Arctic Ground Squirrels are perfectly adapted to life in the cold. They hibernate for eight months, allowing their body temperature to drop to minus three degrees. Other mammals would not survive that, because at this temperature the blood actually freezes and deadly ice crystals form in the body. But the almost 50 centimeters large croissants form proteins that prevent this. They only breathe once a minute, and even in this almost frozen state, they make it Animals nor to produce enough heat so that their body temperature does not drop any further. In their icy hole in the ground, the temperature can drop to almost minus 20 degrees. The squirrels wake up twice a month to check if their brains are still working. They then freeze again until spring when they emerge from hibernation and emerge from their burrows to mate.

A study just published in Science Journal Science has appearednow shows that climate change is causing the sophisticated adaptation of animals to the extreme living conditions in the Arcticthat has worked well for centuries: with major implications for the animals themselves and possibly other species as well.

For their study, scientists led by Helen Chmura from the University of Alaska Fairbanks combined long-term measurements of ground and air temperatures with information about the body temperature of the ground squirrels during hibernation, which they had recorded with the help of so-called biologgers. All data was collected over a period of 25 years at the two research stations Toolik and Atigun.

The females want to mate, but the males are still asleep

The study shows that the permafrost soil freezes more slowly in autumn due to climate change and thaws earlier in spring. “Combined, this resulted in the ground being 10 days less frozen per year at the end of the study period than at the beginning,” writes the group in Science. The minimum ground temperature rose by almost two degrees Celsius every ten years. The ground squirrels, which overwintered in frozen sleep, responded by turning on their internal heating later and later: “There was a delay of about 15 days per decade,” the researchers write.

At first glance, the warmer arctic winters don’t seem to have any disadvantages for the ground squirrels. On the contrary: they use less energy and may even increase the likelihood of waking up from their half-frozen state in spring unscathed.

However, the warming also meant that the females ended their hibernation at the end of the study ten days earlier than at the beginning. Curiously, the males, on the other hand, did not adapt to the changed environmental conditions: They continued to slumber comfortably, as they had always done.

According to the authors of the study, this “mismatch” can have significant consequences “for the population dynamics of Arctic Ground Squirrels and the function of the food web in the Arctic”. To put it simply, the animals probably have fewer offspring because males and females no longer meet as a matter of course at the beginning of spring. At first, the females who are ready to mate do not find any males because they are still sound asleep. And when the males have finally woken up, it may be that the females are tired: they are only ready to mate for a relatively short period of time.