Distribution Of Otters Research Articles

Anthropogenic and seasonal determinants of giant otter sightings along waterways in the northern Brazilian Amazon

Historic anthropogenic impacts affecting the distribution and ecology of Giant otters are well documented, however little is known regarding the factors affecting the current distribution of this species. Our objective was to determine the relative importance of temporal (seasonal river levels), and anthropogenic (presence of houses, boats and fishing nets) factors on the distribution of Giant otters around a sustainable-use protected area in the eastern Brazilian Amazon. We conducted a total of 6836.1km of boat surveys to record locations of both direct and indirect Giant otter sightings along 198.9km of waterways. To understand the importance of the factors at different spatial scales we conducted analysis using data summarized at two spatial scales: 50km river “zones” and 5.1km river sections. Our results showed that anthropogenic disturbances were the most important determinants of the presence of both direct and indirect signs, with Giant otters rarely detected within 40km of the nearest town. Giant otters were present in the waterways throughout the annual water cycle (high, decreasing, low and increasing river levels), with direct observations positively related with the number of fishing nets present in the waterways. Our results suggest considerable spatial and temporal overlap between Giant otters and the activities of local fishermen which must be considered for the effective management of conservation conflicts in this rapidly developing region.

Non-invasive genetic analysis reveals high levels of mtDNA variability in the endangered South-American marine otter (Lontra felina)

Scats from marine otters were collected from the entire Peruvian distribution range along the Pacific coast. Partial mtDNA control region sequences (265 bp) were successfully amplified and analysed in 37 out of 87 samples. Based on spatial distribution and home range information of marine otters we assumed our final data set to represent at least 24 different individuals, yielding surprisingly high genetic variability (11 haplotypes, h = 0.86, π = 0.0117). No unequivocal evidence of genetic substructuring, a bottleneck or isolation by distance could be detected. This study presents the first genetic data in this endangered species and highlights the significance of the Peruvian gene pool for the establishment of reserves, potential future expansion, recolonisation or translocations.

Análisis de la alimentación y distribución del visón americano (Neovison vison) y de la nutria (Lutra lutra) en la población simpátrica del río Moros (Sistema Central, Segovia)

The distribution of the American mink (Neovison vison) has been continuous in the last decades in the river Moros basin (Segovia) and in its tributary streams and reservoirs at all altitudes , while the otter distribution (Lutra lutra) is linked to the river Moros, mainly to the middle course, alter the recolonization which began less than two decades ago and with a seasonal presence in the high altitude stretches of the river. The trophic ecology was studied by the analysis of 321 feces (spraints) (130 of otters and 191 of mink) collected during 13 months in 5 study sites located 64 in the high and middle stretches of the river, including 2 small mountain dams and a large dam in the middle stretch with a great human presence. Fish are the fundamental prey of the otters throughout the year and at all altitudes, the rest prey are accidentals. Mammals and fish are the fundamental prey for the American mink. The diversity of the otter’s diet is considerably smaller than that of the mink in all the stretches of the river. The overlap of the diets between otters and minks throughout the study is over 83%. Considering the sites in sympatry for both species is greater than 89%. The distribution of otters in the river Moros seems to be stable in the last samplings. The American mink distribution did not become reduced in the area and it is present in all the same river courses in which it was detected more than 25 years ago. Trapping minks has been insufficient to control this alien carnivore, which seems to tolerate the presence of otters in seasonal sympatry avoiding competition for trophic resources and shelters.

Interactions of exotic and native carnivores in an ecotone, the coast of the Beagle Channel, Argentina

In coasts bordering highly productive seas, there can be a flux of resources to the terrestrial ecosystem, and terrestrial carnivores can use marine prey extensively. Two native, endangered species (otter Lontra provocax and culpeo fox Pseudalopex culpaeus lycoides) and two exotic species (mink Neovison vison and grey fox Pseudalopex griseus) inhabit the Beagle coast. The objectives of this paper are: (1) to describe the diet, habitat use and distribution of otters, mink and foxes on the coast of the Beagle channel and (2) to discuss the role of marine resources in the ecological interactions among these species. Diet was determined from the analysis of 245 faeces, and distribution was established from sign surveys. Marine prey occurred in the scats of 98.3, 70.4, 35.5 and 18.2% of otters, mink, culpeo and grey foxes, respectively. Other terrestrial species also use marine resources in Southern Patagonia. All this evidence suggests that the Fueguian coastal channels provide an illuminating example of allochthonous food subsidies from the sea. In the community of four sympatric predators, two native (and endangered) and two exotic, coexistence appears to be facilitated by a renewing marine food subsidy.

