N.D. bighorn sheep numbers increase despite decline in southern Badlands population
North Dakota's bighorn sheep population stands at a minimum of 283 in western North Dakota, up 7 percent from 2017 and equal to the five-year average, the state Game and Fish Department said Monday in reporting results from its 2018 bighorn sheep survey.
Biologists counted 84 rams, 161 ewes and 38 lambs. Not included are approximately 20 bighorns in the North Unit of Theodore Roosevelt National Park.
Big game biologist Brett Wiedmann said he was pleased to see an increase in the survey, after a decline in 2017.
"The increase in the 2018 count reflects lessening effects of bacterial pneumonia that was detected in 2014," Wiedmann said.
The northern Badlands population increased 9 percent from 2017 and was the second highest count on record, the department said. The southern Badlands population declined again to the lowest level since 1999.
"The total count of adult rams declined in 2018 but adult ewes increased," Wiedmann said. "Most encouraging was the significant increase in the lamb count and recruitment rate following record lows in 2016 and 2017."
Game and Fish Department biologists count and classify all bighorn sheep in late summer and then recount lambs the following March, as they approach 1 year of age, to determine recruitment.
"Fortunately, annual survival rates of adult bighorns are similar to those prior to the die-off, and lamb survival is improving, which could indicate the population is becoming somewhat resilient to the deadly pathogens first observed in 2014," Wiedmann said. "The next few years will be important in determining if the state's population shows signs of recovering from the disease outbreak, or if the pathogens are likely to persist and cause a long-term population decline."
Four of the 15 adult bighorns tested for the deadly pathogens last winter were positive, said Dr. Charlie Bahnson, Game and Fish wildlife veterinarian.
A bighorn sheep hunting season is tentatively scheduled to open in 2019, unless there is a recurrence of significant adult mortality from bacterial pneumonia. The status of the bighorn sheep season will be determined Sept. 1, after the summer population survey is completed.
Game and Fish issued three licenses in 2018, and all hunters were successful in harvesting a ram.