Although 2010 was technically the year of the Tiger, it was a real bear for most people. 2010 was also the year of a really big discovery: the polar-grizzly hybrid. In an early 2010 study, researcher Robert Rockwell reported that Grizzly bears had begun moving into the polar bear habitat, which was remarkable since the two bears fill very different ecological niches. Polar bears hunt and breed on the ice; they are kings of the tundra. Grizzly bears roam the rocky mountain forests and fish in trout streams. Their worlds should hardly collide—except for climate change and the problem of habitat loss. Due to the warming Arctic, the receding sea ice has displaced polar bears, forcing them into a warmer climate, where they are more likely to come into contact with Grizzlies. http://dotearth.blogs.nytimes.com/2010/12/20/polar-scientists-discuss-polar-bears-fate/ And for some reason, the Grizzlies are wandering onto the tundra. (The Grizzly bear is not to be confused with the Kodiak, or “Alaskan brown bear,” which is native to that region.)
What happens when a Grizzly bear and a polar bear meet up in the same territory? Like schoolyard bullies, Rockwell explained in Canadian Field Naturalist, the two pretty much steer clear of each other, both being top predators, unless there is a female polar bear with cubs, in which case she’d be protective. Grizzly bears that catch a caribou will abandon their prey rather than compete with a polar bear, so the polar bears might get extra food. But Rockwell claims that the hybridization of the two species is a rare event. http://news.nationalgeographic.com/news/2010/02/100226-grizzly-bears-polar-bears-hybrid-canada/
Despite the polar bear’s larger size, if a Grizzly decided to compete for food, it might win a battle because the polar bear’s skeleton is weaker than that of the Grizzly—and the two bears can bite equally hard. It makes me think of the great battle scene between the Ice Bears in “The Golden Compass” http://www.youtube.com/watch?v=2FBXOrb6loQ&amp;feature=related (only without the armor). Currently, there are no reports of a polar bear and Grizzly bear fighting—so it is indeed the stuff of science fiction.
Grizzly bear + polar bear = a whole new bear? The rare sightings of the hybrid have spurred a lively debate over whether hybridization is good or bad for the bears.
When hunters have killed bears confirmed as polar-Grizzly hybrids, Canadian officials have suggested calling the polar-Grizzly hybrid a “nanulak,” a combination of the Inuit names for polar bear and Grizzly bear. “Pizzly” and “Grolar” are also ideas for nicknames that scientists have proposed—without reaching any consensus. There just aren’t enough cases to merit a final decision on the name yet. As for learning the characteristics of hybrids, scientists turn to the cases in captivity. The two polar-Grizzly hybrids born at a German zoo in 2004 acted more like polar bears than Grizzlies—stamping like polar bears do on the ice and hurling prey. The hybrids lie down on their stomachs with their rear legs splayed out—just like polar bears do on the ice. However, they are poorer swimmers than the true polar bear. A number of hybrid bears live in zoos all over the world. But seeing a hybrid polar-Grizzly in the wild is a rare sight. Usually it is happenstance when a hunter has shot a bear that is later identified as a hybrid. http://news.bbc.co.uk/earth/hi/earth_news/newsid_8321000/8321102.stm
A recent study published in Nature asserted that reducing greenhouse gas emissions and curbing carbon can help the polar bears and other wildlife living on the sea ice: http://www.documentcloud.org/documents/19384-nature-report-on-polar-bears.html For two related articles, see: http://www.washingtonpost.com/wp-dyn/content/article/2010/12/20/AR2010122004298.html and “Arctic melting pot: Whales, seals and bears having sex?” http://www.alaskadispatch.com/dispatches/arctic/7853-arctic-melting-pot-whales-seals-and-bears-having-sex
Steven C. Amstrup, the chief scientist at Polar Bear International and the author of that study, argued that “interbreeding might be the final straw” for species already imperiled by climate change, loss of habitat and other stressors. Polar Bear International is a conservation organization responsible for studying the bears: http://www.polarbearsinternational.org/research Also in the discussion of hybridization of Arctic species are many marine animals. Porpoises and seals, desperate to find mates in the stressed Arctic, also hybridized in 2010: narwhal-beluga whales and mixed porpoises, as well as mixed seals. http://www.livescience.com/animals/hybrid-animals-arctic-climate-101215.html
In addition to climate change discussions, loss of biodiversity is a main concern with the occurrence of hybrids, especially of endangered species. http://news.discovery.com/animals/arctic-animal-hybrids-threaten-biodiversity.html
Hybridization of species is sometimes a normal part of evolution. There are many known cases of hybridization creating a new species, such as the northeastern coyote. http://www.wildlifetech.com/pages/necoyote.htm
As of yet, the fate of the polar bear is uncertain. The future of the nanulak bears the burden of proof of more sightings in the wild before it goes beyond theory and speculation.
Strange Wetlands will return in the New Year.
Update: April 2012: New IMAX Film, “To the Arctic,” about the polar bears and the Arctic in the face of climate change. For a preview of the film, narrated by Meryl Streep, go to: http://www.imax.com/tothearctic/site.html