Ussurian tube-nosed bats spend the coldest months in snow-covered dens—the only mammal species known to do so besides polar bears.
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A surprising creature lies inside these snow holes in Japan. The golf ball-sized fur balls are Ussurian tube-nosed bats. Scientists have determined that the bats hibernate in snow dens—the only known mammal to do so, besides polar bears. But, unlike polar bears, these bats are not insulated by heavy fur and fat layers. To survive winter, the tiny mammals drastically lower their body temperatures and heart rates, to minimize energy use.

Previously, it was unknown where the bats spent the sub-freezing winter months. After years of observation, researchers now believe the bats hibernate in cylindrical or cone-shaped holes under the snow. Thermographic images show the bats rapidly increasing their body temperatures before taking flight. They fly away soon after the snow starts to melt and the dens become exposed. The bats may hibernate in snow because it offers protection from predators, easy access to water, and thermal insulation.

Read more in “These Bats Make Tiny Igloos to Survive the Winter”

Watch Rare Video of Bats Hibernating in Snow Dens | Nat Geo Wild

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