Bighorn Research Articles

Investigation on dynamic impact behavior of bighorn sheep’s horn

Investigation on dynamic impact behavior of bighorn sheep’s horn

Genetic parameters for Mycoplasma ovipneumoniae nasal DNA copy number provide progress to promote domestic and bighorn sheep coexistence on public lands

Discord between domestic sheep producers and bighorn sheep conservationists primarily involves concerns over the transmission of Mycoplasma ovipneumoniae between domestic and wild sheep. To discern if selective breeding within the Rambouillet could serve to reduce transmission, a genetic approach utilizing an existing phenotype was evaluated for additive genetic variance. The phenotype employs the measure of nasally shed bacterial DNA, or M. ovipneumoniae nasal DNA copy number (MONCN). Following estimation of the additive genetic variation associated with MONCN, the heritability and repeatability for this trait was calculated. The level of MONCN was measured at least three times per year at the U.S. Sheep Experiment Station (USSES) from ewes ranging from 1 to 7 years of age. Repeated measures animal models were evaluated from 320 ewes with a total of 1223 samples (mean = 3.8 per ewe). The MONCN values ranged from 0 (non-detected) to 71,654 copies per 2 μl of extracted nasal swab DNA. Four genetic models were evaluated with the categorical model having the highest heritability (0.12 ± 0.09) and repeatability (0.60 ± 0.05). Fixed effects included season/year (n = 9) and ewe age (n = 7). Outcomes from this research resulted in heritability estimates from which breeding values can be estimated to select USSES ewes and rams for reduced MONCN. This research provides a practical approach that can be immediately implemented to manage domestic sheep to be more compatible with bighorn sheep on public lands, providing positive welfare benefits for both species.

Horns, hunters, and harvest: re‐examining management paradigms for pronghorn

AbstractThe sustainable use of wildlife is foundational to the success of the North American model of wildlife conservation. Harvest management often is shaped through both species biology and public desires. The long timespan it takes males of most ungulate species to reach peak weapon size has created a situation in harvest management in which harvest strategies cannot prioritize both generous hunter opportunity and opportunities to pursue large‐weaponed males; therefore, current harvest paradigms prioritize one at the expense of the other. In contrast to other species, pronghorn (Antilocapra americana) attain the majority of their peak horn size early in life. The rapid development of horns relative to their age may allow for liberal harvest without sacrificing the opportunity for hunters to harvest males with large horns. We evaluated the influence of sex ratios and average age of harvested males on the average horn size of harvested male pronghorn from 2019 to 2022 in 9 hunt areas in Wyoming, USA. Although mean age of harvested males was negatively affected by rate of harvest, increases in mean age at harvest led to only slight increases in mean horn size (i.e., a 1‐year increase in mean age increased mean horn size by 2.1 cm [~1 inch]). The proportion of the harvest composed of large‐horned males was not influenced by mean age of harvest or sex ratio of the population. Based on simulated populations, increasing harvest led to an increase in the number of large‐weaponed pronghorn in the harvest—a relationship that existed for bighorn sheep (Ovis canadensis) and elk (Cervus canadensis) but only at low to moderate rates of harvest. The comparatively young age that pronghorn attain near‐peak horn size alleviates what is otherwise a tradeoff between hunter opportunity and managing for large horn size that is evident in management of other ungulate species. Though rarely a reality in management for large ungulates, for pronghorn, liberal harvest may be possible while still providing opportunity to harvest males with large horns.

Mapping core habitats, landscape permeability, and movement corridors for conservation of desert bighorn sheep in Sonora, México

Mapping core habitats, landscape permeability, and movement corridors for conservation of desert bighorn sheep in Sonora, México

Climate Change and Herbivores: Forty Years in a Bunchgrass Prairie.

Wild herbivore responses to anthropogenic climate change are often projected to be habitat and geographic range shifts as warmer conditions reduce the quantity and nutritional quality of forage plants, which makes species presence/absence a focus. Since 1978, herbivore abundances at the National Bison Range, MT, USA, were measured for grasshoppers (catch-effort), microtine rodents (runway density), and ungulates (drives and round-ups), along with climate and vegetation quantity (biomass) and quality (nitrogen content and chemical solubility related to digestibility). Counter to expectation with warming and drying, forage biomass increased as grass biomass increased more than dicot biomass decreased, and forage quality (solubility) increased. Consequently, herbivores that consume a grass diet (>25% grass: certain grasshoppers, microtines, bighorn sheep, elk, bison) increased in abundance, while herbivores consuming less grass declined (certain grasshoppers, pronghorn, whitetail, and mule deer). The result is an 18% increase in herbivore abundance and herbivory, counter to climate change expectations. Historically, grasshoppers consumed 46% more vegetation than mammals; now, they consume only 14% more, as grasshoppers did not increase as expected with climate change. Therefore, herbivores respond rapidly to climate-induced vegetation changes, and this is not a simple loss/addition of species, but changing trophic dynamics, which requires more knowledge of ecosystem dynamics.

