Habitat correlates of the Eurasian otter Lutra lutra recolonizing Central Poland

The increase in Eurasian otter Lutra lutra populations in their natural range and recolonization processes are recently observed in several European countries. We address the process of otter recolonization and habitat utilization in Central Poland over 14 years. Field surveys in 1998 and 2007 documented increase in occurrence of the species. The frequency of positive sites denoted 15 % in 1993, 38 % in 1998, and 89 % in 2007. Otter occurrence at study sites was positively affected by river width while negatively affected by presence of buildings at the site and river regulation. During the most intensive colonization process in the 1990s, the habitat preferences of the otter did not change. However, the sites inhabited by otters after 1998 were characterized by lower river width and tree cover and were more often located on regulated river sections, suggesting change in habitat tolerance during expansion. The otter abundance in transformed habitats is a result of increasing population numbers and the necessity to inhabit suboptimal sections of watercourses. Thus, it seems that presence–absence data for otter populations cannot be considered a reliable indicator of habitat quality, being depended of the population density.     

Diet of coastal foraging Eurasian otters (<Emphasis Type="Italic">Lutra lutra</Emphasis> L.) in Pembrokeshire south-west Wales

The importance of the marine environment to Eurasian otters is currently poorly understood. Wales is one of the few countries where coastal activity has been recorded and an increase in marine otter sightings could indicate remarkable developments within Welsh populations. The trophic niche of coastal otter populations around Pembrokeshire was investigated over a 12-month period. Marine activity was more widespread than previously thought and marine prey formed the largest component of otter diet, although, otters also consumed freshwater and terrestrial prey throughout the year. Otter diet was very diverse compared to other European coastal populations and a spring contraction in trophic niche width coincided with the estimated timing of breeding activity. Seasonal variation in prey composition was predominantly due to differences in the consumption of alternate prey types. In areas where wetlands are fragmented and populations of freshwater fish are declining, the marine environment may become an increasingly important habitat for otters. It is necessary to define the historical importance of coastal populations to otter conservation. Coastal areas are often subject to pressure from human activities, so the impact of disturbance needs to be assessed. Importantly, there is no verified otter survey method for coastal areas, so the use of marine habitat is likely to be underestimated.     

Review and quantitative meta-analysis of diet suggests the Eurasian otter (Lutra lutra) is likely to be a poor bioindicator

The Eurasian otter (Lutra lutra L.) is a top predator in aquatic systems and plays an important role in ecosystem functioning. However, it has undergone dramatic declines throughout Europe as a result of environmental degradation. We examine the putative role of the otter as a bioindicator in Ireland which remains a stronghold for the species and affords a unique opportunity to examine variation in its ecological niche. We describe diet, using spraint contents, along rivers during 2010 and conduct a review and quantitative meta-analysis of the results of a further 21 studies. We aimed to assess variation in otter diet in relation to river productivity, a proxy for natural nutrification and anthropogenic eutrophication, and availability of salmonid prey (Salmo trutta and Salmo salar), to test the hypothesis that otter diet is related to environmental quality. Otter diet did not vary with levels of productivity or availability of salmonids whilst Compositional Analysis suggested there was no selection of salmonid over non-salmonid fish. There was a distinct niche separation between riverine and lacustrine systems, the latter being dominated by Atlantic eel (Anguilla anguilla). Otters are opportunistic and may take insects, freshwater mussels, birds, mammals and even fruit. Otters living along coasts have a greatest niche breath than those in freshwater systems which encompasses a wide variety of intertidal prey though pelagic fish are rarely taken. It is concluded that the ability of the otter to feed on a wide diversity of prey taxa and the strong influence of habitat type, renders it a poor bioindicator of environmental water quality. It seems likely that the plasticity of the habitat and dietary niche of otters, and the extent of suitable habitat, may have sustained populations in Ireland despite intensification of agriculture during the 20th century.     

Is the standard Eurasian otter Lutra lutra survey strategy suitable for surveying the American mink Neovison vison?

