Low but highly geographically structured genomic diversity of East Asian Eurasian otters and its conservation implications

Populations of Eurasian otters Lutra lutra, one of the most widely distributed apex predators in Eurasia, have been depleted mainly since the 1950s. However, a lack of information about their genomic diversity and how they are organized geographically in East Asia severely impedes our ability to monitor and conserve them in particular management units. Here, we re-sequenced and analyzed 20 otter genomes spanning continental East Asia, including a population at Kinmen, a small island off the Fujian coast, China. The otters form three genetic clusters (one of L. l. lutra in the north and two of L. l. chinensis in the south), which have diverged in the Holocene. These three clusters should be recognized as three conservation management units to monitor and manage independently. The heterozygosity of the East Asian otters is as low as that of the threatened carnivores sequenced. Historical effective population size trajectories inferred from genomic variations suggest that their low genomic diversity could be partially attributed to changes in the climate since the mid-Pleistocene and anthropogenic intervention since the Holocene. However, no evidence of genetic erosion, mutation load, or high level of inbreeding was detected in the presumably isolated Kinmen Island population. Any future in situ conservation efforts should consider this information for the conservation management units.

Applying molecular genetic data at different scales to support conservation assessment of European Habitats Directive listed species: A case study of Eurasian otter in Austria

Evaluating intraspecific genetic structure and diversity is fundamental to assessing a species' conservation status, but direct incorporation of such information into legal frameworks such as the EU's Habitats Directive is surprisingly rare. How genetic structure aligns with EU member state boundaries or biogeographic regions may be very important in designing management plans or achieving legislative goals. The Eurasian fish otter experienced a sharp population decline during the 20th century but is currently re-expanding in several countries. The species is listed under Annex II and IV of the European Habitats Directive, and member states are obliged to assess the species separately across different biogeographic regions. We genotyped 2492 otter spraints across four provinces in Austria, collected between 2017 and 2021. A total of 384 different genotypes were identified, supporting densities along river habitats from 0.1 to 0.47 otters per river km (mean: 0.306), with a resampling-based simulation supporting limited density overestimation at survey lengths of 20 km or more. Three distinct genetic clusters were revealed, two of them presumably reflecting two relict populations whereas the source of the third cluster is unknown. The geographic extent of the three clusters does not coincide with provincial or biogeographic boundaries, both relevant for assessment and management within existing national or European legislative frameworks. We advocate more consideration of genetic structure in the assessment and conservation management planning of species listed in the European Habitats Directive.

The Different Fate of the Pyrenean Desman (Galemys pyrenaicus) and the Eurasian Otter (Lutra lutra) under Climate and Land Use Changes

Climate and land use change can affect biodiversity in different ways, e.g., determining habitat loss, altering reproduction periods or disrupting biotic interactions. Here, we investigate the effects of climate and land use change on the spatial distribution of two semi-aquatic mammals, the Pyrenean desman (Galemys pyrenaicus) and the Eurasian otter (Lutra lutra). We first modeled the current potential distribution of the desman and the otter in the Iberian Peninsula, considering topographic, climatic and land use variables. Second, we predicted their potential distribution in 2050 under climate and land use change scenarios. We calculated the percentage of range gain/loss and shift predicted for the two species under such scenarios and quantified the present and future spatial overlap between the two species distribution. Irrespective of the scenario, desman models show loss of suitable habitat, whereas the otter will undergo an opposite trend. Aside from a preponderant habitat loss, the desman is predicted to increase its spatial overlap with otter range under the optimistic scenarios, potentially meaning it will face an exacerbated predation by otters. The potential increase of both habitat loss and otters' predation might represent a major threat for the desman, which may affect the long-term persistence of this endemic species in the Iberian Peninsula.

