January is the coldest month of the year in Montana. The warmest we can typically hope for is a temperature in the low 30s.

Luckily for wildlife in Montana, they have ways to stay warm.

Take the river otter for example. This small mammal, which will weigh from about 10 to 30 pounds, actually goes swimming in the cold water during the winter. On some winter days, though, the water is probably warmer than the air.

Otters are a member of the weasel family. While swimming in rivers, creeks and lakes they’re looking for food like fish and crayfish. They can swim at speeds up to 15 mph when they want to catch a fast-moving fish. While hunting underwater, or just swimming, they can hold their breath for two to three minutes.

To stay warm in such cold water, the otters’ fur has long strong outer hairs – called guard hairs. The guard hairs are hollow and have scales, almost like a snake’s scales. They help keep densely packed finer hairs – called underfur – dry. The underfur has a scaly surface also, which helps them lock together to keep out water.

The otter’s hairs are also very oily, which makes water slide off instead of soak in. The oil comes from a gland next to the base of the hair in the otter’s skin. They can also fluff up their fur when they get out of the water to trap air between the hairs. The trapped air can help insulate them from the cold, as well.

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Otters have to rely on their hair to keep them warm because they don’t have a thick layer of fat for insulation, like a lot of other animals, and they can’t build a campfire like you or I would to warm up.

Otters are fun to watch because they look so playful, piling on top of each other, sliding down snowy hills on their stomach and popping their heads up out of the water to see what you are up to. They are also a sign that the water is clean.

Keep an eye out for otters the next time you are near a river, creek or lake, and keep in mind the special way they stay warm in the cold of winter.

— Brett French, french@billingsgazette.com

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