Bighorn Sheep - Ovis canadensis
FWP Conservation Tier
Coat grayish-brown with yellowish-white underparts; creamy-white rump patch around small brown tail; horns of adult rams massive and curled, up to 45 inches long; horns of adult ewes thin, slightly curved, 6 to 13 inches long; horns of yearling rams wider at the base with more divergent tips than those of ewes, and 7 1/2 to 17 inches long; old rams may exceed 300 lbs., ewes seldom exceed 150 lbs. Most sociable of Montana's big game species; herds segregate according to age and sex; ewes, lambs and yearling males band together; adult males band in herds spanning 2- or 3-year classes; subject to die-offs related to severe winter weather and pneumonia.
Map images and GIS layers of general and winter range for populations of this and other hunted wildlife species can be found on Montana Fish, Wildlife, and Parks GIS Layers web page
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Records associated with a range of dates are excluded from time charts)
Uses seasonal ranges. Generally winter and summer ranges.
Cliffs, mountain slopes, rolling foothills; sometimes cross intermountain valleys. Minimum snow depth most important in winter, available high quality green forage most important in spring and summer. Selected elevations vary accordingly. Immediate or nearby cliffy-rocky areas important year-round. Semi-open to open vegetation types preferred. Often use south aspects.
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at email@example.com
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2001. The wild mammals of Montana. Special Publication No. 12. Lawrence, KS: The American Society of Mammalogists. 278 p.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Bunchgrasses and shrubs on winter range; wide variety of grasses, sedges and forbs on summer range. Diets of graminoids, forbs, browse with order of importance varying between seasons and ranges. Generally graminoids most important but on NW ranges browse may be the dominant food during winter.
Male agonistic interactions intense in prerut; established dominance. Very susceptible to disease, lungworm-pneumonia complex. Some previously extirpated herds now doing well (e.g. Rock Creek). Compete with elk for winter forage; cattle less so.
Breed in November; usually one young; rams battle for dominance by crashing horns together; ewes usually breed at 2 1/2 years of age, but may breed as yearlings. Promiscuous. Breeding begins mid- to late November. Asynchronous estrus in ewes within rut. Intense mate competition among males. Lambing occurs late April to late June (sometimes early July).
- Additional ReferencesLegend: View WorldCat Record View Online Publication
Do you know of a citation we're missing?
- Aderhold, Michael W. 1972. The history, winter range, and current status of the Rock Creek, Montana, bighorn sheep herd. M.S. Thesis, University of Montana, Missoula. 104 pp.
- Andryk, T. A. 1983. Ecology of bighorn sheep in relation to oil and gas development along the east slope of the Rocky Mountains, northcentral Montana. M. S. Thesis. Montana State University, Bozeman. pp 100.
- Andryk, T., and L. Irby. 1986. Population characteristics and habitat use by mountain sheep prior to a pneumonia die off. Proc. Bien. Symp. N. Sheep Goat Counc. 5:272-289.
- Anonymous. 1948. Bringing back our bighorns. Outdoor Montana. FebruaryMarch: 11.
- Anonymous. 1987. Interagency Rocky Mountain Front Wildlife Monitoring/Evaluation Program Management Guidelines for Selected Species. USDI Bureau of Land Management. 71 pp.
- Arnett, E. B., L. R. Irby and J. G. Cook. 1993. Sex- and age-specific lungworm infection in Rocky Mountain bighorn sheep. J. Wildt. Dis. (in press).
- Becklund, W. W., and C. M. Senger. 1967. Parasites of Ovis canadensis canadensis in Montana, with a checklist of the internal and external parasites of the Rocky Mountain bighorn sheep in North America. J. Parasitol. 53 :157-165.
- Berwick, S. H. 1968. Observations of the decline of the Rock Creek, MT, population of bighorn sheep. M.S. thesis, University of Montana, Missoula. 245 pp.
- Brown, G. W. 1974. Distribution and population characteristics of bighorn sheep near Thompson Falls in northwestern Montana. M.S. thesis. University of Montana, Missoula. 134 pp.
- Brown, W. S. 1978-79. Habitat partitioning and niche overlap between bighorn sheep and mountain goats. In K. L. McArthur, comp., 1978-79 Annual Research Summaries, Unpubl. Rep., USDI National Park Service, Glacier National Park, MT. 66 pp.
