Ovis Dalli Research Articles

SNP discovery in candidate adaptive genes using exon capture in a free-ranging alpine ungulate.

Identification of genes underlying genomic signatures of natural selection is key to understanding adaptation to local conditions. We used targeted resequencing to identify SNP markers in 5321 candidate adaptive genes associated with known immunological, metabolic and growth functions in ovids and other ungulates. We selectively targeted 8161 exons in protein-coding and nearby 5' and 3' untranslated regions of chosen candidate genes. Targeted sequences were taken from bighorn sheep (Oviscanadensis) exon capture data and directly from the domestic sheep genome (Ovisaries v. 3; oviAri3). The bighorn sheep sequences used in the Dall's sheep (Ovis dalli dalli) exon capture aligned to 2350 genes on the oviAri3 genome with an average of 2 exons each. We developed a microfluidic qPCR-based SNP chip to genotype 476 Dall's sheep from locations across their range and test for patterns of selection. Using multiple corroborating approaches (lositan and bayescan), we detected 28 SNP loci potentially under selection. We additionally identified candidate loci significantly associated with latitude, longitude, precipitation and temperature, suggesting local environmental adaptation. The three methods demonstrated consistent support for natural selection on nine genes with immune and disease-regulating functions (e.g. Ovar-DRA, APC, BATF2, MAGEB18), cell regulation signalling pathways (e.g. KRIT1, PI3K, ORRC3), and respiratory health (CYSLTR1). Characterizing adaptive allele distributions from novel genetic techniques will facilitate investigation of the influence of environmental variation on local adaptation of a northern alpine ungulate throughout its range. This research demonstrated the utility of exon capture for gene-targeted SNP discovery and subsequent SNP chip genotyping using low-quality samples in a nonmodel species.

Genome-wide set of SNPs reveals evidence for two glacial refugia and admixture from postglacial recolonization in an alpine ungulate.

Past glaciation events have played a major role in shaping the genetic diversity and distribution of wild sheep in North America. The advancement of glaciers can isolate populations in ice-free refugia, where they can survive until the recession of ice sheets. The major Beringian refugium is thought to have held thinhorn sheep (Ovis dalli) populations during times of glacial advance. While isolation in the major refugium can account for much of the genetic and morphological diversity seen in extant thinhorn sheep populations, mounting evidence suggests the persistence of populations in smaller minor refugia. We investigated the refugial origins of thinhorn sheep using ~10000 SNPs obtained via a cross-species application of the domestic sheep ovine HD BeadChip to genotype 52 thinhorn sheep and five bighorn sheep (O. canadensis) samples. Phylogenetic inference revealed a distinct lineage of thinhorn sheep inhabiting British Columbia, which is consistent with the survival of a group of thinhorn sheep in a minor refugium separate from the Beringian refugium. Isolation in separate glacial refugia probably mediated the evolution of the two thinhorn sheep subspecies, the white Dall's sheep (O. d. dalli), which persisted in Beringia, and the dark Stone's sheep (O. d. stonei), which utilized the minor refugium. We also found the first genetic evidence for admixture between sheep from different glacial refugia in south-central Yukon as a consequence of post glacial expansion and recolonization. These results show that glaciation events can have a major role in the evolution of species inhabiting previously glaciated habitats and the need to look beyond established refugia when examining the evolutionary history of such species.

Identification of landscape features influencing gene flow: How useful are habitat selection models?

