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Arctic melting pot: Whales, seals and bears having sex?

  • Author: Doug O'Harra
  • Updated: May 13, 2016
  • Published December 16, 2010

The news swept the media like a tabloid scandal on ice, or maybe a Z-grade horror film about how some unnatural creature lumbers in from the blank Arctic prairie to frighten and amaze.

Some called it a "Pizzly" or a "Grolar" -- a brown-splotched bruin with the claws and hump of a grizzly and the iconic white fur of a polar bear.

Shot by an Idaho sport hunter on the southern tip of Banks Island in the High Arctic of the Northwest Territories, the weird-looking animal immediately struck his Inuit guide, Roger Kuptana of Sachs Harbor, as deeply suspicious.

Soon DNA testing confirmed what scientists had considered highly unlikely, though genetically possible. The 7-foot-tall bear taken in April 2006 was the offspring of a female polar bear and male barren-ground grizzly, an improbable match that created a hybrid animal previously not seen outside of captivity.

In 2010, it happened again. Only this time, the animal was second generation. Its mother was the hybrid. And that may only be the beginning.

The possibility of interbreeding between species has been increasing throughout the Arctic -- and it's a trend that will almost certainly spell bad news for vulnerable polar animals and their genetic diversity, according to a commentary titled "The Arctic Melting Pot," published this week in Nature, the prestigious journal of natural science.

Along with the two confirmed polar bear-grizzly bear hybrids, there have been a presumed cross between beluga and narwhal, a right whale and bowhead, and more than 30 other possible combinations, wrote three Arctic researchers -- Alaska federal biologist Brendan Kelly, University of Alaska Southeast biologist David Tallmon and University of Massachusetts Amherst biologist Andrew Whiteley.

"Rapidly melting Arctic sea ice imperils species through interbreeding as well as through habitat loss," they warned. "As more isolated populations and species come into contact, they will mate, hybrids will form and rare species are likely to go extinct."

People need to start responding to this new threat with monitoring and policies, they argued.

"Plans must be developed immediately to monitor the genetics of Arctic animals and to deal with hybrids before currently discreet populations merge and at-risk species are bred out of existence," they wrote. "The rapid disappearance of sea ice leaves little time to lose."

1216-hybridanimalsThe startling prospect of some Arctic species interbreeding themselves into oblivion is just one more biological consequence triggered by the loss of summer sea ice and thinning of entire ice pack due to global climate change.

Polar bears were listed as threatened with extinction under the U.S. Endangered Species Act in 2008, partly because calculations suggested Arctic ice had declined past a point-of-no-return. This year, federal biologists have proposed that they lend similar protections to seals.

But writing in the same issue of Nature, a team of bear biologists and atmospheric scientists offered a less pessimistic view -- that time has not yet run out on saving polar bears from extinction due to shrinking sea ice cover.

After running a sophisticated array of computer models, the team found that the polar ice will wax and wane in sync with global temperatures and might not suddenly disappear at some critical threshold.

But like the scientists raising the alarm about the dangers of Arctic hybrids, they say successful conservation depends on humans responding fast.

Only if people significantly reduce greenhouse gas emissions during the next two decades can they preserve enough sea ice for the Arctic's iconic top predator to survive the annual summer shrinkage of its habitat, according to the team, including former federal biologist Steve Amstrup, who studied Alaska's polar bears across three decades as a researcher for the U.S. Geological Survey in Anchorage.

"Conserving polar bears appears to be largely a matter of minimizing temperature rise," Amstrup told an international press teleconference held in London on Tuesday.

"Because they're the apex predator in the ecosystem, they integrate everything else that's going on underneath them," Amstrup added. "Polar bears represent the health and status of the Arctic marine ecosystem, and their demise would represent the demise of that ecosystem as we know it."

To rise -- or fall -- with the ice cap

Both articles highlight how global climate change has the potential to impact the Arctic and its resident life with an intensity not yet seen in more temperate areas of the planet.

Vegetation has begun shifting north; wildlife populations have started to show up in new areas. Wildfires are spreading; shrubs colonizing tundra; walruses forced to the beach. Grizzly bears are spending more time prowling the tundra and ice, while polar bears have increasingly been forced to hunt on land.

The biggest factor driving wildlife together? Shrinking polar ice due to climate change.

Over the past few decades, summer sea ice cover has thinned and melted back, in effect seasonally wiping out vast tracts of habitat necessary for the health of species like polar bears, ringed seals and walruses.

This year was no exception. Sea ice shrank to 1.78 million square miles on Sept. 19, the third-smallest extent seen in the Arctic since satellite monitoring began in the late 1970s, according to the National Ice & Snow Data Center. To put that statistic in perspective, the polar ice of summer 2010 was about 815,000 square miles smaller than the 30-year average. Basically, a polar bear lunch box three times larger than Texas has melted into the sea.

So far this winter, the long polar cold snap hasn't exactly been chilling itself to the rescue.

"Arctic sea ice grew more slowly than average in November, leading to the second-lowest ice extent for the month," the NSIDC reported on Dec. 6. "At the end of November, Hudson Bay was still nearly ice-free."

Concerns over this trend -- plus some legal prodding by conservation groups like the Center for Biological Diversity -- led the U.S. federal government to list polar bears as a threatened species in 2008.