Distribution and diet of reintroduced otters ( Lutra lutra ) on the river Ticino (northern Italy)

Abstract On the River Ticino (northern Italy), the release of a pair of otters Lutra lutra in 1997, followed by the escape of an otter female with her cub in 2001, allowed the establishment of a small population. In summer 2008, a survey has been carried out by the standard method to draw a first picture of current otter distribution. Some data about otter diet have been obtained through the analysis of 36 spraints. Otter presence has been recorded for 3 out of 10 sampling stations, corresponding to a 2.6 km long stretch of the river. Considering only this stretch, the mean number of sprainting sites per 100 m was 0.10, while the mean number of spraints per 100 m was 0.19. Fish - mainly Salmo trutta , Perca fluviatilis , Phoxinus phoxinus and Chondrostoma genei -, formed the bulk of otters’ diet. The prosecution of the reintroduction project requires an updated feasibility study which provides for management actions aimed to favour the expansion of the species in northern Italy. Riassunto Distribuzione e dieta delle lontre Lutra lutra reintrodotte sul fiume Ticino (Italia settentrionale). Il rilascio, nel 1997, di una coppia di lontra Lutra lutra sul fiume Ticino (Italia settentrionale), unitamente alla fuga, nel 2001, di una femmina con i piccoli, ha portato alla formazione di una piccola popolazione. Per ottenere un primo quadro dell’attuale distribuzione della specie, nell’estate 2008 e stata condotta un’indagine tramite il metodo standard. Inoltre, dall’analisi di 36 feci, sono stati ottenuti alcuni dati sulla dieta. La presenza della lontra e stata accertata per 3 delle 10 stazioni monitorate, corrispondenti a un tratto di fiume pari a 2.6 km. Considerando solo le stazioni positive, il numero medio di siti di marcamento per 100 m e stato pari a 0,10, corrispondente a 0,23 feci per 100 m. I pesci – in particolare Salmo trutta , Perca fluviatilis , Phoxinus phoxinus and Chondrostoma genei -, rappresentano la principale risorsa trofica della lontra. La prosecuzione del progetto di reintroduzione richiede uno studio di fattibilita che contempli interventi gestionali atti a favorire l’espansione della specie in Italia settentrionale.

Scale-dependent analysis of an otter–crustacean system in Argentinean Patagonia

The Southern river otter or 'huillin', Lontra provocax, is an endangered species endemic of the Andean Patagonian region of Argentina and Chile. It feeds almost exclusively on the genera of macro-crustacea: Aegla and Sammastacus. The aim of this study was to analyse the role of food availability on the huillin's distribution using a scale-dependent analysis of crustacean and otter distributions. We compared the distributions of otters and macro-crustaceans along a north-south regional gradient, between river basins of northern Patagonia, in an altitudinal gradient within a river basin, and between habitat types within a lake. We investigated the distribution of otters by sign surveys along lake shores, river banks and marine coasts, and of crustaceans using surveys in the water, undigested remains in mink (Mustela vison) scats, presence of external skeletons at the waterside and through interviews with local people. Our results show that there were heterogeneities in the distributions of macro-crustaceans at four scales and these were generally reflected in the distributions of freshwater otters. We conclude that the main factor limiting the distributions of L. provocax in freshwater environments is the availability of macro-crustaceans. This paper shows how scale-dependent type analyses of population distribution serves as a method for identifying key environmental factors for species for which the use of long-term demographies is unfeasible.

