Missoula sheep's appetite for weeds has paid off on Mount Jumbo – in a way that's both unexpected and "remarkable," according to conservation lands manager Morgan Valliant.
"We're seeing what we believe is a large-scale population crash of spotted knapweed on the saddle," said Valliant, with the city Parks and Recreation Department.
The weed-eating sheep won't graze the North Hills this year because it's time for other tools in that area, Valliant said Monday. In the middle of June, however, the animals will return to Mount Jumbo.
"We'll do one more year on the south face of Jumbo, and then the plan is to stop grazing the south face of Jumbo next year. We will continue to graze the saddle," Valliant said.
There, photos show the knapweed is dying, he said. Parks and Rec anticipated the sheep could help knock back the leafy spurge and toadflax, but he said there was little research to suggest sheep would have a measurable effect on spotted knapweed.
"It's quite amazing, actually," Valliant said of the results.
If the knapweed goes to seed, it will set the clock back, so Parks and Rec will let the sheep keep doing their work on the saddle.
Parks and Rec started using sheep to cut down on weed density. The animals have historically munched on weeds in the North Hills in the spring and later on Jumbo.
"(But) the long-term goal of the grazing program was never eradication," Valliant said.
In the last couple years, he hasn't seen an appreciable drop in the density of leafy spurge on the North Hills, an indication the sheep's work has reached its limits.
"That tells us the tool, sheep grazing, has done what it can do for us," he said.
With weed density down, the department has been able to work on seeding in the North Hills. He said other tools the department uses are herbicides and hand pulling.
"This year, we did a fall and a spring seeding, and we've just seeded more than we have in the past," Valliant said.
In previous years, Enrique Marquez Banda of Mexico has overseen the sheep. Earlier this year, it appeared changes in immigration regulations would jeopardize the ability of the Chihuahua shepherd to participate in the program.
Valliant, though, said Banda arrived in Missoula in February to help sheep rancher John Stahl with lambing, and he would care for the sheep on Jumbo this year, as he has in the past.