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Michigan Wolves Under Threat From Inbreeding

April 5, 2009

Nearly thirty gray wolves living on an island chain in northwestern Lake Superior have backbone malformations as a result of genetic inbreeding, presenting yet another hurdle for the wolves’ long-term survival, wildlife experts say.

Although only confirmed recently, the problem has seemingly been in existence or decades in the tiny, isolated wolf packs in Isle Royale National Park in Michigan.

The abnormalities are also found in some domestic dogs, and can cause pain, partial paralysis and can limit the critical range of motion needed by these wild predators.

The discovery presents the ethically ambiguous question of whether biologists should seek to dilute the gene pool by introducing wolves from other places, said researchers at Michigan Tech University in Houghton.

The University hosts a 51-year-old study of the park’s wolves and moose that is one of the world’s longest continuing observations of the symbiotic relationship between predator and prey species and their environment.

Biologists have historically taken a hands-off approach as wolf and moose numbers have risen and fallen over the years, choosing instead to let nature take its course –even if that meant extinction of the species.   

However, there are strong arguments to support intervening as well, according to project leaders.

“This is not a decision just for scientists to make any more,” Rolf Peterson, who has been involved in the study since 1970, told the AP.

Although formally part of Michigan, Isle Royale is actually closer to Minnesota and Ontario.   Scientists believe moose likely found their way to the island by swimming the 15 miles from Canada around 1900.   And a few arrived during the late 1940s, crossing a rare ice bridge from the mainland.

The two species’ populations have fluctuated over the years as a result of disease, weather, food availability and other factors.   But the wolves’ most dangerous period was during the 1980s, when their numbers dropped to just 12 due to a parvovirus outbreak.

This winter, their population stood at 24, a number roughly equal to the long-term average.  The wolves were divided into four packs.

Researchers had long looked for signs of potential problems from inbreeding, such as poor survival rates for pups.  

However, the first firm evidence emerged when Jannikke Raikkonen of the Swedish Museum of National History, a wolf anatomy expert, visited the islands many years ago to examine the project’s bone collection. During her visit, she identified malformed vertebrae in all wolf remains found the previous twelve years.   Normally, such abnormalities are found in just 1 percent of non-inbred observed populations.

Peterson, along with biologist John Vucetich, discovered two dead wolves this winter with deformed vertebrae, one of which had been killed by fellow wolves.   The other had remarkably severe arthritis for its age, and a neck injury indicative of a moose kick. The bone malformation may have lessened its ability to evade the lethal blow, Vucetich told the AP.

Peterson said that spinal malformation due to inbreeding poses no immediate threat of extinction.  However, the most significant short-term problem is a drop-off in moose, the wolves’ primary food supply, for which scientists blame climate change.

This winter’s moose census revealed only 530, roughly half their long-term average, and a steep drop-off from last year’s estimated 650 moose.

According to Vucetich, inbreeding is just one of many reasons the wolves will always be living on the edge, one disaster away from extinction.

“It just makes everything a heck of a lot more complicated,” he told the AP.

The researchers are considering whether to embark on a “genetic rescue” that would trap unrelated mainland wolves and transport them to Isle Royale.  They hope such an approach would breed and mix the outside wolves’ genes with the existing wolf population.

But the issue brings to light competing scientific and ethical values, Vucetich said.

Opponents of intervention believe humans should not interfere with wilderness systems, even if it means the Isle Royale wolves ultimately die out. Their loss, they say, would provide valuable information that could save other endangered species elsewhere.

However, supporters of intervening argue that attempting to save the wolves also could provide valuable data, at the same time sparing individual animals from painful bone deformities.

“We have an incomplete understanding of genetic rescue – when and how and why it works,” said Vucetich.

“Even so, it may be an important conservation tool as more population species become rare.”

The researchers reported their findings this week in the journal Biological Conservation, and are soliciting public comments on their Web site.
 

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On The Net:

 Isle Royale National Park

Michigan Tech University




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