Establishing the foundation for an applied molecular taxonomy of otters in Southeast Asia

Four species of otters (Mustelidae, Lutrinae) occur in Southeast Asia and are considered to be of conservation concern: Aonyx cinerea (Asian small-clawed otter), Lutra lutra (Eurasian otter), Lutra sumatrana (Hairy-nosed otter), and Lutrogale perspicillata (Smooth-coated otter). Among these, L. sumatrana is endemic to the region, yet little is known about its biology, and the precise distribution of all four species in Southeast Asia is not well known. Furthermore, the taxonomy and systematics of L. sumatrana and L. perspicillata have been the subject of controversy, which has implications for the legal protection and for conservation programs of these taxa. To resolve these controversies, we used a multigene data set comprised of segments from 13 nuclear and 5 mitochondrial loci (11,180 nucleotides) to evaluate the phylogenetic relationships of Asian Old World otters. Phylogenies were also estimated using two mitochondrial loci (1,832 nucleotides) obtained from two or more individuals of the four Southeast Asian species. The results from maximum parsimony, maximum likelihood and Bayesian inference showed that L. sumatrana and L. lutra are sister taxa, whereas L. perspicillata is sister to A. cinerea. Furthermore, the results from the two-mitochondrial gene analyses indicate that L. sumatrana is reciprocally monophyletic with respect to L. lutra, supporting the specific validity of the former taxon. Signs such as tracks and feces are often used in field surveys to provide information on the distribution and abundance of otters, but the accuracy of these methods may be compromised when several closely related species occur sympatrically. Therefore, the two-gene data set was used to develop a provisional set of diagnostic nucleotides that can be potentially used to identify the four species of Southeast Asian otters from noninvasively collected biological samples, such as feces.

Distribution and habitat choice of Cape clawless otters, in South Africa

Cape clawless otters, Aonyx capensis, are widely distributed in South Africa, as elsewhere on the continent. They occur in a wide variety of environments and most aquatic habitats, from freshwater lakes to the marine littoral, and even in episodic rivers in arid areas, provided freshwater sources are adequate and sufficient food is available. This animal is not much affected by turbid water as it locates prey by touch, and usually forages close to shores or banks. Evidence of presence in given localities and habitats, distributed over a large area of the Northern, Western, and Eastern Cape provinces, was deduced from signs (faecal deposits or distinctive tracks) on land. Accepting the inherent pitfalls of this approach we nevertheless feel using it is acceptable for a first approximation of habitat preferences over a large geographical area. Results point to areas with dense reed beds and a rocky substrate on banks being used most intensively, probably on account of a localized high food biomass.

Decline of invasive alien mink (Mustela vison) is concurrent with recovery of native otters (Lutra lutra)

ABSTRACTInvasive species often cause the decline of native prey or competitors. We highlight a contrasting example of the large‐scale recovery of a native species and the concurrent decline and likely displacement of an established invasive competitor. Invasive American mink Mustela vison became widespread in the British Isles at the same time as native Eurasian otters Lutra lutra were declining as a result of water pollution. In common with other invasive predators, mink cause conservation problems for a range of native prey species, most notably water voles Arvicola terrestris. Recent trends in the distribution of native otters and invasive mink in north‐east England were examined using a novel regression modelling approach to analyse presence/absence data from field surveys, corroborated by contemporary predator culling records. Between 1991 and 2002, the percentage of sites where mink signs were found decreased from 80% to 20%, while otter signs increased from 18% to 80%. Annual indices of mink captures on shooting estates increased between 1980 and 1996, but were followed by a decline thereafter. Indices of the incidence of native otters were significantly related to those indicating the decline or displacement of invasive mink. This large‐scale field study is supportive of localized experimental evidence for the return of dominant, native otters being concurrent with the decline of the invasive alien mink. The recovery of a dominant native species may represent a reversal of the mesopredator release that allowed invasive mink to establish and may eventually serve to mitigate their impact on native prey species.

Landscape genetics applied to a recovering otter (Lutra lutra) ppopulation in the UK: preliminary results and potential methodologies