- Buechner, H. K. 1960. The bighorn sheep in the United States-its past, present and future. Wildlife Monograph No. 4. 174pp.
- Butts, T. 1980. Distribution and population characteristics of the Upper Rock Creek bighorn sheep. M.S. thesis, University of Montana, Missoula.
- Camp Dresser & McKee, Inc., 1990, Stillwater Chromite Project Baseline Data Report: Hydrology and Wildlife Monitoring, Hydrology - November 1988 through November 1989, Wildlife - November 1988 through February 1990. June 30, 1990
- Camp Dresser & McKee, Inc., Wheat Ridge, CO., 1981, Anaconda Stillwater Project 6-month environmental baseline report. CDM Project No. 3139. Vol. I Appendix. Jan. 15, 1981.
- Chapman, J. A., and G. A. Feldhamer, editors. 1982. Wild mammals of North America: biology, management, and economics. Johns Hopkins University Press, Baltimore, Maryland.
- Constan, K. 1967. Bighorn sheep range use, food habits and relationships to mule deer and elk in Gallatin Canyon. State of Montana, Project No. W-98-R-7-8.
- Constan, K. 1975. Report from Montana. In The wild sheep of modem North America. J. B. Trefethen, ed., the Boone and Crockett Club and Winchester Press, New York. 302 pp.
- Cooperrider, A. Y. 1969. Competition for food between mule deer and bighorn sheep on Rock Creek winter range, Montana. M.S. thesis. University of Montana, Missoula 92 pp.
- Couey, F. M. 1944. Rocky Mountain bighorn sheep in Montana. Montana Fish and Game Department Report. 65 pp.
- Couey, F. M. 1950. Rocky Mountain bighorn sheep of Montana. Mont. Fish & Game Comm., Bull. No. 2.
- Couey, F. M. 1953. Are the bighorns doomed? Mont. Wildl. Winter.
- Couey, F. M. 1955. Montana bighorn sheep. Proc. West. Assoc. State Game and Fish Comm. 35: 162-166.
- Couey, F. M. 1955. The bighorns are back. Mont. Wildl. Fall.
- Eichhorn, L. C., and C. R. Watts. 1971. Bighorn sheep in the Missouri River Breaks of Montana. Unpubl. rep. USDI, Bureau of Land Management, and Montana Fish and Game Dept., Lewistown. 21 pp.
- Eichhorn, L. C., and C. R. Watts. 1976. Two Calf bighorn sheep prog. rep. USDI, Bureau of Land Management, and Montana Fish and Game Dept., Lewistown. 18 pp.
- Erickson, G. L. 1972. The ecology of Rocky Mountain bighorn sheep in the Sun River Area of Montana with special reference to summer food habits and range movements. M.S. thesis. Montana State University, Bozeman. 50 pp.
- Farmer, P. J. 1986. Stillwater Valley bighorn sheep monitoring study phase one: December, 1985-May, 1986. Helena, MT: Western Technology and Engineering, Inc., 78pp.
- Farmer, P. J. 1987. Stillwater Valley bighorn sheep monitoring study, phase two: December, 1986-May, 1987. Helena, MT: Western Technology and Engineering, Inc., 64pp.
- Farmer, P. J., and S. Stewart. 1988. Stillwater Valley bighorn sheep monitoring study, Phase Three: December, 1987 May, 1988. Tech. Rep. by Western Tech. and Engr. for Stillwater Mining Co.
- Farmer, P. J., S. Stewart and J. Richter. 1990. Stillwater Valley bighorn sheep monitoring study, Phase Four: December, 1989 - May, 1989 and Phase Five: June, 1989 - May, 1990. Tech. Rep., Western Tech. and Engr. for Stillwater Mining Co.
- Farmer, P. J., S. Stewart, and J. Richter. 1991. Stillwater Valley highorn sheep monitoring study, Phase Six: June, 1990 May, 1991. Tech. Rep. by Western Tech. and Engr. for Stillwater Mining Co.
- Foresman, K. R. 2001. The wild mammals of Montana. American Society of Mammologists, Special Publication Number 12. Lawrence, KS. 278 p.
