Bighorn sheep in winter: do rams maximize reproductive fitness by spatial and habitat segregation from ewes?

1977 ◽  
Vol 55 (11) ◽  
pp. 1802-1810 ◽  
Author(s):  
Valerius Geist ◽  
R. G. Petocz
Keyword(s):  
Habitat Selection ◽  
Social Behaviour ◽  
Habitat Preference ◽  
Bighorn Sheep ◽  
Ovis Canadensis ◽  
Habitat Segregation ◽  
Adult Males ◽  
Behavioural Types ◽  
Wintering Area ◽  
Continuous Range

In bighorn sheep (Ovis canadensis canadensis) the segregation of adult males from females is explained by two hypotheses: first, males exhausted by the rut must avoid females to escape culling predators; second, males ought to segregate from females in such a fashion as to minimize competition and disturbance for the mothers of their prospective offspring. Only the second hypothesis coincides closely with previously known facts about sheep. It predicts that on common winter ranges adult males ought to minimize competition for females by segregating spatially and by habitat selection. This was verified. Although both sexes may occupy a continuous range, they concentrate in different areas; rams have a greater preference for open slopes and ewes for cliffs. This segregation held true even in a winter with exceptional snow depths. Sheep occupied the wintering area in a similar manner in successive years; females were found to be more affected by snow than males. In their habitat preference, rams and ewes acted in accordance with their behavioural types, much as was found to be true for their social behaviour.

Roads, routes and rams: does sexual segregation contribute to anthropogenic risk in a desert-dwelling ungulate?

2016 ◽  
Vol 43 (5) ◽  
pp. 380 ◽  
Author(s):  
Vernon C. Bleich ◽  
Jericho C. Whiting ◽  
John G. Kie ◽  
R. Terry Bowyer
Keyword(s):  
Bighorn Sheep ◽  
Ovis Canadensis ◽  
Sexual Segregation ◽  
Adult Males ◽  
Large Mammals ◽  
Male And Female ◽  
Use Of Resources ◽  
Core Areas ◽  
Males And Females ◽  
Time Of Year

Context Little is known about the consequences of sexual segregation (differential use of resources by the sexes outside of the mating season) for the conservation of large mammals. Roadways (i.e. the strip of land over which a road or route passes) are ubiquitous around the world, and are a major cause of wildlife mortality, as well as habitat loss and fragmentation. Many populations of bighorn sheep (Ovis canadensis) occur at low densities and in a metapopulation structure. Roadways could affect movements of males and females differentially, an outcome that has not been considered previously. Aims We investigated the propensity of the sexes to cross a paved two-lane road and a single-lane, maintained dirt route and predicted that adult males, because of their life-history characteristics, would cross those roadways more often than females. Methods We investigated movements of male and female bighorn sheep from 1986 to 1990. We used a fixed-wing aircraft with an H-antenna on each wing strut to locate individuals each week from October 1986 to December 1990. We estimated the degree of overlap among 50% core areas of use by males and females with the utilisation distribution overlap index (UDOI). Key results We relocated male and female bighorn sheep on 948 occasions during sexual aggregation and on 1951 occasions during sexual segregation. More males than females were likely to cross both types of roadways during segregation, and the dirt route during aggregation. Propensity of males and females to cross roadways was strongly influenced by time of year (i.e. whether the period of sexual aggregation or sexual segregation). The lowest overlap in 50% core areas was between females and males during periods of segregation (UDOI = 0.1447). Conclusions More males than females crossed Kelbaker Road and the unnamed dirt route during segregation, as well as the unnamed route during aggregation. Both of those features could affect males more than females, and could result in reductions in the use of habitat or increased mortality of bighorn sheep from vehicle collisions as a result of spatial segregation of the sexes. Implications During environmental review, biologists should consider sexual segregation when assessing potential anthropogenic effects on movements of bighorn sheep. Biologists also should consider sexual segregation and how roadways, even lightly traveled routes, affect movements of male and female ungulates differently before manipulating habitat, translocating animals, or constructing or modifying roadways.

