Otter Lutra Research Articles

Assessing the Diet of a Predator Using a DNA Metabarcoding Approach

The diet of top predators is vital information needed to determine their ecological function and for their conservation management. However, the elusive habit and low population density of many predators constrains determination of their diets. While the morphological identification of scat contents is the traditional method, DNA metabarcoding has lately proven a more efficient and accurate method of identifying prey taxa. We applied DNA metabarcoding to analyzing the diet of the Eurasian otter (Lutra lutra), a top predator in freshwater ecosystems, using 12S and 16S rRNA mitochondrial primers target vertebrate prey. Diet did not vary among different data removal thresholds of 0.1, 1, 3, and 5%, comprising fishes (>90%), amphibians and birds (>2%), and occasionally mammals (<2%). Both 12S and 16S primers revealed similar otter diets, indicating that a single set of primers with a higher threshold is cost-effective for detecting the main prey taxa. Using 12S primers and a 5% threshold, we found no seasonal variation of otter diet in the Tangjiahe National Nature Reserve. A different prey community was found outside the reserve, which resulted in different prey composition for otters. However, prey taxon richness was not different between otters in- and outside the reserve. Otters preferred Schizothorax spp., the largest-sized fish species in the reserve, whereas they mainly preyed on Triplophysa bleekeri, a small-sized fish species, outside the reserve. Otters’ flexible feeding strategy reflect their high adaptability. However, greater human disturbance outside the reserve may present significant challenges to otters by altering prey communities and reducing prey profitability. Combining fecal DNA metabarcoding and local fish survey will provide opportunities for more detailed studies on the impact of different levels of human disturbances on prey communities and otters.

Human pressures constrain Eurasian otter occurrence in semiarid Northern Africa

Populations inhabiting the periphery of species distribution ranges may experience suboptimal environmental conditions and higher vulnerability to anthropogenic pressures. Disentangling the role of natural and human-related factors and the relationships among them in these marginal areas is thus key to understand and prevent species declines and range reductions. We analysed Eurasian otter (Lutra lutra) occurrence patterns in relation to anthropogenic pressures and natural environmental gradients in Morocco, an area constituting the arid limit of the species’ global range. The probability of otter occurrence was higher as terrain ruggedness increased and at intermediate elevations, and lower in catchments exposed to higher anthropogenic pressures. Otters tended to be rare at higher elevations and in areas with less annual precipitation, probably as a result of trophic resource limitations and large water flow fluctuations, respectively. A combination of natural and anthropogenic factors, both at drainage area and local scales, was needed to understand the current occurrence of the species. Our study highlights a need for urgent action to conserve the Eurasian otter in northern Africa, where freshwater ecosystems and their associated biodiversity are threatened by rapid human development in areas of marginal climatic conditions.

Retrospective detection and sequencing of Canine Distemper Virus in road-killed Eurasian otter (Lutra lutra) samples from the last two decades

Retrospective detection and sequencing of Canine Distemper Virus in road-killed Eurasian otter (Lutra lutra) samples from the last two decades

Toxic trace elements in spraints of Eurasian otters (Lutra lutra) in the Daechung Lake area

Toxic trace elements in spraints of Eurasian otters (Lutra lutra) in the Daechung Lake area

On the “otter-fish producers conflict” in South-Eastern Bulgaria

Predatory mammals compete with humans for game, livestock and fish. The otter (Lutra lutra L.) inhabits the whole river system in Bulgaria, including fish ponds, coming into conflict with fish producers causing damage due to its feeding habits. To clarify the manifestations of the conflict, an anonymous questionnaire among fish farmers and workers was provided. According to the survey, the market-sized fish was affected the most (93.75% of the respondents) by otter’s attacks, to a lesser extent the juveniles - 63.75% and the broodstocks - 62.5%, respectively. In the current study, 43.75% of respondents claimed that weed fish also suffers damage. A total of 77.5% of the respondents have tried to overcome the problem. In the present study, there was no report for using a non-lethal method. It can be concluded that the "Otter-fish producers conflict" in Bulgaria will be mitigated if compensations are provided for the economic losses.

Factors influencing genotyping success and genotyping error rate of Eurasian otter (Lutra lutra) faeces collected in temperate Central Europe

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.