Understanding how dispersal patterns are influenced by landscape heterogeneity is critical for modeling species connectivity. Resource selection function (RSF) models are increasingly used in landscape genetics approaches. However, because the ecological factors that drive habitat selection may be different from those influencing dispersal and gene flow, it is important to consider explicit assumptions and spatial scales of measurement. We calculated pairwise genetic distance among 301 Dall's sheep (Ovis dalli dalli) in southcentral Alaska using an intensive noninvasive sampling effort and 15 microsatellite loci. We used multiple regression of distance matrices to assess the correlation of pairwise genetic distance and landscape resistance derived from an RSF, and combinations of landscape features hypothesized to influence dispersal. Dall's sheep gene flow was positively correlated with steep slopes, moderate peak normalized difference vegetation indices (NDVI), and open land cover. Whereas RSF covariates were significant in predicting genetic distance, the RSF model itself was not significantly correlated with Dall's sheep gene flow, suggesting that certain habitat features important during summer (rugged terrain, mid‐range elevation) were not influential to effective dispersal. This work underscores that consideration of both habitat selection and landscape genetics models may be useful in developing management strategies to both meet the immediate survival of a species and allow for long‐term genetic connectivity.

Cadmium and other elements in tissues from four ungulate species from the Mackenzie Mountain region of the Northwest Territories, Canada

Tissue samples from four ungulate species from the south Mackenzie Mountain region of the Northwest Territories (NT), Canada, were analysed for stable and radioactive elements and 15N and 13C stable isotopes. Elevated Cd concentrations in moose (Alces americanus) kidney have been observed in the region and are a health care concern for consumers of traditional foods. This study examined the factors associated with, and potential renal effects from, the accumulation of cadmium, and interactions with other elements in four sympatric ungulate species. Mean renal Cd concentration was highest in moose (48.3mg/kg ww), followed by mountain caribou (Rangifer tarandus caribou) (13.9mg/kg ww) and mountain goat (Oreamnos americanus) (5.78mg/kg ww). No local sources of Cd were evident and the elevated levels in moose are considered to be natural in origin. Conversely, total Hg concentration was significantly higher in mountain caribou kidney (0.21mg/kg ww) than in moose (0.011mg/kg ww). 134Cs (t½=2.1 y) in mountain goat and Dall's sheep (Ovis dalli) muscle is evidence of deposition from the Fukushima reactor accident in 2011. 137Cs (t½=30.2 y) in all four ungulates is primarily a remnant of the nuclear weapons tests of the 1960s. The levels of both nuclides are low and the risk to the animals and people consuming them is negligible.Stable isotope δ15N and δ13C signatures in muscle showed a separation between the mountain caribou, with a lichen-dominated diet, and moose, which browse shrubs and forbs. Isotope signatures for mountain goat and Dall's sheep showed generalist feeding patterns. Differences in elemental and radionuclide levels between species were attributed to relative levels of metal accumulation in the different food items in the diets of the respective species. Kidneys from each species showed minor histological changes in the proximal tubule and glomerulus, although glomerular changes were rare and all changes were rare in mountain goat kidney. Kidney function was not expected to be affected in any species.Provisional Monthly Intake recommendations from the WHO indicate that Cd in moose organs will continue to be a public health care concern. However, traditional foods continue to be an important nutritional component of northern diets, particularly in consideration of the shift towards store-bought food.

Shrubline but not treeline advance matches climate velocity in montane ecosystems of south-central Alaska.

Tall shrubs and trees are advancing into many tundra and wetland ecosystems but at a rate that often falls short of that predicted due to climate change. For forest, tall shrub, and tundra ecosystems in two pristine mountain ranges of Alaska, we apply a Bayesian, error-propagated calculation of expected elevational rise (climate velocity), observed rise (biotic velocity), and their difference (biotic inertia). We show a sensitive dependence of climate velocity on lapse rate and derive biotic velocity as a rigid elevational shift. Ecosystem presence identified from recent and historic orthophotos ~50 years apart was regressed on elevation. Biotic velocity was estimated as the difference between critical point elevations of recent and historic logistic fits divided by time between imagery. For both mountain ranges, the 95% highest posterior density of climate velocity enclosed the posterior distributions of all biotic velocities. In the Kenai Mountains, mean tall shrub and climate velocities were both 2.8 m y(-1). In the better sampled Chugach Mountains, mean tundra retreat was 1.2 m y(-1) and climate velocity 1.3 m y(-1). In each mountain range, the posterior mode of tall woody vegetation velocity (the complement of tundra) matched climate velocity better than either forest or tall shrub alone, suggesting competitive compensation can be important. Forest velocity was consistently low at 0.1-1.1 m y(-1), indicating treeline is advancing slowly. We hypothesize that the high biotic inertia of forest ecosystems in south-central Alaska may be due to competition with tall shrubs and/or more complex climate controls on the elevational limits of trees than tall shrubs. Among tall shrubs, those that disperse farthest had lowest inertia. Finally, the rapid upward advance of woody vegetation may be contributing to regional declines in Dall's sheep (Ovis dalli), a poorly dispersing alpine specialist herbivore with substantial biotic inertia due to dispersal reluctance.

