What’s Black and White and One of Earth’s Rarest Bears?

Legend says supernatural forces turned the Kermode bear’s coat white. Science says a gene mutation put white fur on the black bear species.

By Patricia Edmonds
Published 21 Nov 2017, 11:13 GMT
Photograph by Paul Nicklen, National Geographic Creative

For millennia the Kitasoo native people on Canada’s Pacific coast have known this bear and its legend. As the elders tell it, Raven the Creator had turned Earth from a frozen rock into a green garden. But as a reminder of the ice age, he caused every 10th black bear to be white. The formal name is Kermode bear. Locals call them ghost, or spirit, bears, and some believe they’re sacred or supernatural creatures.

There is science, not just folklore, behind several of the spirit bear’s traits.

By genus and species, it’s an American black bear. But if both parents (no matter their colour) have the same mutation in a gene that affects pigment production, their offspring will have white fur. To confirm this, researchers used wire snares to collect samples of bears’ hair, then analysed the DNA. Of 220 bears, 22 had inherited the recessive white-coat gene from both parents—and all 22 were white.

Mating season lasts from May through July. As in all bear species, fertilised embryos delay implantation in the female’s uterus. If a sow isn’t vigorous enough to sustain a pregnancy, embryos won’t implant and she’ll bear no cubs that year. But if she’s healthy and strong, the embryos will implant in the fall and a one- to five-cub litter will be born that winter.

In this matter the spirit bear uses its white magic. To store fat for winter, the bears spend fall days gorging on salmon. According to a 2009 study, during daylight the fish are twice as likely to evade the grasp of a black predator as a white one, faint as a ghost against the pale sky.

This story appears in the December 2017 issue of National Geographic magazine.(Learn more in National Geographic magazine’s 2011 feature article “Spirit Bear.”)


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