Population response of reintroduced bighorn sheep after observed commingling with domestic sheep

Bighorn sheep (Ovis canadensis) often die from respiratory disease after commingling with domestic sheep. From 2000 to 2009, we observed commingling between domestic and reintroduced bighorn sheep in 3 populations in UT, USA. We investigated how commingling affected survival of radio-collared female bighorns that were released initially (founder) and those that were subsequently released (augmented). We predicted that the proportion of young surviving to their first winter and population growth would be lower after observed commingling with domestic sheep. We observed groups of bighorns year-round on 2,712 occasions and commingling between domestic sheep and bighorns in 6 instances. On Mount Timpanogos, survival rates were best modeled as constant for females (n?=?57) before and after observed commingling with domestic sheep. Survival rates of female bighorns, however, decreased significantly in Rock Canyon (n?=?21) and on Mount Nebo (n?=?22) for founder, but not augmented bighorns after observed commingling with domestic sheep. Also, the proportion of young surviving to their first winter was almost 3 times lower and population growth was reduced for bighorns after observed commingling with domestic sheep in Rock Canyon and on Mount Nebo. Commingling between domestic and bighorn sheep reduced population parameters in 2 of 3 bighorn populations we studied; however, on Mount Timpanogos, interactions between those 2 species were not fatal for radio-collared female bighorns. Wildlife biologists should manage for spatial separation of these 2 species and consider the location of hobby farms and trailing operations of domestic sheep near release sites for bighorns.     

An epizootic of Mycoplasma ovipneumoniae infection in captive Dall's sheep (Ovis dalli dalli)

In late spring of 1986, 10 of 23 Dall's sheep (Ovis dalli dalli) at the Metropolitan Toronto Zoo were moved to a new exhibit, where all developed severe respiratory signs refractory to anthelmintic and antibiotic therapy. In July, two animals died with chronic active bronch-pneumonia, and a third was euthanized because of pneumonia several months later. Bacteria were not isolated from the lungs of the first, steptococci and Pasteurella hemolytica were isolated from the other two, respectively; Mycoplasma ovipneumoniae was isolated from both. Pulmonary lesions in all three sheep were consistent with Mycoplasma sp. infection. Nasal swabs of the remaining animals yielded no consistent bacterial isolates; however, four of eight sheep were positive for M. ovipneumoniae. Viral cultures yielded an as yet unidentified herpesvirus. Sheep in the original and new herds had no serologic titers to parainfluenza-3, equine viral rhinopneumonitis, or infectious bovine rhinotracheitis, and had variable titers against bovine respiratory syncytial virus. No titers against M. ovipneumoniae were present in 13 sheep still in the original exhibit, but titers varied from 1:32 to 1:256 in eight pneumonic sheep. Sera taken from three sheep before or early in the outbreak were all negative for antibody to M. ovipneumoniae. Two of the affected Dall's sheep had been in contact with domestic sheep in the winter of 1985-1986, and M. ovipneumoniae was subsequently cultured from the domestic flock. Exposure to a new pathogen, and environmental and social stress in a new exhibit may have resulted in this severe disease in Dall's sheep.     

Infectious keratoconjunctivitis in bighorn sheep, Silver Bell Mountains, Arizona, USA

An infectious keratoconjunctivitis (IKC) epizootic in bighorn sheep (Ovis canadensis) occurred in the Silver Bell Mountains, Arizona, USA, from 1 December 2003 to 31 March 2004. We used standard culture methods and polymerase chain reaction (PCR) amplification of the 16S rRNA gene to test for the causative agents of IKC and other diseases reported to be associated with bighorn sheep populations. All bighorn sheep and domestic goat test results were negative except for Mycoplasma spp. and Branhamella spp. The culture and PCR results differed. Conjunctival swabs from four of 19 IKC-affected bighorn sheep tested by culture were positive for Mycoplasma spp., whereas 22 of 22 bighorn sheep samples tested by PCR were positive for Mycoplasma spp. None of 13 domestic goats tested positive by culture for Mycoplasma spp., whereas five of 16 tested positive by PCR. Three of 16 domestic goats and seven of 24 IKC-affected bighorn sheep tested positive for Branhamella spp. by culture. Bighorn sheep began showing clinical signs of IKC between 21 and 28 days following initial detection of domestic goats in bighorn sheep habitat. The IKC epizootic lasted 122 days, and individual bighorn sheep were blind for an average of 38.4 days. Given the clear potential for disease transmission to bighorn sheep, we recommend that land managers not allow the pasturing of domestic goats near occupied bighorn sheep habitat.     

