I read an interesting article in the Alaska Dispatch News which examined interactions between arctic grizzly bears and polar bears. They found that although polar bears are larger, they tend to leave food sources when grizzly bears are around. This may be because polar bears typically spend a lot of time on sea ice without the need to be aggressive towards competitors. Of concern is that the relatively passive nature of polar bears may be detrimental considering these animals are increasingly spending more time foraging on land during the summer and fall months.
It is thought that grizzly bears evolved into polar bears as the climate cooled. It is interesting, therefore, that scientists and hunters are increasingly coming across "Pizzly" or "Grolar" bears which, as the names imply, are grizzly and polar bear hybrids. Second generation pizzly bears have also been discovered. Hybridization is one strategy to speed up adaptation, which is important for a polar bear living in a warming environment.
So does this mean that polar bears will evolve back into grizzly bears?