Montana Bighorn Sheep Survey Indicates Record High Population

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The most recent aerial survey of bighorn sheep habitat in the Missouri River Breaks indicates that the population of wild sheep in Hunting District 680 is at a record-high level.  

A total of 532 sheep were observed during the annual helicopter survey, conducted in mid July in the hunting district that extends from U.S. Highway 87 south of Big Sandy east to U.S. Highway 191 south of Zortman. The district includes nearly all the Missouri Breaks National Monument in southern Chouteau and Blaine counties.

The survey was coordinated by FWP biologist Al Rosgaard and conducted by FWP biologist Mark Sullivan, who noted that the observed population was 98 sheep higher than last year's survey. The ratio of lambs to ewes was 50 lambs per 100 ewes, and the ratio of rams to ewes was 55 rams per 100 ewes. Those ratios are high for mountainous bighorn sheep habitat, but fairly typical for the Missouri Breaks hunting district, he says. Seventy-five of the rams observed were ¾-curl or larger, including 29 that won Sullivan's "pig" designation, meaning trophy-class rams typically at least 6 years old.  

"Sheep are doing well in 680, and continue to exhibit high reproductive success and good recruitment, possibly due to liberal license quotas and the periodic removal of animals for transplant stock into other areas," says Sullivan. Last winter 20 sheep were transplanted from District 680 to Wyoming's Bighorn Mountains. "Even with the removal of 20 individuals, record numbers of sheep were observed this year in both the eastern and western portions of District 680, although no range expansion was noted in either area," continued Sullivan.

That means all the available habitat in the district is filled, a condition that will require active management to ensure that the Breaks sheep herd doesn't exceed the carrying capacity of its habitat. In addition to the 532 sheep Sullivan counted in District 680, FWP biologist Tom Stivers counted 365 sheep in District 482 south of the Missouri River. The total number of sheep observed in the Missouri Breaks National Monument this year was 897.  

"FWP's goal for District 680 is to manage the sheep population at a level that prevents over-utilization of sheep habitat and reduces the chances for disease transmission," says Sullivan. "The best way to achieve this goal appears to be a combination of liberal license quotas and periodic removal of sheep for transplant into other areas."

This year the license quota for adult ewes in District 680 was increased from 30 to 45. Another 15 coveted either-sex licenses were issued in the district.  

"Breaks sheep have become a highly sought-after commodity," says Sullivan, "both by hunters and biologists looking for transplant stock, due to the rams' rapid and heavy horn growth and the overall success of the population."

Requests for Breaks sheep have been received this year by FWP's Region 5, North Dakota Game and Fish Department and Nebraska Game and Fish.