Detection of Mycoplasma ovipneumoniae and M. arginini in bighorn sheep using enrichment culture coupled with genus- and species-specific polymerase chain reaction

Mycoplasma species are of interest as possible primary pathogens in the pneumonia complex of bighorn sheep (Ovis canadensis). Previous investigations have not commonly detected low frequencies of Mycoplasma spp. from free-ranging bighorn sheep, possibly due to the fastidious and slow growth of these organisms. We developed a culture protocol that employed an average initial 3-day enrichment culture in liquid Hayflick broth in a CO(2)-enhanced atmosphere. The broth was plated to solid Hayflick medium and the cultures observed for growth for up to 30 days. Polymerase chain reaction (PCR) was performed on DNA isolated from the enrichment broth and on isolates obtained from culture using Mycoplasma genus-specific PCR assays and species-specific PCR assays for M. arginini and M. ovipneumoniae. Some cultures that grew on Hayflick plates were picked as single colonies but were mixed because two organisms may grow together and appear as a single colony. Culture and PCR tests produced similar results for M. arginini, but for M. ovipneumoniae, culture alone was less accurate than PCR. Use of genus-specific primers also may allow detection of other species in samples negative for M. arginini and M. ovipneumoniae. Two methods of transport from field to laboratory (Port-a-Cul? tubes, cryoprotectant in liquid N(2) and Fisher Transport System) gave similar results under our study conditions.     

A bighorn sheep die-off in southern Colorado involving a Pasteurellaceae strain that may have originated from syntopic cattle

We investigated a pasteurellosis epizootic in free-ranging bighorn sheep (Ovis canadensis) wherein a Pasteurellaceae strain carried by syntopic cattle (Bos taurus) under severe winter conditions appeared to contribute to pneumonia in affected bighorns. Twenty-one moribund or dead bighorn sheep were found on the "Fossil Ridge" herd's winter range, Colorado, USA, between 13 December 2007 and 29 February 2008. Eight carcasses examined showed gross or microscopic evidence of acute to subacute fibrinous bronchopneumonia. All eight carcasses yielded at least one β-hemolytic Mannheimia haemolytica biogroup 1(±(G)) strain, and seven also yielded a β-hemolytic Bibersteinia trehalosi biogroup 4 (CDS) strain; evidence of Pasteurella multocida, Mycoplasma ovipneumoniae, and parainfluenza 3 and bovine respiratory syncytial viruses was also detected. Isolates of β-hemolytic Manneimia haemolytica biogroup 1(G) from a bighorn carcass and a syntopic cow showed 99.5% similarity in genetic fingerprints; B. trehalosi biogroup 4(CDS) isolates were ≥94.9% similar to an isolate from a nearby bighorn herd. Field and laboratory observations suggested that pneumonia in affected bighorns may have been caused by a combination of pathogens including two pathogenic Pasteurellaceae strains--one likely of cattle origin and one likely of bighorn origin--with infections in some cases perhaps exacerbated by other respiratory pathogens and severe weather conditions. Our and others' findings suggest that intimate interactions between wild sheep and cattle should be discouraged as part of a comprehensive approach to health management and conservation of North American wild sheep species.     

