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A study plot on Sheldon National Wildlife Refuge in Nevada shows how non-native horses destroy a desert wetland. After just two months, an area open to horses, at left, has little uneaten vegetation; the soil and water have been trampled into mud. At right, in an area protected from horses, healthier vegetation provides nesting cover for birds and food for wildlife, while the stream channel starts to recover
A study plot on Sheldon National Wildlife Refuge in Nevada shows how non-native horses destroy a desert wetland. After just two months, an area open to horses, at left, has little uneaten vegetation; the soil and water have been trampled into mud. At right, in an area protected from horses, healthier vegetation provides nesting cover for birds and food for wildlife, while the stream channel starts to recover.
Credit: Gail Collins, USFWS

Sheldon Refuge to Get Tough on Invaders

How does one exotic invasive species destabilize a sensitive desert habitat, like that of Sheldon National Wildlife Refuge in northwest Nevada? First, it multiplies, unchecked by predators. Then it tramples native grasses and flowering plants, degrades springs and streams, erodes the soil and shrinks forage and ground cover vital to pronghorn antelope and declining species, such as the sage grouse and other migratory birds.

National Wildlife Refuges are a network of lands and waters established to conserve native wildlife and ecosystems for the public benefit. Horses have become a problem on Sheldon National Wildlife Refuge, which was created to protect pronghorn antelope, sage grouse and other species of the sagebrush steppe ecosystem.

"You hear some folks say, 'It's not the horses that are doing it; it's the cattle,'" said Paul Steblein, project leader at Sheldon Refuge. "Well, the cattle have been off the refuge for 15 years. 'Well then,' they retort, 'it's the wildlife.' So we set up this five-year study to look at the effect of horses on the ecosystem." Refuge staff fenced off multiple one-acre plots to keep out horses, but not pronghorn, deer and bighorn sheep. "This is after two months," said Steblein, showing a photo of the exclosure. Inside, the grass reaches 18 to 20 inches in height; outside, growth is maybe a half-inch. "Look at the difference. We see this pattern on springs and streams across the refuge."

Before the release this fall of a new draft environmental impact statement, Steblein briefed Congress on the problem and the proposed response:  removing all horses from Sheldon Refuge within 5 to 15 years to restore habitat for sage grouse and other wildlife. Horses would be adopted out, or as a last resort, auctioned. The refuge now gathers 350 to 400 horses a year, adopting out about half of them (at a cost of about $2,500 per horse) and spaying the rest (at about $500 a horse) before returning them to the refuge. All activities are conducted in a humane and professional manner.

Those measures still leave Sheldon with more than 800 horses, more than the land can support, said Steblein. Refuge staff will seek public comment on the plan before it becomes final.

Steblein said many studies show that development, invasive weeds, wildfire and climate change are squeezing the Great Basin, a biodiverse region covering most of Nevada and parts of Utah, California, Idaho, Wyoming and Oregon. Its sagebrush ecosystem is degrading, threatening at least a dozen bird species considered national conservation priorities. These include the Brewer's sparrow, sage sparrow, loggerhead shrike, horned lark, sage thrasher and prairie falcon. "What we're talking about," said Steblein, "is having one place in the West that has great sagebrush habitat, where wildlife species that are declining can prosper."

Contrary to popular belief, wild horses are not in danger of extinction: Herds increase at the rate of about 20 percent a year. Roughly 33,700 wild horses occupy 31.9 million acres managed by the Bureau of Land Management (BLM). BLM also cares for another 35,000 wild horses in short-term corrals and long-term pastures at a cost of tens of millions of dollars per year.

"If we want to preserve the natural heritage of the Great Basin, Sheldon is a critical refuge for conservation," said Steblein. "And the wild horses make that impossible."

For more information, contact Sheldon-Hart Mountain National Wildlife Refuge Complex at http://www.fws.gov/sheldonhartmtn/Sheldon/index.html or call 541-947-3315.

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