The American mink Neovison vison is an elusive mustelid that is monitored mostly through the detection of its field signs, namely, footprints and scats. In Europe, the American mink has been often monitored using the standard otter survey strategy developed specifically for the Eurasian otter Lutra lutra, requiring to walk transects of 600 m spaced at least 5 km apart. We tested whether the standard otter survey strategy was appropriate for surveying mink. We studied a high-density population of mink along a 9-km stretch of river between December 2004 and April 2005. Monthly surveys were conducted and scats and footprints were recorded within 100-m sections along the river. The results showed a monthly variation in signs recovery, with the months of December, January and February being the best ones for surveying. Transects of 600 m detected mink between 74 and 90 % of the times in all months, excluding March when detection was as low as 56 %. Taken all together, the results suggest that the standard otter survey strategy was adequate to detect mink, at least in this case where species density was high. The study also highlighted monthly differences in signs detection, suggesting that temporal variations should be taken into account when designing the sampling strategy and the length of the sampling units (transects). In the months immediately following the mating season (and possibly in lower-density mink populations), it may be advisable to increase the length of transects to increase detection of mink.     

Biology and conservation of the Giant Otter Pteronura brasiliensis

The Giant Otter Pteronura brasiliensis (Zimmermann, 1780) is endemic to South America, distributed throughout the Orinoco, Amazon and La Plata River basins and numerous localities in the Guyanas. This otter is the largest member of the family Mustelidae, clearly distinguished from other South American otter species by morphological and behavioural characteristics. Large-scale pelt hunting in the 1950s and 1960s led to the classification of the species as 'vulnerable' by the World Conservation Union (IUCN, 1990). Habitat degradation and destruction now present the largest threat to remaining populations. The current distribution of the Giant Otter is presented, emphasizing recent information collected in the Amazon Basin. Morphology, systematics, habitat, behaviour, diet, predation, competition, reproduction, development and physiology are discussed. New data on habitat use and preference, behaviour and diet in northern Amazônia are included, and recommendations for future conservation measures are made. Because of the decimation of the Giant Otter in its southern distribution and the habitat destruction occurring in the remainder of its range, we recommend that this species be elevated to 'endangered' status in the IUCN Red Data Book.     

中国水獭保护现状及珠江口水獭种群重建探讨

顶级捕食者在生态系统中发挥着重要作用，受到研究者们的广泛关注。水獭作为很多淡水生态系统的顶级捕食者，在我国却长期处于被忽视的状态。我国分布有3种水獭--欧亚水獭、亚洲小爪水獭和江獭，曾经遍布我国中东部和东北地区，包括珠江口地区。但在20世纪，3种水獭均经历了大规模的种群下降，甚至区域性灭绝。在全球13种水獭中，已有3种（海獭、北美水獭和欧亚水獭）通过种群复壮和重引入实现了种群重建，这为其它水獭物种的种群重建提供了重要参考和建议。同国内其它地区类似，珠江口地区的水獭种群在20世纪后期大量减少，目前只在少数几个地点还有确切的欧亚水獭分布记录，亚洲小爪水獭和江獭已无近期记录。在珠江口重建水獭种群具有重要的生态意义和社会价值。本文对重建珠江口水獭种群的相关问题进行了分析。     

A comparative analysis of the complete mitochondrial genome of the Eurasian otter <Emphasis Type="Italic">Lutra lutra</Emphasis> (Carnivora; Mustelidae)

Otter populations are declining throughout the world and most otter species are considered endangered. Molecular methods are suitable tools for population genetic research on endangered species. In the present study, we analyzed the complete mitochondrial genome (mitogenome) sequence of the Eurasian otter Lutra lutra. The mitochondrial DNA sequence of the Eurasian otter is 16,505 bp in length and consists of 13 protein-coding genes, 22 tRNAs, 2 rRNAs, and a control region (CR). The CR sequence of otters from Europe and Asia showed nearly identical numbers and nucleotide sequences of minisatellites. Phylogenetic analysis of Mustelidae mitogenomes, including individual genes, revealed that Lutrinae and Mustelinae form a clade, and that L. lutra and Enhydra lutris are sister taxa within the Lutrinae. Phylogenetic analyses revealed that of the 13 mitochondrial protein-coding genes, ND5 is the most reliable marker for analysis of phylogenetic relationships within the Mustelidae.     

