Conservationists have reason to be optimistic
The grizzly-polar bear hybrid «grolar» remains rare in the wild, a study has found. DNA analysis of old samples revealed only five historical cases, which gives hope for the existence of polar bears as a separate species.
Photo: wikipedia.org
Family “grolar” in the Canadian Arctic remains the only confirmed example of hybrid offspring between polar bears and grizzly bears, according to a new study that may give some optimism to conservationists concerned about the future of polar bears as a distinct species.
As The Guardian writes, a team of North American researchers looked at old bear samples collected between 1975 and 2015, using a newly developed tool to find previously unknown specimens of hybrid bears.
Their results, published this month in the journal Conservation Genetics Resources, found no new examples of crossing polar bears and grizzly bears.
Polar bears (Ursus maritimus) evolved from grizzly bears (Ursus arctos horribilis) several hundred thousand years ago and remain so closely related genetically that they are capable of interbreeding. Until recently, their distinct habitats separated the two species, but that is changing as climate change shrinks the polar bear's range.
The researchers used a kind of glass slide smaller than a smartphone, called the Ursus maritimus V2 SNP chip, to analyze the DNA of 371 polar bears and 440 grizzly bears in Canada, Alaska and Greenland.
The only confirmed hybrid bears in the sample were already known to science, and all originated from a female polar bear born in 1989 who mated repeatedly with two grizzly bears and produced four offspring. One of her cubs also eventually mated with the same male grizzly bears, producing five more «grolars».
According to Ruth Rivkin, a postdoctoral researcher at the University of Manitoba and one of the study's authors, the study's findings show that hybridization remains rare, but she expected to see more examples in the future.
“It is important that we continue to monitor these polar bears to see if hybridization starts to increase,” she told CBC.
An increase in interbreeding would raise concerns among conservationists, who worry that hybrid bears would be less able to survive or that polar bears would cease to exist.
“This report emphasizes that hybridization is extremely rare and that hybridization does not is an adaptive capacity of polar bears,» said Jeff York, senior director of research and policy at Polar Bears International, who was not involved in the report.
A separate study published this month warns that the change sea ice is making it difficult for polar bears to survive in their existing habitats.
A study published in Nature predicts that one community of polar bears in Hudson Bay could go extinct within a decade if thinning sea ice can no longer to support their weight.
Because longer periods of ice-free conditions on this inland sea limit the bears' ability to hunt, «the extirpation of polar bears in this region may already be inevitable,» writes a second team of researchers from the University of Manitoba.