Tracking grazing’s impacts on bugs

A Montana biologist studies how livestock influence a favorite sage grouse food source.

 

Hayes Goosey on rangeland near Ryegate, Montana, where he uses traps to assess grazing’s impact on food arthropods and pollinators.
Marian Lyman Kirst

On a hot June morning, I follow Hayes Goosey across a wide, lonely stretch of fragrant rangeland 12 miles north of Ryegate, Montana. Scanning the ground for snakes while sidestepping clusters of blooming cactus, we arrive, finally, at a strange scene: Soapy water-filled plastic bowls scattered among sagebrush and grama grass, next to a line of plastic Solo cups buried to their rims in the ground. It resembles the remnants of a rained-out, hastily abandoned prairie cookout, but it’s actually one of Goosey’s study sites. And the Montana State University entomologist seems pleased: The picnic-ware traps are literally crawling with bugs. I count nine coffee-colored dung beetles in one cup alone. In others, inch-long, Halloween-hued carrion beetles serve as life rafts for smaller, less buoyant insects. Meanwhile, the surface pan-traps are a witch’s brew of butterfly wings and bee bodies. Most people, Goosey says, “have no idea that all of this stuff is out here or how important it is.”

The range, it turns out, is not so lonely after all: It supports a mini-metropolis of arthropods that pollinate forbs and break down dung and carrion. But Goosey is primarily interested in their role as food for other rangeland creatures — particularly sage grouse. During their first three weeks of life, sage grouse chicks feed almost exclusively on arthropods, which are rich in proteins, fat and nutrients essential for early development.

Thanks to habitat loss and fragmentation, the bird is a candidate for endangered species protection, inspiring a raft of conservation and research projects to help with recovery. In Montana, where sage grouse share nearly 100 percent of their core habitat with domestic livestock, grouse conservation efforts often focus on resting pastures for a year or more, or rotating livestock more quickly through them, in order to avoid overgrazing and ensure the vigorous return of grouse-concealing, forage-providing grasses and shrubs. Despite this, Goosey says, few people have looked into how grazing practices influence an equally vital component of sage grouse habitat: food arthropods. So, in 2012, he tackled the problem.

This site — which he’s currently using for a related project involving rangeland pollinators — lies just across the road from some of the 26 sites Goosey used during the resulting three-year study. The sites were spread across five different ranches between Roundup and Ryegate. Each was implementing a grazing plan under the Sage Grouse Initiative, a federal program that uses Farm Bill money to promote conservation practices on private lands. Using the same Solo cup-fashioned pitfall traps as the current study, as well as sweep net passes of the rangeland vegetation, Goosey collected beetles, grasshoppers, butterflies and other arthropods from grazed and rested pasture sites. He timed his collecting to coincide with the sage grouse’s nesting and early brooding periods during the spring and early summer, when the chicks — and their recovering moms — depend most on rangeland bugs.

Hayes Goosey holds dung beetles, one kind of arthropod that is affected by grazing.
Marian Lyman Kirst

Goosey’s preliminary analysis (he plans to submit final reports for publication this fall), suggests that rested pastures harbor significantly more food arthropods than grazed pastures, as well as taller vegetation, which shelters and feeds both the birds and their arthropod prey. That suggests that deferring grazing during the early brooding period may increase the number of chicks that survive to adulthood, he says.

And while some recommend removing cows altogether, healthy ranches are a bulwark against sod-busting for farms — a much bigger threat to grouse survival. “Sage grouse can coexist with grazing,” says Lorelle Berkeley, a research biologist with Montana’s Department of Fish, Wildlife and Parks. But row crops wipe out the woody shrub that defines the bird’s habitat, and “it takes decades to grow back.”

Indeed, given the often knotty and contentious nature of sage grouse conservation, Goosey feels his findings represent a refreshingly win-win situation. “Because (conservation) grazing is supposed to help decrease the percentage of bare ground,” he says, “and because bare ground means less forage for livestock and is also a detriment to food arthropods … what is good for grouse is good for cattle is good for bugs.”

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