No abstract

The North American river otter ( Lontra canadensis) is the largest mustelid in North Carolina, USA, and was once extirpated from the central and western portions of the state. Over time and after a successful reintroduction project, otters are now abundant and occur throughout North Carolina. However, there is a concern that diseases may have an impact on the otter population, as well as on other aquatic mammals, either through exposure to emerging diseases, contact with domestic animals such as domestic cats ( Felis catus), or less robust condition of individuals through declines in water quality. We tested brain and kidney tissue from harvested otters for the pathogens that cause leptospirosis, parvovirus, and toxoplasmosis. Leptospirosis and toxoplasmosis are priority zoonoses and are maintained by domestic and wild mammals. Although parvovirus is not zoonotic, it does affect pets, causing mild to fatal symptoms. Across the 2014–15 and 2015–16 trapping seasons, we tested 220 otters (76 females, 144 males) using real-time PCR for Leptospira interrogans, parvovirus, and Toxoplasma gondii. Of the otters tested, 1% (3/220) were positive for L. interrogans, 19% (41/220) were positive for parvovirus, and 24% (53/220) were positive for T. gondii. Although the pathogens for parvovirus and toxoplasmosis are relatively common in North Carolina otters, the otter harvest has remained steady and the population appears to be abundant and self-sustaining. Therefore, parvovirus and toxoplasmosis do not currently appear to be negatively impacting the population. However, subsequent research should examine transmission parameters between domestic and wild species and the sublethal effects of infection.

The North American river otter (Lontra canadensis) serves as an indicator species for environmental monitoring, is prized as a valuable furbearer, and is a popular display animal in zoologic collections. Nephrolithiasis has been reported as a frequent problem in other free-ranging and captive otter species but is rarely reported in North American river otters. In this study, we compared the prevalence of nephrolithiasis diagnosed using routine gross pathologic examination techniques with the use of computed tomography (CT) of excised kidneys. We also evaluated whether otter nephroliths could be accurately classified by their CT densities, and we examined the renal tissue uric acid concentrations in free-ranging otters in North Carolina, USA. Kidneys were collected from carcasses of legally trapped, free-ranging animals. Nephroliths were observed in 16.2% of the individuals (n = 229). Associations were found between age and nephrolith status and between capture location and nephrolith status (P = 0.026 and< 0.001, respectively). Computed tomography Hounsfield unit density measurements were not useful in determining nephrolith chemical composition in this study. Renal tissue uric acid concentrations were similar across genders, age groups, and stone status. The chemical composition of the nephroliths was determined by scanning electron microscopy-energy dispersive X-ray spectroscopy to be calcium phosphate in the carbonate form.

Historically, the North American river otter (Lontra canadensis; otter) was distributed across North Carolina, USA, but populations were decimated by the early 1900s. Otter trapping was prohibited in 1938, reopened in 1947, and gradually expanded until it was opened statewide in 2005. Between 1986 and 1992, the North Carolina Wildlife Resources Commission and Great Smoky Mountains National Park released 404 otters to restore populations in western North Carolina. Our objective was to determine if the age structure and reproductive rates of otters throughout North Carolina shifted from 1978 to 2018 between remnant and reintroduced populations. During the 1978–1980 (period 1; Coastal Plain) and the 2009–2013 and 2014–2016 (period 2; statewide) trapping seasons, we collected 1,439 otter carcasses from licensed trappers, fur buyers, and wildlife damage control agents throughout the 3 Furbearer Management Units (FMUs) and 14 river basins in North Carolina. We conducted necropsies, used cementum annuli of the lower canine for age analysis, and counted corpora lutea and fetuses for fecundity estimates. Age distributions for all otters were skewed toward the younger age classes and did not differ between collection periods. During period 1, adults in the Coastal Plain had higher corpora lutea counts than during period 2, whereas Coastal Plain yearlings and juveniles had higher numbers of corpora lutea during period 2. During period 2, corpora lutea counts differed among FMUs; counts in the Mountain FMU (x̄ = 2.56) were higher than in the Coastal Plain FMU (x̄ = 1.62) or the Piedmont FMU (x̄ = 1.91). Within the Coastal Plain FMU and pooling all age classes, fecundity increased by 45% from period 1 to period 2. Adult fecundity in the Coastal Plain FMU declined 16% from period 1 to period 2, while juveniles and yearlings began reproducing between the periods, indicating that reproduction has shifted to younger age classes between 1978 and 2018.