Range reexpansion after long stasis: Italian otters (Lutra lutra) at their northern edge

Species range shifts and expansion are subjects of primary research interest in the context of climate warming and biological invasions. Few studies have focused on reexpansion of species that suffered severe declines. Here, we focused on population recovery of Eurasian otters (Lutra lutra) in Italy, first detected in 2003 after a southward range contraction. We modeled the rate of range expansion and occupancy at the northern expanding front (central Italy), to gain insights into the progress of recovery and mechanisms of reexpansion. We performed a field survey in 2021, which redefined the northern limit of distribution further north, in close proximity to the Gran Sasso National Park. Then we analyzed a time series (1985-2021) of distances of northernmost occurrences from the center of the 1985 range. Using segmented regression, we were able to identify a prolonged stasis of the northern range edge and a simultaneous increase in occupancy from 0.151 to 0.4. A breakpoint was estimated in 2006, after which the range expanded northwards at an average rate of 5.48 km/year. From 2006 to 2021, the overall northward shift was about 80 km. Occupancy continued to increase until 2019 and abruptly declined in 2021. These patterns suggest that the reexpansion of the range can be limited by low occupancy at the expanding front. As occupancy increases, long-distance dispersal increases and then range expands. The low occupancy at the current distribution limit of otters may reflect a higher anthropogenic pressure on northern habitats, which could slow down the reexpansion process.

Mercury concentration in the tissues of the Eurasian otter: a seasonal dependance in Slovakia

The river otter is considered to be an important bioindicator of water clarity. This study focuses on mercury contamination within this species. Throughout the study, individuals from habitats in the foothills and surroundings of the Liptovská Mara reservoir were analyzed. Twenty-three samples of liver tissue, and twenty-two samples of hair and kidney tissue were collected. Of these samples, the average mercury concentration detected in tissues was 10.6 mg/kg in guard hairs; 12.9 mg/kg in under hairs; 3.3 mg/kg in kidney tissue; and 4.3 mg/kg in liver tissue. Analysis of certified reference material (ERM-BB186-Pig Kidney) was used to assist in the development of an accurate method for total mercury determination in animal tissues, to check the quality of measurements, and to validate the measurement method. Our method represented a high average percentage of recovery (> 95%) in the standard reference material matrix and a relative standard deviation (RSD) of 5% or less. Seasonality was determined to be a significant factor influencing the level of contamination of a given individual, both through mercury methylation within the aquatic environment and through fish ingestion by this apex semi-aquatic predator (guard hairs (p = 0.01); underfur (p = 0.04); kidney (p = 0.03); liver (p = 0.03)). Sex, location, and body size were not found to have a significant influence on heavy metal concentrations in river otters sampled in terms of season.

Taxonomic status of otter species in Nakai-Nam Theun National Park, Lao PDR, based on DNA evidence

Otter populations are threatened by habitat loss, pollution, conflicts with humans, and illegal wildlife trade to meet the demand for pets, for their fur, and for parts used in traditional medicines. Baseline information on the distribution, population genetic diversity, and connectivity is crucial to inform conservation management decisions; however, reliable data from otter populations in Southeast Asia remain scarce. In this study, we conducted baseline otter fecal DNA surveys based on mitochondrial DNA (mtDNA) to identify species, assess the occurrence, and map the spatial distribution of genetic diversity and evolutionary relationships of otter populations using 1700 bp Cytochrome B - Control Region and mitogenome from Nakai-Nam Theun National Park in the Annamite Mountains of Lao PDR. Of the total 56 samples identified to species, the majority (87.5%) was of the widely distributed Eurasian otter with three haplotypes (Lutra lutra; LLLA01-LLLA03), with a calculated haplotype diversity of 0.600 and a nucleotide diversity of 0.00141 based on mitogenome. The second species was the Asian small-clawed otter with only one haplotype detected (Aonyx cinereus; ACLA01). All Eurasian otter haplotypes were newly characterized and clustered within the strongly supported South-Southeast-North Asian clade of Lutra lutra. Compared with the European clade, the high mtDNA diversity of Lutra lutra in Nakai-Nam Theun National Park potentially reflects long-term demographic stability and lesser degree of population bottleneck during the last glacial maxima (LGM, ~21,000 years ago). The single haplotype detected in Asian small-clawed otters had not been detected in previous genetic studies. Our research is the first otter-specific noninvasive genetic study in Lao PDR and provides baseline insights into the otter population diversity in a regional priority site for biodiversity conservation.

