Stirling said polar bears and grizzlies have been successfully paired in zoos and that their offspring are fertile, but there had been no documented case in the wild.
Kuptana, a guide from Sachs Harbour in the Northwest Territories, was tracking with Idaho big-game hunter Jim Martell, who paid $45,450 for a license to hunt polar bears.
The DNA results were good news for the 65-year-old hunter, who was facing a possible $909 fine and up to a year in jail for shooting a grizzly. The Northwest Territories Environment and Natural Resources Department now intends to return the bear to Martell.
"It will be quite a trophy," Martell told the National Post last week, even before the DNA results were in. He returned to Yellowknife for another hunt, this time for a grizzly bear. He told the newspaper he has dubbed the creature "polargrizz."
Stirling said his colleagues have come up with a few names of their own for the hybrid: a "pizzly" or a "grolar bear." One colleague suggested calling it "nanulak," combining the Inuit names for polar bear - "nanuk" - and grizzly bear, which is "aklak."
"He has a remarkable trophy from his perspective and from the perspective of this whole fraternity of people who like to go big-game hunting for trophies," said Stirling.
When asked how he felt about the rare beast being killed, the biologist would only say that Canada's polar bear hunt - which runs from December through the end of May - is done on a sustainable basis.
Colin Adjun, a wildlife officer in Kugluktuk on the northern mainland in western Nunavut, said he's heard stories about an oddly colored bear cavorting with polars.
"It was a light chocolate color along with a couple of polar bears," Adjun said. Though people have talked about the possibility of a mix, "it hasn't happened in our area," he said.
Three years ago, a research team spotted a grizzly on uninhabited Melville Island, 215 miles north of where Martell bagged his crossbreed.
Polar bear and grizzly territories also overlap in the Western Arctic around the Beaufort Sea, where the occasional grizzly is known to head onto the sea ice looking for food after emerging from hibernation. Some grizzly bears make it over the ice all the way to Banks Island and Victoria Island, where they have been spotted and shot.
That might explain how a grizzly got to the region, but few can explain how it managed to get along with a polar bear long enough to mate.