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The study aimed to evaluate the comparative anatomy of the liver and intrahepatic branching of the portal vein of the Eurasian otter (Lutra lutra) and the American mink (Neovison vison). Due to their highly valuable fur, minks have expanded their range to many parts of Europe and become available for many biomedical studies. In this study, ten adult minks and five otters were used. The intrahepatic branching of the portal vein was studied by the combined injection and dissection technique. The macroscopic anatomy of the liver revealed that both species have six-lobed livers, although differences in shape, size and some additional fissures were documented. The portal vein, upon entering the liver, divides into the right and left branches. The branching pattern in otters had an additional branch at this level with a caudate process branch. The right branch of the portal vein ramified in the right lateral lobe and the caudate process in the mink livers, while the right branch in the otter livers only distributed functional blood to the right lateral lobe. The larger left portal branch, with its transverse and umbilical parts, ramified in the left liver portion, along with the quadrate, right medial lobe and papillary process.

The Eurasian Otter Lutra lutra is an elusive, solitary animal that has one of the widest distributions of all palearctic mammals. Once widely distributed in Asia, the Eurasian Otter population is now vulnerable to urbanization, pollution, poaching, and dam construction. Eurasian Otter distribution in the Indian Himalayan rivers is little explored, and information from this high-altitude riverine ecosystem is sparse. This publication reports a rare photographic record of the Eurasian Otter which confirms its presence in the high-altitude temperate forest of the Upper Bhagirathi Basin, western Himalayan region. The otter was recorded during investigations of terrestrial and aquatic fauna in the Bhagirathi Basin (7,586 km2, 500–5,000 m) of Uttarakhand State, India from October 2015 to May 2019. Among aquatic fauna, Brown Trout were found to be abundant in high altitude river stretches, with a catch per unit effort of 1.02 kg h–1. Additionally, 26 families of freshwater macroinvertebrates underscored a rich diet available for the Brown Trout, which in turn is a potential food source for the otters. The riverine ecosystem is undergoing dramatic changes because of the increasing demand for hydropower plants in the Bhagirathi Basin. Although mitigation measures are currently in place for fish, the presence of otters further necessitates the need for targeted management for high-altitude Himalayan rivers. There is an imperative need for intensive otter surveys using methods such as camera traps in riparian habitats along the Bhagirathi River and its tributaries.

On the River Ticino in northern Italy, a small number of captive Eurasian otters Lutra lutra, belonging to the European breeding programme for self-sustaining captive populations, were reintroduced in 1997, after the species had been declared locally extinct in the 1980s. We surveyed for otter signs in 2008, 2010, 2016–2017 and 2018, confirming the presence of what is probably a small population. To assess the abundance and viability of the population, we genotyped fresh spraints collected during the last two surveys, using 11 microsatellite markers, and modelled the population trend using Vortex. A minimum of six individuals were identified from 25 faecal samples. The analysis of mitochondrial DNA determined that the reintroduced otters share a transversion that is characteristic of the Asiatic subspecies Lutra lutra barang, confirming the contribution of the Asiatic subspecies to the genetic pool of the captive-bred founder population. Population size was consistent with the release of three pairs of otters and all models implied that the number of founders was too small to ensure the long-term survival of the population. Stochastic factors are therefore likely to threaten the success of this reintroduction.

While it is well known that Eurasian otters principally feed on fishes and crustaceans, their detailed diet taxonomies are not fully understood. This is partly due to their nocturnal behavior and the limited resolving power of traditional morphological identification from scat. A suitable, reliable molecular method for diet studies is therefore needed.I performed a series of Sanger‐sequencing reactions, utilizing nine primer sets for Eurasian otter diet research. These are mainly based on the barcoding concept to determine the taxonomic composition of spraints. The primer sets target different types of animals, amplifying each separately. This procedure was used to detect the prey contents of 64 spraint samples collected from Kinmen Island. Through high‐resolution gel electrophoresis and sequencing, it was evident that PCR products could be successfully amplified by the different primer sets and from spraint samples comprising multiple prey species.Extracted DNA from all spraint samples was PCR‐amplified with 9 primer sets. In total, 16 prey types were identified across all 64 samples. Fourteen were identified at the species level.The aim of this study was to develop and apply a novel diet research method to Eurasian otters. Eight of the primers are universal primers designed for COI segments of different animal groups, and one primer set was designed specifically for tilapia groups. This method can be applied to study the diets of not only Kinmen Eurasian otter populations, but also other Eurasian otter populations and other small carnivorous animals., A Eurasian otter eating a tilapia in Tai Lake, Kinmen. The photograph was taken by Fu‐Sheng Huang in June 2020.

Perceived as an indicator of the balance in wildlife and clean nature, the Eurasian otter (Lutra lutra L.) is near-threatened due to the fact that its fur is valuable, the increase in environmental pollution, the decrease in wetlands, the rivers in their habitats are turned into channels. There are 86 rainbow trout (Oncorhynchus mykiss) farms legally licensed by the Provincial Ministry of Agriculture and Forestry Mugla - Turkey. Since otter meets 70% of its nutrient need from fish, it is seen as a predatory species by aquaculture producers. For this reason, it is necessary to work on establishing otter habitats and breeding farms jointly with rainbow trout farmers in order to eliminate the negative effects of both rainbow trout farms and Eurasian otters. In this way, Eurasian otters that are near-threatened, will be saved and also a different contribution will be made to our economy.

Information on the feeding habits of species is essential to develop appropriate conservation actions. This study aimed to assess spatial and temporal variation in the diet of the Eurasian otter, Lutra lutra in the Anzali Wetland, through fecal and stable isotope analysis. Seven main prey items were observed in the analysis of 300 fresh spraints. The highest feeding index was observed for fish, followed by snakes. Among the fish species consumed, the index of preponderance of Prussian carp (Carassius gibelio) was the highest followed by pike (Esox lucius) and white bream (Blicca bjoerkna). Results of Shannon diversity index suggest spatial variation of species diversity within and between feeding items (p < 0.05); snakes, frogs, and oriental river prawn (Macrobrachium nipponense) showed a seasonal variation. The otter’s trophic level (TL) (3.79) was higher than the TLs of other Anzali Wetland predators, such as pike. Bayesian mixing model showed source proportion contributions of fish 49.5%, reptiles 16.7%, insects 14.8%, crustacean 10.5%, amphibians 4.3%, birds 4.1%, and mollusks 0.1%. When considering only fish species in the Bayesian mixing model, Prussian carp was the main fish prey in the otters’ diet accounting for 47%. Based on the results of this study, the Eurasian otter plays an important role in the ecology of the Anzali Wetland ecosystem even though it preys on exotic species, such as the Prussian carp and the oriental river prawn.

