According to the Bangor University led research, warming winters as a result of climate change poses a “substantial threat” to ectotherms, which are animals that rely on external heat sources, like the sun, to regulate their body temperature.

Researchers experimentally changed temperatures for the common wall lizard from a population introduced in southern UK during its usual hibernation period.

They were able to assess the effects of different winter warming regimes on activity, body condition, and oxidative stress, which is an imbalance between two different types of molecules called free radicals and antioxidants within life forms.

In humans, oxidative stress is thought to be involved in the development of cancer Parkinson's disease, and Alzheimer's disease. In animals, it’s linked to ageing, reduced survival, and reduced fertility.

The study published in the Journal of Experimental Biology and led by Miary Raselimanana a conservation biologist, examined lizards by exposing them to three treatments for 3.5 months, which were a typical cold winter, a constant mild warm winter and a fluctuating winter temperature.

Constant mild warming was found to significantly increase activity, whereas the fluctuating regime did not, suggesting the duration of a temperature change matters.

The constant mild regime showed a trend toward increased DNA damage as a result of oxidative stress.

Miary Raselimanana from Bangor University said, “Winter is warming faster than summer, posing substantial threat to hibernating ectotherms, whose physiology depends directly on environmental conditions. While the effects of active season warming are increasingly well-understood, the consequences of winter warming remain understudied. Research has largely focused on single, constant temperature regimes, overlooking the role of variable temperature. In addition to this, the specific warming patterns most disruptive to hibernation, their effects on winter activity, and the subsequent physiological consequences are poorly understood.”

Study supervisor Dr Kirsty Macleod, from Bangor University’s School of Environmental and Natural Sciences said, “Overall, our findings suggest resilience in the behaviour of common wall lizards to moderate winter warming. However, hidden costs at a molecular level could emerge under sustained mild conditions. We encourage integrating behavioural sensitivity and subtle physiological responses into models predicting species resilience to climate change. Our study highlights a previously unrecognised physiological vulnerability that merits further investigation.”