Bighorn Sheep Population Increases

The North Dakota Game and Fish Department’s annual bighorn sheep survey revealed a minimum of 292 bighorn sheep in western North Dakota, up 8 percent from last year and 3 percent above the five-year average.

Altogether, biologists counted 88 rams, 160 ewes and 44 lambs. Not included are approximately 30 bighorns in the North Unit of Theodore Roosevelt National Park.

Big game biologist Brett Wiedmann said the survey is good news after an all-age die-off that began in 2014.

“This year’s number was encouraging given the ongoing effects of bacterial pneumonia throughout most of the badlands,” Wiedmann said.

The northern badlands population, which was hit the hardest from the die-off, increased 13 percent from last year. However, the southern badlands population was down 19 percent.

“Overall, rams, ewes and lambs all increased from last year,” Wiedmann said. “We were also pleased to see that 76 percent of lambs counted during last summer’s survey survived the winter, which is above average. The recruitment rate of lambs per adult ewes was 31 percent, equal to the long-term average.”

Game and Fish Department biologists count and classify all bighorn sheep in late summer, and then recount lambs the following March, as they approach one year of age, to determine recruitment.

“Adult mortality slowed significantly in 2015, and we had a good number of lambs survive in 2014 and 2015 to compensate for most of the adult losses,” Wiedmann said. “The bad news is that many bighorns are still showing signs of pneumonia, so next year’s survey will be important in determining if the state’s population is continuing to recover from the disease outbreak, or if the pathogens are likely to persist and cause a long-term population decline.”

Dr. Dan Grove, Department veterinarian, said disease testing last winter revealed that deadly pathogens were still present in 16 of 22 bighorns tested. He said animals continue to succumb to pneumonia, albeit at a much slower rate.

A bighorn sheep hunting season is tentatively scheduled to open in 2016, unless there is a recurrence of bacterial pneumonia. The status of the bighorn sheep season will be determined Sept. 1, after summer population surveys are completed.