In the catchment of the River Segura (SE Spain), ongoing Eurasian otter (Lutra lutra) recovery and concurrent spread of human settlements are resulting in increasing otter records into urban areas. We analysed otter diet along a natural-to-urban gradient, with the main aim of assessing to which extent man-driven variation in food availability affects its feeding habits and how this secretive mustelid can thrive in apparently unsuitable habitats. From 2016 to 2019, we collected 521 spraints, monitoring 37 sampling stations (mean length ± SD = 0.5 ± 0.3 km). In natural areas, the percent cover of undisturbed banks was the highest, with the lowest number of water abstraction systems, whilst water pollution was the highest in urban areas. Introduced red swamp crayfish (Procambarus clarkii) and fish formed the bulk of otter diet. The two most preyed fish, Luciobarbus sclateri and Pseudochondrostoma polylepis, were among the most abundant species in the river, confirming the generalist feeding behaviour of the otter. The contribution of non-native fish was on average low, while invasive crayfish exceeded the overall importance of fish in all habitats except urban areas. Overall, diet data did not allow attesting food as a limiting resource for otters in urban areas. In contrast, marking intensity varied consistently with the natural-to-urban gradient (from 0.31 to 0.65 spraints/100 m in urban- and natural areas, respectively), suggesting that human disturbance (i.e. habitat modification and water pollution) may play a major role in shaping otter distribution.

American mink Neovison vison is a semi-aquatic mustelid that has been introduced throughout Europe. Several attempts to eradicate this invasive species have been carried out since its spread. In the Iberian Peninsula, an eradication program has started since 2001, as part of the national action plan for the conservation of European mink Mustela lutreola. Proper detection is crucial for management, both for monitoring variation in mink abundance and prevent the recolonization of cleared areas. Mink scats can be confounded with those of several same-sized mustelids, and with the spraints of Eurasian otter Lutra lutra, which also occur along watercourses. However, these difficulties can be overcome by non-invasive genetic methods. With the aim of providing a cost-effective and reliable technique for differentiating mink scats from those of the largest possible number of species with morphologically similar scats, we tested the effectiveness of an already available faecal mtDNA-based PCR–RFLP method for distinguishing mink- and otter faeces. We then applied the method for analysing scats collected and identified in the field by trained surveyors for monitoring the success of mink control operations. The PCR–RFLP method clearly differentiated mink scats from those of otters, as restriction enzymes produced well-defined different patterns. Eighty-five percent of 94 faecal samples could be assigned to a mustelid species. Only three out of seven putative mink samples were confirmed, suggesting that the accuracy of the visual identification of scats is questionable and genetic methods are needed for the reliable assessment of the success of eradication programs.

As a top predator, the Eurasian otter (Lutra lutra) is an indicator of healthy freshwater ecosystems and a flagship species for conservation. Once widespread in China, the species is now distributed mainly in the upper reaches of the great rivers of western China. However, a lack of knowledge on local otter populations continues to hinder their conservation in China. Here, we conducted a detailed study on habitat use of Eurasian otters in Yushu City and Tangjiahe National Nature Reserve in western China using transect surveys. At both study sites, otters preferred to defecate on large rocks close to or protruding from the river and about 50 cm above the waterline. In Yushu, no spraints were found along the 5 km river bank section in the downtown area, with otters preferring sprainting sites with natural banks, riparian zones, and lower human population density. However, this pattern was not obvious at Tangjiahe, where river transformation and human disturbance are minor. Otter river use intensity was negatively correlated with elevation and human population density in Yushu in both seasons. In Tangjiahe, otter river use intensity was positively correlated with prey mass and flow rate and negatively correlated with human population in spring, but positively correlated with human population and negatively correlated with flow rate in autumn. These results reflect the flexible habitat use strategies of otters at different sites, underlining the necessity to study otters living in different regions and habitat types. We provide suggestions for river modification and call for more site-specific studies to promote otter conservation in China.

An eighteen-year-old female Eurasian otter became emaciated and died. Necropsy examination revealed nose and thoracic cutaneous masses, abdominal subcutaneous mass, and multiple nodules in the liver and lungs. Malignant melanoma was found in the nose cutaneous mass and to have metastasized to the liver, lungs, kidneys, adrenal glands, mammary glands and left mandibular lymph node. The neoplastic cells were labeled for vimentin, melanoma, and S100. The cutaneous mass in the thoracic area consisted of spindle shaped neoplastic epithelial cells and was diagnosed as trichoblastoma. Mammary gland adenoma was observed in the abdominal subcutaneous mass. This is the first report of primary three neoplasms of malignant melanoma, trichoblastoma and mammary gland adenoma in a Eurasian otter.

We report the complete mitochondrial genome sequence of the endangered Eurasian otter, Lutra lutra. The complete mitochondrial genome is 16,537 bp in length and contains 13 protein-coding genes, 22 transfer RNA, two ribosomal RNA, and one control region. The mitogenome is A + T rich, with a composition of 32.2% A, 27.5% C, 14.5% G, and 25.8% T. Phylogenetic analysis based on 13 protein-coding mitochondrial genes of Mustelidae supports the conventional systematic treatment with eight subfamilies. Lutra lutra is closely related to Lutra sumatrana and the subfamily Lutrinae was closely grouped with the Ictonychinae. This study provides genetic and taxonomic information for future studies of Eurasian otters and the Mustelidae.

