Grape news! Sheep trained to weed vineyards

updated 2:32 p.m. ET July 11, 2007

HOPLAND, Calif. — Call them mutton mowers. University researchers are training sheep to clean up vineyard weeds but stay off the grapes.

Enthusiastic and unpicky eaters, sheep are already being used in some vineyards as a green alternative to tractors. They don't use gasoline and keep down weeds — a necessary task to deter pests and keep vines healthy — sans herbicides.

Unfortunately, sheep will chew up thousands of dollars worth of grapes if left to their own devices.

That's why University of California, Davis researcher Morgan Doran and his colleagues are experimenting with aversion therapy and other techniques to turn sheep into better field hands.

Sheep ranchers get a new market for their flocks while vineyard managers get ''another tool in the tool box,'' says Doran. ''It's a win-win.''

But just how do you teach sheep?

'Very good at what they do'
It's not as tough as you might think, says Doran, who thinks sheep are unfairly maligned as wooly minded creatures. They may not be the brightest lights around, but ''they're very good at what they do,'' he says.

What they do is eat — all day, every day.

''Everything that we're doing is based on their skills at eating different foods and detecting different flavors and associating positive or negative effects of those foods with different flavors,'' he says.

Doran's project is based on the recommendations of aversion therapy techniques developed by an animal behaviorist at Utah State University.

Sheep that had never tasted grape leaves were brought in and allowed to stuff themselves on vines. The animals then got a small dose of lithium chloride, a drug that doesn't produce any outward signs in the dosed sheep but leaves them feeling queasy, Doran said.

Some sheep got the dose in liquid form, some in capsules and two other groups of sheep got placebos to serve as a control.

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