- Forrester, D. J. 1960. A preliminary investigation of the protostongylin lungworm-bighorn sheep relationships in Montana. M.S. thesis. University of Montana, Missoula. 79 pp.
- Forrester, D. J. 1960. Population dynamics of North American bighorn sheep. Ecology of Wildl. Populations, Montana State University. 28 pp.
- Forrester, D. J. 1962. Land mollusca as possible intermediate hosts of protostrongylus stilesi, a lungworm of bighorn sheep in western Montana. Proc.Montana Acad. of Sci. 22:82-92.
- Forrester, D. J. and R. S. Hoffmann. 1963. Growth and behavior of a captive bighorn lamb. J. Mamm. 44(1):116-118.
- Forrester, D. J., and C. M. Senger. 1960. Experimental infestation of a Rocky Mountain bighorn lamb with Melophagus ovinus (diptera:hippoboscidae). J. Parasit. 46(5). 598 pp.
- Forrester, D. J., and C. M. Senger. 1963. Bighorns and lungworm. Montana Wildl. Pp. 2-7.
- Forrester, D. J., and C. M. Senger. 1964. A survey of lungworm infection in bighorn sheep of Montana. J. Wildl. Manage.
- Forrester, D. J., and C. M. Senger. 1964. Intestisital infection of bighorn sheep with protostrongylid lungworms. Nature 201(4923).
- Forrester, D. J., and C. M. Senger. 1964. Prenatal infection of bighorn sheep with Protostrongy lungworms. Nature 201 (4923:1051).
- Forrester, D. J., and R. C. LitleI. 1976. Influence of rainfall on lungworm infections in bighorn sheep. J. Wildl. Diseases 12:48-51.
- Frisina, M. R. 1974. Ecology of bighorn sheep in the Sun River area of Montana during fall and spring. M.S. thesis. Montana State University, Bozeman. 68 pp.
- Frisina, M. R. 1974. Physical condition, productivity and quality of nutrition of bighorn sheep in the Sun River area, Montana. Proc. of the Northern Wild Sheep Council, April 23-25, 1974. Abstract, p. 127.
- Hoffmann, R. S. and D. L. Pattie. 1968. A guide to Montana mammals: identification, habitat, distribution, and abundance. University of Montana, Missoula. 133 p.
- Hogg, J. T. 1984. Mating behavior in Rocky Mountain bighorn sheep: male and female strategies in reproduction. Ph.D dissertation. University of Montana, Missoula. 181 pp.
- Irby, L. R., J. E. Swenson and S. T. Stewart. 1989. Two views of the impacts of poaching on bighorn sheep in the Upper Yellowstone Valley, Montana, USA. BioI. Cons. 47:259-272.
- Irby, L., and T. Andryk. 1987. Evaluation of a mountain sheep transplant in north central Montana. J. Environ. Manage. 24:337-346.
- Irby, L., S. Stewart and J. Swenson. 1986. Management of bighorns to maximize hunter opportunity, trophy availability, and availability to nonconsumptive users. Proc. Bien. Symp. N. Wild Sheep Goat Counc. 5:113-127.
- Janson, R. C. 1974. Wild sheep transplanting in Montana. Proc. N. Amer. Wild Sheep Conf. Montana Fish and Game Dept., Helena.
- Keating, K. 1988. Insular ecology of bighorn sheep. Page 29 in K. Dimont, compo and ed., 1988 Science Summary, Glacier National Park, West Glacier.
- Keating, K. 1989. The genetic structure of bighorn sheep populations in Montana. Page 48 in K. Dimont, compo and ed., 1989 Science Summary, Glacier National Park, Glacier Natural History Assoc., West Glacier.
- Keating, K. A. 1982. Population ecology of Rocky Mountain bighorn sheep in the upper Yellowstone River drainage, Montana/Wyoming. M.S. thesis, Montana State University, Bozeman. 79 pp.
- Keating, K. A. 1985. Evaluating the natural status of bighorn sheep epizootics in Glacier National Park, Montana. Unpubl. Final Rep., USDI National Park Service, Glacier National Park. 76 pp.
- Keating, K. A. 1985. Many Glacier bighorn sheep study. Unpubl. Prog. Rep., Glacier National Park, West Glacier. 8 pp.
