Standing polar bear and grizzly bear.

Although polar bear-brown bear hybrids are rare, they do happen. The mix of traits makes these bears poorly adapted to both sea ice and land.

© Daniel J. Cox/Natural Exposures

4/27/2021 7:43:12 PM

Pizzlies? Grolars? Why Hybrids Aren’t an Answer for Polar Bears

"People often ask if 'grolars' or 'pizzlies' will be better adapted to the changing Arctic. The most likely answer is no. In general, hybrids likely make for pretty poor brown bears and pretty poor polar bears. Their mix of physiology, coat color, dentition, and behavior is likely not well suited to either a terrestrial or marine existence."

By Dr.  Evan Richardson

In the twenty years that I've been studying polar bears in the Arctic I've learned a lot about their ecology and have been very fortunate to spend many amazing days out on the sea ice. Through all of that time, if there's one thing that I've learned it's to expect the unexpected.

In April 2012, I was part of a research team that was headed to Viscount Melville Sound, an area at the very western edge of the Northwest Passage. Viscount Melville Sound is home to one of the world’s 19 polar bear populations, a place that is infrequently visited due to its remote nature. The last research team to check up on the polar bears in this area was there in the mid-1990s. It was time for another check-up on how the bears were doing.

Our research program would make use of three small cabins and two remote tent camps that we would have to establish. In total, we planned on being in the field for 4-6 weeks, depending on weather. Our jumping off point in 2012 was a small cabin on the north end of Victoria Island in a place called Wyniatt Bay. On April 23, 2012, the thermometer sat at a brisk -25C and the winds were calm as the sun crested the horizon. I rolled out of my bunk, put on my parka, and grabbed our Honda generator. I gave a couple pulls and the Honda fired up. (I had kept it inside the cabin to help with the morning ritual of warming up the helicopter’s engine. It is one thing to try and cold start your 1981 Pontiac Grand Prix in Winnipeg, quite another to try cold start a million-dollar helicopter in the middle of nowhere!)

This was our first of three years in Viscount Melville Sound and we set off to get a feel for where the bear activity was. Polar bears are usually not uniformly distributed; they’re drawn to areas with greater seal densities and better hunting opportunities. We got geared up and headed east across Wyniatt Bay to work our way through a number of small inlets that run like fingers into the rocky shore. These areas of consolidated sea ice attract ringed seals as they make for good pupping habitat and often attract bears.

We flew through several inlets, seeing nothing but old tracks and no bears. As we turned into the mouth of one of the larger inlets, the silence was broken by a call over the radio: “What is that?” I peered from the back seat of the helicopter and saw a dark shape moving quickly across the sea ice. As we approached, it was evident that it was a large brown bear, chasing what appeared to be a smaller polar bear. We swung in for a closer look. The smaller bear began running up a steep rocky slope. As we got closer, we could see that it was no regular polar bear. It had a brown streak down its back, brown circles around its eyes (almost like spectacles) and longer claws. It was a hybrid!

Hybrids had been previously observed by Inuit in this part of the Canadian Arctic and this little bear fit the bill. The brown bear was standing at the base of the rocky slope and the small bear continued to climb. It was evident from the steam coming from both of them that the chase had been going on for a while. With both bears too warm to safely handle, we snapped a couple quick photos and marked the GPS location in hopes that we would find them another day.

Second chances

The next day we returned to the area, but there was no sign of either bear. The following day we were flying over the sea ice north of Wyniatt Bay in Viscount Melville Sound. Tracking conditions were difficult, and we were not having much luck finding bears. We had been flying for almost two hours and had only seen a handful of old windblown tracks.

Sea iceThe polar bear's sea ice habitat is vastly different from the terrestrial world of the grizzly bear.

Scouring the ice for tracks and bears for hours at a time can be very fatiguing. We decided it was time to take a break and landed the helicopter close to a large iceberg. After a quick cup of coffee, we climbed up on the iceberg to have a look around. At the top, we could see to the horizon in every direction, looking out over the vast areas of sea ice that are so critical to the polar bear’s existence.