Is scat marking a reliable tool for otter census and surveys at the landscape scale?

Biological significance of scat marking by otters has been a controversial subject among scientists. Using multiyear (2014-2017) data of otter spraint counts in South Korea, this study aimed to test whether the observed pattern of spraint presence/absence is driven by detection error and if/how scat counts can be a proxy for otter abundance at the landscape scale. To test the first hypothesis, spraint presence/absence was analyzed through occupancy models, which relied on environmental variables related to otter detectability and presence. Spraint count models were used to test the second hypothesis against resource-related covariates in combination with landscape, anthropogenic, and climate variables through machine learning algorithms (MLAs). The detection probability has specifically decreased in areas characterized by high rainfall and human population densities, whereas the probability has increased near food-rich sites, characterized by high marking frequencies. The temporal trends of spraint count predictions were in line with changes in the diversity of fish communities in 2014-2017 instead of fish biomass, suggesting that the availability of feeding resources is higher where fish communities are more diverse. Because diverse fish communities can attract otters, fish diversity conservation is critical for preserving this mammal's populations. This fine scale four-year monitoring has contributed to the disentanglement of the role of spraint presence/absence and spraint counts in detectability and population trends. This will assist in identifying key resource areas and planning strategies to promote otter conservation and dispersal dynamics.

Occurrence of multidrug resistant Gram-negative bacteria and resistance genes in semi-aquatic wildlife - Trachemys scripta, Neovison vison and Lutra lutra - as sentinels of environmental health

Emergence of antimicrobial resistance (AMR) in bacterial pathogens has been recognized as a major public health concern worldwide. In the present study, antimicrobial resistant Gram-negative bacteria (AMRGNB) and AMR genes were assessed in semi-aquatic wild animals from a highly populated and intensive farming region of Spain, Catalonia. Cloacal/rectal swab samples were collected from 241 animals coming from invasive species Trachemys scripta (n = 91) and Neovison vison (n = 131), and endangered-protected species Lutra lutra (n = 19). Accordingly, 133 (55.2%) isolates were identified as AMRGNB. Escherichia coli and Pseudomonas fluorescens were among the bacteria most frequently isolated in all animal species, but other nosocomial agents such as Klebsiella pneumoniae, Salmonella spp. or Citrobacter freundii, were also prevalent. The phenotypic susceptibility testing showed the highest resistance to β-lactams (91%). Molecular analysis showed 25.3% of turtles (15.4% ESBL/Ampc genes), 21% of Eurasian otters (10.5% ESBL/Ampc genes) and 14.5% of American minks (8.4% ESBL/Ampc genes) were positive to AMR genes. The genotyping frequency was tetM (20.6%), blaCMY-2 (13%), ermB (6.1%), blaCMY-1 (4.6%), blaCTX-M-15 (3.1%) and mcr-4 (0.8%). Turtles had a larger prevalence of AMRGNB and AMR genes than mustelids, but American mink carried mcr-4 colistin-resistance gene. Moreover, cluster analysis of AMR gene distribution revealed that an ESBL/AmpC cluster in a highly populated area comprising big metropolitan regions, and another tetM/emrB cluster in an expended area with highly intensive livestock production. Although the mcr-4 positive case was not included in those clusters, that case was found in a county with a high pig farm density. In conclusion, semi-aquatic wild animals are a good sentinel for environmental contamination with AMRGNB and AMR genes. Therefore, One Health Approach is urgently needed in highly populated regions, and with intensive livestock production like Catalonia.

