Could polar bears learn to hunt like grizzlies?
Answered by Dr. Andrew Derocher, professor of biological sciences with the University of Alberta and a scientific advisor to PBI. "Climate change is by far the biggest threat to polar bears and finding viable conservation measures is important."
Q. I've been watching, with growing concern, reports about the shortening winters and time available for polar bears to hunt on the sea ice. It is sad to think that these wonderful creatures could be wiped off the planet in 100 years because of human activity.
It appears to me that one of the problems here is that the polar bear is a specialist when it comes to its hunting and lifestyle. Would a polar bear cub be able to learn another way to live?
My suggestion may be weird, but, perhaps, it may be a way to preserve a wild population of polar bears: take an extremely small polar bear cub out of its den, and put it into a grizzly bear den with a couple of other cubs. If this were done during the time when the females were hibernating, and the cubs close-eyed, it would simply be accepted.
Perhaps then we could find out if a polar bear could learn to live and hunt like a grizzly. If it could, then polar bears could be moved into areas to hunt caribou, etc.
A. This idea involves the fostering of young. This method has been used on other species, but usually the young are raised in captivity and then placed with wild parents of the same species. Fostering to a different species has been tried but there are often problems with the behavior of the young. How such a method would work on polar bears is difficult to say.
It is likely that a polar bear fostered into a grizzly bear family would behave much like a grizzly bear would. The recent discovery of a polar bear-grizzly bear hybrid in the wild shows that the offspring behaved like the mother (a polar bear) and lived out on the sea ice hunting seals.
It is generally assumed that many behavioral traits in bears are derived from the prolonged period of the mother-offspring bond. However, there could be problems. Polar bears grow to a much larger body size than northern grizzly bears, and it is not clear how a polar bear cub would grow under such a calorie-limited diet. Typical of other species, there may also be difficulties in mate identification: would a polar bear raised by a grizzly look for a polar bear or a grizzly bear to mate with?
Other issues come to mind. The habitat on the mainland for a terrestrial bear is already filled by the grizzly bear. Nature rarely allows two species to fill the same ecological niche. Further, it is unlikely that the High Arctic islands would provide much sustenance for a polar bear trying to live like a grizzly bear.
Further still, polar bears have evolved adaptations for a predatory lifestyle. The claws of a polar bear would be unsuitable for digging out roots or ground squirrels.
There are also problems associated with activities like overwinter denning. All age and sex classes of grizzly bears den overwinter. However, only pregnant female polar bears den in winter to raise young. Terrestrial-living polar bears would do poorly over winter.
Polar bears are formidable predators but grizzly bears are much more opportunist predators. I do not think polar bears raised with grizzlies would find much success in hunting caribou. Caribou are pretty adept at avoiding grizzlies. Changing 400,000 years of evolution—in the span of 100 years—is not a trivial task.
Polar bears and grizzly bears are closely related but, ecologically, they are far apart in how they make a living. At the end of all our interventions, would a polar bear raised as a grizzly bear still be a "polar bear"?
In summary, I hope we never have to resort to such efforts to maintain polar bears in the wild. It seems to me that the solutions are before us and the wise use of resources with incentives to reduce energy consumption are obvious options. Technology can help us achieve climate stabilization—but we need politicians willing to view the world 50 or 100 years ahead and not simply over the span of the short election cycles that are failing our planet.