Changes in horn size of Stone's sheep over four decades correlate with trophy hunting pressure.

Selective harvest may lead to rapid evolutionary change. For large herbivores, trophy hunting removes males with large horns. That artificial selection, operating in opposition to sexual selection, can lead to undesirable consequences for management and conservation. There have been no comparisons of long-term changes in trophy size under contrasting harvest pressures. We analyzed horn measurements of Stone's rams (Ovis dalli stonei) harvested over 37 years in two large regions of British Columbia, Canada, with marked differences in hunting pressure to identify when selective hunting may cause a long-term decrease in horn growth. Under strong selective harvest, horn growth early in life and the number of males harvested declined by 12% and 45%, respectively, over the study period. Horn shape also changed over time: horn length became shorter for a given base circumference, likely because horn base is not a direct target of hunter selection. In contrast, under relatively lower hunting pressure, there were no detectable temporal trends in early horn growth, number of males harvested, or horn length relative to base circumference. Trophy hunting is an important recreational activity and can generate substantial revenues for conservation. By providing a reproductive advantage to males with smaller horns and reducing the availability of desirable trophies, however, excessive harvest may have the undesirable long-term consequences of reducing both the harvest and the horn size of rams. These consequences can be avoided by limiting offtake.

Dietary overlap and potential competition in a dynamic ungulate community in Northwestern Canada

ABSTRACTThe potential for interspecific competition for food resources is a key consideration when newly introduced ungulates occupy a shared range with resident native species. Management plans in Yukon, Canada, for reintroduced bison (Bison bison) and introduced elk (Cervus canadensis) called for an assessment of competition for food resources between these species and resident populations of caribou (Rangifer tarandus), thinhorn sheep (Ovis dalli), and moose (Alces americanus). To assess potential competition among ungulates, we examined dietary overlap of 7 ungulate species in southwestern Yukon, Canada. We compared diet composition at the forage class level and composite diet indices (diversity, evenness, and niche breadth) among species found at 2 elevation classes (high [≥1,200 m ASL] and low [<1,200 m ASL]) during summer and winter, using data derived from microhistological analyses of feces. Composite indices and percent of key forage classes in diets differed among ungulates during summer and winter and at both high and low elevations. Potential dietary overlap for most species pairs was low to moderate (0.07–0.60). However, for bison and thinhorn sheep at high elevations, and bison and semi‐feral horses (Equus ferus caballus) at low elevations, it was high (0.82–0.97) during both summer and winter, indicating potential for food competition. Dietary overlap between species appeared to be based primarily on morphophysiological classification (i.e., browser‐intermediate‐grazer), rather than body size. Bison, horses, and sheep were all grazers. Intermediate species, such as introduced elk, had only moderate dietary overlap with several species. We concluded that the potential for competition for food resources based on dietary overlap between bison and sheep and bison and horses may be high in our study area, depending on forage availability, but for all other species pairs in our study area the potential for forage competition is low to moderate. © 2015 The Wildlife Society.