Health and Mortality Monitoring in Threatened Mammals: A First Post Mortem Study of Otters (Lutra lutra L.) in Italy

Dead specimens provide valuable data for the conservation of threatened species, allowing investigations of mortality, health conditions, and demographic parameters. The Eurasian otter (Lutra lutra) is a semiaquatic carnivore listed as endangered in Italy. In 2009, we started the first post mortem (PM) study of otters in Italy, through collaborative research between mammal ecologists and veterinary pathologists, using standardized protocols. Twenty-eight otters, mostly collected between 2009 and 2017, were examined. Most otters were males (67%), between 1 and 3 years old (64%), and predominantly in good nutritional condition. Adult males were significantly larger than adult females (p < 0.02), as expected for the species, although both sexes appeared to be smaller than otters examined in Central−northern Europe. The youngest sexually mature female was 3 years old. Road traffic collisions were the major cause of death, especially in young individuals, and mainly occurred in autumn−winter, particularly for females. Investigations of the scene of death contributed to revealing factors forcing otters to travel out of the water and move over the road, suggesting appropriate measures to reduce vehicle collision risk. Other causes of death included blunt chest trauma of uncertain origin, dog and conspecific attacks, or diseases of infectious or non-infectious origin, such as ulcerative gastritis, pleuropneumonia and peritonitis. Other diagnosed diseases included lymphoma. Ecto- and endoparasites were rarely detected, although we report the first documentation of heartworm and Ixodes hexagonus infestation in Italian otters. It is important to continue comprehensive, standardized PM investigations of otters in Italy to define baseline health, biometric and demographic parameters, collect biological samples for comparative analyses, and to reduce road-kill mortality. The present study suggests that the timely collection of carcasses and collaborative and coordinated research efforts are essential for obtaining useful data for the conservation of otters.

Site-specific and seasonal variation in habitat use of Eurasian otters ( Lutralutra) in western China: implications for conservation

As a top predator, the Eurasian otter ( Lutralutra) 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.

Systematic examination of the cardiopulmonary, urogenital, muscular and gastrointestinal parasites of the Eurasian otters (Lutra lutra) in Denmark, a protected species recovering from a dramatic decline

The Eurasian otter (Lutra lutra) is a protected species in Denmark and at present, the population is recovering due to conservation efforts. The Danish otters are mainly found in the continental part of Denmark (Jutland), but establishment in the main islands (Fyn and Zealand) has been observed. While there is a lack of systematic studies on the parasite fauna of otters in Denmark, this study aims to screen otters for their parasite fauna, especially those of zoonotic and/or veterinary importance. Thirty-three otter carcasses, road-killed (n = 30), found dead (n = 2) and shot (n = 1), were collected between June 2013 and May 2014 and examined for cardiopulmonary, urogenital, gastrointestinal, and muscle helminths by post mortem examination. Faecal samples were analysed by modified concentration McMaster technique and direct immunofluorescence test for Giardia and Cryptosporidium. At least one parasite was found in 75.8% of animals. The parasite fauna included 13 species, consisting of five nematodes: Molineus patens (30.3%), Aonchotheca putorii (27.3%), Strongyloides sp. (24.2%), Physaloptera sp. (12.1%), Eucoleus aerophilus (10.0%); one cestode: Schistocephalus solidius (6.1%); four trematodes: Metorchis bilis (33.3%), Isthimiophora melis (15.2%), Cryptocotyle sp. (3.0%), Plagiorchis sp. (3.0%); one acanthocephalan: Acanthocephalus ranae (18.2%); and two protozoans: Giardia spp. (3.1%), and Eimeria spp. (3.1%). The study showed that otters carry parasites of zoonotic and veterinary importance. Many of these parasites can also infect native carnivores and birds, and the distribution of these parasites may be affected if the otter population continue to increase in Denmark.

A barcoding-based scat-analysis assessment of Eurasian otter Lutra lutra diet on Kinmen Island

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.

Complete mitochondrial genome sequencing of Lutra lutra (Linnaeus, 1758) (Carnivora: Mustelidae) and its phylogenetic status in Mustelidae

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.

