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Surf Scoter (Melanitta perspicillata), a sea duck that winters commonly along the coast of the Pacific Northwest states, was observed exhibiting unusual foraging behavior in the swash zone of a beach on the Point Reyes Peninsula, California, in mid-January of 2015. This note reviews the literature involving scoter foraging behavior, discusses the likely prey items targeted, and the potential risks posed by such behavior.

River otters (Lontra canadensis) are widespread in the United States and are managed for sustainable fur harvest throughout much of their range in the United States. Despite their widespread distribution, river otters can be difficult to monitor due to their cryptic nature and the inaccessible habitats they often occupy. Additionally, there has been little research conducted to quantify winter habitat selection patterns of river otters. We used 4 years of aerial survey data conducted during the winter to quantify habitat selection patterns of river otters inWisconsin, USA, and to determine factors associated with survey efficacy. We used a mixed-effects logistic regression framework to evaluate habitat and anthropogenic factors at 2 spatial scales. We found that river otters were positively associated with the amount of forested and wetland habitat within a 1 km buffer around sampling locations, but that no factors we measured were influential at a local (100 m) scale. River otters were more likely to be detected when ice cover was only partial as opposed to when ice coverage was complete or when it was completely absent. Our results suggested that river otter habitat selection in Wisconsin is not strongly affected by anthropogenic influences but instead by broad-scale habitat configuration. Furthermore, our results suggested that aerial survey approaches for river otters can be optimized by conducting surveys during periods when ice coverage is sufficient to allow for clear tracking substrate without being prevalent enough to limit movements into and out of corresponding aquatic habitats.

River otter (Lontra canadensis) predation of seabirds has been periodically documented throughout North America, but most knowledge about this subject exists as anecdotal observations in the memories of experienced seabird biologists. Using surveys, interviews, white papers, and published literature, we collected detailed records of seabird predation by river otters at 73 islands on the coasts of North America. From this dataset, we were able to draw conclusions about the seabird species experiencing river otter predation, the geographic distribution of predation records, and factors associated with river otter occurrence at colony islands. River otters preferentially select for small‐bodied burrow‐nesting species, with predation of ground‐nesting species occurring mostly opportunistically. Predation of nesting seabirds occurs across the entire Pacific range of the river otter and throughout the northern Atlantic, but we did not locate a single record of this behavior on the Atlantic coast south of Maine; we hypothesize that this is due to geographic differences in nesting seabird assemblages. The presence of burrow‐nesting seabirds and proximity to the mainland are both strong predictors of river otter occurrence at colony islands. River otters will swim up to eight kilometers across open ocean to access seabird colonies, but predation is significantly more common at nearshore islands (median distance of 1.7 km). Reports of seabird predation by river otters in published literature are rare, are heavily biased toward an ornithological audience, and have decreased over time as “Field Notes” style publications have decreased in popularity. Despite being more widespread than previously reported, predation by river otters appears to be sustainable for most colony nesting seabird populations. Northern river otter predation of nesting seabirds is rarely reported in published literature, but this behavior is common throughout the Pacific coast and on the northern Atlantic coast. Through surveys of seabird field biologists, we documented records of river otters hunting eighteen different species of nesting seabirds at 73 different colony islands in the United States and Canada. River otters show a selective preference for small‐bodied burrow‐nesting seabird species, with predation of larger surface‐nesters occurring mostly opportunistically.

Semiaquatic mammals serve as ecosystem engineers and indicator species in their environment. While they play important roles in both terrestrial and aquatic systems, the relative importance of each ecosystem in shaping semiaquatic mammal distributions remains unclear. Additionally, occupancy studies generally focus on a single type of waterbody (e.g., lentic or lotic systems), limiting a holistic understanding of factors impacting these species distribution. To address the relative importance of terrestrial and aquatic environments to semiaquatic mammal distributions, we surveyed 67 sites across four counties in southern Illinois, USA, from March to May 2023 for American beaver (Castor canadensis), muskrat (Ondatra zibethicus), river otter (Lontra canadensis), and American mink (Neogale vison). Sites were distributed evenly between waterbody type and size. Given the elusive nature of these species, we combined two detection methods, sign surveys and camera traps, to increase detection. We applied a Bayesian multi‐method occupancy model that incorporates both detection methods to estimate a single occupancy probability for each target species. To evaluate the relative importance of aquatic and terrestrial factors on occupancy, we built candidate models of aquatic and terrestrial covariates separately to identify the most important covariates of each category. The individual top model varied by species, but a combined model of the top aquatic and terrestrial models provided the best overall predictions for each species. Beaver, otter, and mink occupancy showed positive associations with large waterbodies, while muskrat occupancy was positively linked to lotic systems. Additionally, muskrat and mink occupancy were positively related to increasing distance from roads. Our results suggest that while aquatic and terrestrial factors have varying influences in predicting semiaquatic mammal occupancy, considering both yields the most accurate results. All four semiaquatic mammal species we studied were impacted differently by lentic and lotic waterbodies, highlighting the importance of considering both types to better understand their distributions. Our framework is applicable to numerous environments and has the potential to enhance efforts to sustain semiaquatic mammal populations and their habitats.

