Polar Bear-Grizzly Bear Hybrids


The cross breeding of species to create hybrids has been done throughout human history. In recent years, however, hybrids have been popping up in the wild with no direct human influence. A hybrid is two individuals of different species brought together while under human care to create an offspring that is a mix of both parents. Some of the commonly known hybrids are the mule, a cross between a horse and donkey, and the liger, a cross between a lion and tiger. These are species who are either domestic animals or whose home ranges are far apart and would never interact without human intervention. 

In recent years, wild hybrids have been found. These hybrids were not created in human captivity and have attracted both the public and scientific interest. One of these wild born hybrids caught the public interest in 2006 when a hunter shot what he assumed was a polar bear in Banks Harbor, Canada. This bear had the creamy fur coloring found on polar bears. A closer inspection of the bear revealed the bear had features of a grizzly bear, including the hump on the back, long claws, and a grizzly bear head shape. 


Polar-grizzly hybrid


DNA samples were sent in to investigate. The bear was found to be a first generation hybrid, with a polar bear mother and a grizzly bear father. Before this case, it was known that these two species could hybridize as they had done so in captivity. This bear became the first documented case of a polar bear-grizzly bear hybrid found in the wild. Since the discovery of this bear, 8 other bears have been found to be hybrids. Of these 8 bears, 4 are first generation hybrids and 4 are the offspring of a hybrid and a grizzly bear. 

What does this mean for the two species? 

The hybridization of these two species could mean one of two things for these species. First, is that this is a random occurrences.The second is that this is the foretelling of a breakdown of species barriers and mating between these species will become commonplace. 

Both are possible outcomes and only time will tell which will be the true outcome. Both of these results have occurred in the wild. With the first, the hybrids are not as successful at surviving in their range as their parent species. The hybrids still pop up in the wild but due to the hybridization lack something that is essential to their survival in the wild.

For breakdown of species barriers the offspring are for one reason or another more successful at surviving in their home range than either of their parents. For this to occur the offspring must be able to produce offspring of their own. It is unusually for hybrids to be able to reproduce but there are cases where they do so successfully. Since second generation hybrids have been found in the wild, we know that the polar bear-grizzly bear hybrids are able to reproduce. This could result in genetic material entering the population that has a negative impact on the population.

These two species also only split on the evolutionary tree a mere 150,000 years ago. So their genetic material is very similar and the males will be attracted to females of both species. The hybridization between these two bears has the potential to lead to the creation of a new species of bears. So even as the parent species dies of there is the creation of  a new species. Either way there is much we can learn from the hybrid offspring of these bears.