The listing was intended to help protect the bears under U.S. management, an estimated 1,586 bears of the Beaufort Sea and 2,000-to-3,000 bears roaming the Chukchi Sea. Seventeen other polar bear populations rim the Arctic, some already in sharp decline.

Since then, the issue over how to manage polar bears has continued to be embroiled in controversy and lawsuits.

The state of Alaska and others argue that the bears don't need protection under the ESA and, in any case, the listing will interfere with proposed offshore oil and gas exploration. Conservation groups and some Native organizations counter that drilling in Arctic remains far too dangerous, plus the feds still have not done enough to help the bears. In November, for instance, a federal judge gave the federal government until Dec. 23 to explain why the bears weren't listed as "endangered" instead of the less stringent "threatened."

Meanwhile, last month, the federal government designated 187,157 square miles of land and sea near Alaska as habitat critical to the survival of the species in U.S. territory. At least 95 percent of the protected area lies offshore, much of it over Arctic's shallow continental shelf where oil companies want to search for large deposits of oil and gas. And so it goes on.

What happens when polar species overlap?

A few years ago, Kelly, Tallmon and Whiteley began pondering what the loss of "a continent-sized chunk of ice" would mean for Arctic seals and whales, Tallmon said. At the time, Kelly and Tallmon were studying ringed seals, and Whiteley was working with Tallmon as part of the International Polar Year.

"We started looking in the literature and saw that seals and whales have lots of similarities in their chromosomes, despite big differences in their appearances and behaviors," Tallman said in an e-mail message. "At the same time, people were reporting increased frequencies of things like the pizzly/grolar bears.

"We realized then that this problem of increased hybridization could push Arctic species that are experiencing lost and altered habitat over the edge."

Their commentary cited the "media frenzy" that erupted in 2006 after a "white bear with patches of brown fur" was shot by a hunter and DNA tests confirmed that it was a hybrid.

But even more alarming, an Inuvialuit hunter shot and killed what he thought was a polar bear last April 8 on the frozen sea just west of Ulukhaktok, Northwest Territories. He was wrong.

"This time, the animal was a second-generation cross - its mother was a hybrid and its father a grizzly," the three scientists wrote. "More cases are probably out there."

The crosses between polar bears and brown bears weren't the first Arctic animals to stray across the genetic line.

Among other possible pairings in a list of 34 examples: belugas and narwhales, harbor and Dall's porpoises off British Columbia, bowhead whales and north pacific right whales, ringed seals (which live their lives entirely around ice) and other seal species, Pacific and Atlantic walruses.

What scientists believe may be a cross between a beluga whale and a narwhal was killed by an Inuit hunter in the 1980s near Disko Bay in West Greenland, according to an article published in Marine Mammal Science.

When Danish and Canadian researchers later examined the skull, they found it was larger than either normal belugas or narwhals - with teeth that mixed the two species. Though it was an old animal, the creature lacked a narwhal's tusk, a feature important for successful breeding among narwhals.

In 2009, a cross between a bowhead whale and a North Pacific right whale was photographed in the Bering Sea, a prospect that the scientists said was particularly alarming. The right whales that roam the ocean near Alaska are considered the most critically endangered marine mammals on the planet.

"Interbreeding between the North Pacific right whale, of which there are probably fewer than 200, and the more numerous bowhead whale could quickly push the former to extinction," they wrote.

Don't the 'fittest' species win the evolution game?

But what's ultimately wrong with all this inter-species mating anyway? Isn't something like this the crux of survival-of-the-fittest - just a modern-day example of old-fashioned evolution at work?

As the authors themselves note, "hybridization is not necessarily a bad thing."

But there's a difference between natural evolution slowly rolling forward outside of human influence and what has started to occur in the Far North, according to the scientists.

Rather than species mixing and adapting over many centuries, these Arctic animals are being thrown together within a generation or two as climate warms and the ice cap barrier disintegrates.

"Where human-mediated hybridization occurs, (hybrids and offspring) should generally be considered a loss to the wildlife species and a threat to its persistence," according to a recent report on "manipulated populations" by the Committee on the Status of Endangered Wildlife in Canada.

"Hybrids do not represent either original taxonomic group, and they do not contribute to the evolutionary lineage of either group."

It's true that hybridization is one evolutionary process, Tallmon explained in an email. But the latest developments in the Arctic are just happening too fast.

"It's a bit like extinction," Tallmon told Alaska Dispatch. "We're in the midst of the 6th major extinction event in the history of the planet and it is human caused. ... So, in that sense, it's not a natural phenomenon.

"We argue that anthropogenic hybridization of species that are threatened with habitat loss and other threats could well push them over the edge toward a more rapid extinction than they otherwise might face."

It's not just about protecting the big white bears of the Arctic from their amorous grizzly cousins - or from becoming museum curiosities reduced to remnant wild populations.

"The Arctic is the fastest warming on Earth," Amstrup told reporters during the teleconference earlier in the week. "Changes there -- including sea ice loss and diminishing polar bear populations -- are more obvious now than changes in other regions. Because human-caused warming is global, however, these changes foreshadow those that will come to the rest of the world.

"Reducing greenhouse emissions to save polar bears, therefore, would have worldwide conservation benefits."

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