Factors controlling lambing period of 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.

Download Full-text

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

Canadian Journal of Zoology ◽

10.1139/z02-207 ◽

2002 ◽

Vol 80 (12) ◽

pp. 2108-2117 ◽

Cited By ~ 36

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.

Download Full-text

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

BMC Research Notes ◽

10.1186/s13104-021-05590-z ◽

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.

Download Full-text

Superovulation in Dall's sheep (Ovis dalli dalli)

Theriogenology ◽

10.1016/0093-691x(90)90625-4 ◽

1990 ◽

Vol 33 (1) ◽

pp. 201 ◽

Cited By ~ 2

Author(s):

B.C. Buckrell ◽

C.J. Gartley ◽

K.G. Mehren ◽

K.L. Goodrowe

Keyword(s):

Ovis Dalli ◽

Dall’S Sheep

Download Full-text

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

Canadian Journal of Zoology ◽

10.1139/cjz-2017-0259 ◽

2018 ◽

Vol 96 (10) ◽

pp. 1170-1177 ◽

Cited By ~ 2

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.

Download Full-text

Altered body size distributions in a large river fish community enriched by sewage

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f02-056 ◽

2002 ◽

Vol 59 (5) ◽

pp. 819-828 ◽

Cited By ~ 17

Author(s):

Adrian M.H deBruyn ◽

David J Marcogliese ◽

Joseph B Rasmussen

Keyword(s):

Body Size ◽

Upper Bound ◽

Fish Community ◽

Local Variation ◽

Large River ◽

Habitat Characteristics ◽

Size Distributions ◽

Treated Sewage ◽

Energetic Constraints ◽

River Fish

We used two approaches (interspecific upper bound and normalized biomass spectrum, NBS) to study size distributions in a littoral fish community across a natural gradient of epiphytic primary production and at sites enriched by primary-treated sewage. The upper bound of the interspecific density body size relationship supported universal energetic constraints on the regional assemblage but revealed substantial variation in size distributions at a local scale. Multivariate analysis of the modes composing the NBS suggested possible mechanisms for this local variation in size distributions. Only the largest organisms had higher densities at higher levels of productivity. Densities of smaller organisms could be explained by a combination of habitat characteristics and feeding interactions.

Download Full-text

NOTES ON POPULATIONS OF Bovicola jellisoni ON DALL'S SHEEP (Ovis dalli)

Journal of Wildlife Diseases ◽

10.7589/0090-3558-13.4.427 ◽

1977 ◽

Vol 13 (4) ◽

pp. 427-428 ◽

Cited By ~ 2

Author(s):

KE CHUNG KIM

Keyword(s):

Ovis Dalli ◽

Dall’S Sheep

Download Full-text

Exceptional body sizes but typical trophic structure in a Pleistocene food web

Biology Letters ◽

10.1098/rsbl.2016.0228 ◽

2016 ◽

Vol 12 (5) ◽

pp. 20160228 ◽

Cited By ~ 3

Author(s):

Angel M. Segura ◽

Richard A. Fariña ◽

Matías Arim

Keyword(s):

Body Size ◽

Trophic Position ◽

Negative Relationship ◽

Additional Energy ◽

Quaternary Period ◽

Species Vulnerability ◽

Body Sizes ◽

Energetic Constraints ◽

The Relationship

In this study, we focused on the exceptionally large mammals inhabiting the Americas during the Quaternary period and the paramount role of body size in species ecology. We evaluated two main features of Pleistocene food webs: the relationship between body size and (i) trophic position and (ii) vulnerability to predation. Despite the large range of species sizes, we found a hump-shaped relationship between trophic position and body size. We also found a negative trend in species vulnerability similar to that observed in modern faunas. The largest species lived near the boundary of energetic constraints, such that any shift in resource availability could drive these species to extinction. Our results reinforce several features of megafauna ecology: (i) the negative relationship between trophic position and body size implies that large-sized species were particularly vulnerable to changes in energetic support; (ii) living close to energetic imbalance could favour the incorporation of additional energy sources, for example, a transition from a herbivorous to a scavenging diet in the largest species (e.g. Megatherium ) and (iii) the interactions and structure of Quaternary megafauna communities were shaped by similar forces to those shaping modern fauna communities.

Download Full-text

Interspecific Comparisons of Endothermy in Honey-Bees (APIS): Deviations from the Expected Size-Related Patterns

Journal of Experimental Biology ◽

10.1242/jeb.127.1.1 ◽

1987 ◽

Vol 127 (1) ◽

pp. 1-26 ◽

Cited By ~ 2

Author(s):

FRED C. DYER ◽

THOMAS D. SEELEY

Keyword(s):

Body Size ◽

Honey Bees ◽

Wing Loading ◽

Physiological Mechanisms ◽

Colony Demography ◽

Nesting Behaviour ◽

Asian Honey Bee ◽

Energetic Constraints ◽

Interspecific Comparisons ◽

Anatomical Evidence

We report the first measurements of thoracic flight temperature (Tth) in foragers of the three Asian honey-bee species (genus Apis), which, together with the European species A. mellifera, span a five-fold range in body mass from the smallest species to the largest. Over a 15°C range in ambient temperature (Ta), we found that Tth in each species is strongly dependent upon Ta, as previously shown for A. mellifera. However, the temperature gradients (Tth-Ta) at a given Ta do not appear to increase with body size in the four species, as expected from many previous studies of endothermy in insects. The smallest species, A.florea, shows the smallest Tth-Ta, but the intermediate-sized A. cerana and A. mellifera both show a consistently higher Tth-Ta than the largest species, A. dorsata. We found that the rate of passive convective heat loss from the thorax scales linearly and inversely with body size in the four species, as in most insects, and that there is no striking anatomical evidence for differences in efficiency with which heat flow from the thorax to the abdomen is restricted. However, two important correlates of heat production - wing-loading and flight speed - are disproportionately high in A. cerana and A. mellifera relative to A. dorsata and A. florea, suggesting that an elevated mass-specific metabolic rate in flight may account for their unexpectedly high Tth-Ta. Furthermore, compared on a mass-specific basis, A. dorsata and A. florea are more similar to each other than either is to the other two species. This physiological dichotomy among the four species parallels a dichotomy in nesting behaviour and colony demography. Hence our results, in addition to raising many questions about physiological mechanisms in the energetics of honey-bees, suggest that there may be functional links between the energetic constraints on individuals and on colonies.

Download Full-text