Play is a privilege in both humans and animals: how our recreation influences wildlife

AbstractNature‐based tourism nets roughly 8 billion annual travelers globally to all regions of Earth, with many visiting around 200,000 formally protected areas. Financially well‐off tourists pay for playful activities and effects on wildlife are potentially large and relatively uncertain. Our commentary makes 3 points. First, variation in resource privileges and associated benefits characterizes not only humans but other species. Among animals, well‐nurtured populations engage in more playful and leisurely activities than do those nutritionally impoverished. Privilege depends partially on birth sites, parents, and local conditions, but for humans recreation expands with monetary advantage. Second, nature‐based tourism has 2 generalizable effects on wildlife, each involving degree of habituation. Among non‐habituated populations, local site abandonment is frequent and modulated by seasonality, individuals' physiological states, and whether recreation is motorized or not. For habituated populations, tolerance emerges to increasing recreational exposure with some populations of species learning to rely on humans to shield as a buffer against possible predation. Third, desert bighorn sheep (Ovis canadensis nelsoni) offer a robust example of the issues surrounding the effects of tourism on wildlife because of the geographically complicated relationship between recreational pursuit and wildlife on public lands of the western United States. While protected for decades, females have failed to habituate to different forms of recreation at certain sites. The result has been flight or site abandonment. Biodiversity protection at numerous scales has made strong gains but is still needed where progress is stymied by income disparities, privilege, and increasing recreation ventures.

Movement decisions driving metapopulation connectivity respond to social resources in a long-lived ungulate, bighorn sheep (Ovis canadensis).

The spatial availability of social resources is speculated to structure animal movement decisions, but the effects of social resources on animal movements are difficult to identify because social resources are rarely measured. Here, we assessed whether varying availability of a key social resource-access to receptive mates-produces predictable changes in movement decisions among bighorn sheep in Nevada, the United States. We compared the probability that males made long-distance 'foray' movements, a critical driver of connectivity, across three ecoregions with varying temporal duration of a socially mediated factor, breeding season. We used a hidden Markov model to identify foray events and then quantified the effects of social covariates on the probability of foray using a discrete choice model. We found that males engaged in forays at higher rates when the breeding season was short, suggesting that males were most responsive to the social resource when its existence was short lived. During the breeding season, males altered their response to social covariates, relative to the non-breeding season, though patterns varied, and age was associated with increased foray probability. Our results suggest that animals respond to the temporal availability of social resources when making the long-distance movements that drive connectivity. This article is part of the theme issue 'The spatial-social interface: a theoretical and empirical integration'.

First report on the occurrence of psoroptic mange in llamas (Lama glama) of the Andean region.

An outbreak of Psoroptes sp.-caused mange was detected in a llama herd of Larcas, Jujuy province, Argentina. Infested llamas showed alopecia, erythema, hyperpigmentation, hyperkeratosis, and inflammation of the ear pinnae, as well as crusts and serous, serosanguineous, or purulent drainage with unpleasant smell in the external ear canal. Microscopic evaluation of skin scrapings revealed 0.5- to 0.7-mm-long acari identified as Psoroptes sp. based on their morphology. Histology showed a typical allergic reaction with perivascular to periadnexal mixed inflammatory infiltrate. Phylogenetic tree analysis showed that the cytochrome c oxidase subunit I gene sequences analyzed from the sampled acari clustered into a single P. ovis clade including sequences isolated from rabbits and bighorn sheep, with P. natalensis as a sister taxon that infested bighorn sheep from the USA. Phylogenetic analysis of cytochrome b sequences showed three well-supported clades, one of which contained the sequences of the Larcas llamas and US bighorn sheep isolates. This is the first report on P. ovis infestation of llamas raised in their original location. Investigations on mange etiological agents acting on South American camelids and their distribution are necessary to implement control strategies to mitigate the negative impacts of these parasitic infections.

