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Bighorn Sheep - Ovis canadensis
General Description
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.
Species Range
Range Comments
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
Observations in Montana Natural Heritage Program Database
Number of Observations: 5964
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Migration
Uses seasonal ranges. Generally winter and summer ranges.
Habitat
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 cliff-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 (common or occasional) 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 2012, 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 observation 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 listed as associated with 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 listed as 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.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific 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 assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
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:
mtnhp.org/requests) 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.
Literature Cited
- 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. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- 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
Alpine Systems
Forest and Woodland Systems
Grassland Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Grassland Systems
Human Land Use
Recently Disturbed or Modified
Food Habits
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.
Ecology
Male antagonistic interactions intense in pre-rut; 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.
Reproductive Characteristics
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).
Stewardship Responsibility
References
- Additional ReferencesLegend:
View Online Publication
Do you know of a citation we're missing?- Aderhold, M.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.
Anaconda Minerals Company, and Camp, Dresser & McKee. 1981. Anaconda Stillwater Project 6-month environmental baseline report. CDM Project No. 3139. Vol. I Appendix. Jan. 15, 1981.- 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.
- 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.Sc. Thesis. Bozeman, MT: Montana State University. 100 p.
- Anonymous. 1948. Bringing back our bighorns. Outdoor Montana. FebruaryMarch: 11.
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- 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.
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- Butler, C.J. 2017. Assessing respiratory pathogen communities and demographic performance of bighorn sheep populations: A framework to develop management strategies for respiratory disease. M.Sc. Thesis. Bozeman, Montana: Montana State University. 138 p.
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- 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
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- Couey, F. M. 1944. Rocky Mountain bighorn sheep in Montana. Montana Fish and Game Department Report. 65 pp.
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- 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.
- Enk, E.A. 1999. Population dynamics of bighorn sheep on the Beartooth Wildlife Management Area, Montana. Ph.D. Dissertation. Bozeman, MT: Montana State University. 177 p.
- 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.Sc. Thesis. Bozeman, MT: Montana State University. 50 p.
- 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 Mammalogists, Special Publication Number 12. Lawrence, KS. 278 pp.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- 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 R. C. LitleI. 1976. Influence of rainfall on lungworm infections in bighorn sheep. J. Wildl. Diseases 12:48-51.
- 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 Wildlife 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. Proceedings of the Montana Academy of Sciences 22:82-92.
- Forrester, D.J. and C.M. Senger. 1964. A survey of lungworm infection in bighorn sheep of Montana.The Journal of Wildlife Management. 28:481-491.
- Forrester, D.J. and C.M. Senger. 1964. Prenatal infection of bighorn sheep with Protostrongy lungworms. Nature 201 (4923:1051).
- Forrester, D.J., and C.M. Senger. 1963. Bighorns and lungworm. Montana Wildl. Pp. 2-7.
- 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.
- Frisina, M.R. 1974. Ecology of bighorn sheep in the Sun River area of Montana during fall and spring. M.Sc. Thesis. Bozeman, MT: Montana State University. 68 p.
- Grigg, J.L. 2007. Gradients of predation risk affect distribution and migration of a large herbivore. M.Sc. Thesis. Bozeman, MT: Montana State University. 94 p.
- Hansen, J. J. 1987. Effect of stock density on ground cover on a southwest Montana foothills rangeland. M.Sc. Thesis. Bozeman, MT: Montana State University. 65 p.
- Hass, C.C. and D.A. Jenni. 1991. Structure and ontogeny of dominance relationships among bighorn rams. Canadian Journal of Zoology 69:471-476.
- Hatier, K.G. 1995. Effects of helping behaviors on Coyote packs in Yellowstone National Park, Wyoming. M Sc. Thesis. Bozeman, MT: Montana State University. 78 p.
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- Hoar, K.L. 1995. Parasite loads and their relationship to herd health in the Highlands Bighorn Sheep herd in southwestern Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 70p.
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