And yes, snow accumulates on black bears at ambient temperatures below approximately 19 degrees F.
The temperature when this photo was taken was 9 degrees F, (-13 C). The last time it snowed was six days earlier. Her head is to the right, tucked under her chin. That is so she can breathe warm air onto her cubs that were born in mid-January. That's right -- right now is when the black bear cubs are making their first appearance on the Stage of Life. They will stay curled up in the warm fur of their mom, protected from the elements, and all snuggly. Mom wakes up to clean and cuddle, then drifts back into her winter sleep while the cubs burrow under her fur to find the milk-bar.
Black bears have two kinds of fur on their backs -- visible guard hairs about three inches long and, in winter, a hidden layer of fine underfur so dense that water can scarcely penetrate it. This underfur is so insulative that bears in the open become covered with snow when ambient temperatures are colder than about 18 F (-8C). The exact temperature at which snow accumulates varies with individuals. These coats not only keep the cold and wet away from the bear, but keep the bear's body temperature in. Under the snow, under the thick coat, they are warm and dry.
Some bears have longer, denser fur than others Body temperature also varies with individuals -- during hibernation, fat bears usually maintain a body temperature between 95 and 99 F, while skinny bears can reduce body temperatures to as low as 88 to ration fat reserves.
When out in the woods in winter, whenever I find one of these blow-downs or a big tangle of tree trunks, I am always on the lookout in case there is a bear in there. If they are covered with snow, that lovely white mound will contain a small breathing hole. And if you think you might have found one, keep away. Bears can (and do) wake up quite swiftly from hibernation if they need to, and they aren't happy about it.
Thank you Mike McIntosh, from Bear With Us Sanctuary, for the bear facts!!!