LOMPOC, Calif. — Grape grower Steve Pepe has a new crew of weed whackers who lack Social Security numbers, couldn't care less about health insurance and never ask for a raise.

Henley, Matilda and Althea are Babydolls, miniature sheep that top off at 2 feet. If they work out, Pepe can avoid farm chemicals, slash weeding bills and improve his soil.

The sheep have voracious appetites for weeds, but they aren't quite tall enough to reach fruit on trellised grape vines. Looking like muddy cottonballs as they forage on Pepe's Santa Rita Hills farm, the sheep feel like a damp, dirty sweater.

Matilda and her co-workers mow away clump after clump of nettlesome weeds. They seem to digest them almost instantly, producing healthier vines with their natural fertilizers.

That means more flinty chardonnays and pinot noirs with hints of cedar and black cherry for customers who are increasingly demanding organic wines.

Perhaps, Pepe muses, the sheep will bring his prized Clos Pepe Pinot Noir, which retails for $40 a bottle, more gold medals.

In Mendocino County, University of California researchers are trying to train full-size sheep — which can grow upwards of 36 inches tall — to give up eating grape leaves and become biological lawnmowers. Researchers allow the sheep to chomp grape leaves in a small Hopland vineyard, then immediately feed the animals a dose of lithium chloride, which makes the sheep sick to their vinifera-filled stomachs.

"We are trying to create a powerful negative association with grape leaves," said livestock expert Morgan Doran at the UC extension in Fairfield.

Sarah Bennett, whose family owns Navarro Vineyards, said she was surprised at how hard her leased flock of miniatures has worked, even eating the "suckers" or green shoots that grow off the woody lower sections of the vines. "Removing the suckers was something that we had to do by hand," Bennett said.

Miniature animals come with miniature hooves, which are easier on the soil than tractors or even a farmworker's boots. And unlike a John Deere, the sheep never get stuck in the mud and can reach into nooks and crannies.

Unlike goats, which tend to reach up when they forage, "these sheep tend to eat down toward the ground," said Tony Crabb, who leased 12 sheep for $2 a day per head last year. He plans to bring them back to his Puma Springs Vineyard in January.

Pepe, who paid $2,000 for his three animals, figures that by the time his ram and two ewes procreate into a flock of three dozen, he will not have to rely on human and mechanical weeders on his 40-acre farm, saving as much as $3,000 an acre in expenses.

Deborah Walton, who breeds and leases the animals from her Canvas Ranch near Petaluma, won't lease sheep to a vineyard that uses pesticides because she doesn't want them to become toxic sheep. And her clients' farms need to have fencing and guard dogs because predators relish lamb chops. Walton leased 20 sheep to Fetzer Vineyards in 2004, but "two sheep were killed and then I had to take them all out," Walton said. "Once the coyotes knew the sheep were there they kept coming back."

At Clos Pepe, the sheep are protected by Rosa, a grimy black-and-white border collie that chases off coyotes and occasional bobcats. Before the sheep arrived, "Rosa ran around trying to herd people, the other dogs and even cars. Now she doesn't pay much attention to us," Pepe said.