Eurasian otters Lutra lutra are listed as Near Threatened on the IUCN Red List and are imperiled by habitat loss, water pollution, and poaching. Harassment and attacks by stray animals are also recognized threats to the health of wild Eurasian otters. Pulmonary hair embolism is a possible complication in animals with deep traumatic injury, but to date no cases have been reported in wildlife. A free-ranging, adult male Eurasian otter was rescued due to severe emaciation and multiple bite wounds. The otter died 3 d after rescue and was necropsied. Grossly, a 1.5 × 1.5 × 1.5 cm firm nodule was observed in the left cranial lung lobe. Histologically, a fragment of hair shaft surrounded by multinucleated foreign body giant cells was observed in a medium-sized vein, and extensive eosinophilic infiltration was noted in the adjacent vascular wall and lung parenchyma. Based on the gross and histological findings, the pulmonary lesion was consistent with eosinophilic pneumonia and vasculitis induced by hair embolism. The presence of well-formed multinucleated foreign body giant cells and eosinophils may imply a late stage of foreign body reaction, and thus the presumptive source of hair embolism is an animal bite. This is the first report of pulmonary hair embolism associated with animal bite in a rescued free-ranging Eurasian otter.

This study investigated the current distribution of otters (Lutrinae) in all states of Peninsular Malaysia. Four species of otters have been recorded in Peninsular Malaysia in the past based on field survey methodology, namely the Asian small-clawed otter (Aonyx cinereus), smooth-coated otter (Lutrogale perspicillata), hairy-nosed otter (Lutra sumatrana), and Eurasian otter (Lutra lutra). This study aims to determine the current number of otter species and their distribution in Peninsular Malaysia through molecular approaches using D-loop and Cyt b loci of mitochondrial DNA sequences. Our findings indicate that 337 samples were identified as three species of otter that are currently distributed in Peninsular Malaysia: A. cinereus (112 samples), L. perspicillata (218 samples), and L. sumatrana (7 samples). All three species can be found in Perak, Kelantan, Pahang, Selangor, and Johor while other states only contained two species (A. cinereus and L. perspicillata). Seven sympatric locations were recorded between two or three species: Tumpat and Kg. Padang Salim (Kelantan), Penarik and Sg. Kemaman (Terengganu), Taman Negara (Pahang), Tg. Piai (Johor), and Kuala Gula (Perak). The discovery of L. sumatrana in this study has confirmed that this species is still present in Peninsular Malaysia. However, L. lutra was not observed in this study. Our findings successfully highlight the diversity and distribution of Peninsular Malaysian otters that suggest the importance of continuous assessment and population status of otters to ensure their ongoing survival in Peninsular Malaysia.

We characterized the genetic structure of the Eurasian otter (Lutra lutra) meta-population living in the core of its Italian distribution range providing results from 191 fresh spraints, collected from 24 watercourses included in Southern Italy. Furthermore, according to ecological corridors and barriers, we discuss the likely ways of movement and possible evolutionary fate of these populations. We genotyped 136 samples using 11 Lut microsatellite nuclear markers amplified from faecal dna. Microsatellites were moderately variable (Ho = 0.45; He = 0.46), with a total number of alleles and average number of alleles per locus in the meta-population of 50 and 4.54, respectively. No significant heterozygosity excess was observed in meta-population suggesting no recent population bottlenecks. Bayesian clustering discriminated a sub-structuring of the meta-population in five putative clusters, indicating that local populations are genetically differentiated: three of these seem to be identifiable with geographically defined sub-populations (from the Cilento, Agri and Basento river basins). The fourth is represented by multiple sub-populations with admixed genotype, that include genotypes from the Lao, Sinni and Abatemaco river basins, living in a landscape with the higher environmental permeability. Landscape genetic analysis could provide evidence of an unexpected ecological corridor: the seacoast, highlighted, for the first time as a new way for the dispersion of the South-Italian otters. Deepening the knowledge of these perspectives is crucial to identify solid strategies aimed at the future health of the populations of the Italian otters, by restoring dispersal corridors and managing the watercourses.

This study was conducted to identify the habitat selection by the Eurasian otter (Lutra lutra) depending on the type of waterfront in the Geumgang River region near the Daecheong Dam. As a result of the habitat suitability analysis, the suitable region (very suitable and suitable) was found to be 48.8%, accounting for 217.9km of the total of 446.3 km, and 17.2% or 76.5km of the total region was found to be unsuitable (unsuitable and very unsuitable). As a result of analyzing the types of waterfront area, it was found in the order of wetland> forest> grassland> bare land and the number of traces of otters per kilometer of each type of the waterfront areas was found to be rockface (36.0), bare land (0.92)> forest (0.8), grassland (0.76)>, and wetland (0.75). The result shows a relatively high number of otter traces for rockface compared with other waterfront types, though the composition ratio of rockface takes only a small part of the overall waterfront areas. It is because rockfaces are safer from man-made disturbance, while providing homes and shelters, as well as locating nearby open water which has abundant amount of food resources, compared with other types of waterfront.

Otter diet in reservoirs is known to experience seasonal changes. We selected a reservoir with a large population of exclusively wintering great cormorants and seasonal changes in stored water volume to test the relative influence of abiotic and biotic factors on otter foraging ecology. DNA metabarcoding of otter spraints revealed a dietary change from autumn to winter. Otters had a diet dominated by the exotic goldfish in autumn, but predated intensively on the native northern straight-mouth nase in winter. This change was likely caused by predation of cormorants on goldfish and to fish biology. Secondly, macroscopic analysis of spraints revealed that otters shifted from a diet dominated by fish (in terms of biomass) to a diet dominated by red swamp crayfish during spring–summer, when the latter became overabundant. As revealed by modelling, this second shift was most likely influenced by the sudden increase in stored water volume in spring, but also by the cumulative effect of cormorant predation on fish during autumn–winter. Macroscopic analyses of otter spraints collected in a second reservoir with no cormorants revealed a lack of seasonality. Hence, the combined influence of both biotic and abiotic factors explained otter diet seasonality in a lentic-water novel ecosystem.

