While three consecutive severe winters played a significant role in reducing many of the state’s western big game populations, overall bighorn sheep numbers are strong, according to Brett Wiedmann, big game biologist for the North Dakota Game and Fish Department in Dickinson.
A July-August survey in western North Dakota showed 290 bighorn sheep, unchanged from last year and just 26 below 2008’s record summer survey. “After recording dramatic declines in mule deer and pronghorn numbers, we were pleasantly surprised to see that our bighorns have remained stable,” Wiedmann said.
Bighorn sheep can tolerate frigid temperatures, but deep snows can cause problems because of their short legs, Wiedmann said. “Low adult mortality last winter despite very deep snow conditions demonstrates just how hardy bighorns are,” he said.
Survey results revealed 85 rams, 158 ewes and 47 lambs – 233 in the northern badlands (an increase of two from last year) and 57 in the southern badlands (down just one). “Bighorns are doing very well in the northern badlands, and, following three years of declines, have stabilized in the south,” Wiedmann said, while noting that 43 lambs were observed in the north, but only four in the south.
Although the ewe segment of the population actually increased five percent from last summer’s survey, rams saw a 10 percent decline. “Due to an abundance of forage, rams were scattered and in smaller-than-usual bachelor groups,” Wiedmann said. “Consequently, I’m confident that poor detectability had more to do with the lower ram count than an actual population decline.”
The department’s survey does not include an additional 30 bighorns that inhabit the North Unit of Theodore Roosevelt National Park.
Annual bighorn sheep survey statistics are not recorded using a calendar year, but instead are done over a 12-month period beginning each April and ending the following March. Each summer, Game and Fish Department biologists count and classify all bighorns, a process that takes nearly six weeks to complete as biologists locate each bighorn herd in the badlands by tracking radio-marked animals from an airplane, and then hike into each band in order to record population demographics using a spotting scope and binoculars. Biologists then complete the annual survey by recounting lambs in March to determine lamb recruitment.
North Dakota’s bighorn sheep hunting season opens Oct. 21 and continues through Nov. 3. Six licenses were issued.