Newswise — The Badlands bighorn sheep herd is healthy and thriving—and National Park Service Wildlife Biologist Eddie Childers wants to keep it that way.
“It’s one of the largest populations in the state of South Dakota now and the healthiest,” said Childers, who has been managing the Badlands bighorn sheep herd in the north unit since 1999.
Through a three-year National Park Service-funded study, Childers is working with South Dakota State University Department of Natural Resource Management Distinguished Professor Jonathan Jenks and graduate student Austin Wieseler to examine survival and mortality in the Badlands herd. For his work on the project, Wieseler received the 2019 Outstanding M.S. Graduate Student Award from the South Dakota chapter of The Wildlife Society
Though the researchers are looking at a broad spectrum of diseases, one of their biggest concerns is Mycoplasma ovipneumoniae, a pneumonia-causing pathogen that has devastated other bighorn sheep herds, including those in Custer State Park and Rapid City, South Dakota.
“This disease affects bighorn sheep throughout the western United States,” Childers said. The research, which began in February 2017, involves monitoring adult and yearling sheep, as well as lambs.
History of Badlands bighorns
The last Badlands bighorn sheep, an Audubon subspecies, was shot in the 1920s. In 1964, 22 Rocky Mountain bighorn sheep from Pike’s Peak, Colorado, were reintroduced to the Badlands through the efforts of the National Park Service, S.D. Game, Fish and Parks and the Colorado Division of Wildlife, according to a U.S. Department of Interior/U.S. Geological Survey report. Those sheep were to be raised as a captive herd, but when the animals started dying, “they just opened the gate and let them roam,” Childers explained.
In the 1990s, Francis Singer of the U.S. Geological Survey was one of two scientists to assess bighorn populations in and near 15 national parks. Singer collared animals from the Badlands herd, with the herd in the north unit numbering close to 150 animals, Childers recalled. With the data, he developed a model to predict population size.
Then in the late 1990s, the herd numbers crashed due to an outbreak of Pasteurella, a bacterial disease, Childers explained. However, tests to identify Mycoplasma ovipneumoniae were not available in the 1990s.
In 2004, Teresa Zimmerman, then a SDSU doctoral student working under Jenks’ supervision, looked at herd genetics and disease baseline after 23 animals from Wheeler Peak, New Mexico, were translocated to the Badlands.
“We know so much about them as far as genetics and disease resistance,” Childers said, pointing out that population ecologists emphasize the need to have 1,000 ungulates to maintain healthy genetics. Managing these small herds means bringing in animals from other herds to maintain genetic diversity.
“Since then the population has grown—last year we had 180-plus animals in the north unit,” Childers said.
Disease-testing, monitoring movement
Although the herd has previously been exposed to pneumonia-causing pathogens, none are shedders of Mycoplasma ovipneumoniae, according to Wieseler. “It’s a healthy and growing population.”
Last summer Wieseler collared 23 lambs and recorded a 74 percent survival rate through six months of age. When a collared lamb dies, the researchers quickly determine the cause, whether it’s predation, abandonment or simply falling into a crevice.
“The goal is to get them to a year old,” Wieseler said. By the end of May this year, Wieseler had collared 30 lambs.
In addition, the National Park Service monitors wild sheep, particularly young rams, that stray into neighboring domestic flocks. Due to the disease risk, these animals cannot be allowed back into the Badlands herd, according to Childers.
As part of Wieseler’s project, the researchers hope to work with private landowners whose sheep and goats graze within eight miles of the park to help reduce the risk from pneumonia-causing pathogens. Meanwhile, researchers are working on potential treatments, including a vaccine for Mycoplasma ovipneumoniae.
Through this and other research projects, wildlife managers will have the tools to restore and maintain the health of bighorn sheep in the state and, perhaps, the region.