BARROW, Alaska — Most Alaskans and Canadians have a bear story — tales of fearsome grizzlies, even polar bears. But a mix of the two?
They’re known as pizzlies or grolars, and they’re a fusion of the Arctic white bear and their brown cousins. It’s a blend that’s been turning up more and more in parts of Alaska and Western Canada.
Bears sharing both species’ DNA have been recorded several times over the past decade. So why are these two species linking up?
It’s called flexible mate choice: The bears are mating with the best possible partners as opposed to not mating at all, and they’re mating because they share relatively close territories and the same branches of the same evolutionary tree.
Intraspecies mixing between the two happened thousands of years ago, thanks to the advance and retreat of glaciers, and of late, it has been boosted by climate change. Scientists say it’s also probably been assisted by policies that protect both bears from culling and hunting, affording further opportunities for mingling.
The crossbreeds found in Alaska and Canada are not genetic anomalies. Scientists have found the mix in the islands off Southeast Alaska, where bears resemble grizzlies but contain polar bear DNA. That indicates decades of sporadic interbreeding, said Steven Amstrup, chief scientist at Polar Bears International.
The polar-grizzly cocktail is also far from the only recent animal hybrid. The coywolf — a coyote-dog-wolf amalgamation — and a lynx-bobcat mix have been popping up along the northern Atlantic coast. The concept is a romantic construct, an anthropomorphized take on nature. And what may be most surprising about this, researchers say, is the role interbreeding plays in the futures of endangered species — or, as the case may be with polar bears, accelerating their end.
Amstrup has studied bears in the Arctic since the 1970s. He, like other experts, characterizes this “new” bear relationship as more beneficial to grizzlies than polar bears. That’s because there are more grizzlies than polar bears and because grizzly territory is expanding while polar bear territory is contracting. What that adds up to is a good chance grizzlies could essentially dilute the polar bear population until it doesn’t exist at all, they say.
