By Doug Leier, NDG&F Dept
To understand the current North Dakota bighorn sheep population, it’s a good idea to try to understand the past.
And really it’s a past highlighted by a “who’s who” in Midwest wildlife documentation. Writings describing these majestic bighorn sheep were first recorded by the Lewis and Clark expedition in 1805 along the Yellowstone River in what is now North Dakota.
Later, John J. Audubon wrote about bighorn sheep and the frustrations of trying to hunt these rams in the 1840s. Theodore Roosevelt also hunted the badlands for bighorn sheep during his time spent in North Dakota.
From Roosevelt’s time in the 1880s, to the first decade of the 1900s, bighorn sheep in North Dakota did not fare so well. Nor did any of the other big game species that inhabited the state. Bison, moose, elk and bighorn sheep were extirpated from the North Dakota landscape. White-tailed deer, mule deer and pronghorn numbers declined to a a point where they faced an unknown future.
In 1905 the last reported bighorn sheep was killed near Grassy Butte. North Dakota did not have any wild sheep from that time until the mid-1950s, when state Game and Fish Department biologists transplanted bighorns from British Columbia to an area southwest of Grassy Butte.
It took another 20 years or so before the sheep population, through natural reproduction and further in-state and out-of-state transplants, expanding to the point where the Game and Fish Department could open a hunting season.
Since that time in the mid-1970s, the contemporary population of bighorn sheep has provided limited but highly sought hunting opportunities, with the number of licenses typically at a hand-full, plus or minus a few.
The license allocation is based on the recent spring survey numbers, and just recently the 2017 spring survey indicated a minimum of 296 bighorn sheep in western North Dakota, up slightly from last year and 3 percent above the five-year average.
Altogether, biologists counted 104 rams, 170 ewes and 22 lambs. Not included are approximately 20 bighorns in the North Unit of Theodore Roosevelt National Park.
Big game biologist Brett Wiedmann said the survey revealed both good and bad news after a well-documented sheep die-off that began in 2014. “This year’s count of adult bighorn was encouraging given the ongoing effects of bacterial pneumonia throughout most of the badlands, but the lamb count was discouraging,” Wiedmann said.
The northern badlands population, which was hit the hardest from the die-off, increased 2 percent from last year. However, the southern badlands population was down 3 percent.
“The total count of adult rams and ewes was the highest on record, but the total count, recruitment rate and winter survival rate for lambs were all the lowest on record,” Wiedmann said. “The recruitment rate of lambs per adult ewes was 15 percent, well below the long-term average.”
Wiedmann noted that one year isn’t necessarily a trend, but poor lamb survival is typical in populations exposed to Mycoplasma ovipneumoniae, the pathogen responsible for most die-offs of bighorn sheep, and those effects can last many years.
Wiedmann said that because many bighorns are still showing signs of pneumonia, and lamb recruitment was poor in 2016, next year’s survey will be important in determining if the state’s population continues to recover from the disease outbreak, or if the pathogens are likely to persist and cause a long-term population decline.
Game and Fish is tentatively scheduled to open a bighorn sheep hunting season again in 2017, 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.