Warm November temperatures disrupted the sleep schedule of male brown bears in Siberia.
Some of the animals are even wandering around the Amur Region in Russia in a "half-asleep" state, as they've adequately prepared for hibernation but have yet to enter their season-long sleep because of unnatural environmental conditions.
The Department for the Protection of Wildlife of the Amur Region said that abnormally high temperatures in October and November caused the interruption. October temperatures exceeded the average by up to 2 degrees Celsius, or 3.6 degrees Fahrenheit.
The heightened temperatures are delaying the bears' hibernation, the department said in a translated Telegram post on November 20, as is melting snow, which causes wet dens that are unappealing to the bears.
"Warm November prevents bears from sleeping in the Amur region," the post said. "In some areas, half-asleep bears still walk near the dens. They no longer need to eat fat for the winter [most normal bears have long been ready for hibernation], but they are also prevented from finally going to bed by the 'indecently' high air temperature to their taste."
Bears suppress their metabolism during hibernation, although they can continue daytime activity in the early winter months by elevating metabolism while on the move and then slowing it as they rest, according to a LiveScience report. The drowsy bears are likely already in their reduced-metabolism state while not yet entering their winter slumber, Oivind Toien, a zoophysiologist and research assistant professor at the Institute of Arctic Biology at the University of Alaska Fairbanks, told the outlet.
November temperatures in the region are typically below freezing, and the above-average temperatures made for unappealing sleeping environments.
"Temperatures above freezing in wet snowy conditions could cause melt-water to enter dens [and] that could make it uncomfortable for bears to stay in," Toien said.
Newsweek reached out to Toien by email for comment.
Males are more affected by the unpleasant sleeping environment.
"Females with cubs do not face such a problem. These furry mothers took their fluffy offspring into their dens strictly according to the schedule—at the end of October. And no weather anomalies bother them," the Department for the Protection of Wildlife of the Amur Region said in its post.
The region experienced its warmest October on record, The Moscow Times reported, and is particularly susceptible to the changing climate, which affects Russia at a much faster rate than the rest of the world given its proximity to the Arctic.
Warm air in the spring triggers the end of hibernation, and an increase in temperatures by 1 degree Celsius can reduce a bear's hibernation time by several days, California radio station CapRadio reported.
The length of time a bear will hibernate varies according to species, the U.S. National Park Service said. Some species hibernate for only a few days, while species in colder climates hibernate for months. Hibernation allows the bears to withstand food shortages and cold temperatures during the winter months.
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Anna Skinner is a Newsweek senior reporter based in Indianapolis. Her focus is reporting on the climate, environment and weather ... Read more
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