Relationship between predation-risk factors and sexual segregation in Dall's sheep (Ovis dalli dalli)

2002 ◽  
Vol 80 (12) ◽  
pp. 2108-2117 ◽  
Author(s):  
Paulo Corti ◽  
David M Shackleton
Keyword(s):  
Body Size ◽  
Predation Risk ◽  
Canis Lupus ◽  
Reproductive Strategy ◽  
Sexual Segregation ◽  
Lower Altitude ◽  
Nutritional Components ◽  
Ovis Dalli ◽  
Active Feeding ◽  
Dall’S Sheep

Using a population of Dall's sheep (Ovis dalli dalli), we examined two of the four main sexual-segregation hypotheses proposed: (1) the reproductive-strategy hypothesis, which proposes that males feed in the best foraging areas to enhance their reproductive fitness and females use areas with lower predation risk to raise offspring; and (2) the sexual dimorphism – body size hypothesis, which proposes that females use the areas with best forage to satisfy the nutritional demands of gestation and lactation, and that males, owing to their larger body size, have greater absolute metabolic requirements and therefore have to feed on forages which are more abundant but of lower quality. In our study, males were found farther from cover, in gentle terrain, and at lower altitude than were female groups, which were near cliffs or talus at higher altitudes. Female groups without lambs left cover, but were always active (feeding or moving). Forage density index values were higher in areas used by males than in areas used by female groups. Nutritional components were generally similar, but fibre content was higher in male areas. Signs of wolves (Canis lupus) and predation on Dall's sheep were recorded only at male areas. The results support the reproductive-strategy hypothesis, indicating that predation plays a key role in the development of sexual segregation in Dall's sheep.

Factors controlling lambing period of Dall's sheep

1980 ◽  
Vol 58 (6) ◽  
pp. 1027-1031 ◽  
Author(s):  
Fred L. Bunnell
Keyword(s):  
Body Size ◽  
Ovis Dalli ◽  
Study Population ◽  
Energetic Constraints ◽  
Dall’S Sheep

Distribution of birth dates within the study population of Ovis dalli dalli reveal two distinct oestrous cycles with a further 15% of all births resulting from a third cycle. The onset of breeding appears governed by photoperiod. Lambs born early and late in the lambing period suffer higher mortality. Energetic constraints limit both onset and duration of lambing. Onset is delayed beyond the period critical to thermoregulation by lambs and until forage is adequate; duration is limited by the need of lambs to attain adequate body size by winter.

Sexual segregation in bison: a test of multiple hypotheses

Behaviour ◽  
2005 ◽  
Vol 142 (7) ◽  
pp. 897-927 ◽  
Author(s):  
Eric W. Schaad ◽  
David S. Wiseman ◽  
Royce R. Huber ◽  
Michael S. Mooring ◽  
Dominic D. Reisig ◽  
...  
Keyword(s):  
Body Size ◽  
Predation Risk ◽  
Sexual Segregation ◽  
Bison Bison ◽  
Sexually Dimorphic ◽  
Activity Budgets ◽  
Single Sex ◽  
Multiple Hypotheses ◽  
Mixed Groups ◽  
Large Groups

AbstractSexual segregation, in which males and females form separate groups for most of the year, is common in sexually dimorphic ungulates. We tested multiple hypotheses to explain sexual segregation in bison (Bison bison) at National Bison Range, Montana and Fort Niobrara National Wildlife Refuge, Nebraska during June-August of 2002-2003. Fieldwork involved use of GPS to record space use by segregated groups, vegetation transects to measure forage availability, fecal analyses to document diet composition and quality, and behavioural observations to characterize activity budgets. During sexual segregation, males in bull groups used areas with greater per capita abundance of forage, higher proportion of weeds, and less nutritious grasses (as indicated by lower % fecal nitrogen) compared with females in cow or mixed groups. However, there was no difference between the sexes in activity budgets, predation risk factors, or distance to water. Single-sex bull groups were no more synchronized in activity than mixed groups. These results support the 'sexual dimorphism-body size hypothesis', which proposes that males segregate from females because their larger body size requires more abundant forage, while longer ruminal retention permits efficient use of lower-quality forage. The gastrocentric model, based on the digestive physiology and foraging requirements of dimorphic ungulates, supplies the most likely proximate mechanism for bison sexual segregation. Our results would also partly support the 'reproductive strategy-predation risk hypothesis' if females form large groups to reduce predation risk. The predictions of the 'activity budget hypothesis' were not supported for bison.

