Zoologists going down to the woods today are in for a big surprise as bears across the globe are waking up unseasonably early due to warmer winters, the most recent of which was one of the hottest on record. Both captive and wild bears in Russia, Finland, and the UK have been coming out of hibernation early, with some populations never starting hibernation at all.

Hibernation is an annual event for bears. The long sleep over the winter months allows them to wait out the harshest conditions when food is scarce. During hibernation, their metabolism will slow alongside their breathing, heart rate, and physical activity, enabling them to conserve precious fat stores. The exact length of hibernation varies from animal to animal and bear to bear, but it comes to an end when spring arrives, bringing with it warmer temperatures and more plentiful food sources.

In Russia, workers at the Moscow Zoo are expecting the residents of their onsite bear enclosure to emerge four weeks earlier than the year before, as warm temperatures have roused their two Himalayan bears and one Kamchatka brown bear.

In a statement reported by The Moscow Times, Moscow Zoo’s CEO Svetlana Akulova said their zoologists were expecting an early arrival due to the abnormally warm winter. Spikes in their activity indicated to zoo staff that they’d be making an appearance far sooner than is normal, with an expected late-March arrival. Both Kamchatka brown bears and Himalayan bears usually emerge in late-April or May.

The trend is spreading across the continent. Further to the south of Moscow, bears at Voronezh Zoo have already made their “spring” appearance, and to the east hunters in Kirov region have seen a wild bear roaming the forests. This isn’t the first time disruption has been reported in the annual hibernation behaviors of bears in Russia. In 2019, the warm winter meant brown bears in Siberia never went into hibernation and the same effect was seen with hundreds of bears in a Southern Russia nature reserve during the winter of 2018.

Similar impacts from the unseasonably high temperatures have been reported from the Korkeasaari Zoo in Helsinki, Finland, whose resident bears woke up after a brief hibernation of just two months, making their first appearance in February of this year.

Elsewhere in Europe, three European brown bears at ZSL Whipsnade Zoo, England, have made a brief appearance for the first time in February after beginning their hibernation last November. Whipsnade Zoo bear keeper Felicity Ball said in a statement, “They enjoyed the February sunshine for a good 20 minutes before heading straight back to their den for another nap, so they’re obviously not quite ready to be fully up and about yet – when bears come out of hibernation they tend to hit the 'snooze button' a few times, just like some of us in the morning.”

The early emergence of bears across the globe provides further evidence of the impact of climate change on animals’ biological rhythms. Captive bears waking early can have their diets supplemented, with staff at the Moscow Zoo reporting they will start their bears on small portions of berries and fruits before moving on to larger portions including meat. Wild populations, however, will need to fend for themselves, which could prove difficult if native plant species haven’t begun fruiting or cold snaps return between now and the arrival of spring.