Epidemic pasteurellosis in a bighorn sheep population coinciding with the appearance of a domestic sheep

A pneumonia epidemic reduced bighorn sheep (Ovis canadensis) survival and recruitment during 1997-2000 in a population comprised of three interconnected wintering herds (Kenosha Mountains, Sugarloaf Mountain, Twin Eagles) that inhabited the Kenosha and Tarryall Mountain ranges in central Colorado, USA. The onset of this epidemic coincided temporally and spatially with the appearance of a single domestic sheep (Ovis aires) on the Sugarloaf Mountain herd's winter range in December 1997. Although only bighorns in the Sugarloaf Mountain herd were affected in 1997-98, cases also occurred during 1998-99 in the other two wintering herds, likely after the epidemic spread via established seasonal movements of male bighorns. In all, we located 86 bighorn carcasses during 1997-2000. Three species of Pasteurella were isolated in various combinations from affected lung tissues from 20 bighorn carcasses where tissues were available and suitable for diagnostic evaluation; with one exception, beta-hemolytic mannheimia (Pasteurella) haemolytica (primarily reported as biogroup 1(G) or 1(alphaG)) was isolated from lung tissues of cases evaluated during winter 1997-98. The epidemic dramatically lowered adult bighorn monthly survival in all three herds; a model that included an acute epidemic effect, differing between sexes and with vaccination status, that diminished linearly over the next 12 mo best represented field data. In addition to the direct mortality associated with epidemics in these three herds, lamb recruitment in years following the pneumonia epidemic also was depressed as compared to years prior to the epidemic. Based on observations presented here, pasteurellosis epidemics in free-ranging bighorn sheep can arise through incursion of domestic sheep onto native ranges, and thus minimizing contact between domestic and bighorn sheep appears to be a logical principle for bighorn sheep conservation.     

Genomic association with pathogen carriage in bighorn sheep (Ovis canadensis)

Genetic composition can influence host susceptibility to, and transmission of, pathogens, with potential population‐level consequences. In bighorn sheep (Ovis canadensis), pneumonia epidemics caused by Mycoplasma ovipneumoniae have been associated with severe population declines and limited recovery across North America. Adult survivors either clear the infection or act as carriers that continually shed M. ovipneumoniae and expose their susceptible offspring, resulting in high rates of lamb mortality for years following the outbreak event. Here, we investigated the influence of genomic composition on persistent carriage of M. ovipneumoniae in a well‐studied bighorn sheep herd in the Wallowa Mountains of Oregon, USA. Using 10,605 SNPs generated using RADseq technology for 25 female bighorn sheep, we assessed genomic diversity metrics and employed family‐based genome‐wide association methodologies to understand variant association and genetic architecture underlying chronic carriage. We observed no differences among genome‐wide diversity metrics (heterozygosity and allelic richness) between groups. However, we identified two variant loci of interest and seven associated candidate genes, which may influence carriage status. Further, we found that the SNP panel explained ~55% of the phenotypic variance (SNP‐based heritability) for M. ovipneumoniae carriage, though there was considerable uncertainty in these estimates. While small sample sizes limit conclusions drawn here, our study represents one of the first to assess the genomic factors influencing chronic carriage of a pathogen in a wild population and lays a foundation for understanding genomic influence on pathogen persistence in bighorn sheep and other wildlife populations. Future research should incorporate additional individuals as well as distinct herds to further explore the genomic basis of chronic carriage.     

Use of Exposure History to Identify Patterns of Immunity to Pneumonia in Bighorn Sheep (Ovis canadensis)

