Biologists track bighorn sheep in northwest Nebraska as species fights ?to survive amid pneumonia scourge (copy)
CRAWFORD, Neb. — They could call it the Pine Ridge Rodeo.
Eighteen times in recent weeks, a team of wildlife biologists dashed into the hills and canyons of northwest Nebraska in a race-the-clock campaign to capture newborn Rocky Mountain bighorn sheep to help the species survive an ongoing pneumonia scourge.
The conservation cowboys swooped in on the wobbly legged lambs with nets — or desperation tackles — and quickly slid a sock with cut-out toe over the lambs’ heads to blindfold and calm the bighorn babies.
Then they slipped an expandable collar equipped with a transmitter around the neck. They swabbed the critters’ nostrils and throats for evidence of pathogens and plucked a few hairs for DNA analysis before plopping them into a plastic grocery bag to hang from a scale to determine weight.
“It can get crazy,” said Todd Nordeen of Alliance, big-game research and disease program manager for the Nebraska Game and Parks Commission.
Finally, they let the lambs loose, back into the wild to their mothers and an uncertain fate.
Now, the biologists wait.
The three wild bighorn sheep herds in the Pine Ridge of northwest Nebraska produced only two surviving lambs in 2015 and 2016 combined. The culprit was pasteurella pneumonia, a respiratory ailment that is a ruthless killer of bighorns across the West.
Biologists tend to see high rates of lamb mortality 30 to 90 days after birth. If the Pine Ridge’s collared lambs die this summer, the transmitters give biologists a good chance at finding the carcass and identifying the pathogen or other cause of death.
The project is the first time Game and Parks biologists have specifically attempted to capture lambs to outfit them with transmitter collars and take samples to determine what diseases and pathogens the newborns may already carry.
Many of the lambs that Nordeen’s biologists captured and processed this spring were born to pregnant ewes from the Fort Robinson and Barrel Butte herds captured in February and implanted with vaginal transmitters. Ewes ejected the devices as their lambs were born. Biologists monitored the transmitters’ VHF (very high frequency) signals and attempted to pinpoint the whereabouts of the ewe and lamb.
The last of the Fort Robinson ewes with an implanted transmitter to give birth was a 9-year-old known as “Black 98,” for the color of the number on the collar and ear tag biologists gave her when captured during the winter. The arrival of her female lamb last Sunday triggered a cat-and-mouse game of locate, corner and capture over three days.
Erin Wood of Crawford, a bighorn sheep biologist who monitors the Fort Robinson and Sowbelly herds, set out on her rounds under the Cheyenne Buttes shortly after 7 a.m. Monday when the VHF receiver in her Game and Parks pickup truck erupted with the beeping signal she was waiting to hear.
“It’s one of those things that wakes you up,” she said.
Wood stopped the vehicle and decoded the beeps to determine how long it had been signaling. She telephoned Nordeen.
“Black 98 dropped her VIT (vaginal implant transmitter),” she told him. “It’s been 15½ hours since birth.’’
Although it was Memorial Day, Nordeen was already en route to the area to check for lamb births. Wood said she planned to pinpoint the area of the beeping transmitter from below the buttes west of Fort Robinson State Park and then go to the top and attempt to sneak a peek at the ewe and lamb from above and confirm the location.
Then she called Dane Horowski of Alliance, an assistant wildlife biologist, to join the capture team.
Walking out onto an escarpment, Wood spotted the bighorns below her and retreated to await the arrival of Nordeen and Horowski. A few hours later, Nordeen and Wood moved from different directions into a canyon where the transmitter signal indicated the sheep were located. They carried large fishing nets on telescoping poles to nab the lamb. Horowski spotted from above.
But the bighorns were not there.
Moments later, the profiles of Black 98 and the lamb appeared atop a butte 500 yards away. The lamb was nursing. The bouncing signal misled the searchers.
“This terrain plays cruel jokes on you,” Wood said.
Biologists tried again Tuesday and Wednesday morning but backed off after finding the lamb and its mother with a group of other sheep. Nordeen said it was too much of a risk of disrupting the nursery group of ewes and lambs to attempt a capture.
Black 98 and her lamb moved alone to the base of an escarpment Wednesday afternoon.
Nordeen said the ideal capture scenario is to find the sheep in the crevice at the base of a cliff.
“Then we can squeeze in and corner them,” he said.
The ewe can dart to open ground, but the lamb is too young to climb the steep rocks.
Nordeen and bighorn biologists Amy Bleisch of Chadron and Brandon Tritsch of Scottsbluff moved in on Black 98 and the lamb. As they approached the bighorns, the ewe bolted away. Nordeen eased around a corner of the cliff and found the lamb hugging the rocks. He dropped the net over the 72-hour-old bighorn.
“She was just sitting there, laying still to be hidden,” Nordeen said.
Bighorn lambs often are walking within hours of birth. Although their footing is uncertain, they can scamper up hills after a day.
“Every day they gain strength and more agility,” Nordeen said. “It’s amazing how quickly they start keeping up with mom and getting into escape cover.”
The crew outfitted the lamb with a transmitter collar and released her to the waiting ewe. She weighed 11 pounds.
Nordeen estimates that about 35 to 40 bighorn lambs have been born in the three struggling herds across the Pine Ridge this spring.
Nebraska currently has an estimated 350 bighorns spread among five wild herds across western Nebraska. The number has varied from 350 to 390 in recent years. Herd populations fluctuate, primarily due to pneumonia issues.
The Nebraska Big Game Society, the Iowa Foundation of North American Wild Sheep and purchasers of Nebraska hunting permits contributed funding for the implant-and-capture project.