Resource separation by mountain ungulates on a landscape modified by fire

AbstractFire restructures plant communities and can be an important modifier of ecosystems. Increases in forage quantity and quality in burned areas attract large ungulates, and may result in changes to animal distributions. In mountainous northern British Columbia where prescribed fire is used to enhance ungulate range, there is concern that expanding elk (Cervus elaphus) populations will move in response to burning into the traditional ranges of another grazing species, Stone's sheep (Ovis dalli stonei), and have adverse effects on them. We compared patterns of resource selection and use by both species on a landscape with 138 prescribed burns varying from 0 to 31 years of age. Seasonal range sizes of global positioning system (GPS)‐collared individuals were smallest in winter and late winter and largest in summer for both female Stone's sheep and elk. Both species selected for south aspects and against conifer stands in all seasons. Stone's sheep selected for burned areas in fall, winter, and late winter and selected to be close to a burn in every season except summer. Elk selected for burned areas in every season, with the highest selection for burn‐shrub areas. Stone's sheep typically used younger burns, whereas elk were less specific and often used older burns. The highest potential for seasonal overlap in the use of burned areas occurs during winter and late winter, but Stone's sheep and elk at current population levels overlap minimally because they partition their use of the landscape through elevation and topography. Stone's sheep always selected and used steeper rugged terrain than elk, and were at higher elevations, often in rocky areas. Elk avoided alpine and rocky areas, and were at lower elevations than Stone's sheep, on flatter less rugged terrain. We recommend continued monitoring of post‐fire effects on resource selection and use by these sympatric grazers, particularly relative to the distribution of expanding elk populations, which could enable competitive interactions and change predator‐prey dynamics. © 2015 The Wildlife Society.

Optimal predator management for mountain sheep conservation depends on the strength of mesopredator release

Large predators often suppress ungulate population growth, but they may also suppress the abundance of smaller predators that prey on neonatal ungulates. Antagonistic interactions among predators may therefore need to be integrated into predator–prey models to effectively manage ungulate–predator systems. We present a modeling framework that examines the net impact of interacting predators on the population growth rate of shared prey, using interactions among wolvesCanis lupus, coyotesCanis latransand Dall sheepOvis dalli dallias a case study. Wolf control is currently employed on approximately 16 million ha in Alaska to increase the abundance of ungulates for human harvest. We hypothesized that the positive effects of wolf control on Dall sheep population growth could be counteracted by increased levels of predation by coyotes. Coyotes and Dall sheep adult females (ewes) and lambs were radiocollared in the Alaska Range from 1999–2005 to estimate fecundity, age‐specific survival rates, and causes of mortality in an area without wolf control. We used stage‐structured population models to simulate the net effect of wolf control on Dall sheep population growth (λ). Our models accounted for stage‐specific predation rates by wolves and coyotes, compensatory mortality, and the potential release of coyote populations due to wolf control. Wolves were the main predators of ewes, coyotes were the main predators of lambs, and wolves were the main source of mortality for coyotes. Population models predicted that wolf control could increase sheep λ by 4% per year in the absence of mesopredator release. However, if wolf control released coyote populations, our models predicted that sheep λ could decrease by up to 3% per year. These results highlight the importance of integrating antagonistic interactions among predators into predator–prey models, because the net effect of predator management on shared prey can depend critically on the strength of mesopredator release.

Co-occurrence of reintroduced and resident ungulates on a shared winter range in northwestern Canada

For interspecific competition to occur species must use the same limited resources (e.g. food, habitat) and overlap in time and space. Bison (Bison bison) were reintroduced to southwestern Yukon, Canada, where they are sympatric with resident caribou (Rangifer tarandus), moose (Alces americanus) and thinhorn sheep (Ovis dalli). Concerns from local communities regarding potential competition between reintroduced bison and resident ungulates prompted us to test their spatial distribution for co-occurrence. In late-winter, we conducted multiple aerial surveys (n = 1–5) of 12.2 km2 cells (n = 779) to develop a presence–absence matrix (4 species × 779 cells) of the spatial distribution of ungulates. Randomization procedures were used to conduct a null model analysis of co-occurrence. Community-wide null model analysis indicated that community members were neither segregated nor aggregated; rather, their spatial distribution was random because they did not differ from simulated null communities (n = 50,000). Similar analyses conducted on sub-matrices for each species pair also did not find evidence for segregation or aggregation among any species pairs except caribou and sheep, who were spatially segregated. We conclude that the overall potential for competition between reintroduced bison and resident ungulates during late-winter is low, based on spatial overlap. However, further investigations on the potential for competition among other niche dimension axes (e.g. food, habitat use) are recommended. Even though bison are reintroduced, these species had interacted for thousands of years and have probably co-evolved mechanisms to partition resources and co-exist on a shared landscape.

