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IUCN/SCC Otter Specialist Group Bulletin
© IUCN/SCC Otter Specialist Group

Volume 33 A: Proceedings European Otter Workshop, 8 - 11 June 2015, Stockholm, Sweden


In alphabetical order of first author

Otter preference of different mitigation measures at roads: a Swedish evaluation
Johanna Arrendal and Marie Johnsson
MyraNatur and The Swedish Transport Administration, Sweden

To reduce the number of roadkilled otters (Lutra lutra), the Swedish Transport Administration has built mitigation measures at numerous sites, often at bridges and culverts. Many different types of mitigation measures have been built, such as shores, ledges, dry tunnels, spraint sites and fences. Additionally, different materials have been tested through the years. It is important to evaluate these constructions to be able to improve their functionality for otters.
In this study we used tracking and remote cameras to assess the preference of otters to use the different mitigation measures. We also studied if strength of water current and direction of otter movement affected the results. Finally we checked the condition of the construction. In earlier studies otters have used ledges less often than other measures. Therefore, we studied a larger number of ledges made of different materials, to be able to see what otters prefer.
Results and discussion
Of the different mitigation measures, otters significantly preferred shores. Additionally, floating ledges and dry tunnels were used at a high frequency. Ledges were not preferred, but were used when needed (e.g. at strong water current). Even if otters didn’t dislike wooden ledges, we propose to continue with concrete ledges as these were in perfect condition, whereas wooden ledges had a large need of maintenance.
Otters preferred constructions that could be flooded and not constructions built above highest flood level. Thus, otters prefer measures built close to the water and use them when not flooded. However, mitigation measures have to be built above highest flood level, or the otters will be forced to cross the road at floods when the measures are really needed. Therefore, constructions have to be designed so that otters cannot resist them. Spraint sites (stones at ledges, on shores, in dry tunnels) were proven to be of high significance to otters and should therefore always be included in the construction. Otters used the measures both when travelling up and downstream, which means that the constructions are attractive to the animals even when they actually could swim downstream.
Half the number of fences in the study were not working properly. Only correctly built fences had an effect on otters. When not using the measures otters most often passed the bridge or culvert by swimming, i.e. not crossing the road. Thus, otters only seem to cross the road if it is not possible to swim or use the mitigation measure.
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Human dimensions assessment of angler attitudes towards Eurasian Otters and piscivorous birds in Scotland.
Kelsey Baird, Tom Serfass and Sadie Stevens
Frostburg State University; University of Maryland Center For Environmental Science

The conservation of predators is a worldwide challenge because of perceived or actual conflict with humans. Understanding human attitudes towards predators is therefore integral to developing a holistic approach to conserving this important group of wildlife. Conflicts between humans and piscivorous wildlife are well documented in many regions of the world. Landowners, recreational anglers, and commercial fisheries managers in Great Britain have persecuted piscivorous wildlife historically. Now unlike in the past, piscivorous predators are protected under British and EU legislation. Iconic game fish species such as Atlantic salmon (Salmo salar) are also provided legal protection in Britain while in freshwater from certain fishing methods. The inception of legal protection turns potential wildlife-conflict issues between stakeholders and piscivorous predators into increasingly polarized socio-political issues.
More recently, media portrayals across mainland Britain suggest that some recreational anglers are concerned that the predatory habits of Eurasian otters (Lutra lutra) and piscivorous birds are harmful to populations of game fish. However, there is a paucity of studies that assess the actual extent of concerns by anglers towards native piscivores in Great Britain. To make such an evaluation, during the summers of 2013 and 2014 we assessed attitudes and perceptions of 238 recreational anglers in Scotland (n = 203), and England (n = 35) towards the following piscivorous species: Eurasian otter, osprey (Pandion haliaetus), grey heron (Ardea cinerea), sawbill ducks of the Merginae subfamily, and the Great cormorant (Phalacrocorax carbo). In contrast to some media portrayals, participants generally held the Eurasian otter, grey herons, and ospreys in high esteem (78%, 79%, and 94% had favorable attitudes respectively). However, anglers expressed less positive opinions towards sawbill ducks (55% expressed favorable attitudes), and had particularly negative attitudes towards cormorants (75% identified the cormorant as a pest). We review factors, such as socioeconomic indices, familiarity, and media portrayals, which may contribute to the attitudes expressed towards these piscivorous species.
This study highlights the importance of human dimensions research to understanding stakeholder attitudes and perceptions.
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The need of a survey method that will allow monitoring otters during increasing population
Mia Bisther and Oskar Norrgrann
Brandt & Gröndahl AB and County Administration Board of Västernorrland, Sweden

For several countries the otter population have increased remarkably during the last two decades. In Sweden the increase started around 1995 and an Action plan for otters was published 2005-2010. The main threats for the species in Sweden were identified as pollutants, traffic, traps and fishing gear. Today the population has reached in several counties densities that have never been seen for the last sixty years. Nevertheless threats remains, even though their combination differs. There will be no review of the Action Plan, in reality that means less money towards the otter.
Therefore there is a need for a complementary method to monitor otters during times of continues increase. By using a few reference areas (geographically spread) and a statistically minimum numbers of locations there should be an economically bearable situation that can allow the otter to remain monitored.
For Sweden the geographical differences are significant when monitoring otters. The otter’s home range in the northern parts of Sweden is at least twice the size of the home range in the south. Otters were still present in the north even during the time when they were almost totally absent in the south. Sweden is a geographically long country, to get an acceptable spread between reference areas at least five areas are required. Because pollution is still a main threat to the otters, there is a need to continue to monitor the species even when it is increasing both in numbers and distribution. To assure consistence within a national monitoring system they must be financed on a national level.
Bignert and Leander (2013) simulated the amount of locations needed to statistically monitor changes in a population. If the actual difference in the local population is small (5 % or less), a very large number of locations must be monitored to prove a significant change in the population. Should the actual difference instead be 10 % there is a need of 130 to 240 locations depending on if the density of otters are low or extremely high (130-140 locations). A medium-high density will require 230-240 locations. The density of the otter population therefore has a significant part in setting the cost when monitoring otters.
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The Eurasian Otter as a Sentinel of Environmental Health
Elizabeth Chadwick,
Cardiff University Otter Project, School of Biosciences, Cardiff University, United Kingdom

