Global Warming Isn’t the Only Problem Polar Bears Face

Categorized | Global Warming, Nature, Science

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Polar Bear fighting Grizzly Bear

When you think about the falling numbers of polar bears in the wild, you probably think it’s due to global warming. And while the demise of their native habitats is a chief threat, grizzly bears have begun to invade. This is a growing threat to polar bear populations as food is already scarce and polar bears now have to compete for the ever decreasing hunting areas. Polar bears are beginning to become more cannibalistic in nature as they go hungry for longer periods of time. This is a previously unobserved problem by biologists. And it adds to the polar bears killed for dominance, or cubs killed so adult males can breed with their mother.

Barren ground grizzlies are venturing their way onto sea ice because of an absence of caribou. When emerging from hibernation, the grizzlies are hungry and the scent of seal gets them moving into polar bear territory for food. Their presence is confusing biologists and making them rethink whether polar bears and grizzly bears should be separate in their species status. If the caribou populations continue to decline polar bears won’t be the only bears fighting for survival. Recently hybrids were discovered which could indicate that the smaller grizzly bears aren’t planning to return to their original habitats.

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Grizzly-Polar Hybrid Bears Discovered

The first confirmed wild hybrid Grizzly-Polar Bear, known as grolar bears, polizzly, and pizzly, was found in 2006. Although these wild hybrids have been reported in the past, this was the first time DNA testing was used to confirm the bear’s ancestry.

This type of interbreeding has been seen in many zoos around the world, but was still relatively rare in the wild. As global warming continues and the sea ice habitats get smaller it is becoming more common.

From Yale.edu:

Polar bear experts said it is possible that the grizzly bears are leaving from the Arctic mainland and traveling roughly 400 miles north, crossing the sea ice as they pursue a caribou herd that annually migrates over the sea ice to Victoria Island. Unable to get back because of rapidly melting ice, some of these grizzly bears have evidently managed to adapt to life in the polar bear’s world, eating seals, hibernating, and mating with polar bears.

Polar Bear Grizzly Bear Hybrids

Clockwise: A female hybrid, male hybrid, polar bear and brown bear. Source: BBC Images: Alexandra Preuß

Not all hybrids feature the same characteristics, but they share similar traits from their parents. Generally they are smaller than polar bears, but larger than grizzly bears. Their head size and shape is another combination of the two species, as well as the feet and hair follicles.

It appears that when sea ice melts and the arctic habitat warms polar bears will interbreed with grizzly bears. This might be completely due to the overlapping bear ranges as both species search for food, sometimes following their food sources several hundred miles away. This leads polar bears to head to the mainland, while their smaller grizzly counterparts head across the sea ice.

Scientists are split in thinking whether the polar bears will be able to adapt to the mainland if climate change continues as quickly as it is currently heading. In general, grizzly bears are more evolved to adapt learning to live off a wide variety of foods, including roots, berries, and caribou. Even the occasional seal. Polar bears almost only eat seals and will have a harder time adapting to a diet filled with other things. Some believe that they will be unable to adapt this quickly, while others think they will be able to adapt permanently. Only time will tell.

Sources
Grizzly Bears on Ice” (National Wildlife Federation)
Global Warming and Polar Bears” (National Wildlife Federation)

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