Population density of Dall’s sheep in Alaska: effects of predator harvest?

We measured population abundance and density of Dall’s sheep (Ovis dalli) before and during gray wolf (Canis lupus) and coyote (Canis latrans) harvest for 3 years (1998–2000) on two similar and adjacent study sites with treatment (canid harvests) and reference (no canid harvest) in interior Alaska, USA. Between 1998 and 1999, density of Dall’s sheep in the treatment area increased by 0.746 ± 0.163 sheep/km2. Between 1999 and 2000, after a winter with above-normal, crusted snow, density of sheep decreased by 2.1 ± 0.14 sheep/km2. Because of this large decline, sheep density on the treatment area decreased by 1.3 ± 0.08 sheep/km2 over the entire monitoring period. Sheep in the reference area showed no significant change in density between 1998 and 2000. We hypothesize that Dall’s sheep in the treatment area initially benefited from the harvest of wolves and coyotes via reduced predation and predation risk and that resultant high sheep densities coupled with severe winter weather caused a dramatic decline in Dall’s sheep between 1999 and 2000. Thus, this study illustrates the potential consequences of interactions between density-dependent and density-independent factors for the conservation of large mammals, especially those residing at high latitudes and altitudes. These results should serve as a cautionary tale for those wishing to increase ungulate numbers via predator control without regard to other ecological factors, such as the proximity of the prey population to ecological carrying capacity (K).

Lack of sex-biased dispersal promotes fine-scale genetic structure in alpine ungulates

Identifying patterns of fine-scale genetic structure in natural populations can advance understanding of critical ecological processes such as dispersal and gene flow across heterogeneous landscapes. Alpine ungulates generally exhibit high levels of genetic structure due to female philopatry and patchy configuration of mountain habitats. We assessed the spatial scale of genetic structure and the amount of gene flow in 301 Dall’s sheep (Ovis dalli dalli) at the landscape level using 15 nuclear microsatellites and 473 base pairs of the mitochondrial (mtDNA) control region. Dall’s sheep exhibited significant genetic structure within contiguous mountain ranges, but mtDNA structure occurred at a broader geographic scale than nuclear DNA within the study area, and mtDNA structure for other North American mountain sheep populations. No evidence of male-mediated gene flow or greater philopatry of females was observed; there was little difference between markers with different modes of inheritance (pairwise nuclear DNA F ST = 0.004–0.325; mtDNA F ST = 0.009–0.544), and males were no more likely than females to be recent immigrants. Historical patterns based on mtDNA indicate separate northern and southern lineages and a pattern of expansion following regional glacial retreat. Boundaries of genetic clusters aligned geographically with prominent mountain ranges, icefields, and major river valleys based on Bayesian and hierarchical modeling of microsatellite and mtDNA data. Our results suggest that fine-scale genetic structure in Dall’s sheep is influenced by limited dispersal, and structure may be weaker in populations occurring near ancestral levels of density and distribution in continuous habitats compared to other alpine ungulates that have experienced declines and marked habitat fragmentation.