Determining Observer Reliability in Counts of River Otter Tracks

ABSTRACT In many research projects, reliability of collected data is dependent on reliability of field observers. However, it is uncommon for observer reliability to be either measured or reported in wildlife research. We tested whether observer skill affected outcomes of a northern river otter (Lontra canadensis) track survey conducted by the Texas Parks and Wildlife Department. Observers recorded presence of tracks at bridge sites (n = 250) throughout a 27-county region in east Texas, USA. Logistic regression indicated that observers were significantly associated with frequency of reported otter tracks. Because observers were not assigned to bridges at random, we tested and found associations between the bridges surveyed by each observer (SURVEY ROUTE) and habitat variables (WATERSHED, VEGETATION-TYPE, WATER-TYPE, BRIDGE-AREA) that may have influenced otter presence and probability of detection. A standardized tracker evaluation procedure indicated that experienced observers (n = 7) misidentified 37% of otter tracks. Additionally, 26% of tracks from species determined to be “otter-like” were misidentified as otter tracks. We recommend that observer skill in identification of animal tracks and other indirect signs be measured to detect and reduce observer errors in wildlife monitoring.     

Trophic diversity of the otter (Lutra lutra L.) in temperate and Mediterranean freshwater habitats

Aim To analyse the geographical patterns in the composition and diversity of otter's (Lutra lutra L.) diet and their relationship with climatic characteristics. Location European freshwater habitats under Mediterranean and temperate climatic regimes. Methods Thirty‐seven otter diet studies were reviewed, twenty‐one from temperate and sixteen from Mediterranean areas. All studies were based on spraint analysis and their results expressed as relative frequency of occurrence of seven main prey categories. Principal Component Analysis was performed to extract the main gradients of diet composition. Pearson's correlation and t‐tests were used to assess the relationship between diet characteristics (composition, diversity and taxonomic richness) and geographical and climatic variables. Results A clear latitudinal gradient in diet composition was observed. Otter diet was more diverse and featured more prey classes in southern localities, while the species was more piscivorous towards the north, where it predated upon a higher number of fish families. This pattern was similar when temperate and Mediterranean localities of Europe were compared. Mediterranean otters behaved as more generalist predators than temperate ones, relying less on fish, and more on aquatic invertebrates and reptiles. Main conclusions Geographical differences in otter feeding ecology in Europe seem to be related with the two contrasted climatic conditions affecting prey populations. The otter can act as a highly specialized piscivorous predator in temperate freshwater ecosystems, which do not suffer a dry season and have a comparatively stable water regime compared to Mediterranean ones. However, the unpredictable prey availability in Mediterranean areas, affected by strong spatial and temporal water shortages, favours a diversification of the otter's diet.     

Assessing noninvasive hair and fecal sampling for monitoring the distribution and abundance of river otter

Monitoring the distribution and abundance of populations is an important component of efforts to meet management or conservation goals. Although the objectives for such studies are easy to define, cost-effective, precise, and accurate estimates are often elusive. We tested the efficacy and compared the cost-effectiveness of methods for estimating the number and recording the distribution of river otter (Lontra canadensis). We genotyped otter hair sampled using two noninvasive instruments and compared those results with a hypothetical study design based on DNA extracted from fecal matter. Patterns of distribution generated from DNA collected at latrine sites were then compared to observations of otter collected using VHF radiotelemetry. We achieved a high probability of genotyping river otter with a small number of hairs (i.e., 59.0 % probability of producing a genotype with 1 guard hair and >5 under hair samples) collected using wire body snares and knaplock hair snags. Body snares were more effective at collecting otter hair, but there was relatively little additional cost to using both sampling instruments. Genotyped hair resulted in a high multi-year recapture rate (61.9 %). Hair collection and genotyping was the most cost-effective method for monitoring populations of river otter ($168.50 US/datum) followed by radiotelemetry ($264.50 US/datum), and the extraction of DNA from fecal matter ($266.00 US/datum). However, the noninvasive techniques did not represent the full distribution and fine-scale movements of otter, as observed using radiotelemetry. There has been much recent reporting of the efficacy of fecal matter as a source of DNA for conducting mark–recapture population estimates for mesocarnivores. Our data suggested that collecting DNA in hair may be a more cost-effective and efficient approach.     