Since it was established in 1994, Cardiff University Otter Project (CUOP) has collected over 2,500 otter carcasses for post mortem, mostly (>80%) dead as the result of road traffic accident. Data and samples are archived so that research can be carried out retrospectively, as new questions arise, methods develop, or funding becomes available.
As top predator of freshwater systems in the UK, the otter acts as a sensitive early warning system for chemical contaminants such as pesticides, pharmaceuticals and fire retardants. By monitoring concentrations in otter tissues, the project has demonstrated that environmental legislation can be successful at reducing environmental contaminants such as PCBs and heavy metals. Importantly, it can also demonstrate where such legislation is insufficient. The otter’s role as a sentinel can be extended to include monitoring for parasites - as an opportunistic and wide ranging predator feeding across freshwater, terrestrial and marine habitats, the otter is potentially exposed to a wide range of pathogens, and may be an important vector between habitat islands.
For species that are nocturnal, elusive and exist at low density, research can be particularly challenging. Non-invasive research using samples retained post mortem provides valuable opportunities to study key aspects of biology including communication, population structure and diet. Integrating fundamental research into otter biology, with more applied research into environmental contaminants or disease enables a more holistic understanding of otter populations and environmental health.
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The Otter Spotter – Public engagement with otter mortality monitoring in the UK
Elizabeth Chadwick and S.E. Perkins
Cardiff University School of Biosciences, United Kingdom

Eurasian otters are largely nocturnal, cryptic and live at low density, so opportunities for direct observation are limited. Despite this, they are charismatic and popular, and attract keen public interest. By harnessing that interest, it is possible to use citizen scientists to collect or report signs (e.g. spraint) or carcasses. Resulting data are important for our understanding of otter populations, and as an indicator of wider environmental health. Furthermore, otters are a powerful platform for environmental education.
In the UK, reports of otter mortalities are collated by two schemes. Cardiff University Otter Project (CUOP) was established in 1994, and collects carcasses for post mortem. Data and samples are used for research into individual, temporal and spatial variation in otter ecology, health and environmental contaminants. Project SPLATTER (Social media based PLATform for Estimating Roadkill) is a relatively new social media based venture (started in 2013) which monitors wildlife mortality across all wild species, and aims to quantify and raise awareness of the problem of wildlife road-kill in Britain.
The current paper shares lessons learnt by the two schemes. Extensive contact networks are crucial to both, but whereas CUOP relies largely on more traditional contacts with supportive environmental organisations, SPLATTER has achieved rapid growth through effective use of social media. In twenty years, CUOP has examined 2,542 otters, reported by 1404 members of the public – in the past two years, SPLATTER has already received 11,857 reports of 98 species, from nearly 3000 active followers. Gains in data volume necessitate a compromise in terms of location accuracy however, so defining the goals of individual projects, and designing methods accordingly, is critical. Public engagement must work effectively in both directions – reporting mechanisms must be methodical and straightforward, and appropriate feedback to volunteers is essential to maintaining involvement. Appropriate feedback necessitates effective mapping and data analysis, taking into account potential bias involved in opportunistic data collection and uneven distribution of reporters.
Both projects are active participants in public education events, and receive regular attention from the media. Both highlight how citizen science need not end with members of the public providing information to scientists: the next step is to communicate the science back to the public – and ultimately, to help the public understand how their actions can reduce the risk of wildlife traffic mortality, or lessen the impacts of environmental pollution
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Foraging history of Eurasian otters (Lutra lutra) inferred from stable isotopes δ13C and δ15N
Morten Elmeros, Maria Topgaard, Anders Michelsen and Aksel Bo Madsen

Aarhus University; University of Copenhagen, Denmark

The Eurasian otter (Lutra lutra) in Denmark inhabits a closely associated system of freshwater, brackish and marine habitats. Stable isotope values of carbon and nitrogen (δ13C and δ15N) differ between freshwater and marine habitats and trophic level, and these differences are reflected in the stable isotope imprints of the fauna inhabiting these different habitats. To study foraging patterns of otters in associated freshwater, brackish and marine habitats, we analyzed stable isotopes (δ13C and δ15N) in soft tissues (muscle or liver) and bone collagen from 100 otters. Otter carcasses were collected throughout the species distribution area in Denmark. The majority of the specimens were road traffic causalities.
Overall, δ13C and δ15N values in both tissue and collagen correlated with the habitat type where the otter was found and also with the distance to marine waters (δ13C-tissue: r2=0.19, δ13C-collagen: r2=0.19, δ15N-tissue: r2=0.21, δ15N -collagen: r2=0.15), but the variance of the stable isotope patterns was high. Otters with brackish or marine isotope imprints in tissues were usually found up to 3 km from marine waters, but marine imprints were found in individuals up to 30 km from the coast. Most adult otters were found in the same habitat type as the soft isotope imprint indicated as their main foraging habitat. For subadults otters there tended to be a higher discrepancy between the isotopic imprints in soft tissues and the location. Two adult otters from freshwater habitats had freshwater imprints in their soft tissues but marine imprints in their collagen.
The soft tissue stable isotope patterns suggest that otters’ foraging habitat correlate with availability (distance to the coastline) despite the territorial behaviour of otters. Stable isotopes in soft tissue and collagen also confirm that the individual otters may move substantial distances and shift between freshwater and marine habitats.
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Using otter as a tool for aquatic ecosystems conservation. Case study: Conservation campaign – Romania's rivers: last chance.
Bouroș George
University of Bucharest

Since 2012 the rivers of Romania started to be threatened by over 500 micro hydropower plants (MHP) projects, in various stages of approval, construction or operation. In order to mitigate this problem, WWF launched in November 2013 a conservation campaign, in which we used the otter as a flagship and charismatic species. This species was choosen to be the image of this national campaign, taking into consideraton two main factors: it was proven out to be a charismatic mammal but also a threatened species affected by MHP projects, that benefit of national and international legal protection.
We consider that the otters are good flagships and play a reliable sentinel role against pollution and habitat degradation in Romania. More evidences suggest that the sentinel role of otter is justified:
(a) Usually, otters are the first to go extinct in a freshwater ecosystem, as a result of their higher sensitivity. (b) Multiple studies have demonstrated bioaccumulation of toxic pollutants along the food chain. c) Otters are often sensitive to human modifications of landscape structure and composition.
During this campaign, one of the main actions, was an online petition through which were gathered signatures from citizens, stating their willingness against projects of micro hydropower plants that degradate the rivers. In order to motivate citizens to sign, otter’s image was the one which was promoted during this campaign in all mass-media, websites, posters, stickers, brochures and social networks.
The entire campaign couldn’t be effective without the major contribution of the scientific studies regarding the presence, distribution and ecology of the otter but also threatened fish and crayfish species. Most investors in the environmental impact assessments of the MHP construction, did not specify the presence of these protected species, although they existed. The presence of the otter in the area of construction of the MHP, led most of the time to the salvation of that river. These scientifically documented studies were an important argument for us towards: European Commission, national and local authorities, investors and the public opinion.
The campaign reached its goal by: stopping the MHP construction, discouraging investors to develop such projects, the exclusion of MHP construction from European Union funds for 2014-2020 funding, and Environment Ministry official decision to suspend the approval process for all MHP investments until will create a joint working group to develop a set of principles and criteria (high quality of water and the presence of otter and protected species of fish and crayfish) for the development of hydropower, in addition to existing legislation. This has been a premiere at the level of the Danube basin.
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Hydroelectric power stations and fish farming – main threats for otter (Lutra lutra) population in Georgia.
George Gorgadze
Centre for Biodiversity Conservation and Research - NACRES, Tbilisi, Georgia

