Climate Change Fallout: Genetically Inferior Hybrid Grizzly-Polar Bears

As the planet warms, these inter-species meetings will only become more prevalent.
"Life's taken a grizzly turn, okay, pal." - Polar Bear, thoughts on hybrid bears. (Photo: Mark Sullivan / Getty Images)
Aug 3, 2012· 2 MIN READ
The director of the Public Trust Project, Alison Fairbrother has written for Grist and Politics Daily, among others.

If you bookmarked this aww-inducing video of polar bear cubs getting a boost from their loving mama, or spent hours pouring over footage of grizzly bears snacking on salmon, you may be interested to know that there’s a new bear in town.

A hybrid of two of the most ferocious bears on earth: half grizzly, half polar.

Sightings of hybrid bears in the wild are becoming increasingly common, and scientists now believe that hybrids are the result of climate change in the Arctic—the polar region at the top of the world that is fast turning to slush.

MORE: Palm Trees Coming to the Antartic? Blame Climate Change

Grizzlies, which dominate Alaska and parts of Canada, are moving northward as melting ice and milder temperatures in the Arctic enable them to travel further into the realm of their northern cousin, the polar bear.

Just a few decades ago, sightings of grizzlies in the Arctic were a fluke— a sign that a solitary bear had wandered too far. Now, biologists are recording unprecedented groups of grizzlies and hybrid bears at high latitudes in the Arctic, suggesting that some bears have figured out how to live and hunt in a vastly different world than their southern stomping grounds.

In 2006, an American hunter shot a snow-white bear in Canada that had the long claws and humped back of a grizzly: DNA tests later confirmed that this was the first modern hybrid grizzly-polar known in the wild. In 2010, as Mother Jones reports, the first second-generation hybrid bear was shot in Canada—a stunning-looking bear with thick white fur and brown grizzly paws.

Just a few months ago, two biologists from the University of Alberta were flying across the High Arctic when they saw a polar bear traveling with what they thought was a grizzly bear, but later identified as a hybrid. Several days later, they came across a grizzly that, astonishingly, had figured out how to hunt and eat Arctic seals. (Grizzlies traditionally subsist on a variety of foods, including salmon, caribou, berries, and roots; while the polar bear eats only seals).

A recent study found that the breeding of polar and grizzly bears might not be so unusual after all. A team of international scientists conducted the most extensive analysis yet of polar bear DNA, and found that while polar bears likely evolved as a distinct species between four and five million years ago, they may have interacted with brown (grizzly) bears much more recently.

Furthermore, the research, published in the Proceedings of the National Academy of Sciences, identified a number of fluctuations in polar bear populations in the last million years. Polar bear numbers have grown larger in periods when the Earth cooled, and smaller when the weather warmed. Likely, during cooler periods, the polar bears socialized with grizzly bears and had babies—and all this occurred in the not-too-distant past.

As the planet warms due to man-made climate change, these inter-species meetings will only become more prevalent, polar bear biologists predict.

But before you coo over the brown-and-white bears to come, scientists say that contemporary polar bears have low genetic diversity due to their dwindling numbers, and lower resistance to diseases that will become more prevalent as their Arctic habitat warms and melts.

When northern and southern species meet, in fact, interbreeding can pose a threat to the existence of species that have uniquely adapted to live in the Arctic, like polar bears, caribou, beluga whales, and Arctic fox – all of which are increasingly coming into contact with their southern neighbors: Pacific salmon, red fox, white-tailed deer, and killer whales.

On the one hand, as a report by Yale’s Environment 360 shows, interbreeding may help already-endangered Arctic species adapt to the coming threats of climate change. On the other hand, the world may lose some of its Arctic treasures.

What can we do to save polar bears? Let us know in the comments.