Individual host immune responses to infectious agents drive epidemic behavior and are therefore central to understanding and controlling infectious diseases. However, important features of individual immune responses, such as the strength and longevity of immunity, can be challenging to characterize, particularly if they cannot be replicated or controlled in captive environments. Our research on bighorn sheep pneumonia elucidates how individual bighorn sheep respond to infection with pneumonia pathogens by examining the relationship between exposure history and survival in situ. Pneumonia is a poorly understood disease that has impeded the recovery of bighorn sheep (Ovis canadensis) following their widespread extirpation in the 1900s. We analyzed the effects of pneumonia-exposure history on survival of 388 radio-collared adults and 753 ewe-lamb pairs. Results from Cox proportional hazards models suggested that surviving ewes develop protective immunity after exposure, but previous exposure in ewes does not protect their lambs during pneumonia outbreaks. Paradoxically, multiple exposures of ewes to pneumonia were associated with diminished survival of their offspring during pneumonia outbreaks. Although there was support for waning and boosting immunity in ewes, models with consistent immunizing exposure were similarly supported. Translocated animals that had not previously been exposed were more likely to die of pneumonia than residents. These results suggest that pneumonia in bighorn sheep can lead to aging populations of immune adults with limited recruitment. Recovery is unlikely to be enhanced by translocating naïve healthy animals into or near populations infected with pneumonia pathogens.     

Comparison of pulmonary defense mechanisms in Rocky Mountain bighorn (Ovis canadensis canadensis) and domestic sheep

Alveolar macrophages were obtained from Rocky Mountain bighorn sheep (Ovis canadensis canadensis) and domestic sheep for the purpose of comparing pulmonary host defense mechanisms in the two species. Specific variables studied included (1) characterization of the cell types present in the lung, (2) alveolar macrophage phagocytic and bactericidal functions, (3) measurement of protein levels in lavage fluid, and (4) measurement of cortisol levels in lavage fluid. While phagocytic cell populations were similar between bighorn and domestic sheep, a significantly higher percentage of lymphocytes were present in bighorns than domestics (20% in bighorn versus 6% in domestic sheep). Significant differences were not observed in the phagocytic or bactericidal functions of macrophages between the two species. Significant differences were not observed in either lavage fluid protein levels or in cortisol levels.     

Spontaneous pasteurellosis in captive Rocky Mountain bighorn sheep (Ovis canadensis canadensis): clinical, laboratory, and epizootiological observations.

We observed clinical signs, compared adrenal responses, and performed diagnostic tests on 12 captive Rocky Mountain bighorn sheep (Ovis canadensis canadensis) during a spontaneous outbreak of pasteurellosis. Cortisol in urine and feces was measured for bighorns sampled three times between 20 October and 1 November 1986. By 6 November, four of these had developed pneumonia, four showed only mild rhinitis, and four remained clinically normal. Bighorns that ultimately developed pneumonia showed elevated mean urinary (P = 0.003) and fecal (P = 0.046) cortisol excretion over the 12-day sampling period. Twenty-four hour mean urine cortisol: creatinine ratios ranged from 10 to 57 ng/mg dry matter for affected and 5 to 22 ng/mg for healthy individuals; 24 hr mean fecal cortisol concentrations ranged from 7.2 to 20 ng/g dry matter for affected and 3.6 to 9.1 ng/g dry matter for healthy individuals. Elevated cortisol excretion preceded clinical pneumonia in affected bighorns by less than or equal to 16 days. Beta-hemolytic Pasteurella haemolytica biotype T, serotype 3 or 4, was isolated from nasal and pharyngeal swabs from all eight bighorns with pneumonia or mild rhinitis. We detected no evidence of parainfluenza 3, bovine respiratory syncytial virus, or Chlamydia psittaci using fluorescent antibody and/or serologic tests. Although elevated cortisol excretion was associated with pneumonia, we also believe age, reproductive physiology, and/or prior recovery from clinical pasteurellosis may have influenced individual susceptibility to pneumonia during this epizootic.     

