Lutra lutra (Linnaeus, 1758), commonly known as the Eurasian otter, is the most widely distributed of the lutrinids (otters). L. lutra is primarily a piscivorous predator but also preys on ...amphibians, crustaceans, small mammals, birds, and reptiles. Extant populations of this semiaquatic mustelid occur in a wide variety of aquatic freshwater and marine habitats throughout Asia, all of Europe, and parts of northern Africa. Despite the large distribution, habitat loss has led to dwindling L. lutra populations, particularly in Asia, and the species is currently listed as “Near Threatened” by the International Union for Conservation and Nature and Natural Resources.
The threatened Gangetic dolphin (Platanista gangetica) and smooth-coated otter (Lutrogale perspicillata) occuring in the Ganga River Basin (GRB), are experiencing a decline in their population and ...distribution range owing to multiple anthropogenic pressures, including pollution by Potentially Toxic Elements (PTEs). Apex predators primarily encounter contaminants through dietary exposure. Yet, notable gaps persist in our understanding of the risks associated with the ingestion of PTE-contaminated prey for Gangetic dolphins and smooth-coated otters. In this study, we examined the occurrence and spatial variation of PTEs in the prey (fish) of both these riverine mammals across three major rivers of the Basin, while also evaluating the associated risk of ingesting contaminated prey. Our assessment revealed no statistical variation in bioaccumulation profiles of PTEs across the three rivers, attributable to comparable land use patterns and PTE consumption within the catchment. Zn and Cu were the most dominant PTEs in the prey species. The major potential sources of pollution identified in the catchment include agricultural settlements, vehicular emissions, and the presence of metal-based additives in plastics. Zn, As and Hg accumulation vary with the trophic level whereas some PTEs show concentration (Hg) and dilution (As, Cr, Pb and Zn) with fish growth. The Risk Quotient (RQ), based on the dietary intake of contaminated prey calculated using Toxicity Reference Value was consistently below 1 indicating no significant risk to these riverine mammals. Conversely, with the exception of Co and Ni, the Reference Dose-based RQs for all other PTEs indicated a substantial risk for Gangetic dolphins and smooth-coated otters through dietary exposure. This study serves as a pivotal first step in assessing the risk of PTEs for two threatened riverine mammals in a densely populated river basin, highlighting the importance of their prioritization in regular monitoring to reinforce the ongoing conservation efforts.
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•Zn and Cu were the most dominant PTEs in prey fish at all sampling sites.•No spatial variation observed in bioaccumulation of PTEs among three rivers.•As And Co levels in benthopelagic fish were higher than in pelagic and demersal fish.•Hg biomagnifies along the food chain, whereas As and Zn show trophic dilution.•As, Hg, Cr, Zn, Cu, and Cd, poses high risk to these threatened species.
Toxoplasma gondii is a ubiquitous parasitic protozoan that poses a health threat to wildlife and human health worldwide. Oocysts shed into the environment in felid host feces may persist for several ...years. Runoff from rainfall and snowmelt may carry the oocysts into waterways. Semiaquatic mammals such as the Northern American river otter (Lontra canadensis) are particularly at risk of exposure, as they may encounter infective stages in both terrestrial and aquatic environments. Despite this risk, only a small number of studies have examined the prevalence of T. gondii in US river otter populations. Tongue tissue was sampled from 124 otters from the Upper Peninsula of Michigan submitted by trappers to the Michigan Department of Natural Resources in the 2018-19 harvest season. Following DNA extraction, a portion of the B1 T. gondii gene was amplified with PCR. A subset of positive samples was genotyped for comparison with known T. gondii sequences. Of the 124 tongue samples, 35 (28%) were positive for T. gondii. Prevalence did not differ significantly between sexes or age classes across the entire study area. Most (53.8%) of the genotyped samples were type 4 (type 12), a genotype commonly found in North American wildlife. Genotypes 127 and 197 were also found. Three clusters of T. gondii prevalence were identified through SaTScan analysis, although they were not significant. When modeling prevalence of T. gondii with covariates at individual otter locations, the top three models included the presence of Sarcocystis, area of exotic plants, area of agriculture, and sex of the otter. Our results suggest that T. gondii is widespread in otter populations in the Upper Peninsula of Michigan.
Human influences on natural environments are now ubiquitous but manifest in multiple and unique ways depending on local environments and communities. Attempts to control, or mediate, local pests to ...residences or to agriculture can impart important negative consequences on systems. Secondary exposure to anticoagulant rodenticides (ARs) can cause numerous adverse effects on wild carnivores including death. Few studies have quantified AR prevalence, investigated their pathway of exposure, or associations with specific location types in the northeastern U.S. We hypothesized that ARs would be found in the mesocarnivore community throughout Pennsylvania and have the greatest detection rate in highly urbanized or agricultural landscapes. From 2019 through early 2022, we collected carcasses to obtain liver samples ( n = 265) from three species of carnivores: bobcats ( Lynx rufus (Schreber, 1777)), fishers ( Pekania pennanti (Erxleben, 1777)), and river otters ( Lontra canadensis (Schreber, 1777)). We used generalized linear models to test for differences in AR detection rates among species and spatial scales including the six Pennsylvania Game Commission regions and 23 wildlife management units. We detected ARs in all species (44.2% collectively), but detection rates differed among species. Our study is the first to document ARs within North American river otters.