Rocky Mountain bighorn sheep (Ovis canadensis canadensis) winter habitat selection and seasonal movements in an area of active coal mining

2016 ◽  
Vol 94 (11) ◽  
pp. 733-745 ◽  
Author(s):  
Kim G. Poole ◽  
Rob Serrouya ◽  
Irene E. Teske ◽  
Kevin Podrasky
Keyword(s):  
Habitat Selection ◽  
Rocky Mountain ◽  
Bighorn Sheep ◽  
High Elevation ◽  
Ovis Canadensis ◽  
Open Pit ◽  
Selection Function ◽  
Winter Habitat ◽  
Native Grasslands ◽  
Active Coal

Winter is an important period for most mountain ungulates due to limited availability of preferred forage and costs associated with travel through deep snow. We examined winter habitat selection by Rocky Mountain bighorn sheep (Ovis canadensis canadensis Shaw, 1804) where four large, open-pit coal mines are in operation. Sheep in this area generally winter at high elevation on windswept, south-facing native grasslands. We used GPS collars and Resource Selection Function analysis to examine movements and habitat selection. A majority (79%) of the sheep were migratory and fidelity to winter ranges was high (88%). Sheep showed low use (∼10%–20%) of mine areas between November and April, followed by increased use peaking at 60%–65% in September–October. Wintering sheep were positively associated with high elevations, closeness to escape terrain, and warmer aspects. High-elevation, native grasslands were the highest ranked cover class. Most sheep that used mine areas during winter used reclaimed habitats, primarily reclaimed spoils and pits. Primary winter ranges comprised 4.3% of merged sheep range, emphasizing the limited amount of occupied winter ranges within the landscape. Disturbance to native winter range resulting from development should be minimized or be conducted in a manner that effectively manages and (or) mitigates the impacts.

The variables of physical habitat selection by the desert bighorn sheep (Ovis canadensis weemsi) in the Sierra del Mechudo, Baja California Sur, México

2001 ◽  
Vol 49 (2) ◽  
pp. 357-374 ◽  
Author(s):  
Sergio Alvarez-Cárdenas ◽  
Israel Guerrero-Cárdenas ◽  
Sara Dı́az ◽  
Patricia Galina-Tessaro ◽  
Sonia Gallina
Keyword(s):  
Habitat Selection ◽  
Baja California ◽  
Bighorn Sheep ◽  
Ovis Canadensis ◽  
Physical Habitat ◽  
Baja California Sur ◽  
Desert Bighorn Sheep

scholarly journals Model Testing for Future Reintroductions of Desert Bighorn Sheep at Capitol Reef National Park

1989 ◽  
Vol 13 ◽  
pp. 31-36
Author(s):  
Terri Steel ◽  
Michael Machalek ◽  
Gar Workman
Keyword(s):  
Information System ◽  
Geographic Information System ◽  
Habitat Selection ◽  
National Park ◽  
Bighorn Sheep ◽  
Ovis Canadensis ◽  
Desert Bighorn Sheep ◽  
Use Patterns ◽  
Selection Behavior ◽  
Project Objectives

The objective of the 1989 fieldwork was the testing of a model developed in 1988. The main project objectives are to: (1) evaluate the success of the transplant operations; (2) investigate habitat selection behavior of desert bighorn sheep (Ovis canadensis); and (3) develop a model which classifies areas suitable for sheep use. This model will then be incorporated into a Geographic Information System (G.I.S.) to examine macrohabitat use patterns. Software to be used includes: SAGIS, MAP, DBIII, and HOMER.

Body mass and survival of bighorn sheep

1997 ◽  
Vol 75 (9) ◽  
pp. 1372-1379 ◽  
Author(s):  
Marco Festa-Bianchet ◽  
Jon T. Jorgenson ◽  
Céline H. Bérubé ◽  
Christine Portier ◽  
William D. Wishart
Keyword(s):  
Body Mass ◽  
Adult Life ◽  
Mass Gain ◽  
Bighorn Sheep ◽  
Ovis Canadensis ◽  
Adult Males ◽  
Age Classes ◽  
River Population ◽  
Maternal Expenditure ◽  
Chest Girth