Detection probability is an important input when studying and managing species. It reduces the miscalculations of the estimates of occupancy, population abundances and their trends inherent to the imperfect detection during sampling. However, detection probability may vary in relation to environmental and biological factors, such as the presence of other species of similar ecological niche. We used a two-species single-season occupancy model to analyse the detection probability of the native Eurasian otter Lutra lutra and the invasive American mink Neovison vison in the northeast of the Iberian Peninsula and to test for potential differences in their detection when co-occurring and when not. Despite the known behavioural change of American mink towards a more terrestrial diet and a more diurnal activity pattern in the presence of Eurasian otter, their detectability did not vary when both species co-occurred versus when they did not. However, we observed seasonal differences in the probability of detection. Specifically, the probability of detection was higher in winter for both species. Furthermore, Eurasian otter was more often detected in sites with clay substrate, whereas American mink in sites with clay and rocks. These results indicate that the effectiveness of monitoring of Eurasian otter and American mink remains independent of the species co-occurrence. Yet, seasonal variations in the detection should be taken into account when monitoring.

Growing human-wildlife conflicts and legal conservation obligations increased the need for precise information on Eurasian otter (Lutra lutra) population parameters for species status assessment and wildlife management measures. Scat surveys have become the method of choice to monitor species distribution range, abundance and habitat use. Although methodological concerns exist, scat abundance is often used as main indicator for otter population estimates and trends. To evaluate whether scat counts serve as good proxy for otter densities in linear stream habitats, we modelled the relationship between old/fresh scat abundance and otter numbers on two spatial scales, including also seasonal effects. Actual otter densities and marking behaviour were ascertained by genotyping of otter faeces collected at 218 marking sites along 132.6 km of four salmonid streams. Otter densities in our study areas ranged from 0.16 to 0.28 otters per stream kilometre. The age of scats and the level of spatial scale were determining factors when evaluating the suitability of scat abundance as index for otter densities. Covering large parts of an otter’s territory, fresh scat abundance increased with otter density, irrespectively of season. On the spatial scale of single marking sites, the relationship was not well supported, and no relationship could be found when using old scats in the models. Otter marking behaviour and differences in marking site use intensity, as well as seasonal differences in traceability and accumulation of old scats were discussed to bias the relationship between scat abundance and otter numbers.

1. The Eurasian otter (Lutra lutra), Smooth-coated otter (Lutrogale perspicillata) and Asian small-clawed otter (Aonyx cinereus) have all been previously reported from the Indian state of Uttarakhand. However, little information is available about these species’ current distribution in a mountainous region that is subject to increasing human-induced stressors (e.g. hydropower plants, pollution, sand and boulder mining, destructive fishing techniques, poaching). 2. Due to the important role of these otters in structuring riverine food webs (particularly taking account of their roles as top carnivores), it is critical that these animals receive suitable protection in the face of a projected rise in temperature, change in precipitation patterns, and associated river flows in this Himalayan biodiversity hotspot. This study assesses otter distribution in four rivers of Uttarakhand, as a basis for informing future conservation actions. 3. Field surveys were conducted (October 2018 – January 2019) in four Himalayan rivers (reaches of the Kosi, Ramganga, Khoh and Song Rivers), supported by semi-structured interviews (N=379) conducted with members of local communities to ascertain qualitative data on views and perceptions of otter species. In addition, community-based otter awareness camps were organized for local youths (N=105), adults (N=115) and school children (N=256 covering 10 schools). Habitat suitability maps were created using remote sensing data, survey findings and a Geographic Information System (GIS) to provide information about priority river reaches to be targeted for future conservation efforts. 4. This study provides critical interdisciplinary baseline information to guide decision-makers towards developing a targeted, otter-specific conservation program for this important Himalayan biodiversity hotspot. The otter conservation education programs conducted during this study resulted in a proposal to set up a community-based conservation initiative (CBCI) to monitor and report otter sightings from the area, potentially representing a way forward for achieving simultaneous otter conservation and associated ecosystem benefits for local communities.

The Eurasian otter (Lutra lutra) suffered a dramatic population decline in southern Scandinavia in the twentieth century and was subsequently presumed extinct in the Danish archipelago. However, in the 1990s, evidence of a relict population on the island of Zealand was reported. The vulnerability of this small population may be exacerbated by seawater barriers preventing migration to and from the island. To assess whether the Danish Straits have and will present a barrier to future otter migration, we used geometric morphometrics to investigate population structuring and assess the level of differentiation of otters across southern Scandinavia. Utilizing museum collections, we analysed 137 otter skulls from Zealand, Jutland, and southern Sweden. Statistical analyses showed highly significant shape differences between all three localities, likely reflecting migration between the three areas has historically been low. High jack-knife reclassification success rates support divergence among the areas, and directionalities of the vectors describing regional shape differences indicate that differences do not reflect isolation-by-distance.

Gammacoronavirus and Deltacoronavirus are known to circulate among wild birds (Hepojoki et al., 2017;Canuti et al., 2019). [...]a hypothetical transmission of CoVs between wild birds and mammals in the marine environment may occur, as for influenza A virus (Runstadler and Puryear, 2020). Occasional predation of bats has been reported for an aquatic mustelid that can be observed in the sea: the Eurasian otter (Lutra lutra) (Forman et al., 2004). [...]dolphin morbillivirus reservoirs were recently also detected in Eurasian otters along the Mediterranean Sea coast (Padalino et al., 2019). Every year thousands of MA-BA are stranded on the beaches around the world (Alvarado-Rybak et al., 2020), and these animals are generally studied by different local scientific institutions and agencies. [...]a wide range of molecular and cellular tools for CoV detection is now available, either developed for COVID-19 diagnosis, or for CoVs (Woo et al., 2014). [...]marine interdisciplinary science can contribute to answer questions concerning the COVID-19 pandemic and prepare us for future zoonotic disease epidemics by (1) identifying potential CoV reservoirs in the marine environment, and (2) evaluating CoV transmission from MA-BA to humans, from humans to MA-BA, and between MA-BA.