Eurasian otter (Lutra lutra) is fully protected in Georgia and included in the Red List under the category ‘Nearly Extinct Rare Species’. In the past, the otter was widespread throughout the country occurring at almost every river and lake. After the development of different segments of the Georgian economy, water ecosystems and riparian forests came under intense pressure. According to the results of the first National otter survey, otter occurrence was recorded only in 39% of the potential range.
In 2013-2014, the first National otter survey besides assessing main threats and habitat conditions also monitored human-wildlife conflict. At the same time the building of hydroelectric power stations were undertaken. A series of meetings with local stakeholders (e.g. local government, fish farm owners and water resource users) were organized.
The increasing pressure on water ecosystems and riparian forests resulted in wide-scale habitat destruction, water pollution and a decrease of fish resources in rivers. Construction of Run-of-the-river power plants became very popular in Georgia during the last 10 years. More than 80% of the water enters the penstock pipes in these plants in order obtain maximum profit.
The main fish species – trout became extinct in most of the high mountain streams. Construction of fishponds, commercial breeding, and production of fish became widespread in the country within the last 20 years. We have found that otters more often moved to the fish ponds, most likely as a consequence of habitat destruction and declining fish stocks in the country’s rivers.
Small hydro power station operations result in destruction of valleys and decrease as well as pollution of the freshwater supplies. Fish farmers see otters as their competitors. This perception results in persecution and killing of otters at every possible opportunity. Farmers illegally trap otters using leg-hold traps in rivers, streams and particularly near fish ponds. In addition, trees and other vegetation near the ponds are destroyed to deprive wildlife (e.g. otters, raccoons, grey herons) of any shelter.
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Impacts of Roads and Traffic on Otters and Other Mammals
Jan Olof Helldin
Wildlife ecology, Calluna AB, Stockholm, Sweden

Roads and traffic have several negative impacts on individuals and populations of mammals. Individuals may be killed by vehicles, experience barrier effects and habitat loss, and may be disturbed by noise, lights or other visual stimuli. Although roadsides, bridges and other road related structures may be beneficial for some species under some circumstances, the negative impacts prevail. New roads may also have ”contagious” effects impacting mammals, in that they open up for secondary exploitation and facilitates forest cutting, hunting, leisure activities and other potentially adverse human intervention. Population effects on mammals extend up to 5 km from large infrastructures, hence in countries with a developed infrastructure network most of the landscape – and accordingly most of the individuals – are affected in one way or another.
In response to this situation, Swedish transport authorities strive to limit the negative impacts of roads and traffic on mammals as well as other species. One prominent feature of these ambitions are the large resources put on what is labelled ”otter mitigation”, consisting mainly of technical structures aiming at allowing otters and similar sized animals to pass dryshod under roads near rivers and streams. However, not only have monitoring of the effectivness of such structures until now been virtually lacking. Also, available data indicate that roads and traffic are no significant problems for otter conservation in Sweden, that the main effects are rather to be found in other species, and that present mitigation efforts therefore are poorly targeted. Too much of ”otter mitigation” along roads threatens to obscure the true determinants of the otter population status, and ultimately hamper otter conservation. As to road underpasses, it should be better acknowledged that they are needed for an array of medium-sized mammals, and it may well be that their largest favours are in relation to other species than otters. This may in turn affect the design details of such constructions, as well as the priority they are given in the mitigation portfolio.
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Making otters count: a citizen science approach to surveying for otters (Lutra lutra) in north east England.
Vivien Kent
Durham Wildlife Trust, United Kingdom

The Eurasian Otter (Lutra lutra) is the only otter species native to the UK. Between the 1950s and 1970s populations declined dramatically to the point that the species was in danger of extinction in England. Since then, and following the withdrawal from use of organochlorine pesticides and a reduction in other environmental pollutants, the otter has made a slow, gradual recovery in England. It is now important that the population is monitored regularly so that any future declines are picked up before numbers once more reach dangerously low levels, however such monitoring presents many challenges. Surveying for otters is notoriously difficult as they are cryptic, shy, range over large areas and are largely active at night. As a result, data on numbers of individual otters or of otter territories is deficient. In 2013, Durham Wildlife Trust instigated an annual, volunteer-led otter survey taking place over a single weekend in spring which was designed to take a ‘snap-shot’ of otter activity across the whole of historic County Durham on one night. More than 120 volunteer citizen-science surveyors have since been trained in identifying otter field signs. On both mornings of the survey weekend they check a selection of ‘sites’ in an allocated ‘patch’ of watercourse. The same ‘sites’ are checked on both days with fresh field sign found on the second day, that was not present on day one, indicating otter activity the previous night. This data allows us to estimate the minimum number of active otter territories in the area surveyed. Three surveys have now been completed and the number of otter territories identified were 29 in 2013, 35 in 2014 and 36 in 2015. The area and number of patches surveyed as increased each year. Continued annual surveys of this kind will ensure that any future declines in the population will be identified early, the reasons for it investigated and measures taken to address the problem.
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Radio -telemetry to track Eurasian otter (Lutra lutra): a critical review
Hans-Heinrich Krüger
Action for Otter Conservation, Otter-Zentrum, Hankensbüttel, Germany

The Eurasian Otter has been the subject of increasing scientific interest. Although radio-telemetry-tracking on otters has been used in studies for more than thirty years, it is still a species which requires further research. The main reason for the problem of getting reliable data is that otters are difficult to radio tag because of their similar head and neck circumference. Collars cannot be used. And otters are very difficult to trap. In most radiotelemetry studies harnesses and intraperitoneal-implanted transmitters were used. In the last few years, GPS-tags have been developed and some studies have been conducted with this new technique.
This presentation attempts to review all available studies that have used radiotelemetry. It aims to show the amount of individuals that have been tagged with the different types of transmitters, what kind of problems have occured, how many otters have died due to the different techniques, what happened to the individuals after the study, and whether there is a lack of relevent information in the published studies.
The main result of this review is that many radiotelemetry studies have been conducted in a lot of countries in Europe. In ralation to the amount of studies, the quantity and quality of the results is low. In many cases the method and the problems with these techniques are not described in a proper scientific way.
Discussion of the lack of information and the obvious problems with trapping could lead to improvements in methods and to minimisation of the adverse effects of radio-telemetry tracking on the instrumented animals.
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The Otter Action Plan in France, what has been done so far? From coexistence of otter and fish-farming to the creation of Otter Havens 
Rachel Kuhn and Hélène Jacques
Société Française pour l’Étude et la Protection des Mammifères (SFEPM), France

