Climate change is steering grizzly bears and polar bears on a collision course. When they meet in the middle, fights are inevitable. Find out who is favored to win, evolutionarily speaking.
Image by Steven J. Kazlowski.
It's long been shown that the rapidly warming earth is bad news for polar bears. Their habitat is shrinking, as are their food sources and breeding grounds. If global warming continues, they may face a tough competitor. Grizzly bear habitat is limited by frigid winters and sheets of ice. As their world warms up, they're expanding north.
The habitats of the two predators are already beginning to overlap. If they continue to do so, the polar bears, not the grizzlies, are going to be the losers in the competition for survival. This is surprising to some. Grizzlies are just a frighteningly-named subspecies of brown bear. They're not even the biggest of the subspecies of brown bears. Polar bears are bigger, and have a nastier reputation than grizzlies. They are thought to be more aggressive, and are more dependent on meat for food.
It's that protein diet that tips the odds against polar bears if the species are in competition. Polar bears have adapted to eating flesh. Brown bears are omnivorous. The more gentle diet means that the brown bear's jaws and stronger and teeth are bigger. Fat and flesh require less strength to tear and less endurance to break down. A head-on fight would result in a victorious polar bear, but scavenging the same swath of land for food results in a starving one. Unless their exclusive habitat is protected, the world may lose polar bears for good.