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.     

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.     

Latitudinal variation in diet and patterns of human interaction in the marine otter

The marine otter (Lontra felina) inhabits patches of rocky coastline from central Peru to southern Chile and is classified as Endangered by the IUCN. Given the limited information available about the species, we set out to assess marine otter diet with a view to detecting latitudinal differences, and to assess marine otter activity budgets and interspecific interactions (including anthropogenic) at Peruvian fishing villages and to compare results with similar Chilean studies. Nine study sites from central Chile to southern Peru were sampled for otter spraints to assess relative frequency of prey types and two fishing ports in southern Peru were monitored through focal and scan observations to assess activity patterns, interspecific interactions, habitat use patterns, and dive durations. Results indicate that toward the northern part of its range, crustaceans become less important and fish more important in the diet. Interactions were observed between marine otters and other species, including stray dogs and cats. The strong dependence of marine otters on the availability of safe rocky shelters, and the species’ apparent tolerance to living alongside humans raise conservation concerns about vulnerability to anthropogenic threats. These factors, if not correctly managed, could turn some of these rocky seashore patches into population sinks.     

Do alien North American mink compete for resources with native South American river otter in Argentinean Patagonia?

American mink Mustela vison , originally bred in fur farms, have become established in areas occupied by native endangered Southern river otter Lontra provocax , in Patagonia. In accordance with European experience, this biological invasion in South America raises questions about the interaction between invasive mink and native otter, from the viewpoints of both community assembly and conservation. We set out (1) to find which aspects of habitat structure were related to the distribution of signs of both this invasive species and Southern river otter Lontra provocax , in Argentinean Patagonia and their most common prey and (2) to test general predictions of niche partitioning between these two species. Based on surveys of 447 of 600 m transects for otter and mink scats/footprints along the waterside of lakes and rivers in the Andean Patagonian region, we compared diet composition (from scat analysis) and micro-habitat preferences (from field signs) of the two species. Otters were more specialist than mink in habitat use and diet. Mink used different habitats in other river basins where otters were absent. Where they occurred together in the basin of the Limay River, the distributions of their signs were similar, and mink diet was more similar to that of otters. There was no detectable difference in otter diet before and after mink arrival in the Limay basin. Contrary to the prediction of niche partitioning, and to the findings of European studies, resource use by mink was more similar to that of otters where the species occurred sympatrically than where they were allopatric.     

Detecting detectability: identifying and correcting bias in binary wildlife surveys demonstrates their potential impact on conservation assessments

The European Commission Habitats Directive requires that changes in the conservation status of designated species are monitored. Nocturnal and elusive species are difficult to count directly and thus population trajectories are inferred by variation in the incidence of field signs. Presence/absence techniques are, however, vulnerable to Type II errors (false negatives). The Eurasian otter (Lutra lutra), listed by the IUCN as ‘near threatened’, is monitored throughout Europe using the ‘Standard Otter Survey’ method. We explored the reliability of this approach by analysing species incidence at 1,229 sites throughout Ireland. Naïve species incidence was 72 % [95 % confidence interval (CI), 69–75 %] with variation affected significantly by survey team and, at running freshwater sites, the number of bridges present and rainfall during the month, and most notably during the 7 days, prior to survey. Rainfall had no effect on static freshwater sites or the coast. Marginal estimated mean species incidence derived from a GLM assuming the β coefficient of the survey team associated with the highest prevalence, no rainfall in the week prior to survey and sites that had multiple bridges, was 94 % [95 %CI 78–97 %]. We demonstrate that bias and error in binary wildlife surveys can have a major impact on a conservation assessment even when conducted on an apparently well-known species in a developed country with good infrastructure and a long history of similar ecological studies. Our results provide empirical evidence for further criticisms of the Standard Otter Survey method calling into question its value in monitoring changes in otter populations throughout Europe.     