- Keating, K. A. 1985. The effects of temperature on bighorn population estimates in Yellowstone National Park. Int. J. Biometeor. 29:47-55.
- Keating, K. A. 1990. Bone chewing by Rocky Mountain bighorn sheep. Great Basin Nat. 50:89.
- Keating, K. A., L. R. Irby and W. F. Kasworm. 1985. Mountain sheep winter food habits in the upper Yellowstone Valley. J. Wild. Mgmt. 49(1):156-161.
- Klaver, R. W. 1978. A management-oriented study of the ecology of bighorn sheep in the Bitterroot Mountains, Montana, and Idaho. M.S. thesis. University of Montana, Missoula. 111 pp.
- Kopec, L. 1981. The movements, distribution, and population characteristics of the Cutoff Area bighorn. M.S. thesis, University of Montana, Missoula.
- Landusky Mining Inc., Zortman, MT. Assisted by Hydrometrics, Helena, MT., 1985, Operating Permit Application for an Extension of Landusky Mining Incorporated Operations, Phillips County, Montana. June 12, 1985
- Leonard, D. R. 1975. Ecology and effects of human visitation on Rocky Mountain bighorn sheep in the Many Glacier area of Glacier National Park, Montana. Unpubl. report, Dept. of Zoology, Washington State University, Pullman. 62 pp.
- Mack, I. A., F. J. Singer, and M. E. Messaros. 1990. The ungulate prey base for wolves in Yellowstone National Park II: elk, mule deer, white-tailed deer, moose, bighorn sheep, and mountain goats in the areas adjacent to the park. Pp. 2-41 to 2218 in Wolves for Yellowstone A report to the United States Congress, Vol. 2, Research and Analysis. Natl. Park Serv., Yellowstone National Park, WY.
- Marsh, H. 19??. Pneumonia in Rocky Mountain bighorn sheep. J. Mamm. Vol(?):214. 2 copies.
- Marsh, H. 1927. Report of investigation of losses in bighorn sheep in Glacier Park, 11-17 January 1927. Unpubl. rep., Glacier National Park archive file N1427-110-1. 6pp.
- Martin, S. A. 1981. Summer and fall habitat use and migration patterns of the Rock Creek segment of the Beartooth sheep herd. Job Final Rep., Research Proj., Fed. Aid in Wildl. Restor. Proj. W-120-R-l1, Montana Dept. of Fish, Wildl. and Parks, Helena. 68 pp.
- Martin, S. A. 1985. The ecology of the Rock Creek bighorn sheep herd, Beartooth Mountains, Montana. M.S. thesis, Montana State University, Bozeman. 152 pp.
- Martin, S. A., and S. T. Stewart. 1980. Migration of the Beartooth-Rock Creek bighorn sheep herd. Pp. 332-354 in Proc. Northern Wild Sheep and Goat Council, Salmon, Idaho.
- Matthews, J.W. 1973. Ecology of bighorn sheep (Ovis canadensis) on Wild Horse Island, Flathead Lake, Montana. M.S. Thesis:University of Montana, Missoula.
- Montana Dept. of Fish and Game, compiler. 1974. Proc. Biennial Symp. Northern Wild Sheep Council. Montana Dept. of Fish and Game, Helena. 146 pp.
- Montana Dept. of Fish, Wildlife and Parks. 1948-1992. Annual sheep hunting and harvest statistics. Helena.
- Munoz, J. R. 1977. Causes of sheep mortality at the Cook Ranch, Florence, Montana, 1975-76. M.S. thesis. University of Montana, Missoula. 55 pp.
- Ogren, H. A. 1954. A population study of the Rocky Mountain bighorn sheep (OVIS CANADENSIS CANADENSIS SHAW) on Wild Horse Island. M.S. thesis. University of Montana, Missoula. 77 pp.
- Oldemeyer, J. L., W. J. Barmore and D. L. Gilbert. 1971. Winter ecology of bighorn sheep in Yellowstone National Park. Journal of Wildlife Management 35(2):257-269.
- Oldemeyer, J.L. 1966. Winter ecology of bighorn sheep in Yellowstone National Park. Thesis, Colorado State Univ., Fort Collins. 107 pp.
- Pallister, G. L. 1974. The seasonal distribution and range use of bighorn sheep in the Beartooth Mountains, with special reference to the West Rosebud and Stillwater herds. M.S. Montana State University, Bozeman. 67 pp.