Eurasian otters (Lutra lutra) are known to make extensive use of reservoirs in the Iberian Peninsula, where they forage preferentially on small-size fish (10–20 cm). We hypothesized that the usual consumption of small-size fish by otters in reservoirs is not due to prey size preference, but rather to a higher level of difficulty in capturing larger prey. We studied otter diet in a reservoir that experienced an abrupt drop in stored water caused by an unusually severe drought. We compared relative prey size, hunting success, and diving times between the year of the drought (2017) and two standard rainfall years (2015 and 2016). Otters ate a similar proportion of small and large fish during the drought instead of predominantly eating small fish. Mean diving time during the drought was similar to that of the standard climatic years, indicating a similar physiological cost of capture between small and large fish. Otters had higher hunting success in the drought year (89%) than in the standard years (63%) regardless of prey size. This suggests a higher level of catchability of both fish size classes during the drought as the water level was lower. Results suggest that the usual consumption of small-sized fish by otters in reservoirs could not be related to preference or relative abundance but rather to the difficulty of capturing large-size fish when water levels are high.

In order to conserve wetlands, it is crucial to have reliable knowledge of population and community processes. Our aims were to explore the dietary differences that allow coexistence of carnivores belonging to different trophic guilds, and to detect the presence of the relict Pannonian root vole subspecies (Microtus oeconomus méhelyi) within the Kis-Balaton marshland (Hungary). The 1-year dietary study was based on faecal analysis of the main mammalian predators of the area, i.e. red fox (Vulpes vulpes), martens (Martes spp.) and Eurasian otter (Lutra lutra). Small mammals, mainly Microtus species and water vole (Arvicola amphibius), were the primary foods for each carnivore. The dietary pattern of the otter was unique among European studies. Analysis of frequency data and estimated consumed biomass data revealed significant interspecific and intraspecific (seasonal) foraging differences among the three predators. Based on diets and live trapping of small mammals, foxes and martens selected voles, they selected against mice and shrews. The selection of the root vole was confirmed from faecal samples of foxes and martens. Consequently, faecal analysis of common carnivores can be an effective monitoring tool in providing data about prey species under special habitat conditions. Thus, it may contribute to wetland conservation indirectly.

The riparian vegetation belt is one of the few remaining structures that provide coverage for wildlife in many anthropogenic landscapes. It provides shelter for many species and functions as corridors for dispersal. However, this landscape is increasingly utilised by humans for leisure activities. The loss of riparian vegetation with a concurrent increase of human disturbance in these habitats can pose a serious threat to wildlife. One of the species potentially affected is the Eurasian otter Lutra lutra. In the Alps, otters are nocturnal and rest during the day when human activity is high. To study the impact of human presence on resting site selection in otters, we radio-tracked nine otters for up to 30 months in the eastern Central Alps of Austria. We analysed resting site selection in relation to human disturbance. Altogether, we identified 285 resting sites scattered throughout the territories of the individual otters at an average distance of 144 m between sites. Almost all the resting sites (95%) were located in the natural riparian vegetation, making this the most important habitat for resting otters. We found evidence that human disturbance within these riparian habitats shapes resting site selection. Otters preferred narrow riparian strips when there was no human presence, but selected areas with a wider vegetation belt when the disturbance level increased. Outside the vegetation period, animals rested below ground more often than above, which suggests that vegetation also functions as visual cover. Our study highlights the importance of the restoration of the natural riparian vegetation belt for the protection of wildlife, particularly where human activities are intense. We provide information for the effective conservation management of otters considering the combination of spatial distribution of resting sites and specific habitat requirements in the presence of human disturbance. Areas of conservation importance chosen in this way are likely to benefit other wildlife that utilise the riparian vegetation belt.

In South Korea, the Eurasian otter (Lutra lutra (Linnaeus, 1758)), a semi-aquatic carnivore, is found mainly in lower order streams that tend to have a low abundance of preferred prey fish species. To investigate the relationship between resource use and availability, we used DNA barcoding to identify otter diet items in 24 otter spraints (faeces) from 16 sites along the Nakdong River basin from 4 to 6 June 2014. At these sites fish availability was assessed using scoop nets and casting nets. Fish formed the bulk of otter diet, which included also frogs, mammals, and reptiles. By DNA barcoding (success rate: 72.38%), we identified 79 prey items from 105 bone remains. The diet comprised mostly fish, but frogs, mammals, and reptiles were also identified. The fish fauna and otter diet composition differed significantly. Across the study sites, members of the Cyprinidae dominated in netted samples, but occurred less frequently in otter diet. Because most Cyprinidae are fast swimmers, otters also fed on benthic fishes and frogs, suggesting limited foraging flexibility in otters and specialization on more slowly moving prey.

Understanding public preferences is necessary for managing conservation conflicts. We used a face-to-face survey of 514 Greek residents to investigate preferences for managing damage to fis...

The most important Italian population of the Eurasian otter (Lutra lutra) occurs in the southern part of the peninsula with two isolated sub-populations of about 250 adult individuals. The Eurasian otter is considered to be near threatened and it is a fully protected species. The aims of this study were to investigate for the first time the occurrence and characterize the parvoviruses included in the species Carnivore protoparvovirus 1 in seven carcasses of road-killed Eurasian otters from the southern Italy. Carnivore protoparvovirus 1 are responsible for acute gastroenteritis and leukopenia in pets and free-ranging carnivores. Initial screening of tissue samples by real-time PCR revealed CPV/FPV DNA in tissue samples of five Eurasian otters; three of them, showed co-infections by both CPV and FPV. Among the five positive Eurasian otters, we successfully obtained six DNA sequences from four individuals including two CPV-2a, one CPV-2b, one CPV-2c, and two FPV sequences. Comparison of these sequences with 250 VP2 gene sequences deposited in the GenBank database, showed 10 nt differences resulting in two synonymous and eight non-synonymous substitutions. On the basis of these results, two sequences here found were characterized as new CPV-2a, one was characterized as new CPV-2b variant, and one was characterized as FPV-like mutant. The last two sequences belong to a FPV and CPV-2c strain respectively. Carnivore protoparvovirus 1 is reported for the first time in the Eurasian otter showing high infection value in southern Italy. Occurrence of this infection should be studied further to understand its possible pathogenicity and virulence to the fragile and isolate Eurasian otter population which live in southern Italy.