scholarly journals Using next generation sequencing of alpine plants to improve fecal metabarcoding diet analysis for Dall’s sheep

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Kelly E. Williams ◽  
Damian M. Menning ◽  
Eric J. Wald ◽  
Sandra L. Talbot ◽  
Kumi L. Rattenbury ◽  
...  
Keyword(s):  
Sequence Data ◽  
Vascular Plant ◽  
Alpine Plants ◽  
Diet Analysis ◽  
Reference Sequence ◽  
Reference Library ◽  
Ovis Dalli ◽  
Plant Animal Interactions ◽  
Dall’S Sheep ◽  
Northwestern North America

Abstract Objectives Dall’s sheep (Ovis dalli dalli) are important herbivores in the mountainous ecosystems of northwestern North America, and recent declines in some populations have sparked concern. Our aim was to improve capabilities for fecal metabarcoding diet analysis of Dall’s sheep and other herbivores by contributing new sequence data for arctic and alpine plants. This expanded reference library will provide critical reference sequence data that will facilitate metabarcoding diet analysis of Dall’s sheep and thus improve understanding of plant-animal interactions in a region undergoing rapid climate change. Data description We provide sequences for the chloroplast rbcL gene of 16 arctic-alpine vascular plant species that are known to comprise the diet of Dall’s sheep. These sequences contribute to a growing reference library that can be used in diet studies of arctic herbivores.

Superovulation in Dall's sheep (Ovis dalli dalli)

1990 ◽  
Vol 33 (1) ◽  
pp. 201 ◽  
Author(s):  
B.C. Buckrell ◽  
C.J. Gartley ◽  
K.G. Mehren ◽  
K.L. Goodrowe
Keyword(s):  
Ovis Dalli ◽  
Dall’S Sheep

Wolf predation in a multiple-ungulate system in northern British Columbia

1998 ◽  
Vol 76 (8) ◽  
pp. 1551-1569 ◽  
Author(s):  
A T Bergerud ◽  
J P Elliott
Keyword(s):  
British Columbia ◽  
Canis Lupus ◽  
Birth Rate ◽  
Rangifer Tarandus ◽  
Adult Mortality ◽  
Recruitment Rate ◽  
Wolf Predation ◽  
Rate Of Increase ◽  
Ovis Dalli ◽  
Hunting Statistics

Caribou (Rangifer tarandus), elk (Cervus canadensis), moose (Alces alces), and Stone's sheep (Ovis dalli stonei) were either decreasing or stable in numbers in two areas in northeastern British Columbia in 1981-1982, prior to reductions in wolf (Canis lupus) numbers. Following the reduction of wolf numbers, recruitment improved 2-5 times for all four species, and all populations increased, based on either hunting statistics, census results, and (or) recruitments greater than 24 offspring at 9 months of age per 100 females. Recruitment of offspring at 9 months of age, when regressed against wolf numbers, declined with decelerating slopes for all four species. This inverse functional response is hypothesized to result from the preparturient spacing of females to reduce predation risk, and in this regard moose seem the least secure and sheep the most effectively spaced. For the four species, mean recruitment at 9 months of age that balanced adult mortality and provided a finite rate of increase of 1.00 was 24.16 ± 0.91 offspring/100 females (n = 11, coefficient of variation = 12.5%). The predicted recruitment rate for all four species in the absence of wolves was 53-57 offspring/100 females. But the birth rate of moose was much higher than those of the other species, indicating greater loss to other factors of which bear predation may be the greatest. Following wolf reductions of 60-86% of entire travelling packs, the wolves quickly recolonized the removal zones, with rates of increase ranging from 1.5 to 5.6.

