How Birds and Mammals Survive Cold Winter Nights in Norway

Norwegian mammals and birds have many different methods of surviving long, intense winter nights. In a notice published on March 3, 2015, a biologist from the Norwegian University of Science and Technology (NTNU) University Museum reveals their secrets for survival. The author of the notice is Olav Hogstad, Ph.D., a Professor Emeritus at the Department of Natural History at the NTNU University Museum. Dr. Hogstad made the following comments on the survival of birds and mammals during Norway’s long, cold winter nights. For birds and animals that must live out in Norway’s frigid winters, every second has to be spent finding enough food not just to survive the day, but also the long hard night. Not every creature manages to survive — it is not uncommon to find frozen birds in birdhouses after a winter cold snap. Some creatures solve this problem by being inactive. Bears sleep and hedgehogs, bats, and the northern birch mouse all hibernate between October and April or May. But not every animal has this possibility. Surviving the cold is most difficult for small creatures— large mammals and birds can go up to several days without food. Small creatures tend to have a large surface area compared to their total body size, which means that their bodies loose heat quickly when the cold sets in. They also aren’t able to store as much fat, which means less insulation and more heat loss. Surviving is all about preventing this heat loss. Norwegian game fowl, including wood grouse, black grouse, hazel grouse, and willow ptarmigan, all choose to find shelter in snow caves or burrows at night, and when they rest during the day. Snow insulates very well, so these small caves are significantly warmer than if the birds were to sleep in the open.
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