The Japanese otter (Lutra nippon), once inhabited in most islands of Japan, is now considered as an extinct species. Although the Japanese otter is regarded as a distinct species from the Eurasian otter (L. lutra), its phylogeny and taxonomic status are based on limited information on morphological and genetic data, and thus further clarification is required. Here, we assessed the phylogenetic relationship among the genus Lutra and taxonomic status of L. nippon by using the complete sequences of cytochrome b gene of its holotype. The present phylogenic trees supported that the genus Lutra specimens largely formed monophyletic group, with L. sumatrana as a basal to other Lutra species. Within Lutra species, L. nippon was distantly related with L. lutra. The European otter population of L. l. lutra were clustered together with its subspecies, L. l. chinensis rather than the same subspecies, Korean otter population. The discrepancy between the genetic data and traditional taxonomy justifies the necessity of reexamination of the current subspecific classification system of Eurasian otters. Level of genetic divergence between the holotype of L. nippon and L. lutra was two to three-fold lower than those among the other sister species of the Lutrinae. Based on the level of divergence between the L. nippon and L. lutra, and insufficient evidence of morphological difference between them, it is suggested that designation of Japanese otter as a separate species from L. lutra will be reconsidered.

With the aim of examining how Eurasian otters (Lutra lutra) face human-mediated environmental alterations, we assessed their diet by spraint analysis on the River Ticino (NW Italy), where this mustelid has been reintroduced in 1997. From March 2016 to March 2017, a total of 101 spraints was found in 50% of 32 sampling stations (mean length ± SD = 567 ± 263 m). Fish formed the bulk of otter diet (95% of the estimated mean percent volume, mV%). Cyprinids were the most preyed fish (mV% = 44.9), followed by European catfish Silurus glanis (mV% = 24.9%) and eel Anguilla anguilla (mV% = 8.5). Introduced European catfish is an invasive species, which can deeply alter the composition and structure of local fish communities and accumulate large amounts of metals and pollutants through the trophic chain. We also recorded for the first time microplastic particles (

In Italy, the Eurasian otter, Lutra lutra (Linnaeus, 1758) (Carnivora Mustelidae), occurs with two separated populations in the southern regions and recently it has also re-colonized the north-eastern fluvial networks. Here, we present the first photographic evidence of the Eurasian otter presence along a stretch of the Calore river (Campania region, Southern Italy), where this species was generically reported in previous study. Our findings enlighten that the Calore river network might play an important role for the conservation and expansion of this species in Campania.

The Eurasian otter (Lutra lutra) is among the most endangered mammals in Italy, its population being isolated and genetically distinct from other European populations. Yet, its ecology and behavior are largely unknown in Italy, preventing its much-needed effective conservation. We radio-tracked one male and one female otter daily in Southern Italy, for 1 year and 8 months, respectively. The male and female used nearly 30 and 20 km of river, respectively. The extension of the ranges varied among seasons. The male was more conservative in its spatial utilization, being mostly located around a trout farm. These first direct data on space use by wild Italian otters provided preliminary information potentially useful for a sound management of this endangered population.

The status of Asian populations of the Eurasian otter Lutra lutra is largely unknown. Since its designation as a Natural Monument (in 1983) and as Endangered (in 1997) in South Korea the authorities there have been trying to conserve and recover the species. We conducted a national otter survey by standard methods in 2017 and compared the current otter distribution to those recorded in a previous survey (2010). We found otter signs in 84.5% of 1,105 10 × 10 km grid cells, with the highest sprainting intensity in the south-west in the Yeongsan River Basin and on the south coast, where we recorded 7.05 and 6.26 spraints/site, respectively. Despite relatively low spraint densities, the otter has expanded its range since 2010 by colonizing urban areas. This trend suggests that South Korea could be a source area for the recovery of the Eurasian otter in East Asia.

Accidents at mines involving stored tailings have produced catastrophic environmental damage. In April 1998 the dam of the Aznalcóllar mine tailings pond in the surroundings of the Doñana National Park (southwestern Spain) broke, discharging into the Guadiamar River more than 6 million m3 of toxic mud and acidic water with high concentrations of heavy metals and arsenic. We used the Eurasian otter (Lutra lutra) as sentinel species to assess the potential impact of the toxic spill on the river ecosystems and their recovery with time by studying the spatial and temporal variation (1999-2003, 2006) of selected trace element (Cu, Zn, Cd, Pb and As) concentrations in feces. Throughout the sampling period, the highest heavy metal and As levels were found in the most spill-affected reaches of the Guadiamar River (i.e., the Middle and, to a lesser extent, the Lower reaches), pointing out the mining accident as the main origin of the contamination. Overall, levels of trace elements decreased with the time elapsed since the toxic spill, except for Cd (F1,352 = 0.29, P = 0.59). However, rebounds for some elements (Pb, As, and Cu) were also observed, especially in the Middle and Lower reaches of the river, which might be attributed to the residual contamination in abiotic compartments and/or new inputs from industrial and agricultural activities in the nearby areas. Concentrations were relatively high when compared to those reported for both our reference area (Guadalete River) and other metal-polluted zones. We found that the estimated amounts of Pb and As ingested during the first years after the spill in the Guadiamar Middle reach would be high enough to cause reproductive issues. This could affect the local population recovery, although evidence on distribution range and numbers suggests otherwise, with thriving populations at regional scale. Our results support the role of otters as sentinel species for biomonitoring contaminants and thus to evaluate fluvial ecosystem health.

Understanding the gut microbiota characteristics of endangered species such as the Eurasian otter (Lutra lutra), especially in their early stages of life, could be essential for improving their management and ex situ conservation strategies. Here, we analyzed the gut microbiota diversity, composition, and function of captive Eurasian otters at different ages using high-throughput 16S rRNA gene sequencing. We found that: (1) Clostridiaceae was abundant in all age stages; (2) Lactococcus in cubs is thought to predominate for digesting milk; (3) bacteria associated with amino acid metabolism increase with age, while bacteria associated with carbohydrate metabolism decrease with age, which is likely due to decrease in dietary carbohydrate content (e.g., milk) and increase in dietary protein contents (e.g., fishes) with age; and (4) fish-related bacteria were detected in feces of healthy adults and juveniles. Overall, the gut microbiota of captive Eurasian otters was taxonomically and functionally different by age, which is thought to be attributed to the difference in the diet in their life stages. This study provided baseline information regarding the gut microbiota of Eurasian otters for the first time and contributes to improvement in their management in captivity. Supplementary Information The online version contains supplementary material available at 10.1007/s00203-021-02526-w.

