Adders in winter: hibernation and emergence

3 February 2025

Blog by Henry Barrett, Conservation Officer

It’s wintertime in the North Pennines. The landscape is as starkly beautiful as ever and often adorned with a pristine blanket of white snow. As we rise for work on dark mornings and stoke the fires to warm our homes at night, it’s difficult to imagine the coming spring. Soon, however, the ice and snow will thaw and we will once again start seeing some of our favourite species. Hares will box, curlews will whistle, lapwings will flop through the sky, and the adders will be basking – gathering their strength for courtship and the coming summer of activity.

In any given year, the time at which adders emerge from hibernation will vary. Typically in the north of England, this will be around March. If you are lucky, you may come across several male adders lying out in close proximity at this time of year. This generally indicates that you are close to the ‘hibernaculum’ (a place of hibernation). The males emerge from the hibernaculum first in order to gather strength for their ritual dance – a combative show which rarely escalates to violence. The dance aims to win the opportunity to mate with a female as soon as she is in breeding condition. The females, when they emerge, will accept only the most impressive suitor, though polyandry (females accepting more than one male) has been recorded, with some clutches of young snakes reportedly sired by multiple males (1).

In a changing climate, it is unclear how the life cycle of this already vulnerable species will be affected as average temperatures rise. Adders are extremely site faithful and tend to use the same hibernaculum year after year. Given the limited ability of adders to disperse through the landscape, these sites are of great importance for the conservation of our many small, isolated populations. Locating these features is the first step towards protecting them. This can be followed by targeted habitat management or creation works which aim to increase connectivity between populations, supporting genetic mixing and improving the resilience of this species in our landscape.

If you do find adders early in the spring (or at any time of year), we would like to hear from you. Please submit all sightings to iRecord or email Henry Barrett.

If you are interested in joining our effort to conserve this wonderful species – why not attend one of our survey training events? Data collected by volunteers is vital and helps to inform our conservation work. A range of volunteering opportunities can be found via the events page of this website.