Predation Leading Cause of Grouse Mortality
By Martin Kidston
Reprinted from the Billings Gazette
(February 1, 2012) Coyotes, eagles, badgers and ravens all contribute to sage grouse mortality in the Bighorn Basin of Wyoming, an official of the U.S. Department of Agriculture told Park County commissioners in December.
Jim Pehringer, district supervisor with the USDA’s Wildlife Services in northwest Wyoming, offered an update on the first season of his sage grouse predation project.
During the study, which is funded in part by oil and gas interests, Pehringer collared 25 birds in two developed regions of the Bighorn Basin to determine their movement, nesting habits and survival and predation rates.
Among the grouse sampled this year, 10 were collared on the Polecat Bench north of Powell, where predator control practices are ongoing. Another 15 grouse were collared in the Oregon Basin south of Cody, where no predator control efforts are taking place.
“Of the 25 birds we collared, we found 24 nests,” Pehringer said. “Eleven of the birds were predated on. One died of natural causes and one slipped a collar.”
Pehringer said remote cameras near the nesting sites, combined with radio collars, allowed the study to monitor grouse activities daily.
According to Pehringer, coyotes, eagles, badgers and ravens accounted for nest predation. Deer, antelope and cattle also were drawn to nesting sites.
“Thirty-three percent of our nests hatched overall,” Pehringer said. “At 35 days, we’d go in and find how many hatchlings actually made it. Around 35 to 40 percent of the chicks survived to 35 days.”
Pehringer said predation accounted for 81 percent of chick mortality in this year’s study. Grouse were seven times more likely to survive in areas where predator control efforts are under way, he said.
“This certainly would suggest that predator control is the answer for saving sage grouse,” Park County Commissioner Loren Grosskopf said.
“I would say it’s a factor we can control -- we can manipulate,” Pehringer responded. “At this point in Wyoming, we have a good population of sage grouse. They’re hunted every year.”
The presentation, which didn’t find oil and gas development as a contributor for grouse mortality, looked to counter the findings of other biologists who have said grouse shy away from drilling sites and other human activities.
Pehringer said his study found grouse nests in a variety of terrain, including one nest off a busy road used heavily by the oil industry. He added that grouse may also move toward human development, not away from it.
“We’re finding a lot of grouse seem to go toward human activity to nest,” he said. “I think, maybe, it’s because of a lack of prey in that area — all the moving parts, people and oilfield activity may be somewhat of a benefit.”
However, a wildlife biologist with the Bureau of Land Management said Pehringer’s suggestion contradicts years of scientific data.
“That’s not supported by any of the evidence we have,” said Chris Keefe, a wildlife biologist with the BLM specializing in sage grouse. “That’s not something I’m aware of in any of the literature at all.”
Keefe said he hadn’t seen Pehringer’s study and was hesitant to comment on the findings. But he did say that grouse are a prey species for a number of predators and will always face that challenge.
He added that predators also follow development. The solution to grouse recovery isn’t to eliminate predators, he said, but to reduce habitat fragmentation and establish core management areas.
“It’s not to say there isn’t a place for the direct management of predators, but we would need some data to support a need for that,” Keefe said. “I go back to the core areas for being a solution, looking for the best areas to minimize the impacts of fragmentation and human development.”
Keefe said it would take years of study looking at generations of grouse to scientifically suggest that grouse thrive near oil and gas development. It’s something the BLM has done, and the results haven’t led its biologists to make that conclusion.
“Site fidelity is so strong with grouse, and we do see some populations that will nest near or below structures,” Keefe said. “But they’re not terribly successful there. The young birds tend to move out, because it’s not quality nesting anymore.”
Local cooperating officials across the Bighorn Basin have backed Pehringer’s project, primarily for its efforts to look at predation, not oil and gas development, as a cause of grouse mortality.
The study also has gained the support of several energy companies, including Legacy Reserves, Fidelity and Plains Pipeline. Marathon Oil also pledged $10,000 to the predation project this year.
“Fish and Wildlife Service does not recognize predation as a big threat to sage grouse,” said Steve Jones, resource manager for the Meeteetse Conservation District. “This is a long-term project, so it’s going to be several years before the data makes any sense.”
Jones expressed concerns that if the grouse is listed as an endangered or threatened species, it would have dire socio-economic impacts on the Bighorn Basin.
Such concerns have echoed across Wyoming over the past few years, gaining the attention of Gov. Matt Mead and other state officials, who have held a series of recent meetings to address sage grouse habitat and recovery.
In December, Mead met with BLM State Director Don Simpson and Secretary of the Interior Ken Salazar to discuss the issue, while Steve Dondero, manager for the Wind River-Bighorn Basin District of the BLM, named grouse issues among his top priorities.
The BLM and the U.S. Forest Service also announced their initial plans to evaluate greater sage-grouse conservation measures in land-use plans across 10 Western states.
While pressure mounts to keep the bird off the list of threatened species, Pehringer said the USDA will continue its predator management practices to see how grouse respond.
“In some areas, we’ll split the kind of removal we do this year to decide how it affects grouse,” he said. “On Polecat Bench, we’ll focus mainly on the removal of coyotes and ravens. We’ll do coyotes and ravens in the 15 Mile area, but no removal in Oregon Basin.”
Keefe said that naming predation as a causal factor for chick mortality can be hard to document.
One recent BLM study of 12 collared grouse found that hunters had killed eight, making it the leading cause of mortality in that study.
“Does it mean three-quarters of the grouse population is going down to hunting?” Keefe said. “Of course it doesn’t.”