IMMUNOCONTRACEPTION OF CAPTIVE EXOTIC SPECIES: V. PROLONGED ANTIBODY TITERS IN DALL SHEEP (OVIS DALLI DALLI) AND DOMESTIC GOATS (CAPRA HIRCUS) IMMUNIZED WITH PORCINE ZONA PELLUCIDA

Native porcine zona pellucida (PZP) immunocontraception has been used to inhibit fertility in more than 80 species of ungulates, although the duration of contraception efficacy varies among species in both Perissodactyla and Artiodactyla. This study examined anti-PZP antibody titers in Dall sheep and domestic goats at the Milwaukee County Zoo, and also Himalayan tahr and Armenian Mouflon sheep at the San Diego Zoo Safari Park, and, for comparison, Altai wapiti, lowland wisent, Javan banteng, and southern pudu at the San Diego Zoo Safari Park, all were given a primer dose and booster dose of PZP. Of the San Diego Zoo Safari Park animals, the 4 comparison species demonstrated the typical 1-yr pattern of anti-PZP antibodies, whereas the Armenian sheep and Himalayan tahr showed prolonged (2-3 yr) antibody responses after a single primer and booster dose. The Dall sheep and domestic goats had significantly longer durations of antibody titers (3 yr) from a single year's treatment (primer plus booster). Analysis of the data indicates that Armenian sheep, Himalayan tahr, Dall sheep, and domestic goats have prolonged responses, and are more sensitive to PZP in that they produce a protracted antibody response.

Reducing effort while improving inference: Estimating Dall's sheep abundance and composition in small areas

Recent work has demonstrated that aerial distance sampling surveys are more efficient and effective than unadjusted minimum count surveys for estimating Dall's sheep (Ovis dalli) abundance, although large sample size requirements (e.g., 150-200 detections) may discourage implementation of these methods in small (<2,500 km 2 ) or low density areas. However, a Bayesian analytical approach using informed priors and borrowing detection information across surveys can increase precision and decrease required sample sizes. Using these methods, we conducted distance sampling surveys across a majority of the Dall's sheep habitat within National Park Service units in Alaska during 2010-2011. We compared 4 analytical scenarios using increasing amounts of detection information to demonstrate the increases in efficiency that can be gained over time through the use of this approach. Based on our analysis using all available survey information in the estimation of the detection function, we estimated that 2,252 (1,871- 2,765), 2,809 (2,361-3,379), 1,669 (1,339-2,120), and 12,428 (10,780-14,470) sheep occurred in Denali National Park and Preserve (DENA), the Western Arctic National Parklands (WEAR), the Itkillik preserve subarea of Gates of the Arctic National Park and Preserve, and Wrangell-St. Elias National Park and Preserve (WRST), respectively. These estimates were achieved with relatively small numbers of group detections in DENA (n ¼ 57), the Itkillik preserve area (n ¼ 48), and WEAR (n ¼ 100), suggesting that sample size requirements for Dall's sheep distance sampling surveys can be reduced by an additional 50-75% over previously recommended levels when adequate prior information is available. In addition, we describe a formal approach for estimating the size of individual composition classes (i.e., lambs, ewe-like sheep, <full- curl rams, � full-curl rams) and sex and age ratios, corrected for incomplete detection. We implemented the composition analysis within the distance sampling analytical framework as part of the abundance estimation process.This approach to theestimation ofpopulation composition could replace commonly usedindices and provides more detailed and rigorous estimates that are directly comparable among survey areas and years. We found that ratios offull curl rams:100 ewe-like sheep in WEAR and Itkillik preserve subarea populations were less than in the DENA population, whereas lamb:ewe-like ratios were similar across all 4 survey areas, suggesting relatively consistent productivity. We recommend that aerial distance sampling survey methods using prior information, combined with direct estimation of population composition, be used to increase the effectiveness of Dall's sheep population monitoring and management throughout their range. 2013 The Wildlife Society.