A national action plan for the Eurasian otter has been implemented in France since 2010 in order to encourage the natural recolonisation, while avoiding severe conflicts of interests between otters and humans. This is part of the policy and strategy of the Ministry of Ecology. The plan has been compiled in 2009 by the French Mammal Society (SFEPM), which is now the national coordinator. The implementation is at a national and at a local level. Efforts are made to involve all possible key players (NGO’s, scientists, authorities, road contractors, fishers…) and to integrate with existing policies and initiatives.
The strategy presented in the plan covers a broad spectrum of subjects, from monitoring to education work. A key issue is to reconcile otters and fish-farming. This includes raising awareness of problems, convincing fish-farmers to coexist with otters and offering them assistance to protect their facilities against otter predation.
Another initiative is the Otter Haven Project. Each riparian land owner has the possibility to create an Otter Haven by signing an agreement to manage the property in an otter friendly way. Thus the proprietor gets information about otters, management advices, joins an Otter Haven owner network, and is invited to events. It is also possible to get stickers and an Otter Haven sign for the property, which is a way to communicate a message to friends, neighbours and passers-by. The Otter Haven project is not only a way to improve otter habitat, it’s also an education tool and a way to get citizens involved. It’s citizen conservation.
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Experiences from post mortem analysis of otters in Hungary
József Lanszki, Miklós Heltai, Gabriella L. Széles and Éva A. Bauer-Haáz

University of Kaposvár and Szent István University

We examined the mortality causes and some biological parameters on carcasses (n, male: 159, female: 145, unknown: 5) of otters collected in Hungary between 1999 and 2014. Most otter carcasses were collected as road casualties (82.8%). Otter attacks (6.1%) and dog attacks (4.2%) causing mortality was relatively frequent. Poaching (1.9%), assumable poisoning (0.3%) , drowning in fish-traps (1.0%), disease (distemper in one case) and unknown cases were also detected.
The mean body mass of adult males was 8.57 kg and of the females 6.21 kg. Values of the condition index increased across age classes (juvenile: 0.86, subadult: 1.00, adult: 1.12). In adult females (n = 74) the mean (± SE) number of placental scars or embryos was 1.35 ± 0.15. In 39% of the females no placental scars were found. In breeding females (n = 45) 2.22 ± 0.13 placental scars or embryos were counted in the uterine horns. Nine females were pregnant.
One problem is that the age structure of the otter population in Hungary is still unknown. In the otters examined the composition of food items in the stomach (which is nearest to the actual food ingested) and the rectum content (which relates to the composition of diet and allows non-invasive exploration of diet by collecting spraints) were basically similar. Otters preyed primarily on small-sized (<100g) cyprinids, mainly on non-commercial fish.
On the basis of 255 tissue samples analysed (using ten microsatellite markers), a relatively high level of genetic diversity in Hungarian otter populations was found (He: 0.69-0.74; mean number of alleles per locus: 6.8-7.7). Two distinct genetic clusters corresponding to the Danube and Tisza river basins were identified. Overall the research serves the efforts of conservation of otters and otter habitats in Hungary and beyond.
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Non-invasive methods on otters: so hard, so useful
Laura Lerone, Chiara Mengoni, Ettore Randi and Anna Loy

University of Molise
and Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), via Ca’ Fornacetta
In Italy, as in most central European countries, the Eurasian otter (Lutra lutra) is recovering and expanding in its former range after the strong decline of the ’90s. Nevertheless, still little is known on density, structure, and metapopulation dynamics especially along the boundaries of its current range. We conducted a study in the Sangro river basin, at the northernmost boundary of the otter range in south-central Italy. We used two non-invasive methods: genetics on scats and camera trapping, which are particularly hard to perform on otters. We analysed a total of 244 otter spraints and jellies using a panel of 13 microsatellite loci, and the ZFX/ZFY loci for molecular sexing. We performed the sibship analysis using the software Colony.
We also set camera traps during 260 day/traps to record otters marking behaviour and habits. To succeed in camera trapping we modified camera traps to be activated by a pressure trigger instead of the usual infrared sensor. Non invasive genetic samplings, run from April 2011 to September 2012, revealed the presence of at least 14 individuals (8 males, 4 females, and 3 undetermined) along 65 km of river courses, with a mean density of 0.17 individuals/km. A fine scale spatial analysis revealed both intra and inter-sexual overlapping among otters. Related females were confirmed to share their ranges. Moreover, we found both related and unrelated males to share their territories. One male was recaptured 14 times in over 40 km of river courses, while another male covered a 15 km stretch during a single night. Camera trapping provided with the pressure trigger allowed to confirm the otter solitary and nocturnal habits in our study area. In conclusion, non-invasive genetics combined with camera trapping suggests that otters in the study area are nocturnal and solitary even if not strictly territorial, as both males and females were found to share the same river stretches. Also, the long distance daily travels and the extent of male home ranges confirm that a successful otter conservation could only be achieved through management planning at river basin scale
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Monitoring otters and their habitats in Europe. Shall we take advantage from EU directives?
Anna Loy
Università del Molise, Italy
The UTM grid based standard otter survey recommended by the IUCN-OSG since 2000 resulted in an efficient and accurate tool to monitor otters in both space and time in the EU territory. Moreover, the standard survey is in accordance with monitor obligations under art. 17 of the Habitat Directive (HD 1993/43/EC), and, unlike the latter, it also reports on negative results, thus allowing a more accurate evaluation of population trends. By counterpart, habitat evaluations coupled with the standard otter survey have suffered from a lack of accuracy and standardization, and assessments have often been derived from subjective evaluations of different combinations of biotic and abiotic factors (water flow and quality, riverbank vegetation, substrate, feeding resources, water flow, river width, topography, etc.).
The standard methods developed to assess the river ecological and geomorphological quality under Water Framework Directive (WFD, 2000/60/EC) reporting obligations represent an important opportunity to monitor the quality of otter habitat in comparable way throughout EU territory. Recent studies aimed at relating otter occurrence to indices of river quality developed under WFD obligations for Italian rivers, i.e. the Morphological Quality Index (MQI) and the Core Assessment of River Habitat Value and Hydro-morphological Condition (CARAVAGGIO) allowed to identify significant environmental factors affecting otter occurrence at both small and large scale. Results revealed both positive and negative significant effects of individual parameters, sub indices, and indices on otter occurrence and abundance in the study areas. These evidences offer a first contribution to the integration of HD and FWD monitoring obligations, and to the definition of a new standard protocol for monitoring otters and their habitat in EU.
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Designing occupancy studies to monitor otter populations.
Manlio Marcelli and Romina Fusillo
LUTRIA Wildlife Research and Consulting, Rome, Italy