Declining emissions of persistent organic pollutants (POPs), subject to international control under the Stockholm convention, are not consistently reflected in biotic samples. To assess spatial and temporal variation in organochlorine pesticides and PCBs in UK freshwaters, we analysed tissues of a sentinel predator, the Eurasian otter, Lutra lutra between 1992 and 2009. Past declines in otter populations have been linked to POPs and it is unclear whether otter recovery is hampered in any areas by their persistence. PCBs, DDT (and derivatives), dieldrin and HCB were detected in over 80% of 755 otter livers sampled. Concentrations of ∑PCB, ∑DDT and dieldrin in otter livers declined across the UK, but there was no significant time trend for ∑PCB-TEQ (WHO toxic equivalency, Van den Berg et al., 2006) or HCB. In general, higher concentrations were found in the midlands and eastern regions, and lowest concentrations in western regions. Concentrations of PCBs and HCB in otters increased near the coast, potentially reflecting higher pollutant levels in estuarine systems. Decades after legislative controls, concentrations of these legacy pollutants still pose a risk to otters and other freshwater predators, with spatially widespread exceedance of thresholds above which reproduction or survival has been reduced in related species.

Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is a widespread zoonosis capable to affect a wide range of warm-blooded vertebrates. In the past two decades, T. gondii emerged as a significant aquatic pathogen with some pathogenic atypical genotypes isolated and characterized from stranded marine mammals. In contrast, no information is available for mammals in freshwater environment. Although, otters are considered highly susceptible to T. gondii infection, to date molecular evidence of T. gondii in Eurasian otter (Lutra lutra) does not exist. We report the first molecular evidence of T. gondii in a free-ranging Eurasian otter from southern Italy, and characterized the present strain as a mixed genotype type II variant, with all loci type II except PK1 (locus sequence corresponding to type II variant B), B1 (locus sequence corresponding to type II/X A), and C29-2 (locus with SNPs). Our results indicate circulation of a type II variant in freshwater environment which suggests potential risk of transmission to animals and humans. The finding of a potential pathogenic strain is of great concern for future conservation programs of the critically endangered Eurasian otter in southern Italy.

A river otter hemimandible has been rediscovered during the revision of the historical collections of G.A. Blanc from Grotta Romanelli, complementing the ongoing multidisciplinary research fieldwork on the site. The specimen, recovered from the level G (“terre rosse”; early Late Pleistocene or late Middle Pleistocene), is here assigned toLutra lutra. Indeed, morphological and morphometric comparisons with other Quaternary Lutrinae fossils from Europe allow to exclude an attribution to the relatively widespread and olderLutra simplicidens, characterized by distinctive carnassial proportions. Differences withCyrnaonyx antiqua, which possessed a more robust, shellfish-feeding dentition, support the view of a successful niche repartition between the two species during the late Middle to Late Pleistocene of Europe. The occurrence ofLutra lutrafrom the “terre rosse” of Grotta Romanelli suggests deep modifications of the landscapes due to the ecological adaptation of the taxon, and indicates that the Eurasian otter spread into Europe at the Middle–Late Pleistocene transition.

The Eurasian otter (Lutra lutra) is a semi-aquatic predator that lives in a wide range of aquatic habitats. Knowledge of the diet of predators is essential for the management and conservation of the species and their habitats. We assessed the diet of otters in fifty-three faecal samples (spraints) by morphological analysis of undigested prey remains and by DNA metabarcoding approaches with two different blocking primers. The blocking primers were shown to be similarly effective in repressing host DNA, improving amplification of non-host taxa. The analyses were conducted to compare the accuracy of the two methods. The prey items were categorized to the highest possible taxonomic resolution, and relative frequency of occurrence was applied in order to compare the morphological and DNA results. The bulk score for difference prey items in the spraints was based on volume estimates in macroscopic observations. The two methods had an overlap of identified prey species ranging from 69.9 to 72.9% (depending on the kind of primers) meaning that a large portion of prey items found by one method was replaced by other prey items in the other method and that most prey items found through DNA-metabarcoding are considered new when compared with the morphological analysis. Therefore, applying both morphological and DNA analysis is crucial in order to determine the diet of otters and, possibly, other predatory species.

In the past the European otter Lutra lutra was distributed throughout most of Europe but since the 1980s its distributional range has been reduced. Currently, the otter population is increasing. Conservation efforts have been implemented, however due to the natural elusiveness of the species it is difficult to monitor. Non-invasive sampling has proven to be the most effective method to derive population parameters such as presence/absence, genetic variability and population structure in European otters. The method to collect non-invasive samples is robust and provides reliable data. This study investigates the validity of the present state-of-The-Art method of identifying otter feces, and suggests modifications and improvements of the method. Results from the comparison of field collected data and data derived from a blind test show that the method is applicable in areas abundant with otters, however the method loses its power in the periphery of the distributional range. In these areas, it would be relevant to supplement traditional sampling with DNA analysis to verify the identification of the sample.

The use of non-invasively collected DNA source material for genetic and genomic applications is usually characterized by low target DNA concentration and quality, genotyping errors and cost-intensive lab procedures. However, for otters (Lutrinae) as elusive species of conservation concern, genetic non-invasive sampling has become an important tool to study their ecology and demography. To increase cost-efficiency of monitoring programmes and to promote the expansion of genomic approaches to non-invasive samples, we aimed to refine sample collection and preparation. Therefore, we examined the effects of intrinsic sample characteristics (including diet), environmental conditions in the field and sample treatment in the molecular laboratory on the success of genotyping and allelic dropout (ADO) rates using microsatellite markers in 1970 fresh Eurasian otter (Lutra lutra) scats. Using fresh samples only, we probably eliminated one of the most important impediments of genotyping DNA from otter faecal samples beforehand. But, we observed higher genotyping success and lower ADO rates for anal glad secretions and faecal samples containing high proportions of mucus. Moist conditions during sample collection may promote DNA degradation and PCR inhibition, leading to decreased genotyping success rates. ADO was further affected by the type of extraction kit. However, a high proportion of variance remaining unexplained by our models implied that additional parameters were acting (amount of PCR inhibitors, non-uniform distribution of intestinal cells, efficiency of PCRs, specific microclimate at marking sites). We summarized influential factors maximizing genotyping quality of otter scats and give recommendations for sample collection, storage and DNA extraction based on our results and current literature.