Genomic affinity following restoration of a locally extirpated species: a case study of desert bighorn sheep in Texas

Genomic affinity following restoration of a locally extirpated species: a case study of desert bighorn sheep in Texas

Sociality modulates nutritional carrying capacity of an endangered species

Group living has well-known costs and benefits. Large groups may experience greater competition for resources, while simultaneously benefit from reduced risk through predator dilution. When there is a tradeoff between forage acquisition and predation risk, the ability to congregate into large groups may unlock access to previously unavailable habitat with high risk of predation, thereby increasing forage available to the population. We evaluated whether forage availability increased with population size and how it was mediated through changes in group size. There was a tradeoff between forage availability and predation risk. Larger groups used areas with more forage biomass and greater predation risk than smaller groups. Group size also increased with population abundance, meaning bighorn sheep used gentler terrain and areas with more forage biomass at greater population abundance. Group size functionally increased carrying capacity by yielding access to more resources for growing populations of gregarious ungulates.

Prediction of birthdates based on fetal development in Bighorn Sheep (Ovis canadensis)

Abstract Reproductive phenology is a critical element of how animals persist in their environment and affects survival of young, especially in seasonal environments. We investigated the correlation between fetal eye diameter and birth timing to determine if birthdates could be predicted by a prenatal metric. We used ultrasonography to measure eye diameters of fetuses and vaginal implant transmitters to determine birthdates of Rocky Mountain Bighorn Sheep (Ovis canadensis canadensis) in Wyoming, United States, from 2019 to 2023. Fetal eye diameter strongly predicted days until birth (β = −2.8; pseudo-R2 = 0.88). Effective prediction of birthdates via ultrasonography can yield opportunities for logistical planning in neonatal studies, monitoring changes in reproductive phenology, and evaluating questions of resource allocation relative to reproductive processes.

Comparative genomic analysis identifies potential adaptive variation in Mycoplasma ovipneumoniae.

Mycoplasma ovipneumoniae is associated with respiratory disease in wild and domestic Caprinae globally, with wide variation in disease outcomes within and between host species. To gain insight into phylogenetic structure and mechanisms of pathogenicity for this bacterial species, we compared M. ovipneumoniae genomes for 99 samples from 6 countries (Australia, Bosnia and Herzegovina, Brazil, China, France and USA) and 4 host species (domestic sheep, domestic goats, bighorn sheep and caribou). Core genome sequences of M. ovipneumoniae assemblies from domestic sheep and goats fell into two well-supported phylogenetic clades that are divergent enough to be considered different bacterial species, consistent with each of these two clades having an evolutionary origin in separate host species. Genome assemblies from bighorn sheep and caribou also fell within these two clades, indicating multiple spillover events, most commonly from domestic sheep. Pangenome analysis indicated a high percentage (91.4 %) of accessory genes (i.e. genes found only in a subset of assemblies) compared to core genes (i.e. genes found in all assemblies), potentially indicating a propensity for this pathogen to adapt to within-host conditions. In addition, many genes related to carbon metabolism, which is a virulence factor for Mycoplasmas, showed evidence for homologous recombination, a potential signature of adaptation. The presence or absence of annotated genes was very similar between sheep and goat clades, with only two annotated genes significantly clade-associated. However, three M. ovipneumoniae genome assemblies from asymptomatic caribou in Alaska formed a highly divergent subclade within the sheep clade that lacked 23 annotated genes compared to other assemblies, and many of these genes had functions related to carbon metabolism. Overall, our results suggest that adaptation of M. ovipneumoniae has involved evolution of carbon metabolism pathways and virulence mechanisms related to those pathways. The genes involved in these pathways, along with other genes identified as potentially involved in virulence in this study, are potential targets for future investigation into a possible genomic basis for the high variation observed in disease outcomes within and between wild and domestic host species.

Direct and indirect effects of cougar predation on bighorn sheep fitness.

