Genetically speaking brown bears polar bears and grizzly bears are all quite similar. The appearances may vary, but deep down they are very much alike. Which means it is now time to meet the “pizzly” (or grolar bear).
Sometime ago we wrote about a study showing just how closely brown bears and polar bears are related. The study showed that the bears separated into differing populations about a million years ago but have been cross-breeding during that time. Brown bears (Ursos arctos) and grizzly bears (Ursus arctos horribilis) are virtually the same bear. Grizzlies are a subspecies of brown bear. But what about polar bears (Ursus maritimus)? Polar bears are actually almost identical to brown bears.
The differences are habitat and some largely superficial items. Since they live in the snow their fur is actually translucent so it appears white against a white background. In fact they are quite dark. Other appearances are adaptations to living in the polar zone. Some adaptations make it easier for the bears to swim.
So what led us to meet the “pizzly”? The current theory is that a population of brown bears was cut off in the far north during the last Ice Age from 1 million to 70,000 years ago. Most died but a few adapted and over time adapted more. But they remained brown bears at core.
Perhaps it can be considered the opposite of what happened with the Gobi bear. Gobi bears are brown bears that live in the ferocious Gobi Desert. They are listed as endangered and are the focus of conservation efforts. These bears have adapted to the high heat and arid conditions of the desert.
According to A-Z Animals at least eight first-generation hybrids have been found recently by scientists.
Moreover, genetic studies indicate the bears have been occasionally mating for centuries. One tested population of brown bears was a found to be closer to polar bears than to other brown bears.
Advances in genetic science are rapidly changing the way we see relationships among related animals. Tigers for example, are being reclassified into two subspecies, down from seven or nine. Mainland tigers are Panthera tigris tigris and island tigers are Panthera tigris sondaica. Even smaller cats are being reclassified as a new species of wildcat is being proposed on Corsica. The “Corsican cat-fox” may just be different enough from other Eurasian wildcats to merit its own species listing. Wolves are another example. At one time there were considered to be about 40 subspecies of Canis lupus. That number is down to around 27 and probably shrinking as well.