Mitochondrial genetic diversity and structure of the European otter (Lutra lutra) in Britain

The European otter (Lutra lutra) is a focus for conservation efforts throughout Europe due to a population decline in recent decades and because of its importance as a biological indicator of the health of rivers and waterways. The aim of this study was to aid the conservation of this species by adding genetic information from samples originating in the United Kingdom (UK), to help build up a picture of the phylogeographic structure of the European otter throughout Europe. This was done by a comparison of 299 base pairs of the mitochondrial DNA control region. Four haplotypes were identified in the UK, one of which has not been found outside the west of the UK in the wild, and one of which was unique. Populations in the UK, and in particular the west were shown to have a higher haplotype diversity than previously found for the European otter in Europe (h = 0.7338 for the 58 UK otters sampled in this study) and an overall nucleotide diversity of π = 0.003. The western UK population was shown to have a high level of genetic distinctiveness. We discuss possible contributory population processes, the importance of the western UK population for the future conservation of the species and comment on future conservation strategies.     

Factors influencing use of freshwater pools by otters, Lutra lutra, in a marine environment

Eurasian otters ( Lutra lutra ) inhabiting a marine environment need to wash in freshwater in order to maintain the insulating properties of their fur. Use of freshwater pools by otters on the coast of Skye was studied in order to determine factors influencing pool choice. A number of characteristics were recorded for all pools present. Otter spraints were recorded as an indication of pool use. Only 34% of available pools were utilized by otters. Stepwise logistic regression revealed that choice of pools is influenced by pool depth, the percentage of a pool's substratum composed of flat rock, and the surrounding percentage cover of short grass. Possible reasons for these associations are discussed. The information may be of use when selecting and managing coastal areas for otter conservation.     

Decline and recovery in otter Lutra lutra populations in Italy

• 1 Changes in otter Lutra lutra distribution in Italy were examined by analysing geographical, historical and survey data.
• 2 As in other European countries, otters declined sharply in Italy during the late 1970s and throughout the 1980s. Between 1985 and 2004 the species became extinct, except for some reintroductions, in northern and most of central Italy while the species appears to have substantially recovered in its southern range. This recovery of the otter population is apparently not due to increased research effort, but reflects a real expansion of range.
• 3 Differences in the degree of range reduction during the second half of the 20th century and in the availability of suitable habitats are probably the major factors that have determined the two opposite trends shown by otter populations in the last 20 years.
• 4 Better knowledge of otter status and distribution is needed for effective conservation management. We suggest that a national survey of the Italian otter population that employs genetic approaches should represent a first step of the national action plan for otter conservation.

     

Stream community richness predicts apex predator occupancy dynamics in riparian systems

Streams and adjacent riparian habitats represent linked terrestrial and aquatic ecosystems that exchange materials and energy. Recognized relationships among apex predators and ecosystem biodiversity led us to hypothesize that these predators in riparian‐stream systems were more likely to be found in sites with high stream quality, defined as increased ecosystem function and integrity. In our freshwater study system, river otter Lontra canadensis and mink Neovison vison play critical roles as apex predators. We used multi‐season occupancy modelling across three sampling years (2012–2014) to compare aspects of the stream communities that explain occupancy dynamics of river otter and mink, including their interactions with other semi‐aquatic mammals. We surveyed for semi‐aquatic mammals at 77 sites in 12 major watersheds in southern Illinois, USA (44 526 km²). Naïve occupancy differed among years but generally increased for river otter, and remained high (≥93.5%) for mink. Increasing substrate availability increased detectability of river otter, whereas mink detection varied by survey period. Occupancy of river otter during the initial survey period was higher in sites closer to reintroduction points. Probability of colonization of river otter was positively associated with macroinvertebrate index of biotic integrity, fish species richness, and beaver presence. Sites with high species richness of fish families preferred by river otter also had increased river otter persistence. Mink occupied sites with increased fish richness, muskrat presence and mussel community index. Taken together, our results show occupancy of both mink and river otter were predicted by aspects of prey diversity and presence, indicating the importance of community composition in occupancy dynamics of riparian predators. Ultimately, these relationships suggest that habitat heterogeneity and system stability are important to apex predator site use. However, the relative role of bottom–up and top–down forcing in stream systems remains to be resolved.     