DNA-based detection of Leptospira wolffii, Giardia intestinalis and Toxoplasma gondii in environmental feces of wild animals in Korea

Leptospira, Giardia intestinalis and Toxoplasma gondii infections are reported in humans and animals worldwide, but molecular surveillance of these pathogens in Korean wildlife is still limited. Here, we examined the prevalence of these pathogens in environmental feces of Eurasian otters, leopard cats and raccoon dogs using nested PCR followed by DNA sequencing. G. intestinalis was detected in all of three animals, while T. gondii was detected only in leopard cats. Leptospira wolffii was detected in raccoon dog and Eurasian otter. Our results suggest that these animals can act as a reservoir of these zoonotic pathogens. Consistent monitoring of these pathogens in wildlife is needed to prevent from their infections in humans and livestock in Korea.

First study on PCBs, organochlorine pesticides, and trace elements in the Eurasian otter (Lutra lutra) from southern Italy

Persistent organic pollutants (POPs), such as organochlorine pesticides (OCPs) and non dioxin-like polychlorinated biphenyls (ndl-PCBs), or also other toxic and potentially toxic elements tend to accumulate in the trophic web, and are associated with a wide range of deleterious effects in animals and humans. Although these contaminants have been banned since more than 30 years, their occurrence remains widespread in most of natural ecosystems. The Eurasian otter (Lutra lutra), being a top predator may cumulate large amounts of these contaminants, and could represent a keystone species serving as sentinel of ecosystem health in freshwater environments. The aim of this paper was to investigate the concentration of OCPs, ndl-PCBs, and essential and not essential elements in tissue samples of Eurasian otter in southern Italy. Six PCBs, seven OCPs, and thirteen trace elements were detected with high concentrations in few cases, however in general, the amounts of toxic compounds seem unlikely to hazard short-term conservation of this endangered mammal. The present paper is the first to provide baseline information concerning the presence of these substances in the Eurasian otter samples and from its fragile ecosystem in Italy.

Pulmonary hair embolism in a rescued free-ranging Eurasian otter Lutra lutra in Kinmen, Taiwan

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.

Biological and anthropogenic predictors of metal concentration in the Eurasian otter, a sentinel of freshwater ecosystems

Toxic metals have been linked to a range of adverse health effects in freshwater organisms. However, for higher vertebrates, there is little understanding of the large-scale drivers of exposure. We quantified toxic metal/semi-metal concentrations in a sentinel freshwater top predator, the Eurasian otter (Lutra lutra), across England and Wales, and determined how this varied with key natural and anthropogenic factors. We related liver concentrations in 278 otters that died between 2006 and 2017 to habitat biogeochemistry, proximity to point source contamination and to biological characteristics (length, sex, condition). Evidence for any positive association with putative anthropogenic sources (mining, human population, known discharges) was weak or lacking in nearly all cases, with the exception of a positive association between lead and human population density. Despite concerns that burgeoning use of nanosilver in consumer products might increase silver concentrations in waste waters, there was no increase over time. Spatial variation in soil/sediment pH, precipitation, and soil calcium oxide are indicated as significant predictors of metal concentrations in otters (higher cadmium and silver in areas with lower pH and higher rainfall, and higher chromium and lead in areas of lower calcium oxide). Liver chromium and nickel concentrations declined significantly over time (Cr 0.030 ± 1.2 to 0.015 ± 1.3 μg/g dry weight, Ni 0.0038 ± 1.2 to 0.00068 ± 1.5 μg/g, between 2006-2009 and 2014-2017), but other metals showed no temporal change. Biotic associations were important, with age related accumulation indicated for mercury and cadmium (as well as interactions with body condition). Our results suggest that larger-scale geochemical and hydrological processes are important in determining metal exposure in otters, and we provide an indication of risk factors that may be of relevance for freshwater vertebrates in other countries with well-developed water pollution management.

Clinical leishmaniosis in a captive Eurasian otter (Lutra lutra) in Spain: a case report

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.

