Bighorn Sheep Ovis Canadensis Research Articles

PSOROPTES INFESTATION AND TREATMENT IN AN ISOLATED POPULATION OF BIGHORN SHEEP (OVIS CANADENSIS).

The authors captured bighorn sheep (Ovis canadensis) comprising a small population in the San Bernardino Mountains of California and evaluated the degree of infestation by mites of the genus Psoroptes for each individual. The animals were treated with two novel methods: amitraz-impregnated collars and cyfluthrin-impregnated ear tags and recaptured the following year to evaluate the effect of treatment. The authors compared data on degree of infestation for animals recaptured in the posttreatment year, detected no significant interyear differences in infestation severity scores among animals treated with amitraz or cyfluthrin, and could not detect any differences between treatment types. However, a significant (P<0.10) decreased pattern in severity scores from the beginning to the end of treatments was detected, suggesting a cumulative therapeutic value in repeated annual treatments across the 3-yr period. Additionally, the authors detected a lower median mite severity score between 2000 and a later capture in 2006. These positive outcomes may be the result of previous treatments during 2000-2002, but environmental covariates not accounted for could have been contributing factors. Avermectin drugs with longer release profiles may be a more effective treatment option in this and other small bighorn sheep populations that are compromised with mite infestations.

A tale of two markers: Population genetics of colorado rocky mountain bighorn sheep estimated from microsatellite and mitochondrial data

Five native herds of Rocky Mountain bighorn sheep (Ovis canadensis) occupy Rocky Mountain National Park and the immediate surrounding area. One of these herds, the Mummy herd, suffered a significant die-off following a suspected pneumonia outbreak in the mid-1990s with subsequent low population size and low yearling recruitment, as compared to the other 4 herds. To test the hypothesis that the Mummy herd's failure to thrive is due to decreased genetic variation as a result of a genetic bottleneck, we analyzed both microsatellite and mitochondrial data to estimate genetic differentiation, gene flow, and the extent of metapopulation substructure among all 5 herds. Our microsatellite analyses showed no evidence of a recent genetic bottleneck or inbreeding. Our comparisons of overall and pairwise population differentiation (Fst) and effective migration (Nm) from both microsatellite genotypes and mitochondrial haplotypes indicated that low population substructure was being maintained by moderate levels of gene flow among all 5 herds. Effective migration rates were both higher and more uniform among herds for microsatellite genotypes than for mitochondrial haplotypes, which exhibited an asymmetrical pattern among herds. A significant isolation-by-distance relationship for mitochondrial (but not microsatellite) data suggests that gene flow is primarily due to ram migration. Past translocations of sheep into, out of, and among these 5 herds are an important consideration when interpreting these results; however, our data clearly show that all 5 Rocky Mountain bighorn sheep herds have reasonable and equivalent levels of genetic variation. Thus, herd management and restoration efforts should be focused on other factors that might be detrimental to herd health, such as stress, nutritional deficiencies, habitat fragmentation, climactic factors, or disease. © 2015 The Wildlife Society.

The role of hunters in conservation, restoration, and management of North American wild sheep

Wild sheep in North America were abundant and widely distributed prior to European exploration and settlement. By the early twentieth century unregulated hunting, forage competition with domestic livestock, introduced diseases, and human encroachment had dramatically reduced bighorn sheep (Ovis canadensis) numbers and distribution in the western US, southern Canada, and mainland and Baja Peninsula Mexico. The restoration of bighorn sheep has been a remarkable conservation success, as a result of efforts by wildlife and land management agencies, conservation organizations, private landowners and other stakeholders. These efforts have been largely underwritten by pro-hunting conservation organizations.

Use of agave by desert bighorn sheep

Abstract We hypothesized that, if agave (Agave) were used by desert ungulates as a source of moisture, they would be used more during drought than during periods with average or above-average rainfall. From 2004–2012, we counted the number of stalks of agave used by Nelson's bighorn sheep (Ovis canadensis nelsoni) in 10.3 ha in Deep Canyon, Santa Rosa Mountains, California. During years of average or above-average rainfall, bighorn sheep consumed <3% of available stalks of agave. During years with rainfall below average, bighorn sheep consumed from 20–53% of available stalks of agave, thus supporting our hypothesis.