Critical snow density threshold for Dall’s sheep (Ovis dalli dalli)

2018 ◽  
Vol 96 (10) ◽  
pp. 1170-1177 ◽  
Author(s):  
Kelly J. Sivy ◽  
Anne W. Nolin ◽  
Christopher L. Cosgrove ◽  
Laura R. Prugh
Keyword(s):  
Snow Depth ◽  
Animal Movement ◽  
Population Declines ◽  
Snow Density ◽  
Energetic Costs ◽  
Snow Properties ◽  
Ovis Dalli ◽  
Snow Conditions ◽  
Dall’S Sheep ◽  
Density Threshold

Snow cover can significantly impact animal movement and energetics, yet few studies have investigated the link between physical properties of snow and energetic costs. Quantification of thresholds in snow properties that influence animal movement are needed to help address this knowledge gap. Recent population declines of Dall’s sheep (Ovis dalli dalli Nelson, 1884) could be due in part to changing snow conditions. We examined the effect of snow density, snow depth, and snow hardness on sinking depths of Dall’s sheep tracks encountered in Wrangell–St. Elias National Park and Preserve, Alaska. Snow depth was a poor predictor of sinking depths of sheep tracks (R2 = 0.02, p = 0.38), as was mean weighted hardness (R2 = 0.09, p = 0.07). Across competing models, top layer snow density (0–10 cm) and sheep age class were the best predictors of track sink depths (R2 = 0.58). Track sink depth decreased with increasing snow density, and the snowpack supported the mass of a sheep above a density threshold of 329 ± 18 kg/m3 (mean ± SE). This threshold could aid interpretation of winter movement and energetic costs by animals, thus improving our ability to predict consequences of changing snowpack conditions on wildlife.

Behaviour, habitat associations, and intrasexual differences of female Stone’s sheep

2006 ◽  
Vol 84 (8) ◽  
pp. 1187-1201 ◽  
Author(s):  
Andrew B.D. Walker ◽  
Katherine L. Parker ◽  
Michael P. Gillingham
Keyword(s):  
Habitat Use ◽  
Predation Risk ◽  
Growing Season ◽  
Early Summer ◽  
Habitat Associations ◽  
Phenological Stage ◽  
Shrub Species ◽  
Lichen Cover ◽  
Ovis Dalli ◽  
Maternal Status

Stone’s sheep ( Ovis dalli stonei Allen, 1897) in northern British Columbia segregate sexually during most of the year, and intrasexually between maternal and nonmaternal females during spring and early summer. Our objective was to quantify intrasexual habitat use of female Stone’s sheep relative to maternal status using measures of behaviour and habitat use. We reviewed three hypotheses of intersexual segregation (predation-risk, forage-selection, and activity-budget hypotheses) to determine if they also explained intrasexual segregation of female Stone’s sheep. Female Stone’s sheep spent the majority of their active time foraging. Nursery groups spent shorter durations of time active, more time active in solid rock escape features, and less time active in shrub habitat than nonmaternal groups. The best predictive model describing intrasexual differences incorporated distance to nearest escape feature and size of nearest escape feature. Regardless of maternal status, female Stone’s sheep used low-elevation plant communities early in the growing season that were characterized by more shrub species and increased cover. As the growing season progressed, they tracked a phenological stage, moving up in elevation and associating with communities that contained increasing amounts of moss and lichen cover. The patterns in behaviour, habitat use, and vegetation associations between intrasexual groups of Stone’s sheep were best characterized by the predation-risk hypothesis.

Wolf predation risk associated with white-tailed deer movements

1991 ◽  
Vol 69 (10) ◽  
pp. 2696-2699 ◽  
Author(s):  
Michael E. Nelson ◽  
L. David Mech
Keyword(s):  
Predation Risk ◽  
Odocoileus Virginianus ◽  
Canis Lupus ◽  
Climatic Conditions ◽  
Male And Female ◽  
Wolf Predation ◽  
Adult Females ◽  
Disproportionate Number ◽  
Short Time ◽  
Antipredator Strategy

The survival of 159 yearling and adult deer (Odocoileus virginianus) was monitored by telemetry during 282 spring and 219 fall individual migrations to winter deeryards in northeastern Minnesota. A disproportionate number of deer were killed by wolves (Canis lupus) during fall migration relative to the short time they spent migrating, but not during spring migration. Predation was also significantly greater for male and female yearlings and adult females outside deeryards during winter. Survival of 79 yearlings dispersing from natal ranges was high (1.00). It appears that changing climatic conditions combined with unfamiliar terrain and undetermined factors predispose migratory deer to wolf predation during fall. These findings support an earlier hypothesis that winter yarding is an antipredator strategy.

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