Grizzly and Polar Bears Interbreeding is another threat to Polar Bears

It was one of the most awe-inspiring experiences of my wildlife career: in the autumn of 1975 a colleague and I watched a polar bear swim up an inlet toward us on Bathurst Island, then Northwest Territories (now Nunavut). We were near the head of an inlet on a high promontory, and were excited to watch the white bear swim for a mile or so until it reached the shore just below us. There it walked on the the shore and sniffed in the mud where we had walked moments before. We could see him sniffing in our individual footprints. He looked up and around, nose high, testing the wind. Then started following our tracks towards us.

My colleague ran, but since there was nowhere to hide and nothing to climb on the featureless tundra, I stayed put. In a few moments, the bear abandoned our scent trail and went on up the draw, passing out of sight among the rocks.

There are still polar bears throughout the Arctic and some populations are healthy, but some are declining, with low production of cubs and low survival of all age classes. Climate change is the main culprit, but now another threat has appeared.

The confirmation of a grizzly-polar bear hybrid (DNA confirms suspected rare grizzly-polar cross shot in High Arctic, Vancouver Sun, May 1, 2010) at Ulukhaktok, N.W.T, (formerly Holman, on Victoria Island) is part of a trend that began at least 20 years ago.

In the winter of 1951-1952, Frank Banfield, a government wildlife biologist, recorded a grizzly bear taken on Banks Island (Banfield 1974). This was so unusual that he reported it as an “extra-limital record,” that is, outside of the known range.

In the last 19 years, sighting of grizzly bears unusually far north have become common: Melville Sound (1000 km north of mainland) in 1991, Banks and Victoria Islands (160 km north of the mainland), Hudson Bay, and Melville Island in 2003 and again in 2007 (Kaufmann 2007; Struzik 2006). They have become so well established on Victoria Island as to be a significant predator of muskoxen (Gunn and Lee 2000) .
The one shot in May was a second-generation hybrid, the offspring female grizzly-polar hybrid mating with a male grizzly bear. It was the second known grizzly-polar bear hybrid. In April 2006 the first known hybrid polar-grizzly bear in the wild was shot on Banks Island (Roach 2006). DNA tests showed it had a polar bear mother and a grizzly bear father.

After I gave a talk on my grizzly bear research at an international bear conference in 1977, several Norwegian bear researchers rushed up to me. They had read my earlier paper in the Canadian Journal of Zoology on grizzly bear denning on the Arctic coast, in which I mentioned that polar bears also occurred in my study area (Harding 1976). It turned out that this was the first report of grizzly bear and polar bear ranges overlapping, and the Norwegians wanted to know how the two species interacted. Their interest was stimulated because a polar bear and grizzly bear had mated in a zoo and produced fertile offspring (c.f. Stirling 1999), and they wanted to know if this could happen in the wild. I had to disappoint them by explaining that, since polar bears only came ashore in winter when grizzly bears were asleep in their dens, they never had an opportunity to interact, even though they shared the same habitat temporarily.

How times have changed! The recent shrinking of the polar ice cap and withdrawal of seasonal ice from shore has driven many polar bears ashore in the summer, bringing them into contact with coastal grizzly bears. At the same time, more and more grizzly bears are taking up residence on the Arctic Islands. Such hybrids may become more common. Over many generations, this could, hypothetically, destroy the polar bear as a species by genetic contamination. That is, if they aren’t first destroyed by shrinking sea ice seal-hunting habitat.

References

Banfield, A.W.F. 1974. The mammals of Canada. National Museum of Natural Sciences, Univ. of Toronto Press, Ottawa.
Gunn, A., and Lee, J. 2000. distribution and abundance of muskoxen on northeast victoria island, n.w.t., august 1990. Government of the Northwest Territories, Department of Rresources, Wildlife and Economic Development Manuscript Report No. 119.
Harding, L.E. 1976. Den site characteristics of Arctic coastal grizzly bears (Ursus arctos L.) on Richards Islands, Northwest Territories, Canada. Canadian Journal of Zoology 54(8): 1357-1363.
Kaufmann, B. 2007. Grizzly sightings on northern Arctic island.
Roach, J. 2006. Grizzly-polar bear hybrid found -- but what does it mean?
Stirling, I. 1999. Polar Bears. University of Michigan Press.
Struzik, E. 2006. Grizzly bears on ice.

Dog Evolution: Camp Scavenger Hypothesis Denied

The photo of a Tundra Wolf first appeard in BC Outdoors, April, 1985. An abbreviated version of this post was published as a Letter to the Editor in the November/December 2010 issue of Archaeology.

In the September/October 2010 issue of Archaeology is an article, "More than Man’s Best Friend,” that summarizes theories about how dogs' domestication began. All dogs descended from wolves, although the exact location and hence subspecies of wolf is in doubt: some evidence points to China and some to the Middle East. One of these ideas is that wolves evolved as scavengers, hanging around human camps. Anyone who has lived in wolf country as I have would find this untenable. Wolves don't scavenge, unless they're starving, or if they opportunistically stumble upon another predator's kill. And human camps don't usually leave enough meaty refuse to attract a wolf, although they often visit camps out of curiosity. A hunting camp is a different matter: a large mammal carcass would attract a wolf; but humans have been using tools to clean meat from bones for more than 2 million years, and by about 15,000 years ago, when the first unequivocal dogs appear in the archaeological record, humans were very efficient at cleaning up the bones and extracting the marrow. The leftovers would not feed even one wolf, let alone a pack. Human settlements leave enough refuse; but these only appear about 10,000, just before agriculture.

Moreover, anyone who thinks the first dogs evolved as camp-periphery scavengers hasn’t spent enough time sleeping on bare ground where large carnivores might eat you. They can’t know the terror one feels upon hearing heavy footsteps in the dark after the campfire has died; nor can they realize how easy it is to obtain wolf pups. I have many times heard such footsteps and wished I had brought my dog, and later found grizzly bear or other predator prints. Once the footsteps stopped only a few meters away, and stayed. I lay petrified until the first light of dawn revealed a mountain lion watching me. In the Canadian Arctic and Boreal Forest, where I have worked as a biologist, hunted, and camped with Dene and Inuit and hunters and families for many years, every hunter finds wolf dens and many bring home the pups for the kids to play with. I’m too large to crawl into the wolf dens I have found, but the more lightly-built Dene hunters often can. It would not take long—about one night—for a family to realize how good a sentry the wolf can be. If it is a bitch that they have tamed, she’ll likely be bred by a wild wolf. It is not a great leap to think that the family will keep the most docile of the brood. From there to dogs is a short chain. In the Middle East, one of the places posited for dogs’ first progenitors, even into the last century there were wolves, lions, leopards, brown bears, striped hyenas, and wild boar, all of which can kill sleeping humans. After dogs were domesticated, sure, some no doubt became camp scavengers, but I feel in my bones, where terror lives, that they began as pets and sentries.