Berry Consumption By Bighorn Sheep (Ovis canadensis) in the Arid Interior of British Columbia

Berry Consumption By Bighorn Sheep (<i>Ovis canadensis</i>) in the Arid Interior of British Columbia

In vitro prion protein conversion suggests risk of bighorn sheep (Ovis canadensis) to transmissible spongiform encephalopathies

BackgroundTransmissible spongiform encephalopathies (TSEs) affect both domestic sheep (scrapie) and captive and free-ranging cervids (chronic wasting disease; CWD). The geographical range of bighorn sheep (Ovis canadensis; BHS) overlaps with states or provinces that have contained scrapie-positive sheep or goats and areas with present epizootics of CWD in cervids. No TSEs have been documented in BHS, but the susceptibility of this species to TSEs remains unknown.ResultsWe acquired a library of BHS tissues and found no evidence of preexisting TSEs in these animals. The prion protein gene (Prnp) in all BHS in our library was identical to scrapie-susceptible domestic sheep (A136R154Q171 genotype). Using an in vitro prion protein conversion assay, which has been previously used to assess TSE species barriers and, in our study appears to recollect known species barriers in mice, we assessed the potential transmissibility of TSEs to BHS. As expected based upon Prnp genotype, we observed BHS prion protein conversion by classical scrapie agent and evidence for a species barrier between transmissible mink encephalopathy (TME) and BHS. Interestingly, our data suggest that the species barrier of BHS to white-tailed deer or wapiti CWD agents is likely low. We also used protein misfolding cyclic amplification to confirm that CWD, but not TME, can template prion protein misfolding in A136R154Q171 genotype sheep.ConclusionsOur results indicate the in vitro conversion assay used in our study does mimic the species barrier of mice to the TSE agents that we tested. Based on Prnp genotype and results from conversion assays, BHS are likely to be susceptible to infection by classical scrapie. Despite mismatches in amino acids thought to modulate prion protein conversion, our data indicate that A136R154Q171 genotype sheep prion protein is misfolded by CWD agent, suggesting that these animals could be susceptible to CWD. Further investigation of TSE transmissibility to BHS, including animal studies, is warranted. The lack of reported TSEs in BHS may be attributable to other host factors or a lack of TSE surveillance in this species.

Genomic Resources Notes accepted 1 April 2013–31 May 2013

This article documents the public availability of approximately 15000 polymorphic SNP loci for the bighorn sheep Ovis canadensis.

Testing the functionality and contact error of a GPS-based wildlife tracking network

Telemetry is a fundamentally important tool for studying animal movements. Traditional telemetry systems have provided time-specific information on locations of individuals; however, recent developments in instruments allow for the tracking of networks of interactions among individuals. Currently, these devices rely on very high frequency (VHF) radio technology, and cannot precisely gauge where interactions occurred without on-site triangulation. Furthermore, although commercially available devices can log successful communication attempts between collars as little as 1 m apart, researchers cannot accurately determine distances within the pre-set detection (contact) threshold of these units. Data loss from proximity-logging devices, and even traditional telemetry devices that are lost or damaged in the field, poses another obstacle to monitoring wildlife social networks. We have developed a prototype proximity-logging Global Positioning System (GPS) collar that offers greater spatial resolution of social interactions, and reduces probability of data loss. In this study, we used captive bighorn sheep (Ovis canadensis) to test the GPS capabilities, contact rates, and contact distance error of our prototype collars. The GPS fix success rate of our collars was >97.93% (n = 95,041; 95% CI = 97.84–98.02%). The collars were communicating with each other about 98% (n = 22,253; 95% CI = 98.50–98.81%) of the time and reciprocal communication occurred 9% of the time. Contact distance error was 9.5 m, which is what would be expected taking into account a baseline GPS spatial error of ±5 m in open environments. The high GPS fix success, low GPS error, and ability to log accurate social interactions with low contact distance error by our prototype collars suggest that the implementation of GPS with proximity-logging technology has the potential to improve currently available social network data. © 2013 The Wildlife Society.

