My, what a small family tree you have

In the Northern Rockies, gray wolves may face the problems of inbreeding

  • Wolves from the Druid Pack give chase near Soda Butte, Yellowstone National Park


In Yellowstone National Park, a grandfather mounted his granddaughter. A nephew mated with his aunt, and siblings copulated. But you won't find the lurid details in a grocery-store tabloid or the latest tell-all memoir. It's all in a new study by researchers from the University of California, Los Angeles, on the gray wolf's genealogy. And it predicts the predator will get even more incestuous in the future. 

Researchers led by Dr. Robert Wayne analyzed blood and tissue from 200 Yellowstone wolves and constructed a family tree for the park's population. Their research confirms that wolves go to great lengths to find unrelated mates. But in the Yellowstone area, the scientists warn, it's going to become harder and harder for breeding singles to find a mate that's not already part of the pedigree. All the wolves sampled descended from the original 31 released in the park - which means there's been no immigration into Yellowstone since the reintroduction from Canada 10 years ago. 

And now that the U.S. Fish and Wildlife Service proposes to remove the Northern Rockies gray wolf from the endangered species list, states will be able to legally reduce their wolf populations to a fraction of what exists today. Once Idaho, Montana and Wyoming take the reins, scientists fear that the drop in wolf numbers, combined with the lack of safe and passable travel routes between prime habitats, will genetically isolate the remaining packs. "Wolves will become inbred,"Wayne says, "especially in Yellowstone." 

Wolf recovery in the Northern Rockies has been a major success. Meadows and mountains bereft of the gray wolf for nearly 70 years now sustain 1,300 animals in 89 packs. Wayne's team analyzed scat, hair, blood and tissue from more than 500 of those wolves during the past three years. The Yellowstone research is part of this broader study, funded largely by the Yellowstone Park Foundation and the U.S. Fish and Wildlife Service. The current population is genetically diverse, Wayne says: "All the careful planning - picking wolves from different packs in Canada - paid off." 

But that planning may ultimately be for naught. The federal delisting proposal requires a minimum population of 300 wolves in 30 breeding pairs evenly distributed across the three recovery areas: northwestern Montana, central Idaho, and the greater Yellowstone area. That population size severely underestimates the number of wolves needed for a genetically healthy, self-sustaining population, say critics. 

"We believe that the original recovery goals of 300 wolves in the three states are arbitrary, inadequate and unscientific,"says Sylvia Fallon, a conservation genetics fellow with the Natural Resources Defense Council. She helped author a letter to the Fish and Wildlife Service signed by 250 scientists across the country, including Wayne. Because not all wolves in a pack reproduce, scientists estimate that in order to be viable over time, the Northern Rockies population needs to be in the thousands. Citing a 2006 study on the corridors connecting core habitats, the scientists also expressed concern that migration routes between the recovery areas are inadequate. Wolves dispersing to new territories must cross busy highways, skirt fast-growing cities, and resist a tempting array of livestock. Wayne says that preliminary results from the larger study show little evidence of gene flow between packs in the three recovery areas. The delisting proposal will likely lead to even less interchange, he says, and while this lack of connectivity isn't an immediate threat, it will become a problem in the future, especially as human populations grow in the intermountain West. 

As development clogs migration corridors, the harmful effects of inbreeding accumulate. When generations of closely related animals mate, their offspring lack the genetic variability that helps a species evolve disease resistance or adapt to changing environmental conditions. Phil Hedrick, an evolutionary geneticist at Arizona State University, notes that the minimal wolf numbers in the federal plan don't provide much of a buffer against nasty surprises. An outbreak of distemper, which killed 53 Yellowstone wolves in 2005, could be even more lethal to inbred wolves that are all susceptible to the disease. And in a limited gene pool, offspring are more likely to receive a harmful recessive form of a gene from each parent. In humans, such pairing causes diseases like cystic fibrosis and sickle-cell anemia. The UCLA team predicts that unless Idaho and Montana wolves begin mating with Yellowstone wolves, within 60 years one pup in each litter will die from genetic defects. "We have to think about conservation of a species in the long term,"says Hedrick. "Sixty years may seem like a long time, but in the scheme of things it's not." 

But the man most responsible for the gray wolf's recovery isn't concerned that delisting will result in inbreeding. "Everybody agrees that 300 (wolves) and 30 (breeding pairs) is the absolute minimum and that 1,000 wolves is a much more viable population,"says Ed Bangs, wolf recovery coordinator for the Fish and Wildlife Service. But there will always be far more than 300 wolves in the Northern Rockies, he says, because each state will maintain five more breeding pairs than the federal requirement of 10. "The states are committed to wolf conservation,"he says, despite Idaho Republican Gov. Butch Otter's call for hunters to cull 90 percent of the state's wolves. And because states want to allow hunting and trapping, says Carolyn Sime, Montana's wolf program coordinator, they'll maintain wolf populations at levels far above the 15 pairs they must keep "in the bank." 

If Northern Rockies gray wolves do start to show signs of inbreeding, states may be trucking their wolves around to save them from the fate of the Florida panther. This large, very rare predator has suffered severely from inbreeding, and the sad, sensational results would make a great cover for a supermarket tabloid: All of the big cats now have kinky tails, and most of the males have just one testicle. 

The author writes from a fire lookout in southern Oregon.

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