Phylogenetic analysis of snow sheep (Ovis nivicola) and closely related taxa

Based on mitochondrial cytochrome b gene sequence analysis, the history of true sheep (Ovis) began approximately 3.12 million years ago (MYA). The evolution of Ovis resulted in three generally accepted genetic groups: Argaliforms, Moufloniforms, and Pachyceriforms. The Pachyceriforms of the subgenus Pachyceros comprise the thin-horn sheep Ovis nivicola (snow sheep), Ovis dalli (Dall and Stone sheep), and Ovis canadensis (Rocky Mountain and desert bighorn). North America wild sheep (O. canadensis and O. dalli) evolved separately from Eurasian wild sheep and diverged from each other about 1.41 MYA. Ancestral stock that gave rise to snow sheep, Moufloniforms, and Argaliforms occurred 2.3 MYA, which then gave rise to two different extant lines of snow sheep that diverged from each other about 1.96 MYA. The more recent nivicola line is genetically closer to the North American wild sheep and may represent a close association during the refugium when Alaska and Siberia were connected by the Bering land bridge. The earlier period of evolution of the Pachyceriforms suggests they may have first evolved in Eurasia, the oldest ancestor then giving rise to North American wild sheep, and that a canadensis-like ancestor most likely gave rise to nivicola. Cytogenetic analysis further validates that the standard diploid number for modern nivicola is 52.     

Seroprevalence of Toxoplasma gondii in Rocky Mountain bighorn sheep (Ovis canadensis)

Serum samples from 697 Rocky Mountain bighorn sheep (Ovis canadensis) from North America were examined for antibodies to Toxoplasma gondii by the modified agglutination test incorporating mercaptoethanol and formalin-fixed tachyzoites. Antibodies to T. gondii were found in 25 of 697 (3.6%) sheep in titers of 1:25 (8 sheep), 1:50 (4 sheep), 1:100 (7 sheep), 1:200 (1 sheep), 1:400 (1 sheep), 1:800 (1 sheep), and 1:1,600 (3 sheep). This is the first record of T. gondii exposure in bighorn sheep.     

Natural history of a bighorn sheep pneumonia epizootic: Source of infection,course of disease,and pathogen clearance

A respiratory disease epizootic at the National Bison Range (NBR) in Montana in 2016–2017 caused an 85% decline in the bighorn sheep population, documented by observations of its unmarked but individually identifiable members, the subjects of an ongoing long‐term study. The index case was likely one of a small group of young bighorn sheep on a short‐term exploratory foray in early summer of 2016. Disease subsequently spread through the population, with peak mortality in September and October and continuing signs of respiratory disease and sporadic mortality of all age classes through early July 2017. Body condition scores and clinical signs suggested that the disease affected ewe groups before rams, although by the end of the epizootic, ram mortality (90% of 71) exceeded ewe mortality (79% of 84). Microbiological sampling 10 years to 3 months prior to the epizootic had documented no evidence of infection or exposure to Mycoplasma ovipneumoniae at NBR, but during the epizootic, a single genetic strain of M. ovipneumoniae was detected in affected animals. Retrospective screening of domestic sheep flocks near the NBR identified the same genetic strain in one flock, presumptively the source of the epizootic infection. Evidence of fatal lamb pneumonia was observed during the first two lambing seasons following the epizootic but was absent during the third season following the death of the last identified M. ovipneumoniae carrier ewe. Monitoring of life‐history traits prior to the epizootic provided no evidence that environmentally and/or demographically induced nutritional or other stress contributed to the epizootic. Furthermore, the epizootic occurred despite proactive management actions undertaken to reduce risk of disease and increase resilience in this population. This closely observed bighorn sheep epizootic uniquely illustrates the natural history of the disease including the (presumptive) source of spillover, course, severity, and eventual pathogen clearance.     

Brucellosis in captive Rocky Mountain bighorn sheep (Ovis canadensis) caused by Brucella abortus biovar 4

Nine (four female, five male) captive adult Rocky Mountain bighorn sheep (Ovis canadensis) contracted brucellosis caused by Brucella abortus biovar 4 as a result of natural exposure to an aborted elk (Cervus elaphus) fetus. Clinical signs of infection were orchitis and epididymitis in males and lymphadenitis and placentitis with abortion in females. Gross pathologic findings included enlargement of the testes or epididymides, or both, and yellow caseous abscesses and pyogranulomas of the same. Brucella abortus biovar 4 was cultured in all bighorn sheep from a variety of tissues, including testes/epididymides, mammary gland, and lymph nodes. All bighorn sheep tested were positive on a variety of standard Brucella serologic tests. This is the first report of brucellosis caused by B. abortus in Rocky Mountain bighorn sheep. It also provides evidence that bighorn sheep develop many of the manifestations ascribed to this disease and that infection can occur from natural exposure to an aborted fetus from another species. Wildlife managers responsible for bighorn sheep populations sympatric with Brucella-infected elk or bison (Bison bison) should be cognizant of the possibility of this disease in bighorn sheep.     

