O’Hare International Airport is getting some much-needed landscaping from some surprising workers: a herd of goats, sheep, llamas, alpacas and burros that tend to six acres on the other side of the fence from where the planes land.

The Sustainable Vegetation Management Initiative, now in its third year, has been quite a success.

The landscaping program is an efficient way of removing hard-to-access vegetation, which in turn eliminates the habitat for wildlife that could interfere with airport operations (including birds, which can be prove dangerous to planes, especially when concentrated in large numbers). It provides an alternative to simply spraying with toxic herbicides, and reduces soil erosion by eliminating the need for heavy equipment in the area. Plus, it reduces both the cost and pollution associated with gas-powered mowers, trimmers and other lawn equipment.

By having a mixed herd of over 40 grazers, including several types of animals with different tastes, almost all the different types of invasive plants are eaten. Even poison ivy can be cleared with no ill effects on the grazers.

The animals take plenty of breaks, human workers have confirmed. The four-legged workers seem content, and there haven’t been any demands for wage hikes.

“They don’t charge any overtime,” Aviation Commissioner Ginger Evans, visiting the herd on Aug. 4, told ABC News. “No, they just nibble away.”

Are these hooved landscapers poised to take over the jobs of the 888,426 people working for the nation’s approximately 401,473 landscaping businesses? It’s unlikely. But more and more management teams of both private spaces and municipal areas are seeing the benefit of involving four-legged friends in clearing efforts. The Boston Globe reported earlier this summer that Boston, too, would be expanding its use of goat-driven landscaping — noting that last year, the goats “didn’t do such a baaa-d job” of clearing overgrown city land.