Radiotelemetry provides valuable information about wildlife populations that is often unattainable using other methods. Many vertebrate species can carry radiotransmitters on collars or harnesses, but radiotelemetry can be more problematic for other species. River otters (Lontra canadensis) are typically radiomarked by surgically implanting intra-abdominal transmitters under general anesthesia. However, surgical requirements and restrictions on some immobilizing drugs may limit options for implanting river otters with radiotransmitters in the field. To address these issues, we developed a protocol for chemically immobilizing live-captured river otters with nonscheduled drugs (by estimated weight class; dexmedetomidine 0.06 mg/kg and nalbuphine 1.2 mg/kg) and conducting field surgeries at capture sites. We surgically implanted 23 river otters with radiotransmitters in southern Illinois during November 2018−March 2020. A plane of anesthesia suitable for surgery was maintained with isoflurane (1−4%). After surgery, capture drugs were reversed with atipamezole and river otters were typically released in 30−60 min. We recorded one surgery-related mortality and one post-surgery mortality. Our surgical method for radiomarking river otters minimized stress and handling time without compromising their health and demonstrated the efficacy of less-restricted chemical immobilization agents for river otters.

The North American river otter Lontra canadensis is a semi‐aquatic furbearer species that historically ranged throughout North America. Starting in the mid‐1800s and continuing through the early 1900s, the negative effects associated with anthropogenic disturbances (i.e. overharvest, development and ultimately habitat alternation) led to local extinctions. Researchers debate whether current land use patterns are affecting river otter occupancy. New Jersey is the most densely populated state in the United States, thus it provides a perfect study area to test potential anthropogenic effects on river otters. Using occupancy modeling to examine river otter habitat preferences, we measured presence/absence at 244 low order streams from January–April 2011–2012 along with 19 corresponding site/landscape covariates in both northern and southern New Jersey. In southern New Jersey, we detected otters at 83/141 sites (58.9%) with a detection probability of 97.7% across repeat visits and a predicted occupancy of 59.4 ± 0.04%. In northern New Jersey we detected otters at 31/103 sites (30.1%) with a detection probability of 44.5% across repeat visits and a predicted occupancy of 58.8 ± 0.04%. We determined the influence of habitat covariates on otter occupancy and found that water depth, water quality, stream width and mink presence were positively correlated with otter occupancy. The % commercial, industrial, transportation and recreational habitat, % low intensity development, bank slope, and distance to lake were negatively correlated with otter occupancy. Knowing the location of occupied stream and latrine sites will assist biologists in their efforts to monitor river otter populations and help estimate river otter density for harvest and conservation efforts.

River otters (Lontra canadensis) are apex predators that bioaccumulate contaminants via their diet, potentially serving as biomonitors of watershed health. They reside throughout the Green-Duwamish River, WA (USA), a watershed encompassing an extreme urbanization gradient, including a US Superfund site slated for a 17-year remediation. The objectives of this study were to document baseline contaminant levels in river otters, assess otters’ utility as top trophic-level biomonitors of contaminant exposure, and evaluate the potential for health impacts on this species. We measured a suite of contaminants of concern, lipid content, nitrogen stable isotopes (δ15N), and microsatellite DNA markers in 69 otter scat samples collected from twelve sites. Landcover characteristics were used to group sampling sites into industrial (Superfund site), suburban, and rural development zones. Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ether flame-retardants (PBDEs), dichlorodiphenyl-trichloroethane and its metabolites (DDTs), and polycyclic aromatic hydrocarbons (PAHs) increased significantly with increasing urbanization, and were best predicted by models that included development zone, suggesting that river otters are effective biomonitors, as defined in this study. Diet also played an important role, with lipid content, δ15N or both included in all best models. We recommend river otter scat be included in evaluating restoration efforts in this Superfund site, and as a potentially useful monitoring tool wherever otters are found. We also report ΣPCB and ΣPAH exposures among the highest published for wild river otters, with almost 70% of samples in the Superfund site exceeding established levels of concern.