Assessment of ecotoxicological risks to river otters from ingestion of invasive red swamp crayfish in metal contaminated areas: Use of feces to estimate dietary exposure

The invasive red swamp crayfish (Procambarus clarkii) has become a major food resource for Eurasian otters (Lutra lutra) in the Iberian Peninsula. Crayfish accumulate large amounts of metals, and hence otters could be at risk of exposure and intoxication through crayfish consumption. We conducted a food safety risk assessment for otters inhabiting two historical mining areas in central Spain affected by lead (Pb) and mercury (Hg) pollution. Estimated daily intakes (EDI) of Pb and Hg were non-invasively calculated from the proportion of crayfish remains and metal levels in otter feces. We considered that the abdominal muscle and the carcass of crayfish differ significantly in relative weight, total metal content and bioavailability of metals to reduce the uncertainty of risk characterization. Fecal concentrations of Hg and Pb in the polluted areas were 1.878 and 6.554 μg/g d. w., respectively (13-fold and 7-fold higher compared to a non-polluted area). EDI of Hg and Pb in the polluted areas were 66.02 and 78.26 μg/kg-day, respectively (14- and 8-fold higher than in the reference area). EDI from the Hg area were above minimum levels susceptible to cause neurotoxicity in mustelids, and 6.3% were above levels susceptible to cause histopathological lessions. In the Pb area, 16.7% of EDI were consistent with levels causing reproductive effects. Metal exposure through crayfish consumption might prevent or slow the recovey of otters in these polluted environments, thus this factor should be considered in management strategies aimed to protect otter populations.

Dolphin Morbillivirus in Eurasian Otters, Italy

We report biomolecular evidence of dolphin morbillivirus in 4 wild Eurasian otters (Lutra lutra) from southern Italy; 2 animals showed simultaneous immunohistochemical reactivity against morbilliviral antigen. These cases add further concern and support to the progressively expanding host range of dolphin morbillivirus in the western Mediterranean Sea.

What is the taxonomic status of East Asian otter species based on molecular evidence?: focus on the position of the Japanese otter holotype specimen from museum

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.

Molecular detection and characterization of carnivore parvoviruses in free-ranging Eurasian otters (Lutra lutra) in southern Italy

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.

Helminths of Mustelids with Overlapping Ecological Niches: Eurasian Otter Lutra Lutra (Linnaeus, 1758), American Mink Neovison Vison Schreber, 1777, and European Polecat Mustela Putorius Linnaeus, 1758

This study presents the helminthological data on three mustelid species with overlapping ecological niches in Lithuania. In general, 14 helminth species or higher taxa were reported from all mustelids: Isthmiophora melis, Strigea strigis metacercariae, Pseudamphistomum truncatum, Alaria alata mesocercariae, Phyllodistomum folium, Opisthorchis felineus, Metametorchis skrjabini, Mesocestoides sp., Taenia martis, Aonchotheca putorii, Crenosoma schachmatovae, Eucoleus aerophilus, Molineus patens, and Nematoda g. sp. The largest number of helminths was detected in M. putorius (11) and N. vison (10) from wetlands; 7 helminths were detected in M. putorius from forests, and 8 in N. vison and 4 in L. lutra from water bodies. Habitat-related differences were found in the abundance and prevalence of E. aerophilus in M. putorius. M. putorius has higher indices of infection by I. melis, S. strigis metacercariae, and E. aerophilus compared to N. vison in wetlands. Differences in the abundance and prevalence of P. truncatum among N. vison and L. lutra in water bodies have been observed. Helminths detected in N. vison in the present study are native European parasites.

