Climate Corner: Lions and tigers and pizzlies…Oh, my!

Oct 19, 2024

Linda Eve Seth
editorial@newsandsentinel.com

Climate change not only raises global temperatures, it impacts everyone and everything on our planet. As global temperatures rise, ecosystems and the species they harbor are changing in response. Many habitats are either shifting their boundaries polewards, or disappearing altogether – sending wildlife into new regions where they interact with resident creatures in surprising and unprecedented ways. When this geographic collision is between two closely related species, they sometimes cross-breed, leading to the emergence of an entirely new species. One example of this is the grizzly-polar bear hybrid: the “pizzly” or “grolar” bear. Polar bears are significantly larger than grizzlies, with fully grown males weighing around 1,800 pounds and standing nearly 10 feet tall on their hind legs. A typical adult male grizzly will weigh 400 to 600 pounds. Other visible differences are the polar bear’s whitish fur, and their longer skull and snout. A pizzly bear is the hybrid offspring of a male polar bear and a female brown bear. Grolar bears have a brown bear father and a polar bear mother. The first pizzly bear was born in 1936 in The Smithsonian National Zoo, but the first wild hybrid was not found until 2006, when hunters shot a white bear with brown patches in Canada’s Northwest Territories. DNA analysis confirmed that the individual was a hybrid of the two species. Scientists have since documented incidences of second-generation hybrids (e.g. the offspring of pizzly bears and grizzly bears). The interbreeding is surprising since polar bears and grizzlies usually have an adversarial, competitive relationship in the rare incidences when they do meet. These hybrid bears come from areas in northwestern Canada and Alaska where grizzlies and polar bears are crossing paths with increasing frequency as grizzlies encroach on polar bear habitat. This upswing in grizzly and polar bear encounters is almost certainly due to climate change. Rising temperatures and the melting of Arctic ice have led to greater opportunities for these two bear species to come into contact, increasing the chances of interbreeding; for example, when polar bears head further south because the increasingly fragmented summer sea ice makes it harder to hunt prey. These two animals that historically seldom ran into each other are now being forced to share closer quarters. As polar bears are heading further south, warming temperatures are pushing grizzly bears further north, increasing the overlap between the two habitats. This closer contact increases the chances of hybridization. Pizzly bears represent an interesting aspect of the impact of climate change on wildlife and the potential for the hybridization of species due to shifts in their ranges and habitats. Some scientists fear that hybridization could continue to the point where polar bears will one day be subsumed into the general grizzly population, effectively out-breeding them into extinction. Pizzly bears are known to be far less aggressive than either parent species alone and tend to lead solitary lifestyles. Regarding behavior, the hybrids more resemble their polar bear parents, hurling large toys and stamping on objects in a similar fashion. They also lie down with their hind limbs splay-legged–a distinctive polar bear pose. Pizzly bears typically exhibit physical characteristics and traits of both parent species. They may have the body shape and fur coloration of a polar bear, with the hump on the back characteristic of a grizzly bear. The extent of their physical features can vary widely among individual hybrids. Grizzlies don’t typically stray north of the tree line in the Arctic, and permafrost is too frigid for them. But as permafrost rapidly melts and prey moves poleward into polar bear-inhabited regions, grizzlies are bumping into polar bears and mating with them. Likewise, as sea ice wanes, polar bears will likely find themselves stuck in terrestrial locations filling with a slow creep of grizzly invaders. Rather than “grolar bears” or “pizzlies” taking over the Arctic, the real risk is that polar bears will simply be absorbed into a tide of grizzly DNA through successive crossbreeding events. While research suggests that the possibility of climate change-induced hybridization is still low for most species, it is already threatening animals like cutthroat trout, and could someday pose a similar extinction threat to polar bears if it continues unabated. Climate change not only raises global temperatures, it impacts everyone and everything on our planet. Until next time, be kind to your Mother Earth.

*** Linda Eve Seth, M.Ed., SLP, is a mother, grandmother, concerned citizen and member of MOVCA