The complete mitochondrial genome sequence analysis of Tibetan argali (Ovis ammon hodgsoni): Implications of Tibetan argali and Gansu argali as the same subspecies

The genus Ovis (Bovidae, Artiodactyla) includes six species, i.e. Ovis ammon, Ovis aries, Ovis canadensis, Ovis dalli, Ovis nivicola and Ovis vignei. Based on morphology, geographical location, habitat, etc., the species O. ammon is divided into nine subspecies. The near threatened Tibetan argali is distributed across the Tibetan Plateau and its peripheral mountains, and believed to be one of the O. ammon subspecies (O. a. hodgsoni). However, considering its morphological features and distributions, a question has been proposed by some researchers about the subspecies status of Tibetan argali. In this study, we employed complete mitochondrial DNA (mtDNA) to explore the phylogenetic relationship and population genetic structure of Tibetan argali. The results revealed that the nucleotide composition, gene arrangement and codon usage pattern of the mitochondrial genome of Tibetan argali are similar to those of other caprines. Phylogenetic analyses showed that Tibetan argali was clustered with O. ammon. Interestingly, five Tibetan argali individuals and one of the three Gansu argali (O. a. dalailamae) individuals were clustered in the same branch, which is a sister group to other two Gansu argali individuals. Together with morphological characteristics, our results suggested that Tibetan argali and Gansu argali may belong to the same subspecies (O. a. hodgsoni) of O. ammon, rather than two different subspecies.

Quantifying the Role of Viewing the Denali “Big 5” in Visitor Satisfaction and Awareness: Conservation Implications for Flagship Recognition and Resource Management

Wildlife viewing is a primary attraction at Denali National Park (DNP), with most visitors wishing to observe the “Big 5”: grizzly bear (Ursus arctos), wolf (Canis lupus), caribou (Rangifer tarandus), Dall sheep (Ovis dalli dalli), and moose (Alces alces gigas). This study explored the role of individual “Big 5” species on (a) visitors' wildlife viewing satisfaction, (b) overall trip satisfaction, and (c) awareness of fundamental purposes for establishing DNP (i.e., enabling legislation). Data were obtained from 582 DNP visitor surveys during 2007. Grizzly observations yielded significantly higher levels of wildlife viewing satisfaction than all other species except caribou. No significant difference was found between species for overall trip satisfaction. Awareness of enabling legislation improved with higher levels of satisfaction and number of species observed. Grizzly bear and caribou are recommended as flagship species. This could increase viewing opportunities and visitor satisfaction within an experienced-based management framework.

Seasonal habitat use and selection by grizzly bears in Northern British Columbia

AbstractWe defined patterns of habitat use and selection by female grizzly bears (Ursus arctos) in the Besa‐Prophet watershed of northern British Columbia. We fitted 13 adult females with Geographic Positioning System (GPS) radio‐collars and monitored them between 2001 and 2004. We examined patterns of habitat selection by grizzly bears relative to topographical attributes and 3 potential surrogates of food availability: land‐cover class, vegetation biomass or quality (as measured by the Normalized Difference Vegetation Index), and selection value for prey species themselves (moose [Alces alces], elk [Cervus elaphus], woodland caribou [Rangifer tarandus], Stone's sheep [Ovis dalli stonei]). Although vegetation biomass and quality, and selection values for prey were important in seasonal selection by some individual bears, land‐cover class, elevation, aspect, and vegetation diversity most influenced patterns of habitat selection across grizzly bears, which rely on availability of plant foods and encounters with ungulate prey. Grizzly bears as a group avoided conifer stands and areas of low vegetation diversity, and selected for burned land‐cover classes and high vegetation diversity across seasons. They also selected mid elevations from what was available within seasonal ranges. Quantifying relative use of different attributes helped place selection patterns within the context of the landscape. Grizzly bears used higher elevations (1,595 ± 31 m SE) in spring and lower elevations (1,436 ± 27 m) in fall; the range of average elevations used among individuals was highest (500 m) during the summer. During all seasons, grizzly bears most frequented aspects with high solar gain. Use was distributed across 10 land‐cover classes and depended on season. Management and conservation actions must maintain a diverse habitat matrix distributed across a large elevational gradient to ensure persistence of grizzly bears as levels of human access increase in the northern Rocky Mountains. © 2011 The Wildlife Society.