Predation has direct effects on prey population dynamics through mortality, and it can induce indirect effects through fear. The indirect effects of predation have been documented experimentally, but few studies have quantified them in nature so that their role in prey population dynamics remains controversial. Given the expanding or reintroduced populations of large predators in many areas, the quantification of indirect effects of predation is crucial. We sought to evaluate the direct and indirect fitness effects of intense cougar (Puma concolor) predation using 48 years of data on marked bighorn sheep (Ovis canadensis) on Ram Mountain, Alberta, Canada. We compared years of intense cougar predation with years with no or occasional cougar predation. We first quantified the effects of predation on neonatal, weaning, and overwinter lamb survival, three metrics potentially affected by direct and indirect effects. We then investigated the possible indirect effects of intense cougar predation on lamb production, female summer mass gain, and lamb mass at weaning. We found strong effects of cougar predation on lamb survival, lamb production, and seasonal mass gain of lambs and adult females. In years with high predation, neonatal, weaning, and overwinter lamb survival declined by 18.4%, 19.7% and 20.8%, respectively. Indirect effects included a 14.2% decline in lamb production. Female summer mass gain decreased by 15.6% and lamb mass at weaning declined by 8.0% in years of intense cougar predation. Our findings bring key insights on the impacts of predation on prey fitness by reporting moderate to large effects on recruitment and illustrate the importance of indirect effects of predation on population dynamics.

Infection-nutrition feedbacks: fat supports pathogen clearance but pathogens reduce fat in a wild mammal.

Though far less obvious than direct effects (clinical disease or mortality), the indirect influences of pathogens are difficult to estimate but may hold fitness consequences. Here, we disentangle the directional relationships between infection and energetic reserves, evaluating the hypotheses that energetic reserves influence infection status of the host and that infection elicits costs to energetic reserves. Using repeated measures of fat reserves and infection status in individual bighorn sheep (Ovis canadensis) in the Greater Yellowstone Ecosystem, we documented that fat influenced ability to clear pathogens (Mycoplasma ovipneumoniae) and infection with respiratory pathogens was costly to fat reserves. Costs of infection approached, and in some instances exceeded, costs of rearing offspring to independence in terms of reductions to fat reserves. Fat influenced probability of clearing pathogens, pregnancy and over-winter survival; from an energetic perspective, an animal could survive for up to 23 days on the amount of fat that was lost to high levels of infection. Cost of pathogens may amplify trade-offs between reproduction and survival. In the absence of an active outbreak, the influence of resident pathogens often is overlooked. Nevertheless, the energetic burden of pathogens likely has consequences for fitness and population dynamics, especially when food resources are insufficient.

Comparing camera‐based ungulate density estimates: a case study using island populations of bighorn sheep and mule deer

AbstractCamera‐based abundance estimators are an alternative methodology of growing interest in both research and management applications. The statistical formulations of camera‐based abundance estimators using time‐lapse data should theoretically produce precise and unbiased estimates; however, production of unbiased results also requires meeting several important assumptions, and real‐world case studies evaluating such results remain relatively few. We applied instantaneous sampling (IS) and space‐to‐event (STE) estimators to remote camera data collected in April 2021 via time‐lapse sampling of closed populations of bighorn sheep (Ovis canadensis) and mule deer (Odocoileus hemionus) on Wild Horse Island in western Montana, USA, and compared results for bighorn sheep to aerial and ground‐based counts. Point estimates from camera‐based approaches underestimated bighorn sheep populations by 32–44% (IS estimator) and 62–69% (STE estimator) relative to aerial and ground counts. Patchy spatial distribution and group‐living behavior of sheep resulted in a high degree of noise surrounding the IS estimate. In comparison, a low point estimate with relatively narrow confidence intervals suggested potential sensitivity of the STE estimator to violating assumptions of independence among individual animals and sampling occasions. Estimates of mule deer had improved precision over sheep estimates, as indicated by lower estimated coefficients of variation of the mean (CVmean) derived from the analytic SE estimator. Using 15‐m viewsheds and the IS estimators, mule deer density estimates came with a 26% CVmean compared to 43% CVmean for bighorn sheep. This discrepancy may be a result of differences in distribution, behavior, and relative abundance between the 2 species. Accounting for group size and increasing time between sampling may improve accuracy of density estimates and adhere better to model assumptions when estimating precision. In addition, factors influencing viewshed and resulting density extrapolations must be considered carefully. While camera‐based methods theoretically provide an alternative way to estimate density when traditional methods are impractical, our results suggest that more work is needed to ensure density estimates are accurate and precise enough to inform population management.

Bighorn Sheep (Ovis canadensis) with Higher Whole Blood Selenium Levels Have Improved Survival and Altered Immune Responses.

