In 2006, a hunter from Idaho paid more than $40,000 for a trip to the Deep Yukon, an Inuit tracker, and a license to kill. To be specific, a license to kill a polar bear. And he succeeded, or so he thought. After they brought the animal down, the tracker noted that the bear looked a bit odd: brown spots in its fur, a shallow face, a humped back, and long claws. If the hunter had accidentally killed a grizzly, he'd be in for a hefty fine, because he did not have a license to kill a grizzly. So, they had a DNA test done, and it turns out, he didn't shoot a grizzly or a polar bear... or maybe he shot both. This animal was the offspring of a female polar bear and a male grizzly: the first documented wild grolar bear.

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Polar bears and grizzly bears aren't very similar. It's not like a polar bear is just a white grizzly bear, and they have slightly different facial features or something. They're very separate species! They've diverged evolutionarily 4-5 million years ago, and yet, they can still interbreed and create fertile offspring, indicating that interbreeding has occurred occasionally throughout their evolutionary history.

And this makes sense because polar bears and grizzlies, or brown bears, each have their own evolutionary niche based on climate, and, as the climate changed over the list 5 million years, their range has shifted in and out of the same land. They were bound to overlap sometimes, and if they were overlapping in the springtime... a little bit of lovin' was bound to happen.

Now you've probably heard that, if two animals can breed and produce fertile offspring, then they're the same species. But that was a lie! In fact, we don't really know where the line between species and subspecies is, but we are quite happily sure that polar bears and grizzly bears are not the same species. They're on the not-the-same-species side of that line.

This is because the two species have completely different morphologies, social behavior, feeding behavior, and metabolisms, each of them designed for a very specific ecological niche. But we know that the offspring are fertile, because in 2010, a bear was shot that was one-quarter polar bear: the offspring of a grolar bear and a brown bear.

What's more, the average grizzly bear has about 2% polar bear DNA! In some northern populations, that can go up to 10%. Now, of course the appearance of grolar bears can't be too surprising right now, as the northern range of the grizzly bear has been increasing as temperatures have become mild. Polar bears, additionally, are designed for life on the ice, but as ice in the north melts, polar bears are forced onto land, the domain of the grizzly. Some of the animals, it appears, are... getting along... pretty well, if you know what I mean, but grizzlies have a significant competitive advantage on land over the long term..

Polar bears have survived for millions of years and through some significant changes in climate, and it may be that this interbreeding is part of the strategy that allowed that. Nonetheless, it is concerning that polar bears are being driven from their traditional range. 

Now, a note on naming: I'm calling these animals grolar bears because that's the term I like the sound of the most, but there's no definitive name. One convention when naming hybrids is to put the name of the father first in the portmanteau, and the mother second. So, if the father was a polar bear, it would be a 'pizzly bear,' and if the father was a grizzly, it would be a 'grolar bear.' I think we should just stick to grolar bear, though, because... it's more awesome. Also suggested: nanulak, a portmanteau of the Inuit words for grizzly bear and polar bear, but... 'pizzly bear,' 'grolar bear,' 'pizzy,' 'nanulak', something else, what do you prefer? I'm actually kind of curious to see.