COMPARATIVE ANATOMY OF THE LIVER OF WILD FUR ANIMALS: EUROPEAN BADGER (MELES MELES, L), RIVER OTTER (LUTRA LUTRA, L) AND ORDINARY FOX (VULPES VULPES, L)

Fur production is the most valuable field of animal husbandry in the Russian Federation. Domestication, containment, changes in behavior and diet of fur animals have contributed to both exterior and interior changes in their biology. The biggest interior changes have occurred in the volume and functionality of the digestive system, especially liver. European badger’s (Meles meles) liver mass was determined to be 324-389 g making up 3,20-3,44% of the total body mass. River otter (Lutra lutra) has 489,0-500,0 g and 5,1-5,8%, and ordinary fox (Vulpes vulpes) has 183-195g and 3,4-3,9% accordingly. The sharp end of the badger liver peeks out of the lower end of the ribcage, while the otter liver is perpendicular to the ribcage. Badger liver is yellowish-brown, otter liver is cherry-brown, fox liver is brown. All of them are separated by deep grooves to differently sized parts; badger and otter livers have 7 parts, and fox liver lacks the nipple-like protrusion. The gallbladder is located between the square and left medial parts of the liver; the badger’s is pear-shaped and is easily visible from the diaphragmatic and visceral surfaces of the liver; otter’s is elongated and rounded and has a wrinkle, fox’s is pear-shaped. The contents of the gallbladders of badgers and otters is greenish brown, with badger’s contents having pH of 7,2-7,6 pts., otter’s - 6,5-6,8 pts., while fox’s is brown with pH of 6,0-6,2 pts. That way, different diets and habitats form the visual changes in topography and macro morphology of livers not only in members of different biological families, but different species as well.

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

BackgroundCaptive 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 presentationA 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.ConclusionsThis 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.

Morphological Alterations in the Hepatobiliary and Respiratory System of the Eurasian Otter (Lutra lutra) in Germany

Morphological Alterations in the Hepatobiliary and Respiratory System of the Eurasian Otter (Lutra lutra) in Germany

Impacts of Aquatic and Riparian Environmental Factors on Eurasian Otter (Lutra lutra) Presence Characteristics in the Nakdong River Basin

Impacts of Aquatic and Riparian Environmental Factors on Eurasian Otter (Lutra lutra) Presence Characteristics in the Nakdong River Basin

Special features of otter (Lutra lutra) nutrition in the lowland river of the southern Amur Region on the example of Bolshekhekhtsirsky reserve

Special features of otter (Lutra lutra) nutrition in the lowland river of the southern Amur Region on the example of Bolshekhekhtsirsky reserve

Population dynamics of two sympatric intertidal fish species (the shanny, Lipophrys pholis and long-spined scorpion fish, Taurulus bubalis) of Great Britain

The shanny/common blenny (Lipophrys pholis) and long-spined scorpionfish/bullhead (Taurulus bubalis) are commonly encountered, sympatric species within much of Great Britain's rocky intertidal zones. Despite being prey items of the cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) respectively, and both contributors to the diet of the near-threatened European otter (Lutra lutra), little is known on the population dynamics of the temperate specimens of Great Britain. It is further less known of the degrees of sympatricity between the two fish species and to what extent they are able to coexist. The current study examines spatio-temporal distributions and abundances at various resolutions: monthly population dynamics of both species along England's Yorkshire coast and seasonal population dynamics along the Yorkshire coast and around the Isle of Anglesey, Wales. Studies of their abundances, sizes, degrees of rock pool co-occurrence and diel activities are further examined, which indicate coexistence is maintained when interspecific co-occurrence takes place only between specimens of similar sizes, thus demoting size-related dominance hierarchies.

Craniometric and epigenetic variability of the Eurasian otter (Lutra lutra) in eastern Saxony

Craniometric and epigenetic variability of the Eurasian otter (Lutra lutra) in eastern Saxony

Feeding ecology of Eurasian otters (Lutra lutra) in freshwater habitats: Preliminary results of a stable isotope approach

Feeding ecology of Eurasian otters (Lutra lutra) in freshwater habitats: Preliminary results of a stable isotope approach

The effect of a major drainage divide on the gene flow of a semiaquatic carnivore, the Eurasian otter

AbstractMajor drainage divides (separating the water flow draining to different seas) may significantly affect the dispersal, distribution, and genetic structure of semiaquatic animals. Assessing this effect is important for the proper management of both endangered and invasive riparian species. Here, I determined the fine-scale impact of the drainage divide between the Baltic Sea and the Black Sea drainage basins on the genetic structure and dispersal of the Eurasian otter (Lutra lutra) in the Bieszczady Mountains (Poland and Slovakia). I investigated the genetic structure of the otter population and assessed 3 alternative dispersal models using 6 landscape genetics methods. The analyses were based on 48 individual genotypes obtained from 622 fecal and gland secretion samples collected in 2008–2011. Results indicate that the major drainage divide is not a barrier to gene flow for this population. This was established by analyses of population genetic structure and confirmed by analysis of the spatial distribution of samples originating from closely related individuals. In line with these findings, the best-supported dispersal model assumed that otters migrate through mountain passes, away from streams, thus revealing that they are able to cross a drainage divide. The genetic structure of the population studied exhibits an isolation-by-distance pattern; however, the locations of several repeatedly recorded or closely related individuals revealed the occurrence of long-distance movements. Confirmation of the high mobility of otters and their ability to cross a major drainage divide ridge suggest that landscape obstacles and discontinuity of river network are unlikely to stop otter dispersal, gene flow, and recolonization of new areas.

