Montana Field Guide

Bighorn Sheep - Ovis canadensis

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, 6-13 inches long; horns of yearling rams wider at the base with more divergent tips than those of ewes, and 7 1/2 - 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.

Montana Range

Uses seasonal ranges. Generally winter & summer ranges.

Cliffs, mountain slopes, rolling foothills; sometimes cross intermountain valleys (FWP). Min. snow depth most imp. in win., avail. high quality green forage most imp. in spr. & sum. Selected elev's vary accord- ingly. Immed. or nearby cliffy-rocky areas imp. yr. rd. Semi -open to open veg. types preferred. Often use S aspects.

Bunchgrasses and shrubs on winter range; wide variety of grasses, sedges and forbs on summer range (FWP). Diets of graminoids, forbs, browse w/ order of importance varying btwn seasons & ranges. Generally graminoids most important but on NW ranges browse may be the dominant food during winter.

Male agonistic interactions intense in prerut; estab. dom- inance. V. susceptible to disease, part. lungworm-pneumonia complex. Some prev. extirp. herds now doing well (e.g. Rock Creek). Compete w/ elk for win 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 (FWP). Promiscuous. Can 1st breed as yrlings but most ewes breed during 2nd yr. Breeding begins mid-late Nov. Asynchronous estrus in ewes w/in rut. Intense mate competion amg males. Lambing occurs lt.Apr.-lt.June, (sometimes early July).