The proportion of sampling units in a landscape where a target species is present (occupancy) is a state variable traditionally used to monitor otter populations. Standard surveys for Eurasian otters (Lutra lutra) relies on searching for indirect signs along river transects (sites) 600 m in length. Multiple transects included in larger sites (e.g. 10 km squares) have been also suggested to cope with large scale applications (e.g., national surveys). Traditional approaches were intended to alleviate the issue of imperfect detectability (i.e., false absences) in otter surveys by using spatial replication, and reduce potential bias in occupancy estimates obtained from mere counts of sites where presence of otters is detected.
A best approach is to estimate detection probability by using recent developed occupancy models and derive an optimal transect length, or an optimal number of transects in any given situation, to achieve unbiased and precise occupancy estimates. Occupancy models enable to estimate simultaneously occupancy and detection probabilities using replicate presence-non-detection data collected at each sampling unit. Replication is often achieved via temporal or spatial subsampling. The occupancy modelling framework has been scarcely used for otters, especially to assess changes in occupancy rates and distribution over time.
In this presentation we comment on a number of specific issues related to designing surveys of otter populations, including the size of sample units, the kind of data replication (temporal vs spatial), and allocation of survey effort, given the biology of otters, the typical logistical limitations of stream surveys and the study objectives. We also discuss a recently developed extension of the basic occupancy model that enable to deal with spatially autocorrelated replicates and its potential for designing efficient surveys for otters. We would encourage otter ecologists involved in occupancy studies and monitoring programs to definitively shift from standard transects to estimation of detection probability.
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CURRENT distribution, population and population density of the Eurasian otter (Lutra lutra) in Russia and some adjacent countries – a review
Alexey Yu. Oleynikov and Aleksander P. Saveljev
Russian Academy of Sciences, Russia

In this paper we review the available literature, mainly Russian, and present our data on the distribution, number and population density of otter in Russia and in some adjacent countries. The Eurasian otter is a wide spread species in the Russian Federation, with a distribution from the tundra zone to the subtropics. The description of the northeastern border of the current geographic range of Lutra lutra is presented. Estimated otter population size in Russia is approximately 60-80 thousand individuals. Population density of otters in various habitats can differ within two orders of magnitude, ranging from 5-8 to 0.05 individuals per 10 km of coastline of water reservoirs. The otter is included in Red Data Books of 48 regions of Russia and is a harvested species in 21 regions.
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Noninvasive surveying of otters in Ireland and Wales using a community-based citizen science approach
O’Neill, Sheerin, E., Turner, P.D., O’Meara, D.B., Harrington, A., Macpherson, J., Morris C., Denton A., Clews-Roberts, B., Guest, B., Schofield, H., Halliwell, Liz and
Catherine O´Reilly
Mammals in a Sustainable Environment (MISE) Project: Waterford Institute of Technology; Waterford City and County Council; Natural Resources Wales;The Vincent Wildlife Trust
Monitoring and conserving biodiversity is increasingly being recognized as critical for sustainable development. Developing strategies to maintain biodiversity requires baseline information on the current status of each individual species. The non-invasive approach to monitor mammals, especially elusive species, is an increasingly applied technique in obtaining information on the structure, size, and genetic diversity of a population. The Mammals In a Sustainable Environment (MISE) Project aims to encourage community involvement in mammal conservation and to increase the knowledge base gained from wildlife surveys. A suite of DNA-based assays to monitor otter (Lutra lutra) populations using a non-invasive DNA source (spraints), collected through citizen scientist-based surveys, is presented here.
Methods Volunteer, citizen observers were trained in mammal surveying and in the collection of samples for genetic studies.
Novel species-specific real-time polymerase chain reaction (qPCR) assays using fluorescently-labelled TaqMan® MGB probes were developed to enable species and sex identification from spraints. Haplotypes were determined by DNA sequence analysis of a section of the mitochondrial DNA control region. Previously published microsatellite markers, some of which were redesigned, were also used for genotype analysis to identify individual otters.
Citizen scientists also participated in workshops for otter diet analysis by traditional hard-part examination.
Results and discussion
The novel molecular-based assays have been shown to work efficiently with tissue, hair and spraint DNA.
Since 2011, MISE has engaged with over 3,000 people through project events and surveys and over 2,500 school children. Through otter-focused events alone, MISE accumulated over 5,000 spraints and engaged with over 500 volunteers in more than 25 project surveys and workshops. Example surveys from Ireland and Wales, including a variety of habitats and types of data that can be generated with citizen science, are presented. The MISE project has successfully engaged with thousands of people by working with schools, community groups and the general public. Through science, action and influence, MISE has achieved in increasing awareness towards biodiversity conservation and sustainable environmental development
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Wild mink as a sentinel species in environmental monitoring
Sara Persson, Anna Rotander, Bert van Bavel, Britt-Marie Bäcklin, Björn Brunström and Ulf Magnusson

Swedish University of Agricultural Sciences; Örebro University; Swedish Museum of Natural History; Uppsala University, Sweden

Increasing evidence indicates that pollutants may affect the hormone system of humans and wildlife. These endocrine-disrupting chemicals are related to an increased risk of a variety of diseases and disorders, including adverse effects on the reproductive system. By using a sentinel wildlife species, an early warning of adverse health effects due to pollutants in the environment may be provided. The possibility of establishing the wild mink (Neovison vison) as a sentinel species in Sweden, for both exposure to pollutants and effects of pollutants on the reproductive system was investigated
Wild male mink were collected from local hunters from August to the end of April (year 2004 to 2009) in Sweden and the reproductive system was examined on necropsy. The concentrations of a number of persistent organic pollutants (chlorinated, brominated and perfluorinated) were analyzed in subcutaneous fat and/or liver.
Sample season, age and body condition significantly influenced some, but not all, of the concentrations of chlorinated, brominated and perfluorinated compounds and also some reproductive organ variables. Considerable concentrations of PCBs were found in some areas and the concentrations of PFOS were among the highest ever recorded in mink. Associations were found between measurements on the reproductive organs and pollutant concentrations. The anogenital distance was inversely associated with concentrations of some perfluoroalkyl acids and DDE. Associations were also found between some PCB congeners and measurements on the penis and baculum.
In conclusion, the wild mink males may serve as an indicator for environmental exposure to pollutants in Sweden. In addition, the wild mink seems to be a suitable sentinel species that may provide an early warning of alterations in the male reproductive organs related to environmental pollution
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Recovering Otter (Lutra lutra) carcasses and information on mortality in the NE Iberian Peninsula: 65 years of results.
Jordi Ruiz-Olmo, Francesc Mañas, Antoni Batet, Berto Minobis, Juan Jiménez, Manuel Alcántara and Santiago Palazón