- PARKER, T. AND M. SCOTT, DECEMBER 1985, BIGHORN SHEEP MANAGEMENT PLAN
- Pattie, D. L. and N. A. M. Verbeek. 1967. Alpine mammals of the Beartooth Plateau. Northwest Science 41(3): 110-117.
- Peek, J. M., R. A. Demarchi, D. A. Demarchi and D. E. Stucker. 1985. Bighorn sheep and fire: seven case histories. In Lotan, J. E., and J. K. Brown, eds., Proc. Symp.: Fire's Effects on Wildlife Habitat, Missoula.
- Picton, H. D., and C. Eustace. 1986. Trace element levels in Montana bighorn sheep horns. Proc. N. A. Wild Goat and Sheep Conf. 5:193-204.
- Reid, F. 2006. Peterson Field Guide to Mammals of North America, 4th Edition. Houghton Mifflin Company: Boston and New York, 608 pp.
- Riggs, R. A. 1977. Winter ecology of bighorn sheep. Pp. 53-54 in K. L. McArthur, compiler, 1976 Annual Research Summary, USDI National Park Service, Glacier National Park, MT. 64 pp.
- Riggs, R. A. 1977. Winter habitat use patterns and populations of bighorn sheep in Glacier National Park. M.S. thesis, University of Idaho, Moscow. 85 pp.
- Riggs, R. A. 1978. Winter ecology of bighorn sheep. Page 55 in K. L. McArthur, ed., 1977 Annual Research Summary, USDI National Park Service, Glacier National Park, MT. 62 pp.
- Riggs, R. A. and J. M. Peek. 1980. Mountain sheep habitat-use patterns related to post-fire succession. Jour. Wildl. Mgmt. 44(4):933-938.
- Risenhoover, K. L., J. A. Bailey, and L. A. Wakelyn. 1988. Assessing the Rocky Mountain bighorn sheep management problem. Wildl. Soc. Bull. 16:346-352.
- Roy, J. L. 1992. Re-establishment of Rocky Mountain bighorn sheep in the southern Madison Range, Montana. M.S. thesis, Montana State University, Bozeman.
- Schallenberger, A. D. 1966. Food habits, range use and interspecific relationships of bighorn sheep in the Sun River area, west-central Montana. M.S. thesis. Montana State University, Bozeman.
- Seegmiller, R.F., and R.D. Ohmart. 1981. Ecological relationships of feral burros and desert bighorn sheep. Wildl. Monogr. 78:1-58.
- Shackleton, D.M. 1985. OVIS CANADENSIS. Mamm. Species 230:1-9.
- Smith, D.R. 1982. The bighorn sheep of Idaho: its status, life history and management. Idaho Dept. Fish Game, Wildl. Bull. 1. 154 pp.
- Smith, T.S., J.T. Flinders and D.S. Winn. 1991. A habitat evaluation procedure for Rocky Mountain bighorn sheep in the Intermountain West. Great Basin Nat. 51:205-225.
- Stelfox, J.G. 1976. Range ecology of Rocky Mountain bighorn sheep in Canadian national parks. Canadian Wildlife Service Report Series no. 39. 50 pp.
- Stewart, S. T. 1975. Seasonal ecology of bighorn sheep in the Beartooth Mountains. M.S. thesis. Montana State University, Bozeman. Fish and Game Project #W-120-R-6,7.
- Stewart, S. T. 1980. Mortality patterns in a bighorn sheep population. Pp. 313-330 in Proc. Northern Wild Sheep and Goat Council, Salmon, Idaho.
- Stewart, S. T. 1982. Late parturition in bighorn sheep. J. Mammal. 63:154-155.
- Stewart, S. T. and T. W. Butts. 1982. Horn growth as an index to levels of inbreeding in bighorn sheep. Bienn. Symp. N. Wild. Sheep and Goat Counc. 3:68-82.
- Taylor, R.A. 1962. Characteristics of horn growth in bighorn sheep rams. M.S. Thesis, University of Montana, Missoula. 129 pp.
- Thompson, K. 1943. Historical range and notes on Audubon's mountain sheep. Montana Fish and Game Department Quarterly Report. Typewritten.
