(Vancouver Sun)
The mating game heats up
BY ED STRUZIK, POSTMEDIA NEWSMAY 11, 2011 12:02 PM
Muskox are survivors of the last ice age which killed off many Arctic animals, like the woolly mammoth.
Photograph by: Ed Struzik, Edmonton Journal
University of Alberta scientist John England was flying in the High Arctic last summer when he spotted something large moving on a tiny island in the Beaufort Sea. When he and the helicopter pilot moved in to get a closer look, they were astounded to see a grizzly bear prowling the shoreline.
What this brown bear was doing in the kingdom of its white cousin is not entirely clear. But a week later when I joined England in the field, we found the tracks of a grizzly bear leading to a partially excavated den on Banks Island. There was no way of telling whether this was the same animal. But it was obvious that this one had no intention of going back to the mainland. Up until about 20 years ago, sightings of grizzlies in the High Arctic were relatively rare; a quirk of nature, many biologists thought, that may have simply occurred because the bear ended up walking the wrong way or because it had strayed too far following the mainland caribou that sometimes cross the sea ice to the Arctic islands in the western Arctic.
But that thinking began to change in recent years as more brown bears and a succession of other animals such as red fox, white-tailed deer, Pacific salmon and killer whales began showing up in areas traditionally occupied by polar bears, Arctic fox, caribou, Arctic char, and beluga whales.
Initially, the fear was that some of these Arctic animals would not be able to compete with their southern cousins. Field studies have shown that Arctic fox do not fare well in competition with red fox. Now there's anecdotal evidence to suggest this to be the case in the wild. Killer whales kill and eat beluga and narwhal. Inuit hunters have been reporting this for years. In August 2005, biologists Kristin Laidre, Jack Orr from Canada's Department of Fisheries and Oceans and their colleagues saw this happen at Kakiak Point in Admiralty Inlet, Nunavut. Now the new concern is that interbreeding might result in hybrid creatures that will compromise a unique gene pool that has helped these animals adapt to this harsh environment.
The possibility of this happening came to light for biologist Brendan Kelly in 2006 when an American hunter killed an animal in the Canadian Arctic that turned out to be the offspring of a female polar bear and a male grizzly.
Kelly, who is now the deputy director of the Arctic Sciences Division at the U.S. National Science Foundation, wondered then whether this kind of hybridization was occurring in other species.
Marine mammals such as seals, walrus and sea lions, he knew, are more prone to hybridization, because they share the same number of chromosomes, which allows them to produce offspring. If you removed a continent-size ice sheet that prevented southern marine mammals from moving north, he thought, what might be the outcome?
In a recent paper published in the journal Nature, Kelly, David Tallmon and Andrew Whiteley reported that hybridization had already occurred between harp and hooded seals, narwhal and beluga whales, and very likely between North Pacific right whales and bowhead whales. They also suggested at least 22 Arctic marine mammals are at risk and that many of these species are threatened or endangered. This is important because with only a few hundred North Pacific right whales left in the world, for example, the gene pools of some of these mammals are becoming perilously shallow.
"There is something to be said about species adapting to climate change," Kelly says. "But the kind of adaptation that's necessary is a shift to genes that fit the new climatic environment better than the old genes. That takes time. The change that is taking place in the Arctic now is happening so fast that long-lived animals like whales, seals and polar bears aren't getting the chance to adapt as quickly as it is necessary." Kelly likens the role that sea ice has played in the Arctic to the role South America has played in separating the world's two great oceans. For tens of millions of years, the continent was a barrier to dispersal and gene flow between the South Atlantic and the South Pacific. If you could somehow remove South America, its disappearance would not be that much different than eliminating the big barrier of sea ice in the Arctic world.
University of Alberta scientist Andrew Derocher is well aware of what is going on in the Arctic. He just returned from the Beaufort Sea where he and his students were doing research on polar bears. While they were there, Derocher had heard that two Inuit hunters from the community of Ulukhaktok on Victoria Island had spotted what they thought was a female and cub hybrid. The hunters saw polar bears and signs of grizzlies in the area. The hybrid showed clear sign of a mixed-background: white legs and darker body. Unfortunately, without a camera, everyone is still waiting to see a photo of a live hybrid. Although grizzly bears have been spotted in the Arctic in the past, Derocher has little doubt that they are expanding their range as temperatures in the northern hemisphere heat up.