Direcció general del Medi Natural (DAAM); Generalitat Valenciana, Spain

The Eurasian otter has experienced a significant recovery in the Iberian Peninsula from 1987 to 1990, having been previously close to extinction. This study area of 1.003.442 km2, includes Catalonia, Aragon and Valencia (Spanish state) and Andorra. The aim of this study was to establish how the otters are there, the causes of mortality and other factors affecting the otter conservation.
Since 1985 we carried out a death otter carcasses recovery program in the NE Iberian Peninsula. Previously, we were able to collect the published information on dead otters since 1950. In total a period of 65 years in which it has been collecting information on over 400 specimens of otter was covered. For the carcasses the corresponding necropsies were carried out. Date, location (exact coordinates), cause of death, sex, age (counting the annuli in the teeth), biometrics, body condition, and reproductive status were established, keeping various tissue samples to undertake studies on genetics, diseases, pollution, variables determining the causes of death, and other.
Within this database we included the found-death radiotracked otters, allowing us to make an assessment of the relevant biases when obtaining the carcasses opportunistically.
Results and discussion
Results on geographical evolution, cause of death, population structure, genetics, pollution or condition, among others, are presented. The proportions in causes of death for radiotracked specimens found dead, statistically differed from those which were found opportunistically, which puts us on alert in the interpretation of results. However, the general patterns and the order of importance of each type of cause of death did not differ. Overall, since 1985 the road traffic is the leading cause of death, having been increasing along time. The deaths caused deliberately by humans (ex. firearms or traps, ) have virtually disappeared, although mortality from causes related to human activities explain virtually all deaths that occur.
Finally, we call the fact that we still getting otter samples for analysis, this is not being undertaken because the difficulty of financing, now that the otter is no longer an endangered species.
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Wildlife Conservation in North America: Science, policy, and politics portrayed through the eyes of the North American river otter
Tom Serfass
Department of Biology and Natural Resources, Frostburg State University, USA

The reintroduction of mammalian predators often has been met with controversy among citizens near reintroduction sites primarily because of concern for predation of domestic animals and game species (species popular for recreational hunting). The North American river otter (Lontra canadensis) is an example of a predator widely reintroduced in the United States that has in some cases been negatively depicted in the media because of its predatory habits (i.e., fish eating). The successful reintroduction of river otters in Missouri, Ohio, Kentucky, and Illinois was followed by negative media messages pertaining to otters preying on fish. In contrast, the reintroduction of river otters in Pennsylvania (PA) was accompanied by positive media portrayals and overwhelming public support. I review factors that likely contributed to public acceptance of river otter reintroduction in PA, emphasizing the importance of applying social science theory and methodologies as a basis for determining and accurately depicting public attitudes toward reintroduction of mammalian predators. Throughout I critically review elements of the so called “North American Model of Wildlife Conservation” in relation to the conservation of the river otter.
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Spotted-necked Otters and Rubondo Island National Park, Tanzania: The process of developing an ecotourism flagship
Tom Serfass and Sadie Stevens
Frostburg State University, Maryland, USA

To most North Americans and Europeans otters are highly esteemed for intelligence, playfulness, and attractiveness. In fact, otters are regarded by many conservationists from these regions as key indicators of the health of aquatic and wetland ecosystems. Additionally, the playful behavior and appearance of otters make them particularly appealing to many people with a recreational interest in viewing wildlife. Consequently, in addition to their potential value as 'bio-indicators' in aquatic environments, otters also possess characteristics that make them excellent candidates for use in promoting wildlife tourism in landscapes dominated by aquatic environments.
Unfortunately, otters have received little conservation and research attention in most areas of the world outside of North America and Europe - especially in Africa. During 2007-2008 we conducted human dimensions and ecological studies at Rubondo Island National Park to evaluate the potential of spotted-necked otters (Lutra maculicollis) inhabiting the Island to serve as flagships for promoting tourism to the area. Human dimension studies focused on assessing attitudes and knowledge of local people about otters, the interest of tour operators in taking clients to Rubondo to view otters, and the interest of tourists in visiting Rubondo for otter-viewing opportunities.
Ecological studies focused on assessing where, when, and how to best view otters at Rubondo by assessing habitat preferences, activity patterns, and behavioral responses to the presence of people. We discuss the outcomes of these investigations, how these outcomes can be integrated and applied by the Park for promoting otter-based tourism, and both challenges and opportunities for using the otter as a tourism flagship.
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The Eurasian Otter in Israel: From science to conservation management.
Roni Shachal, David Saltz and Amit Dolev
Jacob Blaustein Institutes for Desert Research and Israel Nature and Parks Authority

The Eurasian otter population in Israel has undergone a dramatic decline in abundance and distribution since the 1960s, largely due to habitat degradation, drainage of water sources, habitat fragmentation and road mortalities. Long-term monitoring of occupancy since 2000 throughout northern Israel indicates that otters in this area exhibit meta-population dynamics with local extinctions and re-colonizations. Identifying the environmental factors affecting the extinction and re-colonization processes is crucial for proper management.
We developed an “occupancy model” using program “MARK”, analyzing presence-absence data (based on spraint detection) over the last 14 years. Environmental variables such as habitat type, patch size, and potential connectivity were incorporated into the model, allowing us to parameterize extinction and re-colonization rates, and identify the key factors affecting the dynamics of the meta-population.
Results and discussion
Findings show a continuous decrease in re-colonization rates and a moderate decrease in the proportion of occupied sites, but only a small increase in extinction rates through the years. Habitat quality, connectivity and the interaction between them were the key factors affecting extinction and re-colonization: overall occupancy and extinction are mostly affected by the above interaction, and re-colonization is mostly affected by connectivity alone. Our results highlight the importance of maintaining connectivity between habitats to ensure the continued viability of the population. Based on our findings, two main management actions at two scales (local and regional) were taken: At the local scale - ledges were constructed under four "hot" bridges to reduce otter road kills. Camera traps and tracks-pads verified that these ledges were being used regularly by mammals (otters, martens, mongoose, and porcupines). Thus, the ledges mitigate road casualties and enhance movement between different habitats. At the regional scale - we are implementing an extensive restoration program of the main corridor connecting the Sea of Galilee basin populations with the less stable costal-region populations. Restoration actions include freeing natural water sources, water quality improvement, and restoration of streambeds, including bank reconstruction and the reintroduction of local vegetation communities. Continued monitoring of the otter metapopulation will reveal the effectiveness of these management actions.
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Gradual recovery and recent strong decline in the Eurasian Otter (Lutra lutra) population in Belarus.
Vadim Sidorovich
Institute of Zoology, National Academy of Sciences of Belarus, Belarus

