Lambs Learn to Love Noxious Weed

BOZEMAN — Imagine a lamb at its first pasture potluck, and you'll see how Montana lambs are learning to eat a noxious weed called Dalmatian toadflax.

The lamb fills her plate with familiar grasses and weeds, and then notices her mom and aunts loading up on a tall plant that's pretty enough to place in a vase. Emboldened by her elders, the lamb nibbles a yellow blossom and decides she likes it. She cleans her plate and returns again and again to the all-you-can-eat buffet until it's time to go home.

That's the scenario Montana State University researchers are seeing after trucking ewes, lambs and goats to Montana pastures infested with Dalmatian toadflax, says Lisa Surber of the Montana Sheep Institute based at MSU. The lambs won't touch Dalmatian toadflax on their own, but they will if they see their mothers or goats eating it. And once they try it, they like it.

'If you look at the plant out on the prairie or out on the range, it's just not a plant that looks conducive to graze,' Surber says of the weed that began as an ornamental plant, but escaped from the garden. 'It basically takes a training period for sheep or goats to figure out that it's an edible plant and something very desirable. Once they start to consume it, they really, really favor the plant.'

Surber and Rodney Kott, director of the Montana Sheep Institute, have sent sheep and goats to private ranches for the past three summers, dividing the animals into groups and watching them graze. It appears, the researchers say, that the lambs go through a learning process when it comes to eating Dalmatian toadflax. The experiment has raised questions that the scientists will investigate further, but they eventually plan to develop a grazing prescription for land managers. Sheep and goats have eaten weeds for a long time, but today's ranchers want to know the exact steps and methods they should take to produce certain results, Kott says.

Surber adds, 'Ultimately, we think we can be very successful in controlling the plant, this noxious weed, with sheep and goats or sheep that have been trained. It's a question of understanding that learning behavior a little bit more. Some herds are not successful, and we need to understand why.'