On a trip to the Northwest Territories last year, Jim Martell spent more than $45,000 for the right to shoot a polar bear. But the animal he killed turned out to have puzzling characteristics - long claws, a humped back and brown patches in its white fur. Had he shot a grizzly by mistake? If so, the American tourist faced up to a year in jail for hunting without a proper licence.
DNA tests showed that the animal in question was not, in fact, a grizzly. But neither was it a polar bear. It was the only confirmed case of a hybrid - born of a polar bear mother and grizzly father - in the wild. This let Mr. Martell off the hook. He even got to take the "grizzlar" home. As he told one newspaper, "It will be quite a trophy."
For conservationists, however, the animal has become more of a booby prize - a symbol of the troubling questions posed by cross-breeding between at-risk species. For example, should the offspring of "animals of special concern" such as grizzlies and polar bears be protected from hunters? Or even encouraged to breed? Or could hybrids actually weaken genetically pure populations of disappearing wildlife?
In Alberta, for instance, hybridization has contributed to the 80-per-cent decline in threatened cutthroat trout. Cross-breeding has similarly affected populations of golden-winged warblers in Manitoba, Ontario and Quebec. And in British Columbia, mating with other species is an insidious threat to the province's tiny population of spotted owls. Such hybridization could also have an impact on other animals and plants in these ecosystems.
"It's godawfully complicated," says Marco Festa-Bianchet, a biologist with Université de Sherbrooke. This week, he led a meeting of wildlife experts in Ottawa for the Committee on the Status of Endangered Wildlife in Canada. The group is drafting recommendations on how to deal with hybridization to be released next year.
"People may say, 'So what if we have no more cutthroat trout and instead we have a swarm of hybrids?' Well, cutthroat trout were selected for a certain ecosystem. We don't know what impact the hybrid will have on the ecosystem," Prof. Festa-Bianchet says. "Hybrids occur in nature, but we're facing a situation worsened by the actions of man."
BREEDING HYBRIDS
Before the 1800s, hybrids were rare. But European arrivals began removing barriers that separated related species.
Take the eastern wolf in Ontario. As settlers cut down trees to create farmland, the animals' forest habitat disappeared and put them in close quarters with gun-toting humans trying to protect livestock. Wolf populations plummeted.
At the same time, coyotes living in the prairies moved east into newly cleared land. According to Brad White, a geneticist at Trent University in Peterborough, Ont., the two species started mating in the early 20th century. And by 1995, DNA tests of eastern wolves in Algonquin Park showed that they all carried some proportion of coyote genes.
"Western coyotes and eastern wolves had reached an equilibrium and along we came and broke everything down," Prof. White says.
Habitat destruction could also be pushing cross-breeding among spotted owls. Extensive logging cut down 80 per cent of the old-growth forest they live in and allowed for the invasion of barred owls. This has resulted in cases of hybridization between the two species - and today the David Suzuki Foundation calls the spotted owl the most endangered bird in Canada.
Climate change is another factor in the rise of interspecies mating. Because of changing temperatures, the blue-winged warbler has been moving north - both competing and mating with its closely related golden-winged cousins.