Using distance sampling and hierarchical models to improve estimates of Dall's sheep abundance

AbstractManagement of large mammal populations has often been based on aerial minimum count surveys that are uncorrected for incomplete detection and lack estimates of precision. These limitations can be particularly problematic for Dall's sheep (Ovis dalli dalli) due to the high cost of surveys and variation in detection probability across time and space. The limitations of these methods have been recognized for some time, but previously proposed alternatives for sheep surveys proved to be too costly and logistically unfeasible in most circumstances (Udevitz et al. 2006). We assessed the potential for a combination of distance sampling surveys and a hierarchical modeling approach to provide a more efficient means for estimating Dall's sheep abundance by conducting aerial contour transect surveys over all sheep habitat in Gates of the Arctic National Park and Preserve (GAAR), Alaska in 2009 and 2010. We estimated the population of Dall's sheep was 8,412 (95% CI: 6,517–11,090) and 10,072 (95% CI 8,081–12,520) in 2009 and 2010, respectively. Abundance within the Itkillik Preserve area within GAAR was 1,898 (95% CI: 1,421–2,578) and 1,854 (95% CI: 1,342–2,488) in 2009 and 2010, respectively. Estimates of lamb abundance in 2010 were more than double those of 2009 after correcting for detection bias related to group size, suggesting that the apparent estimate of lambs in the population may be biased in some years depending on the degree of aggregation. Overall, the contour transect surveys were feasible logistically, cost 70–80% less than minimum count surveys, and produced precise estimates of abundance, indicating that the application of these methods could be used effectively to increase the statistical rigor and spatial extent of Dall's sheep abundance surveys throughout Alaska. These methods could be used to improve the assessment of long‐term trends in populations and productivity and provide valuable information for harvest management at both local and landscape scales at reduced costs in comparison to traditional minimum count surveys. © 2011 The Wildlife Society.

Habitat selection by a focal predator (Canis lupus) in a multiprey ecosystem of the northern Rockies

Abstract Large predators respond to land cover and physiography that maximize the likelihood of encountering prey. Using locations from global positioning system–collared wolves (Canis lupus), we examined whether land cover, vegetation productivity or change, or habitat-selection value for ungulate prey species themselves most influenced patterns of selection by wolves in a large, intact multiprey system of northern British Columbia. Selection models based on land cover, in combination with topographical features, consistently outperformed models based on indexes of vegetation quantity and quality (using normalized difference vegetation index) or on selection value to prey species (moose [Alces americanus], elk [Cervus elaphus], woodland caribou [Rangifer tarandus], and Stone's sheep [Ovis dalli stonei]). Wolves generally selected for shrub communities and high diversity of cover across seasons and avoided conifer stands and non-vegetated areas and west aspects year-round. Seasonal selection strategies we...

Using stable isotopes to define diets of wolves in northern British Columbia, Canada

Wolves (Canis lupus), as both opportunistic and specialist predators, can limit and regulate ungulate dynamics. As part of understanding predator–prey interactions in the largely undisturbed system of the Besa-Prophet area in northern British Columbia, we used stable isotopes of carbon and nitrogen to infer seasonal diets of 5 wolf packs. We selected the hair, tissue, or blood sample of each prey species that could best index within-season diet composition. Seasonal isotopic differences for a given sample type were as much as 0.28% d 13 C and 0.97% d 15 N. The large biomass species of moose (Alces americanus) and elk (Cervus elaphus) dominated the diets of wolves, but caribou (Rangifer tarandus) and Stone’s sheep (Ovis dalli stonei) also were locally or seasonally important to some packs. Mean isotopic determinations of summer food habits were correlated positively (P , 0.001) with proportions of prey by species determined from scat samples. This general agreement lends support for the tissue to diet discrimination values used in the Bayesian modeling and indicates that the longer-term dietary estimates from stable isotopes were reflective of shorter-term recent ingestion. Although moose have been assumed to be the most important prey item for wolves throughout the year in northern British Columbia, our results indicate that dietary dynamics of wolves in the Besa-Prophet area are more complex than previously reported.