- Thompson, Richard W., Western Resource Dev. Corp., Boulder, CO., 1996, Wildlife baseline report for the Montana [Montanore] Project, Lincoln and Sanders counties, Montana. In Application for a Hard Rock Operating Permit and Proposed Plan of Operation, Montanore Project, Lincoln and Sanders Counties, Montana. Vol. 5. Stroiazzo, John. Noranda Minerals Corp., Libby, MT. Revised September 1996.
- Tilton, M. E. 1977. Habitat selection and use by bighorn sheep (OVIS CANADENSIS) on a northwestern Montana winter range. M.S. thesis. University of Montana, Missoula. 121 pp.
- Todd, J. W. 1972. Food habits of the Rocky Mountain bighorn sheep. M.S. thesis, Colorado State University, Fort Collins, Colorado. 60 pp.
- TVX Mineral Hill Mine, Amerikanuak, Inc., Gardiner, MT., 2002, Yearly summary of wildlife observation reports. 1990-2002 Letter reports.
- U.S. Fish & Wildlife Service., 1984, Charles M. Russell National Wildlife Refuge, Montana: Draft Environmental Impact Statement.
- U.S. Forest Service, Kootenai National Forest. Montana Dept. of State Lands., 1978?, Final Environmental Impact Statement. Proposed Plan of Mining and Reclamation. Troy Project, Asarco, Inc., Lincoln County, Montana. Vol. III.
- USDI National Park Service., 2000, Bison Management for the State of Montana and Yellowstone National Park. Final Environmental Impact Statement for the Interagency Bison Management Plan for the State of Montana and Yellowstone National Park. Vol. I. August 2000.
- Wakelyn, L.A. 1987. Changing habitat conditions on bighorn sheep ranges in Colorado. J. Wildl. Manage. 51:904- 912.
- Walcheck, K. C. 1980. Audubon bighorn sheep. Montana Outdoors.
- Watts, C. R., and L. C. Eichhorn. 1972. Two Calf bighorn sheep dieoff. Unpubt. Rep., USDI, Bureau of Land Management, and Montana Fish and Game Dept., Lewistown. 5 pp.
- Westech, Inc. [Western Technology and Engineering] (Stillwater Mining Co., Sponsor). 1987. Stillwater valley bighorn sheep monitoring study, phase two mitigation plan. Prepared for Review Committee Bighorn Sheep Monitoring Study by Western Technology & Engineering, Inc. 36 pp.
- Western Technology and Eng., Inc., 1991, Wildlife resources of the Little Rocky Mountains Environmental Study Area. March 1991. In Application for Amendment to Operating Permit No. 00096, Zortman Mining, Inc., Phillips County, Montana. Vol. 3. Jan. 3, 1995.
- Western Technology and Eng., Inc., Helena, MT., 1996, Terrestrial Wildlife Reconnaissance: Stillwater Mining Company Hertzler Tailings Facility and Tailings Line, 1996. October 1996. In Stillwater Mining Co. Mine Waste Management Plan Amendment to Permit #00118 Supplemental Baseline Reports: Terrestrial Wildlife, Vegetation, Soils, Land Application Disposal, Waters of the U.S. January 1997.
- Woodgerd, W. 1964. Population dynamics of bighorn sheep on Wildhorse Island. The Journal of Wildlife Management 28(2):381-391.
- Woodgerd, W. R. and D. J. Forrester. 1962. Observability of colored ear markers on Rocky Mountain bighorn lambs. Desert Bighorn Council Transactions: 65-68.
- Woolf, A. 1968. Summer ecology of bighorn sheep in Yellowstone National Park. M.S. Thesis, Colorado State Univ., Fort Collins. 112 pp.
- Worley, D. E. 1968. Summer range parasitic infestation (sheep). Montana State University Coop. Ext. Serv. 3-5.
- Yde, C., B. Summerfield and L. Young. 1986. Ural-tweed bighorn sheep - wildlife mitigation project - annual rep. U.S. Dept. of Energy, Bonneville Power Admin. 35 pp.
- Young, D. L., and C. A. Yde. 1988. Design, implementation, and initial response of selected habitat treatments within the Ural-tweed bighorn sheep range. Proc. Bien. Symp. Wild Sheep and Goat Council 6:229-239.