Are Predators Responsible for Sage Grouse Decline?
Local biologist and a rancher give their views
by Rob Shaul

Sometime later this year a coalition of environmental groups promises to petition the U.S. Fish and Wildlife Service to list the sage grouse as a threatened or endangered species. There is no doubt that sage grouse numbers have dropped dramatically across the west. Even in Wyoming, which has one of the largest remaining sage grouse populations, the Game & Fish estimates that the number of these birds has decreased by 30% over the past 15-20 years.

Some in the environmental community blame livestock grazing for this decline and are calling for the end of grazing on public lands. Meanwhile, the ranching community points toward an increase in predation as a major cause for the decline. We asked Pinedale Game & Fish Biologist Doug McWhirter and Daniel-area rancher Albert Sommers for their thoughts on the impacts predation has had on sage grouse in Sublette County and on the Mesa in particular.

Doug McWhirter

"Do predators have an effect on sage grouse?" begins Mr. McWhirter, "without a doubt. There's just a few animals that don't eat sage grouse. They get eaten by everything."

Sage grouse nests are preyed upon by ravens, coyotes, ground squirrels, skunks, and weasels, says Doug. Chicks and adults fall prey to coyotes, bobcats and large raptors. Once, continues Doug making his point, during a sage grouse nesting study in Bates Hole, an elk was filmed raiding a sage grouse nest and eating the eggs.

However, it is not clear how much predation increases overall population trends. Several studies have suggested that predation is not as important as the timing of death. Studies have shown that removing predators has been documented to have a large positive affect on hatching success but was not significant in affecting breeding population size. The idea is that if one predator doesn't get the sage chickens when they're in the eggs, some other predator will eat them later on.

For example, Mr. McWhirter points to a large study conducted back in the 1940s and 50s which found that 42%-46% of sage grouse nest predators were ground squirrels. However, another study conducted from 1994-1996 does not even mention ground squirrels as raiding sage grouse nests but points to badgers, coyotes, red fox, bobcats and ravens. For both studies, the nesting success rate was similar, which Mr. McWhirter says suggests that other predators filled in to eat sage grouse eggs as the ground squirrel predation decreased. "One way or another," he says, "some predator is going to get the birds."

Environmental groups have attacked cattle grazing and argued that overgrazing decreases the sage grouse understory, which therefore decreases the sage grouse nesting cover and leaves the birds and their eggs more exposed to predators.

In general, this is really a discussion of the best habitat for sage grouse. "In concept, that's got to be true," says Mr. McWhirter. "Habitat without cover makes its easier for the predators to find the birds . . . There's been quite a bit of research that shows when you leave a lot of cover, nest success increases."

However, Mr. McWhirter says it's not clear whether nesting success today is down that much from historical levels. What is down 30% is chick survival rate. Why fewer chicks are surviving is not clear. It could be hens are laying fewer eggs, says Doug, or there's more predation, or the chicks are simply starving because there are fewer insects which they survive on their first few days of life.

Seeming unrelated events could also impact predation. Mr. McWhirter notes that there seems to be a scarcity of rabbits the past few years. He remembers flying for the winter deer count 7-8 years ago and seeing rabbits "everywhere" but now rabbits are "noticeably scarce." The low number of rabbits means predators such as eagles and coyotes have to turn to other sources of food - like sage chickens.

"There's pretty good evidence there's more of some predators," says Mr. McWhirter. For example, he knows there are more red foxes now than years ago and suspects there are more coyotes because poisoning has been banned. "But, does that mean fewer sage grouse were getting eaten back then?" he asks, "or were other predators eating them?"

Doug is frustrated by the oversimplification of the whole sage grouse population decline issue. "Some people want to make this simple," he says. "'If we just eliminate sagebrush spraying, we'd have a lot more sage grouse, or if we eliminate predators we'll have more sage grouse,' but it's much more complicated than that." Even if there was perfect habitat for sage grouse, he continues, a late spring cold snap could come along and set the insect hatch back. This would in turn impact the sage grouse chick hatch because chicks depend on a diet of insects for the first weeks of life.

For his part, Mr. McWhirter feels it's wrong to blame livestock grazing for the decline. "I don't think that livestock grazing is responsible for fewer sage grouse," he says. "The fact that both have been done for years here and there's been peaks and valleys of sage grouse tells you it's not that simple."

Albert Sommers

"I have noticed a decrease in sage chickens as a whole," says Daniel rancher Albert Sommers, "especially on the first terrace, or first sage brush benches above the river or meadows." Mr. Sommers remembers seeing lots of sage grouse hens with broods on these first benches but now sees only a few. He doesn't believe the habitat has changed and he knows the grazing on these benches has not increased over the years. Mr. Sommers thinks the difference is an increase and new types of predators.

First, Albert has noted a significant increase in crows and ravens during his lifetime. When he was small, he says he used to see one or two ravens on the whole place, and now the birds are very common. He notes that crows and ravens prey on sage grouse nests.

Also, Mr. Sommers says there didn't used to be any red fox in the area, and now red fox are common.

Finally, Albert says he was ten years old when he saw his first raccoon, but last fall, he caught 20 raccoons in his yard. The animals are "notorious for getting into nests," he says.

Together, the ravens, crows, red fox and raccoons have "taken away a lot of the first bench from the sage grouse," says Mr. Sommers, and forced the birds onto the Mesa, further from water and closer to other types of predators such as eagles and coyotes.

"In my lifetime, since I was little, the major change I've seen is an increase in the numbers and types of predators," says Albert. Another change, though less significant, is an aging of the sagebrush on the Mesa. Mr. Sommers says it's been several decades since the last spraying on the Mesa, and much of the sagebrush has to be getting older and decadent.

Predators aside, Albert is interested in the effect a decline in insects would have on sage grouse populations. Amphibian numbers - frogs and toads - have declined across the nation, notes Mr. Sommers. "Maybe their decline has something to do with insects," he suggests, "and their decline is showing up in a decrease in amphibians."

Concerning grazing, Mr. Sommers rejects the suggestion that cattle are responsible for decreased sage grouse numbers. "There were a lot of sage chickens and a lot of cows in the 1950s and 1960s," he says, "and I don't believe cows have caused the decline. Something has changed, but it isn't the amount of grass."

Further, Albert says the livestock industry has drilled and constructed several stock ponds on the mesa, which have in turn expanded the habitat for sage grouse. "If it weren't for those stock ponds, there'd be far less habitat available than there is now," says Mr. Sommers.