Assessing occupancy and habitat connectivity for Baird’s tapir to establish conservation priorities in the Sierra Madre de Chiapas,Mexico

Baird’s tapir (Tapirus bairdii) is the largest native mammal that inhabits the Neotropics, and it is enlisted as Endangered by the IUCN Red List. The historic distribution of this species included the area from southern Mexico to northern Colombia. However, its distribution and populations have been reduced drastically during the past 30 years. The main threats for Baird’s tapir are the direct persecution for subsistence hunting, habitat destruction, and habitat fragmentation. In this study, we used camera traps and occupancy models to identify the landscape characteristics that were associated with the occurrence of tapirs in the Sierra Madre de Chiapas, which is one of the most important populations of the species in Mexico, with the aim to identify areas with habitat suitability for the species. We used our best occupancy model to generate a resistance matrix to develop a model of habitat connectivity using Circuit Theory. According to the best occupancy model, the most suitable areas for this species were the forested areas located at the highest elevations of the mountain ranges that provided rugged terrain. We identified three critical corridors to allow for the connectivity of tapir populations in the Sierra Madre de Chiapas, and one of these corridors provides connectivity between this population and the population in the Ocote Biosphere Reserve. With this approach, we propose a conservation strategy for the species that incorporates a more realistic and detailed scheme of Baird’s tapir occurrence in the Sierra Madre de Chiapas region. Priority actions to conserve tapirs in the Sierra Madre de Chiapas over the long term include ensuring the complete protection of prime habitat for the species, improved connectivity by protecting forest cover, implementation mitigation measures in areas where paved roads interrupt connectivity of populations, and eradicating poaching of the species in the region completely.     

The status of the otter (Lutra lutra) in the British Isles

National field surveys for otters were carried out between 1977 and 1981. The species is apparently absent from large areas of England, although healthy populations still occur in the south-west. In many other areas, populations are isolated and fragmented and there is some evidence for continuing declines. In Wales the otter is rare or absent from the south and parts of the north. Healthy populations are present in the Highland Region of Scotland, on the north and west coasts and in the islands but there is evidence of a decline in the south and east-central lowlands. Otters are widespread and common in Ireland which sustains the best of the known populations in Europe.
Pollution by pesticides probably caused the initial rapid decline of the species but habitat destruction is increasingly important and where habitat is poor, human disturbance assumes greater significance. There is no evidence of competition with mink. The otter is now a protected species but if it is to recover some of its former range, remaining habitat must be retained.
While otter populations have decreased over much of northern Europe, the animal survives, albeit somewhat precariously, in a few southern parts of the continent.     

Geographic range estimates and environmental requirements for the harpy eagle derived from spatial models of current and past distribution

Understanding species–environment relationships is key to defining the spatial structure of species distributions and develop effective conservation plans. However, for many species, this baseline information does not exist. With reliable presence data, spatial models that predict geographic ranges and identify environmental processes regulating distribution are a cost‐effective and rapid method to achieve this. Yet these spatial models are lacking for many rare and threatened species, particularly in tropical regions. The harpy eagle (Harpia harpyja) is a Neotropical forest raptor of conservation concern with a continental distribution across lowland tropical forests in Central and South America. Currently, the harpy eagle faces threats from habitat loss and persecution and is categorized as Near‐Threatened by the International Union for the Conservation of Nature (IUCN). Within a point process modeling (PPM) framework, we use presence‐only occurrences with climatic and topographical predictors to estimate current and past distributions and define environmental requirements using Ecological Niche Factor Analysis. The current PPM prediction had high calibration accuracy (Continuous Boyce Index = 0.838) and was robust to null expectations (pROC ratio = 1.407). Three predictors contributed 96% to the PPM prediction, with Climatic Moisture Index the most important (72.1%), followed by minimum temperature of the warmest month (15.6%) and Terrain Roughness Index (8.3%). Assessing distribution in environmental space confirmed the same predictors explaining distribution, along with precipitation in the wettest month. Our reclassified binary model estimated a current range size 11% smaller than the current IUCN range polygon. Paleoclimatic projections combined with the current model predicted stable climatic refugia in the central Amazon, Guyana, eastern Colombia, and Panama. We propose a data‐driven geographic range to complement the current IUCN range estimate and that despite its continental distribution, this tropical forest raptor is highly specialized to specific environmental requirements.     