Genetic structure and diversity of a rare woodland bat, <Emphasis Type="Italic">Myotis bechsteinii</Emphasis>: comparison of continental Europe and Britain

The Bechstein’s bat (Myotis bechsteinii) is a rare sedentary bat considered to be highly reliant on the presence of ancient woodland. Understanding the genetic connectivity and population structure of such elusive mammals is important for assessing their conservation status. In this study, we report the genetic diversity and structure of M. bechsteinii across Britain and Europe. Assessments were made using 14 microsatellite markers and a 747 bp region of the mitochondrial cytochrome b gene. Nuclear DNA (microsatellites) showed high levels of genetic diversity and little inbreeding across the species range, though genetic diversity was slightly lower in Britain than in mainland Europe. Bayesian and spatial PCA analysis showed a clear separation between the British and European sites. Within Europe, the Italian population south of the Alps was isolated from the other sites. In Britain, there was genetic structuring between the northern and southern part of the geographical range. Despite there being little genetic divergence in mitochondrial DNA (mtDNA) sequences throughout most of Europe, the mtDNA patterns in Britain confirmed this separation of northern and southern populations. Such genetic structuring within Britain—in the absence of any obvious physical barriers—suggests that other factors such as land-use may limit gene-flow.     

Eurasian otter (<Emphasis Type="Italic">Lutra lutra</Emphasis>) density estimate based on radio tracking and other data sources

Estimating animal population size is a critical task in both wildlife management and conservation biology. Precise and unbiased estimates are nonetheless mostly difficult to obtain, as estimates based on abundance over unit area are frequently inflated due to the “edge effect” bias. This may lead to the implementation of inappropriate management and conservation decisions. In an attempt to obtain an as accurate and conservative as possible picture of Eurasian otter (Lutra lutra) numbers, we combined radio tracking data from a subset of tracked individuals from an extensive project on otter ecology performed in Southern Portugal with information stemming from other data sources, including trapping, carcasses, direct observation of tagged and untagged individuals, relatedness estimates among genotyped individuals, and a minor contribution from non-invasive genetic sampling. In 158 km of water network, which covers a sampling area of 161 km² and corresponds to the minimum convex polygon constructed around the locations of five radio-tracked females, 21 animals were estimated to exist. They included the five radio-tracked, reproducing females and six adult males. Density estimates varied from one otter per 3.71–7.80 km of river length (one adult otter per 7.09–14.36 km) to one otter per 7.67–7.93 km² of range, depending on the method and scale of analysis. Possible biases and implications of methods used for estimating density of otters and other organisms living in linear habitats are highlighted, providing recommendations on the issue.     

Rapid response of Orthoptera to restoration of montane heathland

Understanding how to restore threatened ecosystems is of special relevance for nature conservation. The aim of this study was to use Orthoptera as ecological indicators for the effects of montane heathland restoration in Central Europe. We analysed the three following treatments: (i) montane heathlands (MONHEATH) (N = 7), (ii) restoration sites (RESSITE) (N = 3) and (iii) clear-cuts of spruce forests as unprocessed and ungrazed control sites (CONTROL) (N = 3). Vegetation structure and microclimate differed considerably between MONHEATH on the one hand and RESSITE and CONTROL on the other hand. Orthoptera species richness and density did so too. MONHEATH was characterised by a high-growing dense dwarf-shrub and moss layer having a cool microclimate and high soil moisture. In contrast, RESSITE and CONTROL had sparse vegetation and a warm microclimate; Orthoptera species richness and density was highest on these sites. Our study clearly showed that heathland Orthoptera responded rapidly to restoration measures, while Ericaceae dwarf shrubs slowly established. The vast majority of Orthoptera species found on the restoration sites are early and mid-successional species. The colonization of the sites by late-successional Orthoptera species in the future will depend on the further development of the heathland vegetation; that is, if Ericaceae will expand to the sites. We conclude that the realised restoration measures are suitable to promote heathland Orthoptera of early and mid-successional stages. However, the current management of montane heathlands is insufficient and needs to be intensified in order to provide structurally diverse habitats with their characteristic orthopteran assemblages.     