"In recent years, there have been reports of grizzly bears in northern Manitoba, near Baker Lake and Igloolik in Nunavut and in a number of places in the western part of the High Arctic. It seems to be happening everywhere. There have been two reports of grizzlies making it over to Vancouver Island recently."
Derocher isn't convinced that hybridization is going to become as serious a concern as some biologists suggest, especially when it comes to grizzly bears and polar bears.
"They are so genetically similar that there is little difference between the two animals," he says. "The bigger concern is the rapid loss of sea ice that we are seeing in the Arctic. In pretty well every place in the Arctic where polar bears and grizzly bears meet — and there are not a lot of places like that — the ice will have receded to the point where it will be almost impossible for them to meet up and mate.
"It is a race between expanding grizzly bear populations and disappearing polar bear habitat which will likely take the last polar bears far to the north beyond the realm of grizzlies."
Derocher suspects that the melting sea ice will affect narwhal, beluga and other marine mammals in a similar way. "Beluga and narwhal use the sea ice to hide from killer whales," he points out. "When that ice is gone, they are going to be extremely vulnerable."
Almost lost in the current debate about Arctic hybridization and invasive species from the south is that some southern marine mammals will also bring with them diseases for which Arctic marine mammals have no immunity.
The possibility of this happening came to light several years ago when Canadian scientists were monitoring the spread of Trichinella in the Arctic. The roundworm, which is commonly found in polar bears and Arctic fox, was of little concern in the Arctic until the 1980s when it began to spread to walrus and to humans who had eaten uncooked meat. Symptoms include fever, myalgia, malaise and edema.
Ole Nielsen, a microbiologist working for the Canadian Department of Fisheries and Oceans, was assigned the task of tracking the spread of this parasite and determining whether there might be anything else of concern in the hunter-killed samples he was given.
Initially, he was not altogether surprised to find some evidence of brucellosis, which has been linked to reproductive failure in dolphins and baleen whales. The disease is extremely widespread in the marine world and it wasn't a stretch of the imagination to think it might have got a foothold in the Arctic.
A bigger concern, however, was the discovery that neither beluga whales nor narwhal have antibodies that would help them resist phocine distemper, a deadly virus that was first discovered in the marine environment in 1988 when it killed 20,000 harbour seals in northwestern Europe.
Since then, it has spread to seals in Lake Baikal, striped dolphins in the Mediterranean and to several species in other places of the world. No one knows how phocine distemper made its way into the ocean. But because it is so closely related to canine distemper, it is thought to have its origins in land-based species whose remains were dumped into salt water. "There are a lot of unknowns should distemper make its way to the North American Arctic," says Nielsen. "If distemper gets a foothold here, it could get ugly. With there being as many as 80,000 narwhal and 150,000 belugas in the North American Arctic for most if not all of the year, a massive die-off somewhere is not out of the question."
A die-off isn't as outlandish as it might seem. All that's required is a carrier: a pilot whale, harbour seal, or dolphin — marine mammals that are known to carry the virus for long periods of time before suffering the symptoms. Any number of them could ride a warm current into an Arctic environment that is no longer choked with ice.
Brendan Kelly acknowledges that there is no easy solution to deal with what's happening. Culling hybrids, as some countries do, for example, would be difficult in an environment as large and as hostile as the Arctic. But doing nothing, he adds, forgoes the possibility that a better answer might come up in the future. He advocates more diligent study of hunter-killed mammals in the Arctic world.
"Many of the species that are vulnerable are already endangered or threatened," he says. Roger Kuptana, the Inuit guide who led the American hunter to that grizzly bear/polar bear cross in 2005 is convinced of one thing.
"The world is changing fast up here," he said when I met up with him last summer. "It's not just grizzly bears and polar bears. We're seeing robins and other birds that we've never seen before. Caribou are disappearing. Muskoxen are everywhere. It's not the same world that I grew up in."
Fascinated as he is about how things are unfolding in the Arctic, Derocher notes that hybridization is happening everywhere.
"Down south, we see it happening between coyotes and wolves, between lynx and bobcats, between mule and white tailed deer and other animals.
"What this all means is hard to say. Predicting the future course of evolution, a professor of mine once said, is a fool's game."
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