As we soaked it all in, formulating our plan on where to go next, a familiar phrase was uttered again: “What is that?” A quick glance revealed a dark-colored object moving across the sea ice. A wolverine? A muskox? Another brown bear? We quickly slid down the snow-covered iceberg and fired up the helicopter to go take a closer look. As we closed the gap, there was no mistaking that it was a brown bear walking on the ice in front of us, likely the same one from two days before. With ideal conditions and a well-experienced pilot, the capture went smoothly and before we knew it, we were standing on the sea ice with a brown bear in the middle of the Canadian High Arctic. What was this bear doing out on the sea ice? How was he making a living? There wouldn’t be any vegetation on the surrounding islands for months and there were no caribou or muskoxen to chase out on the sea ice. However, if this was indeed the same bear that we saw in Wyniatt Bay, he likely wasn’t looking for food—he was here to mate.

Love is blind

Both brown bears and polar bears mate in the spring, with females coming into estrus as the days lengthen. One of the interesting aspects of brown bear sightings in the Canadian Arctic Islands is that they are almost exclusively male. Many large mammals have male-biased dispersal, with males dispersing to outlying areas to establish home ranges away from their close relatives, including mothers and sisters. This is likely partially driven by territoriality as well as to avoid inbreeding. Regardless, this male-biased dispersal means that when the spring mating season begins, and big males like the one we had captured are ready to breed, there are likely very few or no female brown bears in the area to breed with.

From an evolutionary perspective, surviving and reproducing are the two biggest drives in an animal’s life. In the absence of female brown bears, the only other option for these male brown bears is to look for female polar bears. Polar bears and brown bears are very closely related species and it has been known for some time that they can hybridize. Why his particular male left his den early to pursue potential mates is anyone’s guess, but a small tissue sample from him would prove to be very informative.

Last chance

Fast forward two years later and we were back in Wyniatt Bay for the final year of our research program. It was April 14, 2014 and we were working the same series of inlets on the east side of Wyniatt Bay in which we had observed the brown bear and suspected hybrid. As we worked our way down the very same Inlet where we had spotted the male brown bears and suspected hybrid two years before we spotted four animals moving across the sea ice. If I hadn’t been harnessed into my seat, I think I would have fallen out at the sight of a cream-colored bear (with brown stripe and circles around her eyes) trailed by three little chocolate brown cubs. Hybrids! This time the conditions were ideal for taking a closer look and before I knew it, we were standing on the ice with four brown bear polar bear hybrids.

From all appearances, the female bear appeared to be the same bear we had last observed scrambling up the rock slope almost two years to the day previously. Even more shocking were her three little cubs, which looked like brown bears from all appearances. The only logical answer was that the female hybrid in question had bred with a brown bear and that her cubs were second-generation hybrid backcrosses. This would make her offspring 75% brown bear and 25% polar bear. Subsequent genetic analysis revealed this to be true. In addition, the big male brown bear we had captured in 2012 was, in fact, her father. Further genetics analysis revealed that another unknown male brown bear in the area had fathered her three young cubs as well as two other first-generation hybrids reported by Inuit hunters.  

Evidence from the past

So how common are brown bear polar bear hybrids? In the Canadian Arctic only four first-generation hybrids and four second-generation hybrids have been observed over a brief period from 2006-2014. However, genetic studies have shown that that hybridization between brown bears and polar bear is not new and has likely occurred in several places in the past. For example, genetic work on brown bears demonstrated that brown bears on Admiralty, Baranof, and Chichagof Islands in Alaska contain up to 8.8% polar bear ancestry. Similar instances of hybridization between these two species have been documented as far away as Ireland.

People often ask if “grolars” or “pizzlies” will be better adapted to the changing Arctic? The most likely answer is no. In general, hybrids likely make for pretty poor brown bears and pretty poor polar bears. Their mix of physiology, coat color, dentition, and behavior is likely not well suited to either a terrestrial or marine existence. Indeed, the genetic work I mentioned shows that hybridization can and has occurred in the past, but that hybrids don’t persist over the long term.

A mother polar bear with a cubFrom their long Roman noses to their paws, polar bears are superbly adapted to a life on the sea ice. Photo copyright BJ Kirschhoffer/Polar Bears International.

Polar bears evolved from brown bears to occupy a specific niche and if anything as the climate continues to warm and the ice-free season lengthens, it is likely that brown bears will continue to expand their range northward. With greater overlap between these two species, the opportunity for more “pizzlies” or "grolars" may increase. However, for the time being the last hybrids were seen in Wyniatt Bay on April 14, 2014. It is anyone’s guess whether they will be seen again or if more hybrids will result from the expansion of brown bears into the Arctic Islands. The only thing that is for certain is that you should always expect the unexpected!

Dr. Evan Richardson is a polar bear research biologist with Environment and Climate Change Canada.

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