Grolar and pizzly bears: What the family drama of interbreeding polar and grizzly bears reveals

Meet the main character of our story: the polar bear. Displaced by shrinking sea ice in the Arctic, it was forced to wander south into Canada's Northwest Territories. Here our lady in white met a couple of beautiful grizzly bears. She fell in love with both of them, and each of them had two cubs – three Grolar bear daughters and a son. Thus began a remarkable dynasty, a lineage as intertwined as any in Shakespearean tragedy.

The next stage was equally unlikely. When one of the daughters reached adulthood, she mated with her biological father, as well as with her mother's other grizzly suitor—essentially, her stepfather. Result? Four cubs who were genetically her siblings, children and cousins ​​all at once.

In 2006, a hunter in the Canadian Arctic shot and killed an animal that had the physical characteristics of both a grizzly bear and a polar bear. Genetic tests later confirmed that it was a Grolar, a member of the modern hybrid family. Ten years later, when researchers uncovered an intriguing relationship between these animals, the scientific community was baffled: the offspring of interspecific matings are usually sterile, but here they were clearly fertile. Biologists wondered if this could be the prelude to the emergence of a new Arctic predator. Could these hybrids be an adaptive success story born out of the chaos of climate change? Or are they an environmental warning sign of things to come? Now, thanks to new research, we can answer these questions.

As the Earth warms, the Arctic is warming four times faster than the rest of the planet, and polar bears (sea ​​bear) are moving south. Their diet consists mainly of fatty seals, making them dependent on sea ice as hunting platforms. As the ice volume shrinks at an unstoppable rate, they are being pushed inland in search of new food sources. Here they increasingly meet with their brothers brown bears, grizzlies (terrible bear), who are moving north as warmer temperatures in the high Arctic allow them to expand their hunting and mating territories. This has prompted speculation that hybridization between the two species may become common, leading to an increase in the number of grolards and “pizzy bears” (hybrids of a polar bear father and a grizzly mother). Some biologists even fear that the flow of genes from polar bears into the brown bear population could contribute to the extinction of the former.

However, the discovery of the Grolar dynasty hints at a more positive outcome: polar bears may be adapting to a new world order. Documented grolars resemble grayish-brown polar bears with slightly larger feet and skulls resembling grizzly bear-like features. These traits have led to speculation that the hybrids may be able to forage for a wider and more terrestrial range of food than their polar parents, perhaps allowing them to hunt on land and not be dependent on dwindling sea ice. In some ways, peepee bears may be a sad but necessary compromise given current warming trends, says paleobiologist Larissa DeSantis of Vanderbilt University in Tennessee. interview in 2021.

One happy family

Nevertheless, large-scale genome research published last year paints a different picture. When researchers are led Joshua Miller MacEwan University in Canada compared the genetic sequences of 371 polar bears, 440 grizzlies and representatives of the Grolar dynasty, and they were shocked. The analysis showed that there are no wild hybrids, except for the grolars known to us. The proven rarity of this mating method now leads experts to believe that the hybrids lack critical skills to thrive in the environment of either of their parents. Really, recent studies demonstrate that they are ill-suited to life in the Arctic because they the unique “non-slip” morphology of the polar bear’s paws is missing. and also not fully equipped physical qualities that grizzly bears possess for huntingsuch as powerful forelimbs and shoulders. In other words, grolars and pizzlies are not evolutionary-adaptive chameleons, but both poor polar bears and poor grizzlies.

At least in the short term, such hybrids will remain rare and therefore will not lead to the emergence of any new species. But what about the long-term evolutionary future of Arctic bears? Perhaps a look into the past can show what lies ahead. During the Pleistocene, a geological era marked by repeated glaciations that began about 2.6 million years ago, the habitats of polar and brown bears also overlapped. Researchers from the University of California, Santa Cruz have discovered that brown bears live on three Alaskan islands today. gradually emerged during this period as a result of male brown bears being dominant in mating with the local polar bear population. If this pattern repeats itself, it is possible that there will be a relentless erosion of the polar bear species until only grizzlies remain.

However, the Pleistocene was characterized by slow, cyclical environmental changes, a time frame that allowed for gradual adaptation. Today's human-caused climate change is happening at an unprecedented rate, so things may be different this time. “The much more serious threat to polar bears today is the loss of their icy habitat due to man-made climate change. This will happen much faster than any threats from hybridization,” says Fiona Galbraith, a geneticist who has worked as a climate change consultant and now leads expeditions to the Canadian Arctic in search of adventure in the natural habitat.

So the Grolar dynasty is a curiosity, but it is also a symbol of the ecological decay of our planet. Similar climate-induced hybridization were observed in other environmentsincluding appearance lynx, hybrid of lynx and lynx in North America and coywolfwhich some studies suggest is the result of recent interspecies mixing between coyotes and eastern wolves. Like bears in the Arctic, these hybrids are the product of habitat overlap caused by rapidly changing conditions. Their success depends largely on the context, but many of them adapt poorly to their new niche and are often fruitless. As such hybrids become more common, there is a risk that this will lead to further loss of biodiversity and ultimately the collapse of entire ecosystems. “If both species play similar roles in their ecosystem, then the number of contacts and hybridization increases. [are] less likely to have a major impact on the functioning and conservation of ecosystems,” says John Whiteman at the International Conference “Polar Bears”. Otherwise it could have serious consequences. For example, grizzly bears often leave carrion to feed other animals, whereas polar bears do not. “The loss of carrion can wipe out scavengers, leading to widespread ripple effects on everything from food webs to disease dynamics,” he says.

Returning to our original mystery – whether this Grolar dynasty could be the next step in the evolution of Arctic bears – the answer is now clear: it's a grim no. Instead of seeing adaptation in action, we hear the fading echo of an endangered species, the result of deep ecological instability and crisis. However, with the holiday season in mind, perhaps we can reflect on the fact that this drama doesn't have to end in tragedy. If the remaining ice holds and the snow remains, polar bear tracks could cross the Arctic for many more winters. It's possible. However, happiness forever depends only on us.