Hired grazers: How a small flock of sheep took on one of Tucson's most invasive species
The University of Arizona Cooperative Extension joined a multi-agency targeted grazing initiative to beat back the buffelgrass on ‘A’ Mountain.
Flavie Audoin
Wildlife encounters on Tucson’s iconic Sentinel Peak – otherwise known as ‘A’ Mountain – aren’t unusual. The mountain is home to Gambel’s quail, desert cottontail rabbits, red-tailed hawks, and even the occasional herd of javelina. But if you visited during the summer months of 2025, you may have noticed some unexpected creatures roaming the slopes: a small flock of Navajo-Churro sheep.
The sheep were on the mountain as part of a buffelgrass removal initiative funded by the Arizona Department of Fire and Forestry Management (DFFM), with support from the Arizona-Sonora Desert Museum, City of Tucson Parks and Recreation, the Tucson Fire Department, Grazing Specialist LLC and the University of Arizona Cooperative Extension. Between May and October, 15 of these desert-adapted sheep chowed down on buffelgrass in a targeted grazing effort to significantly decrease the density of the invasive plants on the mountainside.
Flavie Audoin, a rangeland management specialist with Cooperative Extension, said the project also provided an opportunity to test the effectiveness of virtual fencing collars to manage and move sheep.
“Virtual fencing is a relatively new technology,” she said. “There isn’t much research on using it with small ruminants like sheep and goats, so this project gave us the chance to try it out.”
Natural instincts, technological precision
The project team purchased Nofence virtual fence collars and paid for the subscription fees with funding from the Marley Endowment for Sustainable Rangeland Stewardship.
Flavie Audoin
Targeted grazing is a land management practice that takes advantage of the natural grazing behavior of animals like cattle, goats or sheep to manage vegetation growth, often as a control on invasive species or as a wildfire prevention measure.
Effective use of targeted grazing can reduce the need for chemical herbicides or strenuous hand-pulling. But Audoin noted that forethought is necessary to get the most out of a targeted grazing project.
“Targeted grazing is a tool in the land manager’s toolbox,” Audoin said. “Each livestock species has different diet preferences, so when you’re targeting a specific plant, you have to think about which animal will be best adapted to do that job.”
Grazers also need to think about how to control the animals’ movements, especially in urban or semi-urban environments like ‘A’ Mountain. That’s where virtual fencing comes in.
“Virtual fencing creates invisible barriers for livestock,” Audoin explained. “The animals wear collars that use auditory and mild electric cues to keep them within a defined area established with GPS coordinates.”
The technology is gaining popularity among Arizona’s ranchers as a means of managing livestock without physical barbed-wire fences. It also reduces the need for a constant human presence on the range – or, in this case, the mountain.
“With the virtual fence collars, you can use your phone to keep track of where your animals are instead of having to go out to the field,” she said. “You can also use an app to get alerts if animals escape the virtual fence, so you can react quickly.”
Virtual fences allow for easy adjustments to grazing areas as well.
“When you want to move the animals to a new area, you can just draw a new paddock through the app and they’ll move right into it,” Audoin said.
Sheep for hire
Audoin joined the ‘A’ Mountain project when Sonya Norman, the public programs coordinator for the Arizona-Sonora Desert Museum, reached out for advice on what type of livestock would be best suited for grazing buffelgrass on the mountainside.
“They initially considered goats,” Audoin said. “They’re really good climbers, so when you have a steep place, you generally want goats. But there was some reluctance to do that because goats can be pretty aggressive when it comes to vegetation, and they may eat more than you want them to."
Audoin suggested they try Navajo-Churro sheep instead, because they’re well-adapted to desert environments.
The Navajo-Churro is one of the oldest sheep breeds in North America. Descended from the ancient Churra breed of the Iberian peninsula, Navajo-Churro sheep are well-suited to both semi-arid rangelands and high elevation mountain environments.
Flavie Audoin
“I didn’t know how they’d do in such steep terrain, but I’ve worked with this breed for a while, and they’re very adaptive,” she said. “If they have to do it, they will do it.”
Audoin worked with Grant Tims, the owner of the sheep and a grazing contractor, to train the flock to respond to the collars – and to introduce them to the unfamiliar grass – before moving them to the mountainside.
“Those sheep had never seen buffelgrass before they started that project,” Audoin said. “But once we had them in the training paddock, it was the first thing they went for. It was like they had read the contract!”
Once trained, the sheep moved to their summer home on Sentinel Peak, where they accomplished the project goal of removing 80% of the buffelgrass in their grazing areas.
“We didn’t want them to graze 100% of the buffelgrass because of the steepness of ‘A’ Mountain,” Audoin said. “If you go too harsh, you may have erosion problems.”
The sheep took care of the plant’s above-ground mass in the first half of the two-phase eradication project. Following the targeted grazing efforts, certified contractors applied chemical herbicides to spray the rest of the buffelgrass.
“They did a wonderful job,” Audoin said. “Our grazing partner liked the virtual fence technology so much that now he doesn’t want to do any projects without it.”
Putting their best hoof forward
Flavie Audoin
The sheep were popular on the peak, earning the approval of project partners and community members alike.
“The neighbors were so happy about those sheep,” Audoin said. “People would come up with their kids just to look at the sheep. It was a pretty cool project to educate the public.”
The original DFFM grant funded the targeted grazing effort for one year, but Audoin and her partners hope to be able to try a longer-term project in the future.
“Ideally, you would do at least three years of repetitive grazing for grasses because of the seed bank you have in the soil,” she said. “I’m trying to find funding to do a three-year project and just do targeted grazing [instead of combining grazing with herbicides].”
In the meantime, Audoin said she’s fielded interest from the Tucson Flood Control District, who want to graze the sheep in some of the city’s washes, and from the Tucson Fire Department, who would use them to create natural fire breaks.
“They were very supportive of the ‘A’ Mountain project because the grazing created a fuel break to prevent fires during the Fourth of July fireworks,” she said. “It’s more expensive to fight a fire than to hire some sheep to do the job. With wildfires, it is better to be proactive than reactive.”