their back which is black in colour on males and dark brown on females. There is a similarly coloured X or V on the back of the head before the zig-zag starts, and often oval spots along the flanks.
  • The main body colour is usually grey-white in the male and brownish in the female, however on emerging from hibernation many males have a brownish or greenish appearance. Occasionally, all black individuals have been reported.
  • Both sexes also have a red eye with a vertically slit black pupil.
  • Adders slough (shed) their skin some weeks after emergence from hibernation and again in the summer, prior to this their eyes can appear quite blue as the eye scales start to detatch. After sloughing, the scale colour can be quite bright and shiny.
  • Juveniles are less than 20cm in length and reddish in colour.

Confusion species

There are a few similar species that could potentially cause confusion. Grass snakes are widespread in the UK. They are longer than adders and less stocky in appearance. They also lack the distinctive dark zig-zag pattern along the back (although they do have some dark markings along their sides). They have round not vertically slit pupils, and a distinctive yellow 'collar'.

Slow worms (not actually snakes but legless lizards) are shorter than adders (up to 40cm) and are shiny. Females are brown with dark sides and males are greyish brown. The only other native species of snake present in the UK is the smooth snake but this species is restricted to heathland in Dorset, Hampshire and Surrey.

The non-native aesculapian snake also exists in two known populations (Regent's Park in London and Colwyn Bay in North Wales).

Why we’re interested

Changes to climatic conditions could lead to a significant reduction in the distribution of adders across the UK.

This could possibly lead to them becoming restricted to north-east and north-west England, the Yorkshire coast and south-east and north-west Scotland if future greenhouse gas emissions are low; and even just north-west Scotland if future greenhouse gas emissions are high.

Data collected as part of this survey will be used to track whether the distribution of adders is changing over time, and whether the times they are seen through the year are changing.

Further information about adders and climate can be found in 'Climate change modelling of English amphibians and reptiles: Report to Amphibian and Reptile Conservation Trust (ARC-Trust)'.  


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