North American river otters (
) are top predators in riverine ecosystems and are vulnerable to per- and polyfluoroalkyl substance (PFAS) exposure. Little is known about the magnitude of exposure and ...tissue distribution of PFAS in river otters. We measured 45 PFAS in various tissues of 42 river otters collected from several watersheds in the state of West Virginia, USA. The median concentrations of ∑All (sum concentration of 45 PFAS) varied among tissues in the following decreasing order: liver (931 ng/g wet weight) > bile > pancreas > lung > kidney > blood > brain > muscle. Perfluoroalkylsulfonates (PFSAs) were the predominant compounds accounting for 58-75% of the total concentrations, followed by perfluoroalkyl carboxylates (PFCAs; 21-35%). 8:2 fluorotelomer sulfonate (8:2 FTS), 10:2 FTS, and 6:2 chlorinated polyfluoroalkyl ether sulfonate were frequently found in the liver (50-90%) and bile (96-100%), whereas hexafluoropropylene oxide dimer acid (HFPO-DA) was rarely found. The hepatic concentrations of ∑All in river otters collected downstream of a fluoropolymer production facility located along the Ohio River were 2-fold higher than those in other watersheds. The median whole body burden of ∑All was calculated to be 1580 μg. PFOS and perfluorooctanoic acid (PFOA) concentrations in whole blood of some river otters exceeded the human toxicity reference values, which warrant further studies.
In this study, we investigated the aortic arch (AA) branching pattern in the Eurasian otter (Lutra lutra). We performed arterial silicone casting of the AA of 18 Eurasian otters (8 males and 10 ...females). We analyzed the AA branching pattern at three levels: the AA, brachiocephalic trunk (BCT), and subclavian artery (SB), using different classification methods at each level. We introduced new criteria for classifying the SB branching pattern applicable for Eurasian otter and other carnivores based on the sequence of the four main branches: vertebral artery (VT), internal thoracic artery (IT), costocervical artery (CCT), and superficial cervical artery (SC). In all Eurasian otters, two major branches emerged directly from the AA, i.e., the BCT and left SB. The BCT branched off the left common carotid artery and terminated in the right common carotid artery and right SB in 17 of 18 Eurasian otters; the BCT formed a bicarotid artery in the remaining case. The SBs showed various branching patterns, with the main branching pattern involving branching to the VT and IT at the same position, followed by the CCT and SC. The SB branching pattern in the Eurasian otter differed from that in dogs in that the two first branching arteries were VT and IT, rather than VT and CCT. Here, we present the anatomical characteristics of the AA branching patterns in the Eurasian otter and new analysis methods applicable for comparative studies of other carnivores.
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.
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. Because of the historical otter reintroductions that have occurred in North Carolina, our objective was to determine if the age structure and reproductive rates of otters throughout North Carolina shifted from 1978 to 2018 and whether rates differed between remnant and reintroduced populations and among river basins, Furbearer Management Units, sampling periods, and age classes. Based on age distributions and fecundity estimates, the otter population in North Carolina appears to be stable and healthy with high reproduction and recruitment.
Wildlife managers often rely on analyses conducted prior to the widespread adoption of hierarchical models which can lead to questions about the accuracy of previous inferences. Hierarchical models ...allow observed data to be partitioned into factors that influenced the collection of the data such as detectability of animals (i.e., observation processes) and factors that influence the ecology of a population such as features that affect the distribution of animals (i.e., ecological processes). Population surveys for sea otters in the Aleutian Islands, Alaska, have historically been conducted by conflating the observation and ecological processes potentially leading to inaccurate population estimates. Based on boat and plane‐based sea otter survey data collected in 2017, we sought to overcome many problems of previous sea otter surveys in southwestern Alaska. We developed a spatially explicit hierarchical distance sampling model to estimate the abundance of sea otters in the Eastern Aleutians Management Unit while explicitly accounting for factors that affect the ability to detect sea otters during surveys (i.e., group size, ocean conditions). We also sought to account for the environmental factors leading to the non‐uniform distribution of sea otter groups by identifying relationships between otter group abundance and environmental attributes (i.e., ocean depth, presence of kelp, underwater substrate). Detection of sea otter groups was related to group size, and ocean conditions (e.g., ocean swell size). After accounting for detection, we estimated a mean population size of 8593 individual sea otters (95% CI: 7450–9984) which is considerably higher than previous estimates, although comparisons are difficult given divergent methodologies. Sea otter group density was negatively related to ocean depth and the presence of rock and gravel as underwater substrates. Conversely, sea otter group density was positively related to the presence of kelp and mud as an underwater substrate. Our hierarchical distance sampling model accounted for the observation process which allowed better estimates of the environmental attributes affecting otter abundance. Our research can serve as a template for other study systems requiring spatially explicit density estimates from a distance sampling framework and can help provide a new baseline for managers to gauge future population changes in sea otters.
Toxoplasma gondii, a zoonotic parasite of global importance, infects all endothermic vertebrates, with extensive health implications. The prevalence of this parasite is seldom monitored in wildlife. ...Here, a semi-aquatic species, the Eurasian otter (Lutra lutra) was used as a model to assess the potential effect of climate, land cover and biotic factors on T. gondii seroprevalence in British wildlife. The Sabin-Feldman cytoplasm-modifying dye test identified T. gondii antibodies in 25·5% of blood samples from otters found dead, mainly as road kill, in England and Wales, between 2004 and 2010. Otters in the east of England were more likely to be infected with T. gondii than those in western regions. Land cover and temperature are key determinants of T. gondii infection risk, with more infection in arable areas and lower infection where temperatures are higher. The probability of T. gondii infection increased with host age, reflecting cumulative exposure with time, but there was no association between T. gondii seroprevalence and cause of host death.
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