Identification of novel variants of interferon-tau gene in Bighorn sheep (Ovis canadensis mexicana), Pelibuey sheep (Ovis aries) and its expression in hybrid blastocysts (Ovis canadensis × Ovis aries)

Palma-Irizarry, M., Damian-Matsumura, P., Betancourt, M., Romo, S., Perales, G., Lagunas-Martinez, A., Madrid-Marina, M. V., Mejia, O. and Ducolomb, Y. 2012. Identification of novel variants of interferon-tau gene in Bighorn sheep (Ovis canadensis mexicana), Pelibuey sheep (Ovis aries) and its expression in hybrid blastocysts (Ovis canadensis×Ovis aries). Can. J. Anim. Sci. 92: 275-283. The major signal for maternal recognition of pregnancy (MRP) in ruminants is interferon-tau (IFNT). Four novel sequences of the IFNT gene were isolated from genomic DNA obtained from blood samples of Bighorn, Pelibuey or the hybrid ewes. The deduced amino acid sequence of the hybrid ewe showed 100% identity with one Bighorn sheep IFNT sequence, suggesting that this sequence was inherited from Bighorn sheep. The high degree of identity between Pelibuey and Bighorn sheep sequences could be a possible explanation for the successful MRP in some Bighorn hybrid pregnancies. In vivo and in vitro domestic sheep (Ovis aries) and hy...

Identification of novel variants of interferon-tau gene in Bighorn sheep (Ovis canadensis mexicana), Pelibuey sheep (Ovis aries) and its expression in hybrid blastocysts (Ovis canadensis × Ovis aries)

Palma-Irizarry, M., Damian-Matsumura, P., Betancourt, M., Romo, S., Perales, G., Lagunas-Martínez, A., Madrid-Marina, M. V., Mejía, O. and Ducolomb, Y. 2012. Identification of novel variants of interferon-tau gene in Bighorn sheep ( Ovis canadensis mexicana ), Pelibuey sheep ( Ovis aries ) and its expression in hybrid blastocysts ( Ovis canadensis×Ovis aries ). Can. J. Anim. Sci. 92: 275–283. The major signal for maternal recognition of pregnancy (MRP) in ruminants is interferon-tau (IFNT). Four novel sequences of the IFNT gene were isolated from genomic DNA obtained from blood samples of Bighorn, Pelibuey or the hybrid ewes. The deduced amino acid sequence of the hybrid ewe showed 100% identity with one Bighorn sheep IFNT sequence, suggesting that this sequence was inherited from Bighorn sheep. The high degree of identity between Pelibuey and Bighorn sheep sequences could be a possible explanation for the successful MRP in some Bighorn hybrid pregnancies. In vivo and in vitro domestic sheep (Ovis aries) and hybrid sheep (Ovis aries×Ovis canadensis) blastocysts were obtained, and IFNT expression was measured by semiquantitative RT-PCR. In vivo and in vitro hybrid blastocysts showed lower expression of IFNT when compared with domestic blastocysts. In conclusion this study showed that there exists an effect of hybridization on IFNT expression and this can affect the MRP.

Determinants and consequences of age of primiparity in bighorn ewes

Because variation in age of first reproduction can have major effects on individual fitness and population dynamics, it is important to understand what maintains that variability. Although early primiparity is assumed to be costly, it is sometimes associated with high lifetime reproductive success. We used a long‐term study on bighorn sheepOvis canadensisto determine what variables affect age at first reproduction, investigate the impact of primiparity on body resources and quantify the reproductive performance of primiparous ewes. We then examined the consequences of delayed primiparity on adult body mass, longevity and lifetime reproductive success. Environmental conditions during early development, body mass as a yearling, genotype and maternal effects affected age of primiparity. Primiparous ewes lost more mass in winter and gained less mass in summer than multiparous ewes. Small yearling ewes that postponed reproduction attained similar adult mass than heavy yearling ewes who reproduced at a younger age. Early primiparity did not reduce longevity and was positively associated with lifetime reproductive success. Starting to reproduce as soon as possible appears to maximize fitness of females. When early life conditions are unfavorable, however, delayed primiparity allows greater body growth and likely maximizes survival. The combination of a conservative reproductive strategy and maternal effects on age of primiparity may partly delay population recovery following density‐dependent declines.

