Grolar and Pizzly bears taking over?
As the global climate shifts, brown bears and polar bears are finding themselves wandering into each others' territory more often. The result is an increase occurrence of hybrid bears that are commonly called grolar bears or pizzly bears.
In 2006, a hunter shot what he thought was a polar bear, but which turned out to be a hybrid of a polar bear and a grizzly. This was the first confirmed instance of hybridization between the two species in the wild.
And what's more, the offspring are fertile. This means that polar bears and grizzly bears can affect the other species' gene pools. In 2010, a hunter killed a bear that turned out to be a second-generation hybrid, the offspring of a grolar bear and a grizzly bear.
Dr. Brendan Kelly, chief scientist and director of conservation research at the Monterey Bay Aquarium, told Pacific Standard that the reason hybridization with fertile offspring can occur is that polar bears branched off from brown bears relatively recently in their evolutionary history. Despite distinct appearances and filling roles in different ecosystems, the two species aren't so very far removed from each other. Because our global climate is bringing the two species into more frequent contact with one another, the two branches of the family tree might just be in the process of combining back into one.
Pacific Standard writes, "[s]cientists observing grolar bears in captivity have noted that, on the one hand, the bears exhibit some typical hunting characteristics of polar bears, rather than grizzly bears—and on the other hand, that they are much weaker swimmers than polar bears. Kelly says that can be typical of hybrid species: that they sometimes lack the specialized instincts of either parent species, leaving them caught in between."