If you thought the mule was the only hybrid animal roaming around unfettered, well, you'd be mistaken. BBC News reports that hybrid combinations of polar and grizzly bears are peppering zoos across the world and, in one case, even occurring in the wild. Germany's Osnabruck Zoo is the site of a study of the mysterious mammals (resulting when the two species, housed close together, engaged in some unauthorized hanky panky). Dr. Ute Magiera, conservation coordinator of the facility, says this particular hybrid is very rare, with only 17 confirmed animals in existence.

The first Osnabruck "grolar bears" were the children of a female brown bear and, evidently, a male polar bear. Born in 2004, the cubs were the first hybrids to show up after nearly 25 years of the two species' cohabitating. Researchers observed the cubs and found that the hybrids are a bit smaller than the polar bears, have long necks like their polar parents, but have the shoulder humps typical of brown bears. Other features include thicker heads (like grizzlies), visible tails (like polars), and blended feet — partially insulated with hair like the polar bear, partly long-toed like the grizzly.

BBC News reports that the most interesting feature of the hybrid is the hair. Polar bears typically have hollow hair shafts while brown bears have more solid hair shafts. The hybrids have a blended coat that varies depending on the bear's sex and body part. Males had solid-haired paws with hollow-haired backs while females had largely hollow hairs. When it comes to behavior, the bears seem to act more like polar bears, using their front paws to stamp in the ways polar bears break through ice and tossing toys around with their teeth the way polar bears rattle their prey.

So why should we care so much about the minutia of a hybrid born of two species whose habitats rarely overlap in the wild? BBC News suggests that climate change is shifting the locale of the polar bear, drawing the bears more inland. These shifts might happen too quickly for the species to adapt, but if the bears are able to successfully mate with other species, these hybrids could have interesting implications for adaptation and evolution.

What do you get when you cross a polar bear with a grizzly?
German zoo features rare hybrid species, but there are only 17 confirmed animals in existence.