n Belarus, in the 1980s and 1990s, occasional catches by beaver trappers and extermination by furbearing poachers suppressed the Eurasian otter (Lutra lutra) populations considerably in most of its territory, outside well-protected reserves and hardly accessible wild areas. There the species density was markedly lower than its potential number in connection with the habitat carrying capacity. The late 1990s were characterised by lost of interest in fur production; and finally furbearing declined in Belarus. However, after this period, fishing with fyke nets widely spread in Belarus halt the further restoring of the otter population. At last, fishing with fyke nets was more or less stopped by the increased efficiency of nature protection, increasing the otter population. In the mid 2000s the otter population thrived in Belarus. The species reached its carrying capacity and populated rivers with relatively high density: small rivers: 2-8, mean about 4 inds/10 km of stretch, medium-sized rivers: 4-11, mean about 7 inds/10 km of stretch. Suddenly, in autumn 2008, the otter population declined manifold (20-50 times) in different areas.
Otter survey in 2009-2010 showed that the otter population crashed countrywide. For instance, during the winter of 2005-2006 in Naliboki Forest and its surroundings (central-western part of Belarus) about 580 otters lived in a 2.8 thousands km2, while in December 2008 in 60-70% of that area only 8 otters were registered. In the spring of 2011 in different areas otter population increased again between 5-30% when compared to 2006-2007. During the winters of 2013 and 2015 an additional recover of the otter populations was registered (approximately 20% to 70%) in the central-western, central-northern and north-eastern parts of Belarus. There are no significant data available for other areas of Belarus.
The fast decrease of the otter numbers along with the finding of dead otters around 2008 suggests an epidemic in the population. Although not be directly confirmed the simultaneous fast decline in American mink (Neovision vision) populations in the same areas supports the hypothesis of the presence of a dangerous disease in the both populations.
While examining the semiaquatic predator prey supply in a few small rivers in 2009-2010, no significant changes in fish and common frog biomass were found. Concerning reproduction rate in otters, the data evidenced normal breeding rate – 24% of the individuals registered in 2009-2011 were cubs (n=283). The plausible hypothesis for the decline in otters in the autumn of 2008 may be as follows. Although there is an obligation to vaccinate captive-bred carnivores, owners of furbearing farms may not have vaccinated their American minks in many cases, in order to save money. If an epidemic happened in such a farm, animals that escaped into the wild acted as disease vectors affecting also the otter populations.

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Population structure and recent temporal changes in genetic variation in Eurasian otters from Sweden.
Jean-Luc Tison, Victor Blennow, Eleftheria Palkopoulou, Petra Gustafsson, Anna Roos and Love Dalén.

Swedish Museum of Natural History and Swedish Museum of Natural History
The Eurasian otter (Lutra lutra) population in Sweden went through a drastic decline in population size between the 1950s and 1980s, caused mostly by anthropogenic factors such as high hunting pressure and the introduction of environmental toxic chemicals into the otter’s habitats. However, after legal protection and the bans of PCBs and DDT in the 1970s, the population began to recover in the 1990s.
This study compares microsatellite data across twelve loci from historical and contemporary otter samples to investigate whether there has been a change in population structure and genetic diversity across time in various locations throughout Sweden.
The results suggest that otters in the south were more severely affected by the bottleneck, demonstrated by a decline in genetic diversity and a shift in genetic composition. In contrast, the genetic composition in otters from northern Sweden remained mostly unchanged, both in terms of population structure and diversity.
The results suggest that the decline was not uniform across the country. Moreover, our analyses of historical samples provide an overview of the level of genetic variation and population structure that existed prior to the bottleneck, which may be helpful for the future management and conservation of the species.
This study is in press in the journal Conservation Genetics (DOI: 10.1007/s10592-014-0664-2)

Peter Urban

Department of Biology and Ecology, Faculty of Natural Sciences, University of Matej, Slovakia
The Eurasian otter (Lutra lutra) is a fully protected native animal species in Slovakia. At present the otter occurs in most parts of the country. Coexistence of otters and humans involves many conflicts. The most important negative factors affecting otters are road kills, destruction and fragmentation of habitats, illegal hunting and killing, water pollution, the use of hydrological resources etc. Despite the general prohibition of hunting protected animals in Slovakia, the cases of shooting, beating to death or capture of otters in traps or in fyke nets are considerable and indicate insufficient awareness of their protected status. Most of these threats are tending to increase.
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Distribution, activity patterns and genetic relations of Eurasian Otter (Lutra lutra) in Roaring Water Bay, Ireland.
Jacob van der Ploeg, Teun Smink, Daan Smit, Addy de Jongh, Catherine O'Reilly, Ferdia Marnell, David O'Neill and Edel Sheerin
Van Hall Larenstein; Zambian Carnivore Programme; Dutch Otterstation Foundation; Waterford Institute of Technology; National Parks and Wildlife Service, Ireland

In May – July 2014 a study on coastal otters was conducted in Roaringwater Bay (RWB), County Cork, Ireland. The goal of this study was to find out more about distribution, population makeup (density and diversity) and activity patterns of the animals.
In this study we used a combination of several methods: 1) spraints surveys, 2) visual observations, 3) camera trapping, 4) results from earlier GPS tracking of individual otters and 5) DNA analyses of spraints. Surveys were conducted every eight days to map distribution based on spraint sites. Fresh spraints were collected for DNA analysis and 15 camera traps were deployed to determine activity patterns and estimate population densities. DNA analyses were carried out at the Waterford Institute of Technology, Waterford, Ireland. Population size in RWB was estimated using GPS data of tagged otters and from camera trapping data using the program Presence. Camera trapping data were also used to determine the activity pattern of otters.
Spraint surveys showed that otters are present everywhere in RWB. A minimum convex polygon (MCP) was used to determine home range sizes based on the GPS data from 3 tagged otters. The ranges of the two females were 1,7km2 and 1,6km2 and 7,6km and 6,4km in shore length at the Ilen estuary. The male home range was estimated to be 2,0 km2 with a shore length of 5,6km on Sherkin Island and the coast of Baltimore. The home range size and camera trap data showed that RWB could host between 175 – 219 otters. Activity of the otters in RWB was mainly nocturnal.
Out of the 353 collected spraints, 330 were positively identified as Eurasian otter, 125 of which were suitable for sex-typing. From these 59 tested positive for female and 66 for male. 19 Samples were successfully genotyped, allowing to identify 13 different otters in different parts of RWB .
In contrast to Shetland coastal otters in RWB were found to be mainly nocturnal. Coastal home ranges were slightly larger in RWB than on Shetland. With only 13 different otters the genotyping result was too low to draw any conclusions in comparison with population estimates from home range sizes and trap cams. However genetic relatedness showed that interactions between individuals from different parts of the bay take place..
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Status of the otter population in the Netherlands
Ellen van Norren, Hugh Jansman, Vilmar Dijkstra and Arjen de Groot