Sexual dimorphism of craniomandibular size in the Eurasian otter, Lutra lutra, from South Korea

Sexual size dimorphism of craniomandibular morphology of the Eurasian otter Lutra lutra in South Korea was analyzed using linear measurements. In total, 32 skulls (18 males and 14 females) and 22 linear measurements (16 cranial and 6 mandibular measurements) were used. Our results showed statistically significant sexual dimorphism between male and female skull size. Multivariate analyses using the cranial and mandibular traits showed significant differences between the sexes, respectively. The most dimorphic trait was ectorbital breadth (EOB), and the EOB of the male was approximately 10% greater than that of the female. This type of sexual size dimorphism, in which males are generally larger than females, is a general pattern shown in family Mustelidae. Several researchers have suggested various hypotheses about the factors causing sexual size dimorphism, i.e., 'resource partitioning model' and 'sex-specific pressure model'. Our results are consistent with these hypotheses, and we suggest that these factors would have affected the sexual size dimorphism of the Eurasian otter in Korea.

Fast and cost-effective single nucleotide polymorphism (SNP) detection in the absence of a reference genome using semideep next-generation Random Amplicon Sequencing (RAMseq)

Biodiversity has suffered a dramatic global decline during the past decades, and monitoring tools are urgently needed providing data for the development and evaluation of conservation efforts both on a species and on a genetic level. However, in wild species, the assessment of genetic diversity is often hampered by the lack of suitable genetic markers. In this article, we present Random Amplicon Sequencing (RAMseq), a novel approach for fast and cost-effective detection of single nucleotide polymorphisms (SNPs) in nonmodel species by semideep sequencing of random amplicons. By applying RAMseq to the Eurasian otter (Lutra lutra), we identified 238 putative SNPs after quality filtering of all candidate loci and were able to validate 32 of 77 loci tested. In a second step, we evaluated the genotyping performance of these SNP loci in noninvasive samples, one of the most challenging genotyping applications, by comparing it with genotyping results of the same faecal samples at microsatellite markers. We compared (i) polymerase chain reaction (PCR) success rate, (ii) genotyping errors and (iii) Mendelian inheritance (population parameters). SNPs produced a significantly higher PCR success rate (75.5% vs. 65.1%) and lower mean allelic error rate (8.8% vs. 13.3%) than microsatellites, but showed a higher allelic dropout rate (29.7% vs. 19.8%). Genotyping results showed no deviations from Mendelian inheritance in any of the SNP loci. Hence, RAMseq appears to be a valuable tool for the detection of genetic markers in nonmodel species, which is a common challenge in conservation genetic studies.

UROLITHIASIS IN FREE-RANGING AND CAPTIVE OTTERS (LUTRA LUTRA AND AONYX CINEREA) IN EUROPE

Between 1996 and 1998, 477 dead otters from different Central European countries were examined for urolithiasis, including 449 free-ranging Eurasian otters (Lutra lutra) as well as 17 Eurasian otters and 11 Asian small-clawed otters (Aonyx cinerea) from captivity. In the free-ranging specimens, uroliths (sand or stones) were found in 105 animals (23.4%), with no significant difference (P = 0.77) between the sexes. Uroliths were not present in any juveniles (n = 26) and urolithiasis was not considered the main cause of death in any individual. In captive specimens, uroliths were found in 11 out of 17 Eurasian otters (64.7%; four males and seven females), and in 3 out of 11 Asian small-clawed otters (27.3%). Histology could not find any signs of inflammation in examined kidneys (n = 179) or urinary bladders (n = 66). Analyzed stones of free-ranging and captive Eurasian otters were composed mainly of ammonium acid urate. The stones of three captive Asian small-clawed otters consisted mainly of calcium oxalate. The difference in prevalence of uroliths between free-ranging and captive Eurasian otters was significant (P < 0.001). Nevertheless, the prevalence in free-ranging specimens of this study is higher than reported before. Differences between various habitats, environmental changes, and genetic predisposition all represent potential hypothetical explanations for these findings.

