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Montana Animal Field Guide

Montana Field Guides

Bighorn Sheep - Ovis canadensis

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Global Rank: G4
State Rank: S4

Agency Status
USFWS:
USFS: SENSITIVE
BLM:
FWP Conservation Tier: 3


 

External Links





 
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.

General Distribution
Montana Range



Montana Distribution


Western Hemisphere Range

 


Distribution 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

Summary of Observations Submitted for Montana
Number of Observations: 2691

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Records associated with a range of dates 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 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:
    1. 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);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point database associated with each ecological system;
    4. 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 bmaxell@mt.gov 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.

    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.  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.

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 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.

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).

References
  • Additional ReferencesLegend:   View WorldCat Record   View Online Publication
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    • 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
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    • Chapman, J. A., and G. A. Feldhamer, editors. 1982. Wild mammals of North America: biology, management, and economics. Johns Hopkins University Press, Baltimore, Maryland.
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    • 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.
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    • Keating, K. A. 1985. Many Glacier bighorn sheep study. Unpubl. Prog. Rep., Glacier National Park, West Glacier. 8 pp.
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Bighorn Sheep — Ovis canadensis.  Montana Field Guide.  Montana Natural Heritage Program and Montana Fish, Wildlife and Parks.  Retrieved on August 21, 2014, from http://FieldGuide.mt.gov/detail_AMALE04010.aspx
 
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