What do you get when you cross a polar bear and a grizzly? It sounds like the setup for a joke, but Dr. Joshua Miller’s conservation research and its implications in the Canadian Arctic are no laughing matter. 

Alongside researchers from Environment and Climate Change Canada, Polar Bears International, University of Manitoba, Government of Northwest Territories and San Diego Zoo Wildlife Alliance, Dr. Miller helped to create a Single Nucleotide Polymorphism (SNP) chip – which contains 8,000 SNPs on the chip itself – that the team is using to analyze DNA samples in polar bears, grizzlies and hybrids of the two bear species.

Polar bears have become a symbol for conservation, and as their populations decline, monitoring their genetic health is even more important. But with fewer bears around to study,  doing so is harder than ever. This led to the initial development of a first version of the SNP chip, which assesses over 8,000 genetic markers in polar bears.

But habitat loss complicates things. As ice recedes, polar bears move further south, while grizzly bears are also moving north. As the two species interact more, scientists wondered whether the two species would produce hybrids – called either grolars or pizzlies, depending on which species of bear is the sire. They went back to work on a second version of the chip, expanding it for use on species beyond just the polar bear.

“We designed the second chip to be able to rapidly identify one species versus the other, as well as those hybrids,” says the assistant professor of biological sciences. So far, says Dr. Miller, there have only been eight known hybrid bears found in the wild, and they’re all part of the same family.

“One polar bear female clearly took a liking to grizzly bear males,” he says. “But we wondered about the prevalence – is this just the behaviour of a single female, or is that actually occurring more often than we might think?”

Using the SNP chip, along with existing tracking data from Environment and Climate Change Canada, researchers take genetic samples from the bears and compare them, in some cases building multi-generational pedigrees. When it comes to how the hybrids fit into those pedigrees, some questions remain. Dr. Miller thinks grolars and pizzlies should be able to procreate with other bears. A couple of the known hybrid bears appear to be second-generation, meaning the original hybrids have successfully mated with other bear species.

The possibility of hybrids becoming more common  might seem exciting, but Dr. Miller warns that hybrids aren’t always viewed favourably in terms of conservation.

“They're considered an evolutionary dead end,” he says. “Hybrid offspring could be infertile, or they could be less adapted to their environment. Polar bears are adapted to live in the Arctic and feed on the ice, while grizzly bears are more adapted to warmer climates and lower latitudes, so their offspring might not be able to survive in either location.”

Another potential downside is genetic swamping. Dr. Miller notes that since there are fewer polar bears than grizzlies, if they start interbreeding more frequently, the polar bear population may die out.

But there are potential benefits, too, he says. Hybrid vigour occurs when an offspring receives beneficial traits from both parents and is able to survive in either environment.

The research team’s studies are ongoing. But, for now, Dr. Miller says they’re creating a baseline to analyze trends with hybrid bears going forward. “It’s not all that common now, but that doesn't mean that it won't be in the future if there are more interactions.”