Bighorn sheep (Ovis canadensis) are herbivorous ungulates that live in forage-poor areas of the American west. The trace minerals that herbivores derive from forage are important for immune function. Therefore, identifying trace minerals that affect immune function in bighorn sheep could provide important insights into disease susceptibility and population health in threatened populations. We sought to determine whether trace mineral composition in blood or plasma correlates to survival and determine whether immunologic parameters correlate with any trace minerals that affect survival. We used data collected from 2016 to 2018 as part of a large study on bighorn sheep in southeastern Oregon and northern Nevada, US. We measured the survival of 135 bighorn sheep during the 8-mo monitoring period, including general metrics of immune function and trace mineral levels. We found that animals with higher selenium had improved survival over the monitoring period, with higher peripheral blood mononuclear cell activity (lymphocytes and monocytes) and lower bacterial killing ability in an in vitro assay. This suggests that bighorn sheep may have altered immune function when selenium levels are low, making them more likely to die during the 8-mo monitoring period. Future work should consider whether habitat management strategies that increase selenium intake might improve disease resistance and survival in bighorn sheep in selenium-poor areas.

Headbutting through time: A review of this hypothesized behavior in "dome-headed" fossil taxa.

Headbutting is a combative behavior most popularly portrayed and exemplified in the extant bighorn sheep (Ovis canadensis). When behaviorally proposed in extinct taxa, these organisms are oft depicted Ovis-like as having used modified cranial structures to combatively slam into one another. The combative behavioral hypothesis of headbutting has a long and rich history in the vertebrate fossil literature (not just within Dinosauria), but the core of this behavioral hypothesis in fossil terrestrial vertebrates is associated with an enlarged osseous cranial dome-an osteological structure with essentially no current counterpart. One confounding issue found in the literature is that while the term "headbutting" sounds simplistic enough, little terminology has been used to describe this hypothesized behavior. And pertinent to this special issue, potential brain trauma and the merits of such proposed pugilism have been assessed largely from the potential deformation of the overlying osseous structure; despite the fact that extant taxa readily show that brain damage can and does occur without osteological compromise. Additionally, the extant taxa serving as the behavioral counterpart for comparison are critical, not only because of the combative behaviors and morphologies they display, but also the way they engage in such behavior. Sheep (Ovis), warthogs (Phacochoerus), and bison (Bison) all engage in various forms of "headbutting", but the cranial morphologies and the way each engages in combat is markedly different. To hypothesize that an extinct organism engaged in headbutting like an extant counterpart in theory implies specific striking:contacting surfaces, speed, velocity, and overall how that action was executed. This review examines the history and usage of the headbutting behavioral hypothesis in these dome-headed fossil taxa, their respective extant behavioral counterparts, and proposes a protocol for specific behavioral terms relating to headbutting to stem future confusion. We also discuss the disparate morphology of combative cranial structures in the fossil record, and the implications of headbutting-induced brain injury in extinct taxa. Finally, we conclude with some potential implications for artistic reconstructions of fossil taxa regarding this behavioral repertoire.

Pursuit and escape drive fine-scale movement variation during migration in a temperate alpine ungulate

Climate change reduces snowpack, advances snowmelt phenology, drives summer warming, alters growing season precipitation regimes, and consequently modifies vegetation phenology in mountain systems. Elevational migrants track spatial variation in seasonal plant growth by moving between ranges at different elevations during spring, so climate-driven vegetation change may disrupt historic benefits of migration. Elevational migrants can furthermore cope with short-term environmental variability by undertaking brief vertical movements to refugia when sudden adverse conditions arise. We uncover drivers of fine-scale vertical movement variation during upland migration in an endangered alpine specialist, Sierra Nevada bighorn sheep (Ovis canadensis sierrae) using a 20-year study of GPS collar data collected from 311 unique individuals. We used integrated step-selection analysis to determine factors that promote vertical movements and drive selection of destinations following vertical movements. Our results reveal that relatively high temperatures consistently drive uphill movements, while precipitation likely drives downhill movements. Furthermore, bighorn select destinations at their peak annual biomass and maximal time since snowmelt. These results indicate that although Sierra Nevada bighorn sheep seek out foraging opportunities related to landscape phenology, they compensate for short-term environmental stressors by undertaking brief up- and downslope vertical movements. Migrants may therefore be impacted by future warming and increased storm frequency or intensity, with shifts in annual migration timing, and fine-scale vertical movement responses to environmental variability.