Chlamydial-caused infectious keratoconjunctivitis in bighorn sheep of Yellowstone National Park.

An epizootic of infectious keratoconjunctivitis occurred in bighorn sheep (Ovis canadensis) in Yellowstone National Park during the winter of 1981-82. The causative organism was identified as Chlamydia sp. Mortality related to the epizootic was approximately 60% of an estimated 500 bighorn sheep in the northern range population. The infection probably affected all sex and age classes, but field surveys of live animals and mortality suggested that mature rams died disproportionately. Limited field observations the following winter on individuals having both normal and cloudy-appearing eyes suggested that half of the bighorns then present on the core units of winter range had contracted the disease and survived. By 1988, there were about 300 bighorn sheep in the population.     

Detecting nonhemolytic Pasteurella haemolytica infections in healthy Rocky Mountain bighorn sheep (Ovis canadensis canadensis): influences of sample site and handling

Effects of sampling procedures on ability to culture Pasteurella spp. from Rocky Mountain bighorn sheep (Ovis canadensis canadensis) were examined experimentally. Sample site influenced (P less than 0.0001) recovery of P. haemolytica in adult bighorn sheep. We isolated nonhemolytic P. haemolytica from 18 of 19 tonsillar swabs and 18 of 19 tonsillar biopsies from adult sheep, yet only four of 19 nasal swabs yielded isolates. Sample handling also affected (P less than 0.0001) recovery of P. haemolytica. Nonhemolytic P. haemolytica was cultured from 14 of 19 tonsillar swabs plated directly onto blood agar, but from only two of 19 swabs stored for 24 hr in modified Stuart's medium. We detected nonhemolytic P. haemolytica at least once in bronchial aspirates from four and in nasal swabs from three of six bighorn lambs. Based on direct cultures of tonsillar swabs and/or biopsies, all 26 bighorn sheep (seven lambs, 19 adults) sampled were infected with nonhemolytic P. haemolytica; only two lambs developed pneumonia during the study period. Thirty-four of 37 nonhemolytic P. haemolytica isolates tested were biotype T; three were biotype A. Serotypes 3; 4; 3, 4 and 3, 4, 10 were identified in a subsample of 17 isolates. Our data suggest tonsillar swabs or biopsies plated directly onto blood agar and incubated immediately offer the greatest probability of recovering nonhemolytic P. haemolytica from health bighorn sheep.     

Mannheimia (Pasteurella) haemolytica leukotoxin utilizes CD18 as its receptor on bighorn sheep leukocytes

Pneumonia caused by Mannheimia (Pasteurella) haemolytica is a highly fatal disease of bighorn sheep (Ovis canadensis). Leukotoxin (Lkt), secreted by M. haemolytica, is an important virulence factor of this organism, and is cytolytic to bighorn sheep leukocytes. Previously, we have shown that CD18, the beta subunit of beta2 integrins, serves as the receptor for Lkt on bovine leukocytes. Furthermore, anti-CD18 antibodies inhibit Lkt-induced cytotoxicity of bighorn sheep leukocytes. Therefore, we hypothesized that Lkt utilizes CD18 as its receptor on bighorn sheep leukocytes. Confirmation of bighorn sheep CD18 as a receptor for Lkt requires the demonstration that the recombinant expression of bighorn sheep CD18 in Lkt-nonsusceptible cells renders them susceptible to Lkt. Therefore, we transfected cDNA encoding CD18 of bighorn sheep into a Lkt-nonsusceptible murine cell line. Cell surface expression of bighorn sheep CD18 on the transfectants was tested by flow cytometry with anti-CD18 antibodies. Transfectants stably expressing bighorn sheep CD18 on their surface were subjected to flow cytometric analysis for detection of Lkt binding, and cytotoxicity assays for detection of Lkt-induced cytotoxicity. Leukotoxin bound to the transfectants. More importantly, the transfectants were effectively lysed by Lkt in a concentration-dependent manner, whereas the parent cells were not. These results clearly indicate that M. haemolytica Lkt utilizes CD18 as a receptor on bighorn sheep leukocytes. Identification of CD18 as a receptor for Lkt on bighorn sheep leukocytes should enhance our understanding of the pathogenesis of pneumonia, which in turn should help in the development of control measures against this fatal disease of bighorn sheep.     