Common Functional Correlates of Head-Strike Behavior in the Pachycephalosaur Stegoceras validum (Ornithischia, Dinosauria) and Combative Artiodactyls

BackgroundPachycephalosaurs were bipedal herbivorous dinosaurs with bony domes on their heads, suggestive of head-butting as seen in bighorn sheep and musk oxen. Previous biomechanical studies indicate potential for pachycephalosaur head-butting, but bone histology appears to contradict the behavior in young and old individuals. Comparing pachycephalosaurs with fighting artiodactyls tests for common correlates of head-butting in their cranial structure and mechanics.Methods/Principal FindingsComputed tomographic (CT) scans and physical sectioning revealed internal cranial structure of ten artiodactyls and pachycephalosaurs Stegoceras validum and Prenocephale prenes. Finite element analyses (FEA), incorporating bone and keratin tissue types, determined cranial stress and strain from simulated head impacts. Recursive partition analysis quantified strengths of correlation between functional morphology and actual or hypothesized behavior. Strong head-strike correlates include a dome-like cephalic morphology, neurovascular canals exiting onto the cranium surface, large neck muscle attachments, and dense cortical bone above a sparse cancellous layer in line with the force of impact. The head-butting duiker Cephalophus leucogaster is the closest morphological analog to Stegoceras, with a smaller yet similarly rounded dome. Crania of the duiker, pachycephalosaurs, and bighorn sheep Ovis canadensis share stratification of thick cortical and cancellous layers. Stegoceras, Cephalophus, and musk ox crania experience lower stress and higher safety factors for a given impact force than giraffe, pronghorn, or the non-combative llama.Conclusions/SignificanceAnatomy, biomechanics, and statistical correlation suggest that some pachycephalosaurs were as competent at head-to-head impacts as extant analogs displaying such combat. Large-scale comparisons and recursive partitioning can greatly refine inference of behavioral capability for fossil animals.

Placing linkages among fragmented habitats: do least-cost models reflect how animals use landscapes?

Summary 1. The need to conserve and create linkages among fragmented habitats has given rise to a range of techniques for maximizing connectivity. Methods to identify optimal habitat linkages face tradeoffs between constraints on model inputs and biological relevance of model outputs. Given the popularity of these methods and their central role in landscape planning, it is critical that they be reliable and robust. 2. The most popular method used to inform habitat linkage design, least-cost path (LCP) analysis, designates a landscape resistance surface based on hypothetical ‘costs’ that landscape components impose on species movement, and identifies paths that minimize cumulative costs between locations. 3. While LCP analysis represents a valuable method for conservation planning, its current application has several weaknesses. Here, we review LCP analysis and identify shortcomings of its current application that decrease biological relevance and conservation utility. We examine trends in published LCP analyses, demonstrate the implications of methodological choices with our own LCP analysis for bighorn sheep Ovis canadensis nelsoni, and point to future directions in cost modelling. 4. Our review highlights three weaknesses common in recent LCP analyses. First, LCP models typically rely on remotely sensed habitat maps, but few studies assess whether such maps are suitable proxies for factors affecting animal movement or consider the effects of adjacent habitats. Secondly, many studies use expert opinion to assign costs associated with landscape features, yet few validate these costs with empirical data or assess model sensitivity to errors in cost assignment. Thirdly, studies that consider multiple, alternative movement paths often propose width or length requirements for linkages without justification. 5. Synthesis and applications. LCP modelling and similar approaches to linkage design guide connectivity planning, yet often lack a biological or empirical foundation. Ecologists must clarify the biological processes on which resistance values are based, explicitly justify cost schemes and scale (grain) of analysis, evaluate the effects of landscape context and sensitivity to cost schemes, and strive to optimize cost schemes with empirical data. Research relating species’ fine-grain habitat use to movement across broad extents is desperately needed, as are methods to determine biologically relevant length and width restrictions for linkages.

