2/11/2016 8:01:37 PM
The Winter World of Polar Bears
Winter is a tough time for all northern species, but each have their own adaptations to the harsh conditions. For the polar bear's ancestor, the grizzly bear, the strategy is to curl up and sleep for the winter. Barren-ground grizzlies can spend up to seven months in a den: There's not much point in looking for food when there isn't any!
An Arctic winter brings more than just cold temperatures. The polar night is very long at high latitudes. By mid-February, twilight for a couple of hours a day is just returning to some parts of the polar bear's habitat, while other areas will stay blanketed in winter darkness until March. If you're a polar bear living on the southern edges of the range, you'll never see 24 hours of polar night, but the days are short.
It's hard to know just how challenging loss of light is for polar bears. They rely so much on their sense of smell that it may not be a big issue for them. The bears definitely have better night vision than we do; they have an abundance of rods in their eyes compared to humans.
Polar bears also have dichromatic vision, meaning they are most sensitive to blue-violet and yellow light. Humans have an additional cone that is sensitive to green light and thus we have trichromatic vision.
For polar bears, not being able to see green isn't likely a big loss, given where they live. Hunting ringed seals under the northern lights sounds pretty neat, but we know little about the winter ecology of polar bears because scientists aren't able to be out on the ice at this time of year. It's odd to ponder, though, that polar bears don't see the northern lights as we see them, as the lights are usually dominated by green. Polar bears would see the reds and yellows, but they wouldn't see the same display that we do.
Editor's note: Interested in seeing the northern lights? Check out the Northern Lights Cam on explore.org.