Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Wildlife and Fisheries Science

First Advisor

Thomas McCabe

Second Advisor

Charles G. Scalet


Spatial segregation between Rocky Mountain bighorn sheep (Ovis canadensis canadensis) ram and ewe herds has been documented by Geist (1971), Geist and Petocz (1977), Shank (1979), Morgantini and Hudson (1981), and Hogg (1983), where ram herds consist of mature males approximately 4 years old and older and ewe herds are comprised of all other individuals. Geist (1971), Shank (1979), and Hogg (1983) have shown that segregation occurs year-round except during the breeding season (November and December) when the sexes congregate on a traditional breeding range (cf. Geist 1971, p 209). These studies also have shown that the sexes remain separated during the winter, when segregation should be least likely. During winter, resources, particularly forage, are most limiting and when the sexes would be expected to remain congregated after the breeding season, such as at available foraging sites. However, both Geist and Petocz (1977) and Morgantini and Hudson (1981) reported that the sexes remained segregated on a continuous winter range, even during severe winters. Four hypotheses have been developed to explain sexual segregation of bighorn sheep. Shank (1979) believed sexual segregation was a result of differential habitat requirements due to sexual dimorphism. Segregation has been suggested as an anti-predator strategy for males which are physically weakened after the breeding season (Geist and Bromely 1978). Morgantini and Hudson (1981) suggested that sexual segregation reduces frequency of agonistic interactions among rams during the post-breeding season and maximizes fitness of rams by conserving energy when reproduction is not possible. Geist and Petocz (1977) explained segregation as a mechanism for rams to minimize habitat competition with pregnant ewes and their prospective lambs, thus increasing survival of lambs, and thereby maximizing reproductive fitness of rams.

Library of Congress Subject Headings

Bighorn Sheep -- Habitat
Bighorn Sheep -- Seasonal distribution
Bighhorn Sheep -- Sexing


Includes bibliographical references (pages 48-50)



Number of Pages



South Dakota State University


No Copyright - Non-Commercial Use Only