North Dakota Bighorn Sheep Population Holds Steady
North Dakota's bighorn sheep population has remained stable despite three consecutive severe winters, according to Brett Wiedmann, big game biologist for the State Game and Fish Department in Dickinson.
The 2010 annual bighorn sheep survey, which covers a period from April 2010 to March 2011, revealed a minimum of 283 bighorn sheep in western North Dakota, a 4 percent reduction from 2009 but still 3 percent higher than the five-year average. The northern badlands' population was down just 1 percent from last year, while the southern badlands' population, which has been struggling for several years, saw a 15 percent decrease.
In total, biologists counted 95 rams, 158 ewes and 30 lambs. There are also approximately 30 bighorn sheep in the North Unit of Theodore Roosevelt National Park.
Game and Fish Department biologists count and classify all bighorns in late summer and then recount lambs in March to determine lamb recruitment.
Lamb recruitment was low at only 19 percent, Wiedmann said, which is well below average in North Dakota. Sixty-seven percent of the lambs counted last summer survived the winter. "Due to deep snows that arrived in November, spring survey conditions this year were the most difficult we’ve had in many years," he added. "Herds were scattered and broken into very small bands, which made getting a complete lamb count nearly impossible. Consequently, we likely missed a few lambs as population modeling predicted 46 lambs instead of the 30 that were actually observed."
While lamb recruitment was low, the adult population remained stable. In addition, the ram-to-ewe ratio remained stable at 60 rams per 100 ewes.
"Although last winter's frigid conditions arrived early and stayed late, we only lost three radio-marked adult bighorns all winter," Wiedmann said. "It just goes to show how tough these animals are."
There were six bighorn sheep licenses issued in 2011, the same number as 2010.