Wildlife translocation: the conservation implications of pathogen exposure and genetic heterozygosity

BackgroundA key challenge for conservation biologists is to determine the most appropriate demographic and genetic management strategies for wildlife populations threatened by disease. We explored this topic by examining whether genetic background and previous pathogen exposure influenced survival of translocated animals when captive-bred and free-ranging bighorn sheep (Ovis canadensis) were used to re-establish a population that had been extirpated in the San Andres Mountains in New Mexico, USA.ResultsAlthough the free-ranging source population had significantly higher multi-locus heterozygosity at 30 microsatellite loci than the captive bred animals, neither source population nor genetic background significantly influenced survival or cause of death. The presence of antibodies to a respiratory virus known to cause pneumonia was associated with increased survival, but there was no correlation between genetic heterozygosity and the presence of antibodies to this virus.ConclusionsAlthough genetic theory predicts otherwise, increased heterozygosity was not associated with increased fitness (survival) among translocated animals. While heterosis or genetic rescue effects may occur in F1 and later generations as the two source populations interbreed, we conclude that previous pathogen exposure was a more important marker than genetic heterozygosity for predicting survival of translocated animals. Every wildlife translocation is an experiment, and whenever possible, translocations should be designed and evaluated to test hypotheses that will further improve our understanding of how pathogen exposure and genetic variability influence fitness.

Genetic Analysis of Scats Reveals Minimum Number and Sex of Recently Documented Mountain Lions

Abstract Recent records of mountain lions Puma concolor and concurrent declines in desert bighorn sheep Ovis canadensis mexicana on Kofa National Wildlife Refuge in Arizona, United States, have prompted investigations to estimate the number of mountain lions occurring there. We performed noninvasive genetic analyses and identified species, individuals, and sex from scat samples collected from the Kofa and Castle Dome Mountains. From 105 scats collected, we identified a minimum of 11 individual mountain lions. These individuals consisted of six males, two females and three of unknown sex. Three of the 11 mountain lions were identified multiple times over the study period. These estimates supplement previously recorded information on mountain lions in an area where they were historically considered only transient. We demonstrate that noninvasive genetic techniques, especially when used in conjunction with camera-trap and radiocollaring methods, can provide additional and reliable information to wildlife managers, particularly on secretive species like the mountain lion.

Sexual segregation and use of water by bighorn sheep: implications for conservation

AbstractMales and females of most dimorphic ruminants segregate outside the mating season, which may necessitate that conservation efforts focus on differential resources used by the sexes. Dimorphic bighorn sheep Ovis canadensis are one of the rarest ungulates in North America with some populations listed as endangered. Water sources are important for the persistence of populations of bighorns, especially in a changing climate. Understanding whether the sexes use different water sources could influence the conservation of this species and the habitats they occupy; however, little research exists regarding this important topic. We tested hypotheses relating to use of water sources by reintroduced male and female bighorns in Utah, USA. We investigated whether use of this resource differed across seasons by sex, and if sexes used water more during drought compared with non‐drought conditions. Bighorns used small, adjacent core areas during segregation, and males and females used different sources of water during that time. Males visited water sources used by females more during aggregation. Males and females used water sources more in summer, and males visited water sources more during rut than did females. Males and females did not use water sources more during drought compared with non‐drought conditions; however, sexes visited water sources more during the season following drought than following non‐drought conditions, indicating a time‐lag in use of this resource. Our results highlight the importance of water sources used by sexes of bighorns, and indicate that the existing criterion for distance of bighorn reintroductions from water may be inadequate for successful establishment of populations. We recommend conservationists assess availability of water sources near habitat used by male and female ungulates before conserving and manipulating habitat, siting artificial sources of water and reintroducing animals.

Combining ground count, telemetry, and mark–resight data to infer population dynamics in an endangered species

