Bighorn Sheep Population Up from Last Year

The North Dakota Game and Fish Department’s 2019 bighorn sheep survey, completed by recounting lambs in March, revealed a minimum of 290 bighorn sheep in western North Dakota, up 2 percent from 2018 and 3 percent above the five-year average.

Altogether, biologists counted 77 rams, 162 ewes and 51 lambs. Not included are approximately 30 bighorn sheep in the North Unit of Theodore Roosevelt National Park and 30 bighorns recently translocated to the Fort Berthold Indian Reservation.

Big game biologist Brett Wiedmann was pleased to see another increase in the survey, following a decline in 2017.

“The increase in the 2019 count reflects lessening effects of bacterial pneumonia that was detected in 2014,” Wiedmann said.

The northern badlands population increased 12 percent from 2018 and was the highest count on record. The southern badlands population declined again to the lowest level since 1999.

“The total count of adult rams unfortunately declined for a fourth consecutive year in 2019, but adult ewes remained near record numbers,” 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 one year of age, to determine recruitment.

“Fortunately, annual survival rates of adult bighorns are very high and similar to those prior to the die-off, and lamb survival continues to improve, which could indicate the population is becoming somewhat resilient to the deadly pathogens first observed in 2014,” Wiedmann said. “The deadly pathogen, Mycoplasma ovipneumoniae, has not been detected the last two years in most of the northern herds via annual disease testing and none are currently showing symptoms of pneumonia. However, 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.”

Game and Fish wildlife veterinarian Dr. Charlie Bahnson said that four of the 25 adult bighorns tested for the deadly pathogens last winter were positive.

A bighorn sheep hunting season is tentatively scheduled to open in 2020, 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 five licenses in 2019 and all hunters were successful in harvesting a ram.