The Eurasian otter (Lutra lutra) has declined significantly across its European range. In the UK, the decline was particularly severe during the late 1950’s and early 1960’s, and by the mid 1970’s the population was largely confined to strongholds in parts of Scotland, Northern Ireland, mid and West Wales and south west England. In recent years the otter population has started to recover, with otter surveys confirming an increased distribution of otters in Wales, Scotland and England. In England, population expansion and recolonisation is believed to be occurring both through breeding and by dispersal, from the west (south west England and the Welsh borders) and from the north (Scotland). However, little is known about the degree of genetic loss due to the decline, potential barriers to recolonisation, routes of dispersal, or the contribution of reintroduction programmes to population increases. This project aims to use tissues collected since 1994 (complete with geographic location) from over 500 otters found dead on roads in Wales and England, to analyse the genetic diversity and structure of otter populations. Using molecular genetic analysis of the otter population, we will identify whether and when bottlenecks occurred, whether population decline has resulted in a loss of genetic variability, and to what degree. Preliminaryanalysis from 177 otters has shown that observed is generally lower than expected het- erozygosity, and that the population is in Hardy Weinberg equilibrium for 11 out of the 15 loci. Spatial patterns in genetic data will be analysed, to identify clines, isolation by distance and genetic boundaries to gene flow, the contribution of released animals will also beassessed. Geographical information systems (GIS) will be used to map spatial genetic pat- terns and to generate hypotheses about the potential cause of genetic boundaries such as landscape or environmental features.

Distribution and habitat of otters (Aonyx capensis and Lutra maculicollis) in southern Nigeria

We report new data on the distribution and habitat of two otter species, Aonyx capensis and Lutra maculicollis, from southern Nigeria. Although preliminary, our investigations suggest that these two species may use the available habitat differently. Lutra maculicollis appears more linked to freshwater streams and Aonyx capensis is mainly restricted to brackish water streams (with mangrove vegetation along the banks) and, more occasionally, to transitional habitats between freshwater and brackish‐water environments. The possible reasons explaining habitat partitioning are discussed.

History and status of sea otters, Enhydra lutris along the coast of Hokkaido, Japan

We assessed the original and recent distribution of sea otters (Enhydra lutris) along the coast of Hokkaido, Japan, based on information of remains from archeological sites, old hunting records, and records of recent sightings obtained from interviews. Some remains, including pups from one archeological site, suggested the possibility that some small aggregations had historically been distributed around Hokkaido. However, sea otters seem to have disappeared prior to commercial hunting in the 18th and 19th centuries, as no records could be found documenting the hunting of otters around Hokkaido during that period. Since 1973, intermittent sightings of otters have been made around Hokkaido, and since 1996, the sighting frequency has increased. Between 1962 and 2001, 119 sightings and six dead otters were recorded around Hokkaido. The source population of these otters is probably in the Habomai Islands of the southern Kurils. However, due to increasing anthropogenic habitat disturbance, it is unlikely that a stable habitat for sea otters can be established in the coastal waters of Hokkaido.

Environmental correlates of the distribution of southern river otters Lontra provocax at different ecological scales

Endangered southern river otters Lontra provocax (huillin) are confined to southern Chile and three isolated areas of Argentina, the most important being the Nahuel Huapi National Park, where distribution surveys were conducted in 1983, 1995 and 2000. We used these survey data together with a Geographical Information System analysis to elucidate the factors that are important in determining huillin distribution at different ecological scales. There were significant heterogeneities in the distribution of huillin between river basins, between habitats, between lakes relative to dispersal routes and topography, and between sample points within a lake. From these analyses three factors emerge as potentially related to huillin distribution, and further elucidation of these are suggested as priorities for research to underpin the species' conservation. These factors are: a) the distribution of crustacean prey, with absence of huillin from one river basin and from mountainous streams correlated with low densities of crustaceans in these places; b) human habitation, which may explain why huillin dispersed southwards, but not northwards, from the main lake, although underwater visibility may also be relevant; c) the presence of the introduced American mink Mustela vison, because although there was a positive relationship between the occurrence of mink and huillin in Lake Nahuel Huapi, there was a negative relationship in their occurrence between other lakes. We discuss possible explanations for all three factors.

RFLP analysis of the mitochondrial DNA of otters ( Lutra lutra) from Europe—implications for conservation of a flagship species

The distribution of otters ( Lutra lutra) in Europe is largely fragmented, mainly due to historic anthropogenic causes. Nevertheless, in eastern Germany a large coherent area is inhabited by a viable otter population. In this paper, the mitochondrial genome of 81 otters is studied by RFLP analysis of PCR-amplified 1.5 and 2.5 kb long fragments, particularly to estimate the amount of genetic variability of European otters, and to identify possible geographical population subsets for conservation management. No restriction site polymorphism was detected within the control region (1.5 kb), but polymorphism of cleaving sites in the 2.5 kb fragment could be assigned to three haplotypes. Two occurred exclusively in a comparatively small area northwest and west of Berlin, which may be considered a region of increased genetic variability in otters. The low level of mtDNA variability in European otters might be due to genetic drift in postglacial founder populations with long-term low densities, and continuous historical overhunting.

