Jeff Villepique usually carries bear spray when he goes into the mountains. But the California Department of Fish and Game biologist isn't worried about bears as he walks to the edge of a steep, rocky wash near the Mount Baldy Ski Lifts resort in Southern California. On this bone-chilling, misty morning, he's worried about dogs.

Villepique recalls the macabre scene he recently investigated here: the tracks of three or four dogs in the snow, tufts of hair marking where a bighorn ewe was dragged down the talus slope, and the carcass itself -- mangled and missing a leg and a horn. The prime suspects: a Labrador retriever mix Villepique found still gnawing on the evidence, and its partner in crime, a German shepherd mix that watched menacingly from the top of the wash.

"It's a great loss," Villepique says. State and federal agencies in California have spent three decades and a lot of money trying to recover local bighorn populations. But encroaching development and its encroaching pets -- some abandoned and others simply allowed to run free -- are complicating efforts.

Officials have captured hundreds of feral and free-roaming dogs in the San Gabriel and San Bernardino mountains in recent years, especially around Mount Baldy and Lytle Creek. In addition to bighorn sheep, the dogs are hammering rabbits, quail, mule deer and other wildlife.

The story is similar across much of the West, as swelling ranks of rogue canines increasingly harass wildlife, livestock, even people. But most federal efforts to protect big game and livestock are focused on killing wild predators. With limited funds for trapping dogs, local officials like Villepique can do little but try to educate the public.

"I doubt we're even making a dent in what is going on out there," says California-based Forest Service biologist Kathie Meyer.

Wildlife Services -- the federal agency responsible for predator control -- estimates that more than 33 million feral and free-roaming dogs run loose in the United States, biting 5 million people each year and killing about 10 to 15, usually small children. In rural areas, feral and loose pet dogs often form packs that chase down and kill deer, elk, chickens, goats and even cattle.

"People don't understand that Fido on the couch who is normally so friendly will instinctively hurt or chase big game animals," says Tyler Baskfield, spokesman for the Colorado Division of Wildlife.

At Joshua Tree National Park in Southern California, a ranger recently came across three feral dogs feeding on a bighorn carcass. At the nearby U.S. Marine Corps base at Twentynine Palms, officials have received numerous reports of dogs attacking threatened desert tortoises. In Texas, the dogs go after white-tailed deer and ground-nesting birds. But most incidents go unreported, says Villepique. "There is no reason for me to think we know the full extent of this problem."

Many ranchers are quick to blame wolves, coyotes and grizzly bears for harassing or killing their livestock, but wildlife officials say dogs are often the culprits. Cascade, Idaho, rancher Phil Davis is all too familiar with dog trouble.

"The worst time, we had about a half-dozen dogs that packed up," Davis says. "They were chasing steer and causing some headaches. One time, they chased a yearling steer clear into town. He finally gave up and hid in someone's garage."

Dogs are second only to coyotes as sheep killers. In 2004, coyotes killed more than 135,000 sheep nationwide, while dogs slaughtered some 30,000. The dogs "literally tear the hides off the animals, opening up their gut cavities and tearing up their faces," says Peter Orwick, executive director of the Denver-based American Sheep Industry Association.

"Dogs have been our worst nemesis over the last 20 years," agrees Don Watson, owner of Napa Valley Lamb Company in California and Rocky Mountain Wooly Weeders in Loveland, Colo. His sheep dogs -- Great Pyrenees that can weigh up to 120 pounds -- are effective at keeping wild predators like coyotes and mountain lions away. But dogs are relentless, wearing the Great Pyrenees down, chasing the sheep until they can no longer run and then killing them.

"The worst night I ever had, I lost 17 sheep," Watson says, when dogs from a neighboring ranch miles away got into his Napa corral.

Each year, Wildlife Services receives hundreds of requests to trap, poison and shoot feral dogs. Still, the agency devotes most of its resources to killing wild predators. In 2006, the agency killed more than 87,000 coyotes but only 512 dogs. Hundreds more were taken to animal shelters.

In California's San Gabriel and San Bernardino mountains, officials have removed 350 feral and free-roaming dogs over the past 15 years. The dogs are difficult to catch, and trapping has been sporadic at best. Recent U.S. Forest Service budget cuts will further hamper efforts to address the problem.

That leaves local officials like Villepique groping for a solution.

As the sun breaks through the morning mist off Mount Baldy Road, Villepique recalls how the dog he saw feeding on the bighorn carcass fled to a nearby area pocked with cabins. Unable to locate the dog's owner, he plans to work with animal control to help enforce laws that require folks to keep dogs on leashes or behind fences. He is trying to educate local residents and wants stiffer penalties for repeat violators.

And if that doesn't work, there's always the bear spray.

The author freelances from Claremont, California.