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Meet the Pizzlies!

How polar bears and grizzlies are coming together to fight climate change


This isn’t a muddy bear; scientists say he’s a “grolar” bear – part polar, part grizzly. Is this how polar bears are going to save themselves from extinction? Photo by USGS.

A little over 100,000 years ago, a group of brown bears left their forest and headed north, into the frozen Arctic, in search of something new to eat. As they began to settle in to their new home, they made a few adaptations – like changing the color of their fur. Soon, no longer brown but white, they had established themselves as an altogether new species: polar bears

Today, it seems, polar bears are beginning to make the return journey. As their Arctic home continues to melt, they’re beginning to move back south, and to reunite with their cousins, the grizzlies, another species of brown bear.

Latest estimates from scientists at this year’s meeting American Geophysical Union are that unless dramatic action is taken by the major nations of the world (and the latest international conference in Cancun failed to agree on anything remotely like what’s needed), the Arctic will be essentially free of ice during the summer within as little as 30 years or less from now.

The polar bears are not depending on humans for their survival.

And that’s a recipe for polar bear extinction since they rely entirely on sea ice as floating platforms for hunting and breeding.

It seems, then, that the polar bears are not depending for humans for their survival. The instinct to preserve at least some part of their genetic make-up is driving them to begin to migrate south and mate with their cousins, the grizzlies.

In 2006, hunters shot an unusual-looking polar bear. He was white with brown patches and DNA testing later confirmed him to be a polar grizzly hybrid. Since then, other brown-patched “pizzlies,” as some scientists refer to them, have been spotted in sub-arctic regions.

Is this a good survival strategy for polar bears? Conservation geneticist Andrew Whiteley of the University of Massachusetts Amherst says it’s a mixed blessing. Early on, it can save the genetic traits of a species, but in later generations, genes that once allowed the animal to thrive in a specific habitat can be diluted. For example, zoologists studying polar-grizzly hybrids in a German zoo found that while they showed typical polar-bear behavior associated with seal hunting, they lacked the strong swimming abilities of the Arctic bears. On the other hand, once the Arctic ice has melted, it’s unlikely to be coming back for thousands of years, so the benefits of diluting their polar genes with the grizzlies would outweigh the possible disadvantages.

Other climate change hybrids

Other animals are also teaming up to ward off extinction in the face of climate change.

A hybrid narwhal and beluga whale was spotted off the coast of Greenland, and an apparent hybrid of a bowhead and the North Pacific right whale was photographed in the Bering Sea in 2009. Spotted seals and ribbon seals are also thought to be coming together.

Since the North Pacific right whales are already highly endangered, with fewer than 200 individuals believed to be left, their gene pool would be very diluted by a merger with the bowheads. But then again, this may be their only chance to save any part of their nature.

In all, Andrew Whiteley and his colleagues say they have identified 22 marine mammal species that are likely to be adopting the hybrid strategy as ice barriers disappear, turning the area into what they call an "Arctic melting pot." As their natural habitat is changed to the point that it is difficult for them to survive, or that their specialized features – like hunting on ice – are no longer necessary or helpful, a similar species that can carry on their genes will likely look attractive.

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