Dutch Mammal Society and Alterra
After becoming extinct in the Netherlands in 1988, 32 otters were released in the period 2002-2008 in the northeast of the Netherlands. In this study we explain how they are doing.
The reintroduction is monitored by Alterra and the Dutch Mammal Society. The first focuses on post-mortem examination and DNA typings from spraints. The latter focuses on presence/absence of otter signs with help from volunteers and water boards for gathering fresh spraint.
Since the reintroduction, otters have distributed further away from the reintroduction site, resulting in a distribution especially to north, east and centre of the Netherlands. Even in the west, south of Amsterdam, otters have occupied a new area (Nieuwkoopse Plassen). In 2012-2014 otter signs were found in an area of about 850 square kilometres. In the winter of 2013-2014, 673 fresh spraints were gathered. 33% resulted in a DNA profile. In combination with DNA from traffic casualties, this resulted in 111 unique profiles. This is an underestimation of the population size, because animals are missed. The population is estimated to be around 140 individuals (2014).
The population of otters is growing faster than expected at the moment of the reintroduction in 2002. Success factors are the improved water quality, thanks to the Water Framework Directive measures and the improved connection of waterways, thanks to the National ecological Network (example Nieuwkoopse Plassen). The population of otters is on its way to becoming a sustainable population.
Today inbreeding and traffic casualties are the main problems for the otter in the Netherlands. In 2013 26 otters were found dead of which 23 (88%) near roads. We estimate that 22-26% of the total population died in traffic that year. Other risks for otters are fishnets/fykes and in a less extend traps for muskrats. As a side effect of the DNA based monitoring, insight in the pedigree and inbreeding can be obtained as well. Small populations are prone to genetic drift and inbreeding.
Additional release of genetically unfamiliar otters is recommended to avoid inbreeding on the short term. Natural dispersal with the neighbouring West-European (German) otter population seems to be a matter of time, two otters are already identified as German by DNA.
When is the reintroduction finished, and when is the population sustainable?
When based on genetic monitoring it is proven that there is sufficient influx of neighbouring otters (Germany) spreading there genes in the Dutch population, resulting in a genetically healthy population that is integrated in an international meta population. In addition, the amount of casualties in traffic and fishing nets needs to decrease. Measures need to be taken in the entire country. The water quality is all right, but in some parts, the water quality probably has to improve. The Dutch government has planned to designate the otter in Brussels, as a habitats directive list II and IV species.
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Benefits and disadvantages of anthropogenic modifications to the riparian landscape for the Eurasian otter Lutra lutra in the Alps.
Irene C. Weinberger, Stefanie Muff, Andreas Kranz and Fabio Bontadina

University of Zurich, Switzerland; alka-kranz Ingenieurbüro für Wildökologie und Naturschutz, Austria; SWILD - Urban Ecology & Wildlife Research, Zurich, Switzerland

Animals have different habitat requirements for behaviours such as foraging or sleeping. Information on selection of specific habitats for particular behaviours is particularly important for species in anthropogenically altered landscapes. The riverine landscape in the Alps was one of the last pristine refuges in Europe, but now it is severely reduced by urban sprawl, and modified by alteration of river courses and increasing numbers of hydropower plants. During the last century the Eurasian otter Lutra lutra almost disappeared from the Alpine Arc but recently the species has begun to recolonise parts of its former distribution. The aim of our study was to understand the habitat requirements of the otter in the Alps to facilitate its natural recovery.
Nine otters were radiotracked for between six and 30 months in Styria, Austria. Radio tracking was conducted at night in bouts of several hours for foraging habitat selection, and with single fixes during daytime to identify resting sites. Environmental data and information on human presence along the freshwater courses were collected. Data was analysed using logistic regressions with a used-available design and a step selection function where habitat use was combined with movement.
Home ranges encompassed main river lengths with a mean of 18.3 ± 6.1 km for females and 25.2 ± 4.1 km for males. Within the main river bed, the animals significantly selected the reservoirs (area above the dam) with widths up to 12 m for foraging, but avoided residual waters (area below the dam) of the same width (estimate -2.036, p= 0.035).
In rivers wider than 12 m, this selection was reversed, with residuals being favoured and reservoirs avoided. While foraging, otters were not affected by the degree of modification of the riparian habitat. However, for resting they selected for stretches with natural riparian vegetation. The vegetation width was larger with human disturbance for used resting sites compared to available resting sites (p < 0.001). Our results illustrate a mammal with flexibility in selection of foraging habitats, tolerating or even benefitting from modifications to rivers. In contrast, otters appear to prefer natural riparian habitats when resting. We presume that the availability of optimal habitat for resting sites is one of the limiting factors for otter persistence in human altered landscapes. These findings are encouraging for a return of the species to the Alps as long as the altered riparian landscape is frequently interspersed with stretches of natural habitat.
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The biggest otters you never saw
Lars Werdelin
Department of Paleobiology, Swedish Museum of Natural History, Sweden

In this talk I will briefly review the fossil record of otters, subfamily Lutrinae, which is extensive, as can be expected of a clade of carnivorous mammals that has been semi-to-fully aquatic throughout its existence. I will focus most of my talk on a tribe of extinct Lutrinae, the Enhydriodontini (once thought to be related to the sea otter, Enhydra, hence the name). This tribe had its main distribution in Africa and on the Indian subcontinent, with a possible foray into western Eurasia. It ranged in time from the early Late Miocene, ca 11.5 million years ago, to the latest Pliocene/earliest Pleistocene, ca 2.5 million years ago (with an uncertain record dated to about 1.8 million years). The Enhydriodontini included several genera, with the most diverse being Enhydriodon, with more than half a dozen named species to date. Species of Enhydriodon evolved from being slightly larger than the living clawless otter (Aonyx capensis) in the Late Miocene to being the largest otters that ever existed, with species from eastern Africa attaining truly gigantic size. An approximately 2.5 million year old femur from the Shungura Formation, Omo River Valley, southern Ethiopia is somewhat larger and much more robust than the femur of a male lion, suggesting a body mass somewhere in the range of 250-300 kg and perhaps more. The Enhydriodontini appear to have been somewhat more terrestrial than living Lutrinae, but are always found in association with large bodies of water. We can only speculate about the habits and diet of an animal that different from any living relative, but one possibility is that they fed on armored catfish, which could attain great size in the paleorivers and lakes of eastern Africa.
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