What Is a Polar Bear Grizzly Bear Hybrid
A polar bear grizzly bear hybrid is a rare cross between Ursus maritimus and Ursus arctos, often called a grolar bear, pizzly bear, or nanulak. These hybrids occur where overlapping ranges in the Arctic and subarctic bring the two species into contact. The first confirmed wild hybrid was documented in 2006 on Banks Island, Canada, and subsequent genetic testing has verified additional individuals. The hybrid typically shows a mix of polar bear white or cream fur, grizzly-like shoulder humps, and intermediate skull and paw size.
Genetic studies confirm that polar bear and grizzly bear lineages diverged roughly 500,000 to 600,000 years ago, yet they remain closely related enough to produce viable offspring. Mitochondrial DNA and nuclear genome analyses show that hybrid individuals carry alleles from both parent species. The International Union for Conservation of Nature lists polar bears as vulnerable, while grizzly populations in North America are managed under various national and regional frameworks. As sea ice loss pushes polar bears southward and grizzly bears expand northward, the likelihood of hybridization increases.
Where Hybrid Sightings Occur
Most documented sightings of polar bear grizzly bear hybrids occur in the Canadian Arctic, particularly in the Northwest Territories, Nunavut, and the western Arctic coast. In 2010, hunters shot a confirmed hybrid near Sachs Harbour on Banks Island, and genetic tests at the University of Alberta confirmed its mixed parentage. Additional sightings have been reported along the coast of Victoria Island and in regions where grizzly bears are expanding their range northward due to warming temperatures.
Researchers from the U.S. Geological Survey and Canadian wildlife agencies have mapped overlapping seasonal ranges where polar bears hunt on sea ice and grizzly bears use coastal tundra and interior forests. The Alaska Department of Fish and Game has noted grizzly bears moving into areas traditionally occupied by polar bears along the Arctic coast. These range shifts are driven by changing sea ice conditions, which reduce polar bear hunting platforms and open new habitat for grizzly bears.
Genetics, Appearance, and Conservation Implications
Hybrid bears typically display a blend of traits: cream to brownish fur, a slightly concave facial profile intermediate between both species, and paws larger than a grizzly but smaller than a polar bear. A 2013 study published in the journal Evolution identified specific genetic markers that distinguish hybrids from pure polar and grizzly bears, confirming that first-generation hybrids are fertile and capable of backcrossing with parent species. The U.S. Fish and Wildlife Service tracks hybrid occurrences under its marine mammal and bear management programs.
Conservation agencies treat hybrids as a natural response to changing Arctic ecosystems rather than a separate management unit. The Endangered Species Act lists polar bears as threatened, and any hybridization events are monitored within the context of polar bear recovery plans. The World Wildlife Fund and the Polar Bears International organization cite hybridization as one of several outcomes of rapid Arctic environmental change. For more details on polar bear conservation status, see the U.S. Fish and Wildlife Service International Affairs page, and for genetic research background, see the 2013 Evolution study on bear hybrid genomics.