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Wildlife capture, and the data collection associated with it, has led to major advancements in ecology that are integral to decision making pertaining to wildlife conservation. Capturing wildlife, however, can cause lethal and non-lethal risks to animals. Understanding the factors that contribute to the level of risk involved in wildlife capture is therefore important for the development and implementation of the safest and most effective methodologies. We used data from 736 animal captures of 389 individuals for 2 subspecies of female bighorn sheep (Rocky Mountain bighorn [Ovis canadensis canadensis], Sierra Nevada bighorn sheep [O. c. sierrae]) in Wyoming and California, USA, in 2002–2020 to evaluate the degree and extent of time that capture via helicopter net-gunning affects survival. We compared pre- and post-capture survival during a 10-week window centered on a capture event, and post-capture survival between captured animals and animals that were monitored but not captured during the 10-week window. Additionally, we evaluated the effects of handling techniques (number of times captured, season of capture event, handling time, chase time, and body temp) and biological factors (age and nutritional condition) on probability of capture mortality. Mean daily survival was 0.9992 during a 5-week pre-capture window, dropped to 0.9864 on the day of capture, and rebounded within 3 days of capture to pre-capture levels and that of sheep that were not captured. Overall, direct mortality resulting from capture was 1.36%, with 0.54% mortality occurring within the 3 days following a capture event for an overall 1.90% capture-related mortality. The only handling and biological metrics that influenced the probability of capture mortality were rectal temperature and nutritional condition; high initial rectal temperatures and poor body condition were associated with increased risk of mortality in the days following capture. Overall, helicopter net-gunning imposed low and short-term risk to survival of female bighorn sheep. To reduce bias in survival estimates, we recommend using a 3-day censorship window for post-capture mortalities as opposed to the common practice of a 2–5-week censor window. Helicopter net-gunning, including annual or seasonal recaptures, remains an effective and comparatively safe technique for capture and associated data collection of bighorn sheep.

The spatial distribution of animals has consequences for nutrition, predator–prey dynamics, spread of diseases, and population dynamics in general. Animals must establish a home range to secure adequate resources to fuel their energy needs. Home ranges, therefore, are temporally and spatially dynamic, given the changing requirements of an animal and the availability of resources on the landscape. We used data from two populations of bighorn sheep with contrasting population dynamics following pneumonia epizootics and different habitat quality on their summer range to test the hypothesis that the distribution and size of home ranges are influenced by environmental conditions and reproductive status. We used a combination of data from 768 vegetation transects and remotely sensed metrics to index forage quality of consecutive biweekly home ranges for 27 bighorn sheep, June–August 2019–2021. There were population differences in home range dynamics that were consistent with resource limitations in the population declining in abundance. Animals in both populations increased the size of their home range through the summer in association with declining forage quality indexed by plant phenology. Furthermore, animals in the Whiskey Mountain population without offspring had home ranges more than twice the size of animals with offspring, whereas there were no differences in the home range size between animals with and without offspring in Jackson. We demonstrated that limitations young offspring impose on space use of a mother may have consequences for animals living where larger home ranges are needed to secure adequate resources—sheep on Whiskey Mountain had to travel 1000 m from escape terrain to access the same amount of biomass that the Jackson sheep could access directly adjacent to escape terrain. Forage quality and availability influence movement and space use. In the presence of disease, movement and space use may influence pathogen transmission and persistence. Thus, forage availability may play an indirect role in population dynamics in the presence of disease, which is another line of evidence for how environmental and nutritional conditions may influence population dynamics when coping with disease.

In December 2008, near Flaming Gorge Reservoir in northeastern Utah, a 2 ½-year-old male Rocky Mountain bighorn sheep (Ovis canadensis canadensis) was reported in poor body condition with bloody lesions covering the muzzle area. The sheep was euthanized, and samples were submitted to the Utah Veterinary Diagnostic Laboratory in Logan, Utah. The gross and microscopic lesions confirmed the diagnosis of contagious ecthyma (CE). This is the first documented report of CE in bighorn sheep from Utah.

In December 2008, near Flaming Gorge Reservoir in northeastern Utah, a 2 ½-year-old male Rocky Mountain bighorn sheep (Ovis canadensis canadensis) was reported in poor body condition with bloody lesions covering the muzzle area. The sheep was euthanized, and samples were submitted to the Utah Veterinary Diagnostic Laboratory in Logan, Utah. The gross and microscopic lesions confirmed the diagnosis of contagious ecthyma (CE). This is the first documented report of CE in bighorn sheep from Utah.

Prescribed burning and timber harvesting have been used to restore and maintain Rocky Mountain bighorn sheep (Ovis canadensis) ranges. Intensive study of a bighorn sheep herd in northeastern Utah indicated a need for range improvements. To evaluate the effectiveness of clear-cut logging and prescribed burning, we documented sheep responses to these treatments. Although bighorn sheep exhibited strong fidelity to pre-treatment areas (P>0.05), they significantly altered use patterns to include logged and burned areas (P<0.001). Treated habitats experienced 148% increases in bighorn sheep activity, whereas use in untreated areas declined by 45%. Bighorn sheep responded more favorably to logged units than to burned areas. We conclude that carefully planned clear-cut logging and range burning may be effective to enhance and expand bighorn sheep populations.

