A pizzly bear is a hybrid between a polar bear and a grizzly bear. These hybrids are real, and several have been found in the wild. But the idea that pizzlies are suddenly spreading across the Arctic is not supported by the latest genetic evidence. A 2017 study found that the eight known wild hybrids in Canada’s western Arctic all came from a single female polar bear that mated with two male grizzlies, and in 2024, researchers analysed more than 800 polar and grizzly bears and found no new hybrids at all. Climate change may give the two species more chances to meet, but there is no evidence of a pizzly population boom.
What is a pizzly bear?
Polar bears (Ursus maritimus) and grizzly bears (Ursus arctos) are different species, but they are closely related enough to produce hybrid offspring, and those offspring are fertile. According to Live Science, the two lineages only diverged around 500,000 to 600,000 years ago. The hybrids go by several names, including pizzly bear, grolar bear and polar-grizzly hybrid.
There is a technical difference between the two most common names, though. According to Polar Bears International, a hybrid with a grizzly father and polar bear mother is a grolar bear, and one with a polar bear father and grizzly mother is a pizzly. That creates an amusing problem with the famous Canadian hybrids, because all eight had the same polar bear as their mother, or grandmother, and grizzly fathers. Strictly speaking, all eight were grolar bears, not pizzlies, even though “pizzly” is the name that stuck.
What does a pizzly look like, and how big is it?
There is no single look that every hybrid must have. They can show a mix of features from both parents, such as pale fur like a polar bear combined with a grizzly’s shoulder hump, long claws or dished face. Journalist Gloria Dickie, author of a book on the world’s eight bear species, told IFLScience that they typically look like a whitish or blonde grizzly with patches of brown. But looks alone cannot prove a bear is a hybrid; DNA testing is far more reliable.
Size is one of those questions where a confident internet answer can mislead you. Polar bears are generally bigger than grizzlies, and a hybrid can inherit a mix of traits from both. But so few wild hybrids have been documented, and the known ones span different generations, that there is no reliable average. The safest answer is that a wild pizzly or grolar is a large bear with an appearance somewhere between its parents.
The strange bear found in 2006
The modern pizzly story took off in 2006, when a hunter on Banks Island in Canada’s Northwest Territories shot a bear he thought was a polar bear. It had mostly pale fur, but also brown patches and features that did not fit a typical polar bear. DNA testing confirmed it was a polar-grizzly hybrid, the first documented in the wild, as Live Science reports. That raised an obvious question: was this the start of a new population of hybrid bears?
Eight hybrids, one unusual family
In 2017, biologist Jodie Pongracz and colleagues published a detailed genetic analysis of the known Canadian hybrids in the journal Arctic. They identified eight hybrid bears, but those eight were not the result of eight separate matings. All of them traced back to one female polar bear who had mated with two male grizzlies. According to Wikipedia’s summary of the study, she produced four first-generation hybrids, and one of her hybrid daughters then bred with grizzlies to produce four more, each roughly three-quarters grizzly. What had looked like a sudden rise in hybridisation was really one family. That polar bear, born in 1989, is now considered “famous” by researchers, as CBC News reported.
The 2024 DNA study put the numbers in perspective
The strongest evidence against a pizzly boom came in 2024. A team including Ruth Rivkin of the University of Manitoba used genome analysis to look for hidden hybrids, bears that might look like ordinary polar bears or grizzlies but carry the other species’ DNA. According to Polar Bears International, they tested 371 polar bears and 440 grizzly bears from across Canada, Alaska and Greenland, along with the eight known hybrids, and found no new hybrids at all. That does not prove there are no other hybrids anywhere in the Arctic, since the study was not a census of every bear. But it does show that hybridisation was extremely rare in the populations sampled, which is a very different picture from pizzlies spreading across the north.
Does climate change cause pizzly bears?
This is where the story needs nuance rather than dismissal. Climate change can shift where animals live and how often different species meet. Grizzly bears have been expanding northward into polar bear country, and changes in sea ice affect how much time polar bears spend on land, as IFLScience and Polar Bears International both describe. More overlap means more chances for the two species to meet, and Polar Bears International notes that hybridisation is expected to increase as grizzlies push north. But more opportunity is not the same as frequent hybridisation, and the 2024 study found no new hybrids at all. The most accurate summary is that climate change may increase the opportunity for hybridisation, but the evidence does not show wild hybrid numbers rising now.
Would hybrids thrive, and are they a new species?
Even if more hybrids were born, there is no evidence they would replace polar bears. Polar bears are specialised for life on the sea ice, hunting seals, while grizzlies are adapted to life on land, and a hybrid inherits a mixture of both. Polar Bears International notes that hybrids are still ill-suited to adapt to the changing Arctic, so hybridisation is not a solution to the problems polar bears face. For polar bears, which the IUCN lists as vulnerable, the far bigger threat from a warming Arctic is losing the sea ice they rely on, not interbreeding.
Pizzlies are not a new species either. They are individuals produced by two different species mating. Some can breed, as the later-generation bears in the Canadian family show, but a new species would need persistent separation from the parent populations over many generations, and there is no sign of that.
The pizzly is real, the pizzly boom is not
The pizzly is almost designed for a headline: a bear that is part polar bear and part grizzly, created by a warming Arctic. The reality is more interesting precisely because it is less dramatic. The eight known wild hybrids turned out to be one extended family, and a much larger genetic survey found no others among hundreds of bears. That does not make the animals any less fascinating; it just makes the story more precise. It is a good reminder to check whether a dramatic trend is really a trend or one unusual case. For another popular science story that needed updating, see Zealandia, the lost continent hidden under the Pacific, and for the terms behind another commonly confused climate topic, see climate change versus global warming.
Sources
- Pongracz et al: Recent hybridization between a polar bear and grizzly bears in the Canadian Arctic, Arctic (2017)
- Polar Bears International: Hybridization extremely rare between grizzly and polar bears, study finds
- CBC News: Grolar bear hybrids in N.W.T. all traced back to same female polar bear
- Live Science: Pizzly bear hybrids and the climate crisis (2021)
- IFLScience: Pizzlies are hybrid bears that show a worrying future for the Arctic
- Wikipedia: Grizzly-polar bear hybrid