Summary 1. To successfully manipulate populations for management and conservation purposes, managers must be able to track changes in demographic rates and determine the factors driving spatial and temporal variation in those rates. For populations of management concern, however, data deficiencies frequently limit the use of traditional statistical methods for such analyses. Long‐term demographic data are often piecemeal, having small sample sizes, inconsistent methodologies, intermittent data, and information on only a subset of important parameters and covariates. 2. We evaluated the effectiveness of Bayesian state‐space models for meeting these data limitations in elucidating dynamics of federally endangered Sierra Nevada bighorn sheep Ovis canadensis sierrae. We combined ground count, telemetry, and mark–resight data to: (1) estimate demographic parameters in three populations (including stage‐specific abundances and vital rates); and (2) determine whether density, summer precipitation, or winter severity were driving variation in key demographic rates. 3. Models combining all existing data types increased the precision and accuracy in parameter estimates and fit covariates to vital rates driving population performance. They also provided estimates for all years of interest (including years in which field data were not collected) and standardized the error structure across data types. 4. Demographic rates indicated that recovery efforts should focus on increasing adult and yearling survival in the smallest bighorn sheep population. In evaluating covariates we found evidence of negative density dependence in the larger herds, but a trend of positive density dependence in the smallest herd suggesting that an augmentation may be needed to boost performance. We also found that vital rates in all populations were positively associated with summer precipitation, but that winter severity only had a negative effect on the smallest herd, the herd most strongly impacted by environmental stochasticity. 5. Synthesis and applications. For populations with piecemeal data, a problem common to both endangered and harvested species, obtaining precise demographic parameter estimates is one of the greatest challenges in detecting population trends, diagnosing the causes of decline, and directing management. Data on Sierra Nevada bighorn sheep provide an example of the application of Bayesian state‐space models for combining all existing data to meet these objectives and better inform important management and conservation decisions.

Annual use of water sources by reintroduced Rocky Mountain bighorn sheepOvis canadensis canadensis: effects of season and drought

Water sources are important for the conservation and management of bighorn sheepOvis canadensis (Shaw, 1804). Little is known, however, regarding the use of water by reintroduced Rocky Mountain bighornsO. c. canadensis (Shaw, 1804). Our purpose was to quantify use of water sources by bighorns to test hypotheses related to the value of these sites on Antelope Island, Utah, USA, from July 2005 to December 2006. We predicted that bighorns would increase the number and duration of visits to water during summer. Moreover, we predicted that animals would visit and spend more time at water during drought. Our results indicate that bighorns visited and spent more time around water in summer. These animals, however, did not visit and spend more time at water during drought. Nevertheless, use of water sources increased during times of similar precipitation that followed drought, indicating a potential time-lag in water use by bighorns. Our results underscore the importance of water for reintroduced bighorns in the deserts of western USA, and indicate that animals congregate in riparian areas near water and thereby may facilitate the spreading of diseases and parasites.

Intrinsic and extrinsic sources of variation in the dynamics of large herbivore populations

We evaluated the relative importance of intrinsic (density-dependent) and extrinsic (density-independent) sources of resource variability in the dynamics of bighorn sheep ( Ovis canadensis Shaw, 1804) populations in southwestern USA. We tested the hypothesis that populations experiencing greater variation in forage availability are less likely to be at equilibrium density with forage supplies, and thus, would demonstrate weaker evidence of intraspecific competition. We used regression to relate population growth rate to rainfall (forage conditions) and to abundance (intraspecific competition) for 20 sheep populations, and we estimated the strength of the effects of density and rainfall for each population. Then we compared among populations to look for relationships between the strengths of rainfall and density effects and the variability in rainfall experienced by each population. Populations demonstrating a density effect were associated with environments having lower variability than those that did not. Populations showing a rainfall effect were associated with environments having a variability higher than those that lacked a rainfall effect. These findings are consistent with the hypothesis that populations experiencing higher variation in forage resources are less likely to achieve an equilibrium density with forage supplies where intraspecific competition would be a large determinant to the dynamics of that population.

Many eyes or many ewes: vigilance tactics in female bighorn sheep Ovis canadensis vary according to reproductive status

In gregarious animals, there is usually a negative relationship between individual vigilance and group size. This effect of group size is generally explained by increasing probability of predator detection (the many‐eyes hypothesis) and by the dilution of risk occurring in larger groups. Few studies have attempted to examine the specific implications of either hypothesis on the expected vigilance pattern of an animal. Here we examine whether reproductive status affects vigilance patterns in bighorn sheep Ovis canadensis ewes. We also test whether the observed vigilance patterns are consistent with predictions from dilution or detection models of vigilance. Although vigilance decreased with increasing group size, vigilance tactics differed between barren and lactating females. Lactating ewes relied solely on predator detection. In contrast, barren ewes benefited from both detection and dilution effects when group size increased and adjusted vigilance effort according to the proportion of lactating ewes in their group. It is generally assumed that gregariousness increases safety. Here we further show that reproductive status influenced how animals reduce predation risk and that some individuals take advantage of the vigilance effort provided by others.