In ungulates, body mass is often positively correlated with juvenile survival, but little is known of whether body mass affects survival of other age-classes. We studied two marked populations of bighorn sheep (Ovis canadensis) in Alberta, Canada, to determine if body mass affected the survival of different sex –age classes. Chest girth at weaning was correlated (P < 0.0001) with survival of bighorn lambs in the Sheep River population. In the Ram Mountain population, body mass in mid-September had a stronger effect upon survival than mass in early June, mass gain in summer, or mass loss in winter. Body mass at weaning was correlated with lamb survival (P = 0.004). In both study areas, relationships between size and survival of lambs were similar for the two sexes. At Ram Mountain, survival of yearling and adult males seemed to be independent of body mass. Light yearling females were less likely to survive than heavy yearling females. Among females aged 3 – 6 years, body mass had no effect on survival. Among females 7 years of age and older, mass in mid-September had a weak but significant (P = 0.03) effect on survival. Females were slightly lighter in mid-September in their last year of life than in the rest of their adult life. Maternal expenditure is unlikely to affect the survival of prime-age ewes, but may have a detrimental effect on the survival of older ewes.

scholarly journals Brucellosis in Captive Rocky Mountain Bighorn Sheep (Ovis canadensis) Caused by Brucella abortus Biovar 4

2004 ◽  
Vol 40 (2) ◽  
pp. 311-315 ◽  
Author(s):  
Terry J. Kreeger ◽  
Walter E. Cook ◽  
William H. Edwards ◽  
Todd Cornish
Keyword(s):  
Brucella Abortus ◽  
Rocky Mountain ◽  
Bighorn Sheep ◽  
Ovis Canadensis

scholarly journals Social cues facilitate habitat selection: American redstarts establish breeding territories in response to song

2006 ◽  
Vol 2 (3) ◽  
pp. 337-340 ◽  
Author(s):  
Beth A Hahn ◽  
Emily D Silverman
Keyword(s):  
Habitat Selection ◽  
Local Population ◽  
Breeding Habitat ◽  
Conspecific Attraction ◽  
Adult Males ◽  
Settlement Cues ◽  
Migratory Songbirds ◽  
American Redstarts ◽  
Spring Arrival ◽  
Northern Temperate Forests

For migratory songbirds nesting in northern temperate forests, a short breeding season demands that males rapidly establish territories. Because critical insect and vegetation resources are unavailable during spring arrival, we suggest that conspecifics serve as settlement cues for males new to a local population. To test conspecific attraction, we conducted playback experiments with American redstarts Setophaga ruticilla . Experimental results demonstrate that song playbacks strongly attract conspecifics, recruiting an average of 4.2 additional males per plot; adult males new to our sites increased, while yearling males failed to respond. Yearlings arrived 6 to 10 days later than adults, raising the possibility that yearlings responded to songs of early arriving adults rather than to playbacks. Our work indicates that conspecific attraction is an important mechanism for breeding habitat selection in an established population of a migratory forest songbird, but the effect is moderated by age, reproductive experience and arrival timing.

Observations on social behaviour of Atlantic walruses (Odobenus rosmarus (L.)) during terrestrial haul-out

1980 ◽  
Vol 58 (3) ◽  
pp. 461-463 ◽  
Author(s):  
R. E. Salter
Keyword(s):  
Social Interactions ◽  
Social Behaviour ◽  
East Coast ◽  
Adult Males ◽  
Agonistic Interactions ◽  
Age Composition ◽  
Body Contact ◽  
Adult Females ◽  
Odobenus Rosmarus

Social interactions in walrus herds of mixed sex and age composition were recorded at a haul-out site on the east coast of Bathurst Island, N.W.T., during July–August 1977. Most walruses maintained body contact with at least one other walrus while hauled out on land; herds were usually circular in shape. Adult males, adult females, and immatures all displaced other walruses, and thus entered herds, by jabbing with the tusks. Dominance during agonistic interactions was related to relative tusk length and sex and age of interactants. Behaviour of walruses on land suggested an energetic advantage in mutual body contact, which would be maximized by occupation of interior positions within herds.

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