In the mid-latitude mountains of North America, archaeological materials have been identified in association with kinetically stable \"ice patches\" that attracted animals and their human predators. The stable ice in these features exhibits little internal deformation or movement and can preserve otherwise perishable materials for millennia. Eight prehistoric sites have been identified in association with perennial ice patches within the Greater Yellowstone Area of Montana and Wyoming. Surveys in Colorado have produced paleobiological samples, but no definitive archaeological sites. Archaeological remains include ancient wooden dart shafts and fragments, wooden artifacts of unknown function, a wrapped leather object of unknown function, butchered animal remains, and chipped stone artifacts. Fragments of weapons ranging in age from 200 to 10400 years suggest long-term continuity in ice patch hunting in the region. Paleobiological specimens range in age from several hundred to nearly 8000 years. Bighorn sheep (Ovis canadensis) is a presumed prey species, but the remains of bison (Bison bison) and other large ungulates also occur. Ice patches offer important insights into the use of high-elevation environments by Native Americans. Efforts are ongoing to build and maintain awareness of these resources among federal land managers and the public. Dans les montagnes de latitude moyenne de l'Amérique du Nord, du matériel archéologique a été repéré dans des « névés » cinétiquement stables où évoluaient certains animaux de même que leurs prédateurs humains. La glace stable de ces névés présente une déformation ou un mouvement interne minime, ce qui permet de préserver des matériaux périssables pendant des milliers d'années. Huit sites préhistoriques ont été répertoriés dans les névés pérennes de la grande région du Yellowstone se trouvant au Montana et au Wyoming. Au Colorado, des levés ont permis de prélever des échantillons paléobiologiques, mais aucun site archéologique définitif. Parmi les restes archéologiques retrouvés, notons d'anciennes tiges et d'anciens fragments de propulseurs en bois, des artefacts en bois dont la fonction est inconnue, un objet enveloppé en cuir dont la fonction est inconnue, des restes d'animaux dépecés et des artefacts en pierre taillée. Des fragments d'armes âgés de 200 à 10400 ans laissent entrevoir que la chasse a été pratiquée dans les névés de la région pendant très longtemps. L'âge des spécimens paléobiologiques varie de plusieurs centaines d'années à près de 8 000 ans. Le mouflon d'Amérique (Ovis canadensis) y est une espèce-proie présumée, et des restes de bisons (Bison bison) et d'autres grands ongulés s'y trouvent également. Les névés permettent de mieux comprendre comment les Autochtones utilisaient les milieux en haute altitude. Les responsables fédéraux de la gestion des terres et le public déploient des efforts constants pour sensibiliser les gens à ces ressources.

Anecdotal evidence of a pneumonia epizootic among bighorn sheep (Ovis canadensis canadensis) in Rocky Mountain National Park (RMNP), Colorado, USA, during the mid-1990s prompted park officials to examine the current condition of the herds. Here we present a mark–resight study design to estimate population abundance that, in many circumstances, is a reliable and cost-effective alternative to traditional mark–recapture or to indices of population abundance. We captured 59 adult females and radiocollared them via helicopter net-gunning during winter 2002–2003. From ground resighting surveys conducted May–September, we estimated the total RMNP bighorn population at 389.9 (SE = 34.9, CI = 327.2–464.6) in 2003 and 366.4 (SE = 34.7, CI = 304.4–441.0) in 2004. Previous abundance estimates suggest a park-wide decline has occurred between the late 1980s and the suspected pneumonia epidemic of the mid-1990s. Although the 2 years of data from our study are not enough to predict whether the herds are capable of recovering to previous levels, they provide park officials the tools necessary to make the most informed decisions for future monitoring and management of this fragile species.

Bighorn sheep (Ovis canadensis) use of Sheep Lakes mineral site, Rocky Mountain National Park, Colorado, USA, has decreased since 1996. Officials were concerned that human disturbance may have been contributing to this decline in use. We evaluated effects of vehicular traffic and other road-related disturbance on bighorn use of Sheep Lakes in the summers of 2002 and 2003. We found that the time and number of attempts required by bighorn to reach Sheep Lakes was positively related to the number of vehicles and people present at Sheep Lakes. Further, the number of bighorn individuals and groups attempting to visit Sheep Lakes were negatively affected by disturbance associated with the site. The number of vehicles recorded the hour before bighorn tried to access Sheep Lakes best predicted an animal's failure to cross Fall River Road and reach Sheep Lakes. We conclude that human and road-related disturbance at Sheep Lakes negatively affected bighorn use of the mineral site. Because Sheep Lakes may be important for bighorn sheep, especially for lamb production and survival, the negative influence of disturbance may compromise health and productivity of the Mummy Range bighorn sheep.

We compared allozyme variability in 4 reintroduced populations of bighorn sheep (Ovis canadensis) with their common source population in Wyoming to understand how reintroduction affects genetic variability. Founder size was low (8-69) and effective population size (Ne) remained low 10-20 years after release. Allele frequencies at 2 of 4 polymorphic loci differed between the reintroduced herds and the common source (P < 0.01), and the number of alleles per locus was reduced in reintroduced herds (P = 0.04). Multi-locus heterozygosity (at 29 loci) was lower (P = 0.03) in 3 of the reintroduced herds than in the common source population. Simulations of genetic drift in reintroduced herds indicated that allele frequencies were within expectations of model predictions, but that heterozygosity sometimes varied from predictions. Our results indicate the operation of founder effect and subsequent genetic drift within the small reintroduced herds, but also may be influenced by small sample sizes from herds that were difficult to sample. We suggest management practices that should minimize the loss of genetic variation from reintroduced populations of bighorn sheep.