Habitat use,density, and conservation status of the white-browed guan (Penelope jacucaca Spix, 1825)

The white-browed guan (Cracidae: Penelope jacucaca) is an endemic bird species to the Caatinga, the largest centre of dry forest in South America. This taxon was considered Vulnerable by the International Union for Conservation of Nature (IUCN) due to continued habitat loss within its distribution and intense hunting pressure that contributed to population declines. However, information on population aspects and habitat use by P. jacucaca, which is fundamental for monitoring its conservation status, is not available. We studied habitat use (analysed in a Generalized Linear Model) and population density (estimated by distance sampling) in a specific area in Northeast Brazil. Using species distribution modelling (SDM), forest cover loss data (performed in the MaxEnt program) and quantitative information about hunting, more rigorous estimates of the distribution limits, available habitat, and population declines of P. jacucaca were generated. Based on the IUCN criteria, we applied analysed data to reassess the conservation status of the white-browed guan. Local density was estimated at 13.1 individuals/km² and the estimated number of individuals removed per year due to hunting was 121.7 in the forest cover area (110.46 km²) of the Serra de Santa Catarina. Consequently, the annual removal rate of hunted individuals in the study area corresponds to approximately 11% of the population. The habitat use analysis pointed to a strong positive association with seasonally dry deciduous forest (SDDF) vegetation and with arboreal vegetation. The SDM indicated a potential distribution (climatically favourable) area of 675,823 km², and forest cover and loss calculations indicated a total of 81,307 km² of available suitable habitat in 2013. Therefore, comparing these results to the IUCN criteria, we recommend that P. jacucaca remain in the Vulnerable category.     

Understanding the inter-specific dynamics of two co-existing predators in the Tierra del Fuego Archipelago: the native southern river otter and the exotic American mink

Knowledge about interactions between endangered native southern river otters (Lontra provocax) and introduced American mink (Neovison vison) is essential for effective management of both species. We evaluated competition for spatial and trophic niches between otter and mink in overlapping and non-overlapping areas, comparing distribution, habitat preference, diet and mink marking behavior. We surveyed otter and mink signs along 250 km of Beagle Channel coastline. Habitat suitability models were constructed based on species presence/absence and habitat characteristics, using generalized linear models. Feces were collected for diet analyses. Otters used forested coasts with 12°–32° shoreline slope and without human influence, and our evidence suggests they were not affected by mink presence. Mink preferred forested and shrubland coasts with 10°–28° shoreline slope. Neither human influence nor otter presence affected mink habitat occupation, but in the presence of otters, mink left fewer signs. Otters consumed more aquatic prey than mink, and mink modified their diet in the presence of otters, consuming more exotic small terrestrial mammals and less fish as well as shifting to smaller and shallower fish species that are less consumed by otters. Mink showed more plastic, generalist behavior than otters, being more tolerant of human presence, using more habitat types and having greater diet breadth. At the same time, otters apparently affect mink adversely and could help limit their invasion in sympatric areas. Conservation and recovery of otters, therefore, may produce a secondary benefit of simultaneously reducing the effect of mink, thereby providing an additional way to control this exotic predator’s population.     

Influence of occupation history and habitat on Washington sea otter diet

Habitat characteristics are primary determinants of nearshore marine communities. However, biological drivers like predation can also be important for community composition. Sea otters (Enhydra lutris ssp.) are a salient example of a keystone species exerting top‐down control on ecosystem community structure. The translocation and subsequent population growth and range expansion of the northern sea otter (Enhydra lutris kenyoni) in Washington State over the last five decades has created a spatio‐temporal gradient in sea otter occupation time and density, and acts as a natural experiment to quantify how sea otter population status and habitat type influence sea otter diet. We collected focal observations of sea otters foraging at sites across the gradient in varying habitat types between 2010 and 2017. We quantified sea otter diet composition and diversity, and long‐term rates of energy gain across the gradient. We found that sea otter diet diversity was positively correlated with cumulative sea otter density, while rate of energy gain was negatively correlated with cumulative density. Additionally, we found that habitat type explained 1.77 times more variance in sea otter diet composition than sea otter cumulative density. Long‐term diet studies can provide a broader picture of sea otter population status in Washington State.     