A genome-wide set of SNPs detects population substructure and long range linkage disequilibrium in wild sheep

The development of genomic resources for wild species is still in its infancy. However, cross-species utilization of technologies developed for their domestic counterparts has the potential to unlock the genomes of organisms that currently lack genomic resources. Here, we apply the OvineSNP50 BeadChip, developed for domestic sheep, to two related wild ungulate species: the bighorn sheep (Ovis canadensis) and the thinhorn sheep (Ovis dalli). Over 95% of the domestic sheep markers were successfully genotyped in a sample of fifty-two bighorn sheep while over 90% were genotyped in two thinhorn sheep. Pooling the results from both species identified 868 single-nucleotide polymorphisms (SNPs), 570 were detected in bighorn sheep, while 330 SNPs were identified in thinhorn sheep. The total panel of SNPs was able to discriminate between the two species, assign population of origin for bighorn sheep and detect known relationship classes within one population of bighorn sheep. Using an informative subset of these SNPs (n=308), we examined the extent of genome-wide linkage disequilibrium (LD) within one population of bighorn sheep and found that high levels of LD persist over 4 Mb.     

Some aspects of geophagia in Wyoming bighorn sheep (<Emphasis Type="Italic">Ovis canadensis</Emphasis>)

Geophagia has been commonly reported for bighorn sheep (Ovis canadensis) and other ungulates worldwide. The phenomenon is often attributed to the need to supplement animal diets with minerals available in the soil at mineral lick locations. Sodium is the mineral most frequently cited as being the specific component sought, although this has not been found universally. In this study area, bighorn sheep left normal summer-range to make bimonthly 26-km, 2,000-m-elevation round-trip migrations, the apparent purpose of which was to visit mineral licks on normal winter-range. Lick soil and normal summer-range soil were sampled for their available mineral content and summer-range forage was sampled for total mineral content, and comparisons were made to determine the specific components sought at the lick by bighorn sheep consuming soil. It was concluded that bighorn sheep were attracted to the lick by a desire for sodium but that geophagia also supplemented a diet deficient in the trace element selenium. Where sheep are denied access to licks, populations may be limited by mineral deficiency.     

Experimental contact transmission of Pasteurella haemolytica from clinically normal domestic sheep causing pneumonia in Rocky Mountain bighorn sheep

Two Rocky Mountain bighorn lambs (Ovis canadensis canadensis) were held in captivity for 120 days before being housed with two domestic sheep. The lambs were clinically normal and had no Pasteurella spp. on nasal swab cultures. The domestic sheep were known to carry Pasteurella haemolytica biotype A in the nasal passages. After being in close contact for 19 days. P. haemolytica biotype A was cultured from nasal swabs of one of the bighorn lambs. By 26 days, both bighorn sheep developed coughs, were anorectic and became lethargic and nasal swabs yielded P. haemolytica biotype T, serotype 10. Twenty-nine days after contact, the lambs were necropsied and found to have extensive fibrinous bronchopneumonia. From affected tissues pure cultures of beta-hemolytic P. haemolytica biotype T, serotype 10 were grown. Both domestic sheep remained clinically normal and had no gross or microscopic lesions, but they carried the same P. haemolytica serotype in their tonsils. Behavioural observations gave no indication of stress in the bighorn lambs.