Evaluating the transmission dynamics and host competency of aoudad (Ammotragus lervia) experimentally infected with Mycoplasma ovipneumoniae and leukotoxigenic Pasteurellaceae.

Feral populations of aoudad (Ammotragus lervia) occur in Texas bighorn sheep (Ovis canadensis) habitat and pose several conceptual ecological threats to bighorn sheep re-establishment efforts. The potential threat of disease transmission from aoudad to bighorn sheep may exacerbate these issues, but the host competency of aoudad and subsequent pathophysiology and transmissibility of pneumonic pathogens involved in the bighorn sheep respiratory disease complex is largely unknown. Because the largest population-limiting diseases of bighorn sheep involve pathogens causing bronchopneumonia, we evaluated the host competency of aoudad for Mycoplasma ovipneumoniae and leukotoxigenic Pasteurellaceae. Specifically, we described the shedding dynamics, pathogen carriage, seroconversion, clinical patterns, and pathological effects of experimental infection among wild aoudad held in captivity. We found that aoudad are competent hosts capable of maintaining and intraspecifically transmitting Mycoplasma ovipneumoniae and Pasteurellaceae and can shed the bacteria for 53 days after exposure. Aoudad developed limited clinical signs and pathological findings ranged from mild chronic lymphohistiocytic bronchointerstitial pneumonia to severe and acute suppurative pneumonia, similarly, observed in bighorn sheep infected with Mycoplasma spp. and Pasteurellaceae bacteria, respectively. Furthermore, as expected, clinical signs and lesions were often more severe in aoudad inoculated with a combination of Mycoplasma ovipneumoniae and Pasteurellaceae as compared to aoudad inoculated with only Mycoplasma ovipneumoniae. There may be evidence of interindividual susceptibility, pathogenicity, and/or transmissibility, indicated by individual aoudad maintaining varying severities of chronic infection who may be carriers continuously shedding pathogens. This is the first study to date to demonstrate that aoudad are a conceptual disease transmission threat to sympatric bighorn sheep populations due to their host competency and intraspecific transmission capabilities.

Population and spatial dynamics of desert bighorn sheep in Grand Canyon during an outbreak of respiratory pneumonia

IntroductionTerrestrial species in riverine ecosystems face unique constraints leading to diverging patterns of population structure, connectivity, and disease dynamics. Desert bighorn sheep (Ovis canadensis nelsoni) in Grand Canyon National Park, a large native population in the southwestern USA, offer a unique opportunity to evaluate population patterns and processes in a remote riverine system with ongoing anthropogenic impacts. We integrated non-invasive, invasive, and citizen-science methods to address questions on abundance, distribution, disease status, genetic structure, and habitat fragmentation.MethodsWe compiled bighorn sightings collected during river trips by park staff, commercial guides, and private citizens from 2000–2018 and captured bighorn in 2010–2016 to deploy GPS collars and test for disease. From 2011–2015, we non-invasively collected fecal samples and genotyped them at 9–16 microsatellite loci for individual identification and genetic structure. We used assignment tests to evaluate genetic structure and identify subpopulations, then estimated gene flow and recent migration to evaluate fragmentation. We used spatial capture-recapture to estimate annual population size, distribution, and trends after accounting for spatial variation in detection with a resource selection function model.Results and discussionFrom 2010–2018, 3,176 sightings of bighorn were reported, with sightings of 56–145 bighorn annually on formal surveys. From 2012–2016, bighorn exhibiting signs of respiratory disease were observed along the river throughout the park. Of 25 captured individuals, 56% were infected by Mycoplasma ovipneumoniae, a key respiratory pathogen, and 81% were recently exposed. Pellet sampling for population estimation from 2011–2015 yielded 1,250 genotypes and 453 individuals. We detected 6 genetic clusters that exhibited mild to moderate genetic structure (FST 0.022–0.126). The river, distance, and likely topography restricted recent gene flow, but we detected cross-river movements in one section via genetic recaptures, no subpopulation appeared completely isolated, and genetic diversity was among the highest reported. Recolonization of one large stretch of currently empty habitat appears limited by the constrained topology of this system. Annual population estimates ranged 536–552 (95% CrI range 451–647), lamb:ewe ratios varied, and no significant population decline was detected. We provide a multi-method sampling framework useful for sampling other wildlife in remote riverine systems.