wisepair: a computer program for individual matching in genetic tracking studies

Individual-based data sets tracking organisms over space and time are fundamental to answering broad questions in ecology and evolution. A 'permanent' genetic tag circumvents a need to invasively mark or tag animals, especially if there are little phenotypic differences among individuals. However, genetic tracking of individuals does not come without its limits; correctly matching genotypes and error rates associated with laboratory work can make it difficult to parse out matched individuals. In addition, defining a sampling design that effectively matches individuals in the wild can be a challenge for researchers. Here, we combine the two objectives of defining sampling design and reducing genotyping error through an efficient Python-based computer-modelling program, wisepair. We describe the methods used to develop the computer program and assess its effectiveness through three empirical data sets, with and without reference genotypes. Our results show that wisepair outperformed similar genotype matching programs using previously published from reference genotype data of diurnal poison frogs (Allobates femoralis) and without-reference (faecal) genotype sample data sets of harbour seals (Phoca vitulina) and Eurasian otters (Lutra lutra). In addition, due to limited sampling effort in the harbour seal data, we present optimal sampling designs for future projects. wisepair allows for minimal sacrifice in the available methods as it incorporates sample rerun error data, allelic pairwise comparisons and probabilistic simulations to determine matching thresholds. Our program is the lone tool available to researchers to define parameters a priori for genetic tracking studies.

Diet of otters (Lutra lutra) in various habitat types in the Pannonian biogeographical region compared to other regions of Europe

Knowledge of the effect of habitat type and region on diet and feeding behaviours of a species facilitates a better understanding of factors impacting populations, which contributes to effective conservation management. Using spraint analysis and relative frequency of occurrence data from the literature, we described the dietary patterns of Eurasian otters (Lutra lutra) in 23 study sites within the Pannonian biogeographical region in Hungary. Our results indicated that diet composition varied by habitat type and is therefore context dependant. The differences among habitat types were however lower than expected. We noticed a decline in the fish consumption with a concomitant increase in trophic niche breadth and amphibian consumption in rivers, ponds (fish farms), backwaters, marshes and small watercourses. The main differences in diet were not attributed to the consumption of primary and secondary food types (fish and amphibians), but rather to differences in other, less important food types (mammals, birds). Using hierarchical cluster analysis, rivers and ponds could clearly be separated from other habitat types. We found the main fish diet of otters in most of these areas consisted of small (<100 g), eurytopic, littoral and non-native, mostly invasive species. Dietary studies from 91 sites in six European biogeographical regions showed that fish are consumed most frequently in the Atlantic and Boreal, less in the Continental and Pannonian, and least in the Alpine and Mediterranean regions. Comparative analysis indicated that the Mediterranean region (with frequent crayfish consumption) and Alpine region (frequent amphibian consumption) cluster separate from the other regions.

Molecular prey identification in Central European piscivores

Diet analysis is an important aspect when investigating the ecology of fish‐eating animals and essential for assessing their functional role in food webs across aquatic and terrestrial ecosystems. The identification of fish remains in dietary samples, however, can be time‐consuming and unsatisfying using conventional morphological analysis of prey remains. Here, we present a two‐step multiplex PCR system, comprised of six assays, allowing for rapid, sensitive and specific detection of fish DNA in dietary samples. This approach encompasses 78 fish and lamprey species native to Central European freshwaters and enables the identification of 31 species, six genera, two families, two orders and two fish family clusters. All targeted taxa were successfully amplified from 25 template molecules, and each assay was specific when tested against a wide range of invertebrates and vertebrates inhabiting aquatic environments. The applicability of the multiplex PCR system was evaluated in a feeding trial, wherein it outperformed morphological prey analysis regarding species‐specific prey identification in faeces of Eurasian otters. Additionally, a wide spectrum of fish species was detected in field‐collected faecal samples and regurgitated pellets of Common Kingfishers and Great Cormorants, demonstrating the broad applicability of the approach. In conclusion, this multiplex PCR system provides an efficient, easy to use and cost‐effective tool for assessing the trophic ecology of piscivores in Central Europe. Furthermore, the multiplex PCRs and the primers described therein will be applicable wherever DNA of the targeted fish species needs to be detected at high sensitivity and specificity.