Characterising the phytophagous arthropod fauna of a single host plant species: assessing survey completeness at continental and local scales

Quantifying survey completeness is a key step in designing and interpreting biodiversity assessments. To date this has only been examined either at a local scale through repetitive sampling, or across broader geographic areas through multiple survey sites. In this paper, we determine the completeness of sampling at both local and continental scales, of the phytophagous arthropod assemblage on the Neotropical shrub Parkinsonia aculeata (Leguminosae). We used survey gap analysis (SGA) to determine whether existing surveys adequately sampled the diversity of environments and geographic space covered by the plant. Within defined geographic regions, we determined survey completeness at a local scale with species accumulation curves. SGA identified the highest priority sites for future sampling in the Sonoran Desert and the Pacific Coast of South America. The arthropods sampled on P. aculeata differed significantly between seasons, highlighting the importance of including surveys throughout the year. At the local scale, surveys in most regions were estimated to have sampled <50 % of all species. Only the Mexican Gulf, following 84 samples including 902 individuals, had a reasonably complete sample of all species (more than 50 %). As in other studies, rare species will continue to be detected even after extensive surveying, and it is likely that close to 100 samples or 1,000 individuals will be needed to attain 50 % survey completeness in a region. However, if the objective is to document close “host-associations” then effort may be better directed at surveying ecologically distinct new areas rather than exhaustive sampling in existing ones. Methods such as SGA can direct such surveys, and in conjunction with species-richness estimates, can be used to assess the adequacy of existing surveys.     

Distribution and conservation of the relict interaction between the butterfly Agriades zullichi and its larval foodplant (Androsace vitaliana nevadensis)

Although Mediterranean mountains are considered biodiversity hot-spots, the presence of relict biotic interactions as a testimony of a past colder climate is an aspect frequently missed. Herein we investigate the distribution and conservation problems of a relict interaction in the Sierra Nevada mountains (southern Europe) between the butterfly Agriades zullichi—a rare and threatened butterfly—and its larval foodplant Androsace vitaliana subsp. nevadensis. We designed an intensive field survey to obtain a comprehensive presence dataset. This was used to calibrate species distribution models with absences taken at local and regional extents, analyze the potential distribution, evaluate the influence of environmental factors in different geographical contexts, and evaluate conservation threats for both organisms. We found 39 presence localities inhabited by the larval foodplant and the butterfly comprising 60.93 ha, with 82 % of the area concentrated in ten larger localities. The local and regional distribution models explained 68.7 and 85.0 % deviance, indicating a suitable area of 1,884.8 and 9,621.22 ha respectively. Topography and soil properties were the most important variables in the local model and temperature in the regional model. We observed several threats such as restricted extent of occurrence, lack of larval foodplant regeneration, the negative effect of the ski resort and a potential high sensitivity to climate change. Finally, we recommend some management measures in order to improve the conservation of key populations of both species, reinforcing A. vitaliana nevadensis populations and researching the importance of phenology in the persistence of this interaction under climate change.     

A resource-based conservation approach for an endangered ecotone species: the Ilex Hairstreak (Satyrium ilicis) in Flanders (north Belgium)

Ecotones are often species-rich and harbour specific resources and environmental conditions for invertebrates. Despite their functional significance for conservation, they are often not explicitly included in biotope typologies relevant to conservation policy and management (e.g., the European Habitats Directive). The Ilex Hairstreak (Satyrium ilicis) is a species of European conservation concern and a typical ecotone species inhabiting gradients from open (e.g., heathland, grassland) to closed vegetation (e.g., woodland). Here, we investigated its occurrence and habitat use at different spatial scales in Flanders (north Belgium). At a regional scale, species distribution modelling predicted 1,152 grid cells of 1 × 1 km² to be suitable of which 190 were presumed to occur within colonization capacity (±2.5 km). At a local scale, adult butterflies were more abundant on sites sheltered by bushes and small trees and with nectar sources in the vicinity of tall oak trees (mate locating sites). For egg-laying, females preferred oaks of intermediate height (50–150 cm) with many low branches at some distance from the nearest woodland edge (12 m). Additionally, Alder Buckthorn (Frangula alnus) was abundant as well as a herb layer of 10–15 cm. 73 % of the eggs were parasitized and parasitism occurred more often within sites where small oaks were very abundant. Making use of our results, we suggest conservation measures at different scales for this endangered ecotone species: policy measures at a regional level to delineate functional conservation units and local management measures using a resource-based approach.