Black-footed ferrets (Mustela nigripes) use prairie dogs (Cynomys spp.) for food and their burrows for shelter. Thus, prairie dog colonies are essential ferret habitat. Prairie dog control, which resulted in permanent loss of ferret habitat, is considered the primary reason for the ferret's endangered status today. Northern Pacific Railroad (presently Burlington Northern) lands were surveyed 1908–1914, just prior to the onset of widespread prairie dog control. In Montana the surveyed area included a belt about 483 km long and 192 km wide, from the Montana-North Dakota border westward to Livingston. In all, 6,661 sections (11.8%) of 22 counties were surveyed and 1,662 of these sections (24.9%) contained at least some prairie dogs. Prairie dog colonies (N = 1,985) occupied all or part of 5,186, 16 ha (40ac) parcels and totaled a minimum of 47,568 ha, with mean colony size of 24.5 ha (2.8% of the landscape in colonies). Two township-wide belt transect samples—T4N and R45E—showed colonies were clumped in distribution. Two areas with large complexes of colonies are illustrated, and each area exeeded an estimated 15,000+ ha. The Tongue River–Otter Creek area had at least 20 complexes, with a mean intercomplex distance of 3.4 km; and the Powder River–O'Fallon Creek area had at least 20 complexes, with a mean intercomplex distance of 2.9 km. Historic land uses were similar to today's uses-grazing and a few crops. Historic prairie dog areas in Montana occupied an estimated 5,953 sq km. An estimated 90+% reduction in prairie dogs has occurred since 1914, largely if not totally due to poisoning. The elimination, fragmentation, and greatly reduced size of ferret habitat has undoubtedly contributed to the endangered status of ferrets. A few areas in Montana appear to contain enough prairie dogs to potentially harbor ferret populations. These areas could serve as reintroduction sites for ferrets, as well as examples of complex prairie dog ecosystems.
Flath, Dennis L. and Clark, Tim W.
"Historic status of black-footed ferret habitat in Montana,"
Great Basin Naturalist Memoirs: Vol. 8
, Article 4.
Available at: http://scholarsarchive.byu.edu/gbnm/vol8/iss1/4