Using videotaping to validate the use of spraints as an index of Eurasian otter (Lutra lutra) activity

Eurasian Otter (Lutra lutra) surveys are commonly based on spraints (otter faeces) as an index of use intensity, habitat preference, and to a certain degree, population density. We were interested to know: (1) Does the number of fresh spraints correlate to the number of visits? (2) Can spraints be indicative of activity levels? (3) Is the absence of fresh spraints indicative of no visits? We used videotaping that provided a true picture of otter nocturnal activity at marking sites and compared our findings with the number of fresh spraints the following morning. This enabled us to correlate the number of spraints with the number of otter visits during the night and assess the validity of spraints as an activity index. We carried out a total of 59 videotaping nights and counted spraints in 29 sprainting sites between September 2002 and March 2004. We found a positive correlation between the proportion of nights a latrine was visited and the proportion of nights fresh spraints were deposited. The number of fresh spraints/night/site was positively correlated with the number of otter visits/night/site. Latrines visited on more nights had a higher number of fresh spraints per night visited. However, in about half the nights where no spraints were found, visits were recorded. Spraints are generally a good indicator of use intensity of a specific latrine and consequently a possible indicator of activity level and habitat preference. Understanding what determines scent-marking behaviour and its relationship to actual activity and presence can improve our ability to assess otter populations and design management protocols.     

Habitat factors and the presence or absence of otters Lutra lutra in Denmark

The purpose of the present study was to examine the relative influence of different habitat factors on ottersLutra lutra (Linnaeus, 1758) and to develop a predictive model to better understand the distribution of the otter in Denmark. During the National Otter Survey in 1991 data were collected on 19 variables which reflected aspects of habitat structure, composition, organic pollution and human disturbance. Multiple logistic regression analysis was used to estimate probabilities of the presence of otters as a function of one or more explanatory variables. Six variables (county, pH, water depth, presence of trees, bottom substrate and Saprobien-Index) were identified. In Denmark, otter habitat typically consists of water courses with depths > 1 m over a varied bottom, with pH > 7.0, Saprobien-Index on II–III to III (indicating slight organic pollution) with no trees on the banks. Some of these variables reflect highly productive waters. The use of the otter as an indicator of good water quality and/or aquatic habitat should be used with care.     

A review of otters (Carnivora: Mustelidae: Lutrinae) in Malaysia and Singapore

Four species of otters have been recorded from Malaysia and Singapore in the past: Lutra lutra (Common or Eurasian Otter), Lutra sumatrana (Hairy-nosed Otter), Lutrogale perspicillata (Smooth Otter) and Amblonyx cinereus (Oriental Small-clawed Otter). All four are listed in the Threatened Species Categories of the IUCN Red List of Threatened Animals: L. lutra is designated Vulnerable and the status of the other three Asian species are Insufficiently Known due to lack of information. From a review of the available literature and collation of museum records from Malaysia and Singapore, the past status of the four species are examined. Presently, only L. perspicillata and A. cinereus are common in Peninsular Malaysia where they are widely distributed, but both are rare in Singapore. L. sumatrana is rare but apparently still found in East Malaysia. It is possible that L. lutra did not range in Malaysia this century. Information about the habitat types, group size, range, diet and behaviour for all the species is poorly known. The available information allows a discussion of the Smooth and Small-clawed Otters only. This dearth of knowledge has hampered maintenance and breeding efforts of zoos and conservation activity.     

Ecology and biogeography of the Neotropical otter <Emphasis Type="Italic">Lontra longicaudis</Emphasis>: existing knowledge and open questions

The Neotropical otter, Lontra longicaudis, is considered near threatened by the IUCN, and with declining populations, it is still one of the lesser known species of otter in the world. Like other otter species, L. longicaudis is associated with water courses in a large variety of habitats and biomes across its area of distribution. Here, we present a review of the available literature on L. longicaudis aiming to update information on its distribution, ecology and systematics. We performed online searches using combinations of the words L. longicaudis, river otter, Neotropical otter, nutria and lobito del río, limiting our search to 1972–2016. Recent information on evolutionary history and biogeographic patterns, distribution patterns, as well as on the ecology of the species across a large part of its distribution range, including trophic ecology and intraspecific communication, was retrieved. We found severe gaps in knowledge including aspects of life history, ground validation of new potential distribution areas and long-term population monitoring aiming at designing more efficient conservation measures and techniques. In this context, we conclude by presenting perspectives for future studies.     