In the UK, the native European otter (Lutra lutra) and invasive American mink (Neovison vison) have experienced concurrent declines and expansions. Currently, the otter is recovering from persecution and waterway pollution, whereas the mink is in decline due to population control and probable interspecific interaction with the otter. We explored the potential of DNA metabarcoding for investigating diet and niche partitioning between these mustelids. Otter spraints (n = 171) and mink scats (n = 19) collected from three sites (Malham Tarn, River Hull and River Glaven) in northern and eastern England were screened for vertebrates using high-throughput sequencing. Otter diet mainly comprised aquatic fishes (81.0%) and amphibians (12.7%), whereas mink diet predominantly consisted of terrestrial birds (55.9%) and mammals (39.6%). The mink used a lower proportion (20%) of available prey (n = 40 taxa) than the otter and low niche overlap (0.267) was observed between these mustelids. Prey taxon richness of mink scats was lower than otter spraints and beta diversity of prey communities was driven by taxon turnover (i.e. the otter and mink consumed different prey taxa). Considering otter diet only, prey taxon richness was higher in spraints from the River Hull catchment and beta diversity of prey communities was driven by taxon turnover (i.e. the otter consumed different prey taxa at each site). Studies using morphological faecal analysis may misidentify the predator as well as prey items. Faecal DNA metabarcoding can resolve these issues and provide more accurate and detailed dietary information. When scaled up across multiple habitat types, DNA metabarcoding should greatly improve future understanding of resource use and niche overlap between the otter and mink.

Three-dimensional (3D) surface scans were carried out in order to determine the shapes of the upper sections of (skeletal) crania of adult Eurasian otters (Lutra lutra) from Great Britain. Landmark points were placed on these shapes using a graphical user interface (GUI) and distance measurements (i.e., the length, height, and width of the crania) were found by using the landmark points. Male otters had significantly larger skulls than females (P &lt, 0.001). Differences in size also occurred by geographical area in Great Britain (P &lt, 0.05). Multilevel Principal Components Analysis (mPCA) indicated that sex and geographical area explained 31.1% and 9.6% of shape variation in &ldquo, unscaled&rdquo, shape data and that they explained 17.2% and 9.7% of variation in &ldquo, scaled&rdquo, data. The first mode of variation at level 1 (sex) correctly reflected size changes between males and females for &ldquo, shape data. Modes at level 2 (geographical area) also showed possible changes in size and shape. Clustering by sex and geographical area was observed in standardized component scores. Such clustering in a cranial shape by geographical area might reflect genetic differences in otter populations in Great Britain, although other potentially confounding factors (e.g., population age-structure, diet, etc.) might also drive regional differences. This work provides a successful first test of the effectiveness of 3D surface scans and multivariate methods, such as mPCA, to study the cranial morphology of otters.

Background Captive and free-ranging wild mammals have been recognized as potential reservoirs of Leishmania infantum infection. The aim of this study was to describe the first clinical case of leishmaniosis in the Eurasian otter. Case presentation A case of clinical leishmaniosis is reported in a 4-year-old male Eurasian otter housed at a wildlife park (Murcia, South Eastern Spain). The Eurasian otter showed bilateral epistaxis, anorexia, apathy, and weight loss. A complete blood cell count and biochemical analyses revealed hyperproteinemia, hyperglobulinemia, decreases of paraoxonase-1, increases of haptoglobin and ferritin, and proteinuria. Bilateral nephropathy with hydronephrosis, mesenteric lymphadenomegaly, and ascites were also observed. L. infantum infection was confirmed by microscopy (amastigotes were detected in macrophages from spleen aspirate), molecular diagnosis (L. infantum DNA was detected by real-time polymerase chain reaction), and serology (anti-Leishmania IgG2 antibodies were detected by time-resolved immunofluorometry). The animal was treated with allopurinol for 3 months and gained weight, the epistaxis disappeared, and the ferritin concentration decreased. Conclusions This is the first report of clinical leishmaniosis in the Eurasian otter. Our results suggest that Eurasian otters are susceptible to infection with L. infantum and can develop clinical leishmaniosis in endemic areas.

Cryptic mammals with semi-aquatic habits, like otters, are notoriously difficult to study. Elusive behaviour, low population density, nocturnal habits and the type of continental habitat that characterize this group of species make the estimation of their population density an arduous task. Passive infrared-triggered camera devices are a non-invasive methodology that may present key advantages for the study of otter density. We have evaluated its use for the detection and estimation of the density of the Eurasian otter (Lutra lutra) in seasonal intermittent Mediterranean rivers, where the presence of dry riverbed sections between pools is usual, due to the discontinuity of flow during the summer drought. Through six camera-trapping surveys carried out in the Yeguas River (South Spain), we evaluated the efficiency of camera-trapping in different scenarios of methodological design, including a comparison with the visual census method. The results indicated that camera-trapping can be an optimal method to estimate otter abundance if some conditions are achieved, being the most important to use camera devices with fast trigger speed (0.1–0.2 s), deployed in key places over the river bed. In the case of our best-designed surveys, related to effort and efficiency of camera devices, we found that detection probability could reach asymptotic values in a relatively short time of 1 week, with negligible effects of imperfect detection. Considering the robustness of the collected data from camera-trapping (larger sample size and sampling periods), the density estimation from camera trap method (0.43 otters/km and day) was more accurate than estimation from visual census (0.12 otters/km and day). Camera traps can provide valuable information not only for population size and trends but also for other key demographic parameters, such as sex-ratio and reproduction and activity rhythms.