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.’

Dean Dutton, Cliff Cox, John Potter and Doug Potter own the ranches where the commuting animals grazed. Dutton’s ranch is located at Gold Creek between Butte and Missoula. The others are located in the Spokane Hills around East Helena. Sven Svenson of Reed Point provided hundreds of sheep and goats for the experiment.

‘It’s been fantastic. I hope it continues. It has saved my bacon,’ Svenson says of the study that gave him extra pasture, allowed his own pastures to rejuvenate and provided the opportunity to raise more sheep. He was able to keep his ranch free of noxious weeds by penning the sheep and goats in a small pasture for two or three days after they returned home, Svenson adds.

Dutton says sheep and goats from another producer wouldn’t touch his Dalmatian toadflax in 2005. Why some sheep love Dalmatian toadflax and others don’t is one of the questions that Surber and Kott want to investigate. But Dutton says he was pleased with the performance of Svenson’s animals in 2007. Svenson sent 1,000 sheep and goats to graze more than 2,000 acres, and they were much more effective than chemicals, Dutton says. They and the guard dogs that protected them also got along well with his cattle.

‘I’m very happy with it,’ Dutton says. ‘It looked really good. When toadflax was gone, they worked on the knapweed.’

Dalmatian toadflax is fairly widespread across Montana, but it’s especially prevalent between Missoula and Deer Lodge, Surber says. The Bucksnort fire of 2000 created a welcoming environment in the Spokane Hills near East Helena, too.

–Evelyn Boswell, (406) 994-5135 or evelynb@montana.edu

Published on Jan 1, 2008

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