Segregation in space and time explains the coexistence of two sympatric sub‐Antarctic petrels

Biological communities are shaped by competition between and within species. Competition is often reduced by inter‐ and intraspecific specialization on resources, such as differencet foraging areas or time, allowing similar species to coexist and potentially contributing to reproductive isolation. Here, we examine the simultaneous role of temporal and spatial foraging segregation within and between two sympatric sister species of seabirds, Northern Macronectes halli and Southern Macronectes giganteus Giant Petrels. These species show marked sexual size dimorphism and allochrony (with earlier breeding by Northern Giant Petrels) but this is the first study to test for differences in foraging behaviours and areas across the entire breeding season both between the two species and between the sexes. We tracked males and females of both species in all breeding stages at Bird Island, South Georgia, to test how foraging distribution, behaviour and habitat use vary between and within species in biological time (incubation, brood‐guard or post‐brood stages) and in absolute time (calendar date). Within each breeding stage, both species took trips of comparable duration to similar areas, but due to breeding allochrony they segregated temporally. Northern Giant Petrels had a somewhat smaller foraging range than Southern Giant Petrels, reflecting their greater exploitation of local carrion and probably contributing to their recent higher population growth. Within species, segregation was spatial, with females generally taking longer, more pelagic trips than males, although both sexes of both species showed unexpectedly plastic foraging behaviour. There was little evidence of interspecific differences in habitat use. Thus, in giant petrels, temporal segregation reduces interspecific competition and sexual segregation reduces intraspecific competition. These results demonstrate how both specialization and dynamic changes in foraging strategies at different scales underpin resource division within a community.     

Factors affecting otter (<Emphasis Type="Italic">Lutra lutra</Emphasis>) abundance and breeding success in freshwater habitats of the northeastern Iberian Peninsula

Otters are elusive semi-aquatic mammals, occurring in low densities and difficult to count. A study was conducted in 15 stretches (10–12 km) of four tributaries of the Ebro River, with the aims to understand spatial and temporal changes in otter abundance and breeding success and the causes of such variations. Between 1990 and 2009, both otter parameters were assessed by means of visual spring–early summer censuses, carried out by sets of observers located every 500 m. A total of 134 censuses were carried out, involving 4,540 twilight watches (7,896.5 h) and 520 otter sightings were recorded. Also, 39 different habitat characteristics (including prey species) were established for each stretch. Otter abundance was assessed by means of three indexes related to the census effort and the length and surface units (in terms of otter habitat). Excluding the upper stretches, we found on average 0.07–0.26 adult and subadults per kilometre (1.45–6.26/km²). Important interannual fluctuations in otter abundance and breeding success were found in some Pyrenean stretches located downstream of a large reservoir. This was linked to the effect of autumn floods (in part due to the opening of dams) on the fish stocks (mainly Barbels). Similar habitat conditions resulted in similar abundances between stretches, and different habitat conditions generated different abundances in adjacent stretches of the same river. No significant differences were found for litter size between small cubs (1.60 ± 0.70 cubs per litter) and large cubs (1.39 ± 0.50) as a whole, but differences between stretches were found. On average we found between 0.009 and 0.130 large cubs per year per kilometre. Otters bred more successfully in stretches with higher otter densities. Otter abundance and breeding success correlated negatively with altitude as a consequence of the interaction of several habitat characteristics with altitude. The stepwise linear regression linked the number of adult otters per kilometre with the ecosystem production (chlorophyll a concentration), while the number of large cubs per kilometre per year was linked with the food (fish + crayfish) abundance. The findings bring about a consistent and congruent scenario of otter abundance and breeding success explained by the different steps along the food chain.     

Global habitat suitability models of terrestrial mammals

Detailed large-scale information on mammal distribution has often been lacking, hindering conservation efforts. We used the information from the 2009 IUCN Red List of Threatened Species as a baseline for developing habitat suitability models for 5027 out of 5330 known terrestrial mammal species, based on their habitat relationships. We focused on the following environmental variables: land cover, elevation and hydrological features. Models were developed at 300 m resolution and limited to within species' known geographical ranges. A subset of the models was validated using points of known species occurrence. We conducted a global, fine-scale analysis of patterns of species richness. The richness of mammal species estimated by the overlap of their suitable habitat is on average one-third less than that estimated by the overlap of their geographical ranges. The highest absolute difference is found in tropical and subtropical regions in South America, Africa and Southeast Asia that are not covered by dense forest. The proportion of suitable habitat within mammal geographical ranges correlates with the IUCN Red List category to which they have been assigned, decreasing monotonically from Least Concern to Endangered. These results demonstrate the importance of fine-resolution distribution data for the development of global conservation strategies for mammals.     

The Neotropical otter Lontra longicaudis: a comprehensive update on the current knowledge and conservation status of this semiaquatic carnivore

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