CASE REPORT: A CHRONIC B-CELL LEUKEMIA IN A EURASIAN OTTER (Lutra lutra)

A 12-year-old, female, Eurasian otter (Lutra lutra) reared in Taipei zoo was submitted for necropsy due to sudden death without remarkable clinical history. Parameters of the latest hematology were all within normal limits. At necropsy, there were large amounts of abdominal effusion, diffuse splenohepatomegaly, generalized lymphadenopathy, consolidation of the lung, and bilateral enlargement of both adrenal glands. Histological examination revealed large numbers of small to medium-sized neoplastic lymphocytes disrupting the normal architectures of the spleen, liver, lymph nodes, lung, mesentery, and adrenal glands. Immunohistochemistry showed diffuse positivity of tumor cells for CD79a but negativity for CD3. There were scattered positive signals for Ki-67 mainly in the spleen in sites of extramedullary hematopoiesis and lymph nodes. The neoplasm was considered a chronic lymphocytic leukemia of B-cell origin.

Речная выдра (Lutra lutra) в водоёмах лесостепной и степной зон северо-востока Украины

Речная выдра (Lutra lutra) в водоёмах лесостепной и степной зон северо-востока Украины

Skinning toads is innate behaviour in otter (Lutra lutra) cubs

An experiment was performed with two subadult otters (Lutra lutra) born in captivity that had never seen or eaten amphibians, in which they were fed a new prey with toxic substances in its skin, the Iberian common toad (Bufo spinosus). It was observed that the otters recognised a poisonous amphibian that they had never come into contact with before as a potential prey in the absence of fish, which had previously been their only diet. As from the first test, and as described for wild otters in the literature, they consumed the toads following a learning process that consisted of ventral slicing and skinning in order to avoid contact with the dermal secretions, especially on the head and back, that toads use as a defensive mechanism. We observed the skill of the otters when handling the prey with regards to both killing them and eating them; the otters also immersed their prey in the water of their pond to remove the toxic substances emanating from the toads’ skins. The amount of remains left after the attack was gradually reduced over a period of 16 test experiments. No differences between the skins rejected in the experimental conditions and those found in nature were detected, the otter mainly eating the back legs and taking special care to reject the head, the back and viscera (especially the ovaries in the case of pregnant females). When they had brown trout together with toads in the same biomass, they neither attacked nor consumed the latter.

Assessment of population structure in Hungarian otter populations

The Eurasian otter (Lutra lutra) is widely distributed in Europe and has been down-listed from Vulnerable to Near Threatened on the IUCN Red List in 2004 following successful conservation interventions. River otter recoveries were driven by active and passive protection of wetlands and a decrease in environmental pollutants. In Hungary, although otter populations have been stable in recent decades, there is little information available regarding genetic diversity, population genetic or phylogeographic structure, and potential barriers affecting gene flow. This study, therefore, aimed to determine genetic diversity and structure across the range of this species in Hungary. To achieve this, we analyzed 255 tissue samples collected since 2002, mainly from road-kill incidents, in various regions of Hungary. We found a relatively high level of genetic diversity in Hungarian otter populations (expected heterozygosity: 0.69–0.74; mean number of alleles per locus: 6.8–7.7). At a regional level, we identified 2 di...

Fish selection by riverine Eurasian otters in lowland England

Eurasian otters (Lutra lutra) may conflict with humans using fish stocks for food, income or recreation. Understanding fish selection by otters is important for predicting and managing potential conflicts. We used spraint analysis to describe the diet of Eurasian otters on rivers in the Upper Thames Valley, lowland England, in summer and winter, focusing specifically on the species and size of fish consumed. We assessed the proportion of fish consumed that were of potential commercial or sporting value (the ‘Potential Value’ category). Within this group, we assessed relative selection for family and length by comparing fish found in otter diet with their local availability. Local availability was estimated from UK Environment Agency electrofishing survey data. Fish represented 46 % (relative frequency of occurrence, RFO) of total otter diet, with fish of Potential Value representing 19 % (RFO). In the Potential Value category, cyprinids were relatively avoided; percids and esocids were relatively preferred. Most (∼80 %) fish prey items originated from fish 4–13 cm in length, 3 % from fish > 20 cm. Smaller (0–10 cm) percids and cyprinids, and larger (16–20 cm) esocids, were preferred. In summer, diet was broad, comprising 31 % (RFO) fish, 24 % birds and 14 % crayfish. In winter, diet was predominantly fish (68 % RFO) with crayfish and birds accounting for ∼5 % each. In summer, most fish consumed (70 % RFO) were the relatively slow-swimming common bullhead (Cottus gobio). Significantly more of the faster-swimming cyprinids were consumed in winter, presumably because they are easier to catch when the water is colder.