Previous studies have documented natural infections of SARS-CoV-2 in various domestic and wild animals. More recently, studies have been published noting the susceptibility of members of the Cervidae family, and infections in both wild and captive cervid populations. In this study, we investigated the presence of SARS-CoV-2 in mammalian wildlife within the state of Vermont. 739 nasal or throat samples were collected from wildlife throughout the state during the 2021 and 2022 harvest season. Data was collected from red and gray foxes ( Vulpes vulples and Urocyon cineroargentus, respectively), fishers ( Martes pennati ), river otters ( Lutra canadensis ), coyotes ( Canis lantrans ), bobcats ( Lynx rufus rufus ), black bears ( Ursus americanus ), and white-tailed deer ( Odocoileus virginianus ). Samples were tested for the presence of SARS-CoV-2 via quantitative RT-qPCR using the CDC N1/N2 primer set and/or the WHO-E gene primer set. Surprisingly, we initially detected a number of N1 and/or N2 positive samples with high cycle threshold values, though after conducting environmental swabbing of the laboratory and verifying with a second independent primer set (WHO-E) and PCR without reverse transcriptase, we showed that these were false positives due to plasmid contamination from a construct expressing the N gene in the general laboratory environment. Our final results indicate that no sampled wildlife were positive for SARS-CoV-2 RNA, and highlight the importance of physically separate locations for the processing of samples for surveillance and experiments that require the use of plasmid DNA containing the target RNA sequence. These negative findings are surprising, given that most published North America studies have found SARS-CoV-2 within their deer populations. The absence of SARS-CoV-2 RNA in populations sampled here may provide insights in to the various environmental and anthropogenic factors that reduce spillover and spread in North American’s wildlife populations.

Niche partitioning occurs among coexisting populations to reduce the effects of competitive exclusion among species of similar niche. The aim of the present study is to verify the trophic niche partitioning and feeding behavior between two mustelids, the Giant otter and the Neotropical otter, through the dry and rainy season hydrologic of the Lower Xingu River. Our results suggest that the diets of both mustelids are composed primarily of fish of the family Anostomidae (Headstanders). Despite extensive niche overlap, our results indicate partitioning is facilitated by differences in niche breadth, with potential implications for conservation of both species in the case of declines in prey abundance and diversity. Both species inhabit an area recently impacted by completion of the Belo Monte Hydropower Plant, resulting in large changes to the hydrologic regime. Thus, our results provide important information for conservation efforts regarding the feeding behavior and co-occurrence of both species, as well as providing a baseline for monitoring future health of these mustelid populations. The present study is the first to test the hypothesis of niche partitioning between these two mustelids outside a protected area in the Amazon.

Semi-aquatic mammals are dependent upon streams and riparian areas, which are a product of the landscapes they drain. Both local stream morphology and surrounding land use are likely to have important influences on current occupancy of semi-aquatic mammals and potentially affect future geographic distributions. We identified aspects of the riparian system and stream structure at multiple scales that relate to the presence of river otter (Lontra canadensis) and mink (Neovison vison) to better understand how changing landscapes affect occupancy dynamics of these semi-aquatic mammals and to facilitate future monitoring and management. We estimated multi-season occupancy using 103 sites sampled over 6 seasonal sampling periods in southern Illinois, USA (44,526 km²) during 2012–2014. We hypothesized river otter and mink occupancy were related to multiple aspects of landscape and local habitat attributes including land cover, water availability, human disturbance, and stream characteristics. Occupancy of river otter was predicted by large stream size, less developed area near the stream site, and proximity to areas with reintroduced or remnant populations of river otter. Mink were more likely to occupy sites with small streams and decreased water availability near the site. However, top models for both species had low weights and high uncertainty for multiple variables. Habitat-based models may not be the best predictors of occupancy for these carnivores because they are more likely to respond to prey diversity or availability, but landscape changes that decrease natural water availability and increase human disturbance to the stream at the local scale are likely to negatively affect river otter.