Distribution and status of the smooth-coated otter Lutra perspicillata in National Chambal Sanctuary, India

The distribution and relative density of smooth-coated otters Lutra perspicillata Geoffroy were studied along a 425 km stretch of Chambal river within the National Chambal Sanctuary, Central India, between 1988 and 1992. Sample sites of 1 km were surveyed every 5 km. The study revealed that the distribution of otters along the river is patchy and largely restricted to the upper reaches. During the 1988 survey, 36% of sites were found with otter signs but only 24% in 1992. Recent increases in disturbance along the river due to construction of road bridges and mining activities might have put pressure on the population. Most of the positive sites (66%) were found on rocky banks, followed by clay banks (19%), banks with shoreline vegetation and marsh (11%) and sandy banks (3%). During intensive monitoring of four radio-implanted otters, c. 78% locations were made on rocky banks, 19% on banks with shoreline vegetation and marsh, with < 3% on sandy banks and <1% on clay banks, indicating greater preference for rocky banks owing to the greater availability of den sites. As a conservation measure, monitoring of the otter population should be done regularly and restrictions on cultivation, grazing and mining along the banks should be imposed within the Sanctuary limits, especially in the identified stretches.

Status and distribution of river otters in Kinmen, Taiwan

Surveys of river otters Lutra lutra on Kinmen and Little Kinmen islands were carried out in 1992 and 1993. In order to record sightings of otters in the past, 12 Kinmen residents who had seen or caught otters before were interviewed. Interview results indicated that the otter is a resident, breeding species on Kinmen. Survey results indicated presence of otters throughout Kinmen and in many sites on Little Kinmen. However, habitat degradation, including pollution and drought, may pose serious threats to the continued existence of the species on both islands.

Changes in otter numbers in Shetland between 1988 and 1993

The otter population in Shetland has increased significantly between 1988 and 1993, with more animals being found on all coastal strata and in all parts of the archipelago except South Mainland, the only area to show a decline. South Mainland is where the tanker Braer grounded in January 1993 and the subsequent oil spill might have affected the distribution of otters there. The causes of the changes are unknown and it is not known what happened to the otters in South Mainland after the spill, but it is is highly unlikely that the large increases recorded elsewhere on the archipelago were caused by the movement of animals away from South Mainland.

Regional trends in PCB and pesticide contamination in northern Britain as determined in otter ( [formula omitted][formula omitted]) scats

Organochlorine pesticide residues and PCBs were measured in the scats (faeces) of otters from five regions in southwest Scotland and northern England, U.K. Dieldrin, DDE and PCBs were significantly higher in samples from the two English regions than those in Scotland. There was a trend of increase from west to east. The distribution of otters was inversely correlated to mean concentrations of dieldrin, DDE and PCBs in scats, suggesting that organochlorines may still be exerting a negative impact on the species.

Effects of freshwater availability on the summer distribution of otters Lutra lutra in the southwest coast of Portugal

The availability of freshwater has been suggested to strongly influence the distribution of coastal otters Lutra lutra The test this hypothesis, a study was undertaken on the relationships between otter distribution and freshwater availability in a coast where freshwater is a very scarce resource during the summer In this area otters occur mostly in a few small coastal streams but feed largely in the sea Twentynine streams were surveyed in the summer of 1990, and the presence/absence of otter signs was related to nine habitat variables Freshwater availability was found to be the most important factor influencing the occurrence of otters in summer It is suggested that otters favour large streams with good vegetation cover, for these are the most likely to maintain frestwater during the dry periods The distribution of otter signs m streams was also analysed, and it was found that signs tend to concentrate particularly near the mouth of the streams This habitat analysis has some conservation implications, indicating that the decrease of freshwater availability or quality of streams can make these unsuitable for otters, severely decreasing the areas suitable for the species in the southwest coast of Portugal

Paralytic shellfish poisoning toxins mediate feeding behavior of sea otters

Captive sea otters (Enhydra lutris)fed live Saxidomus giganteus (butter clams) ad libitum either reduced their prey capture and consumption rates or discarded the highly toxic siphons and kidneys when switched from clams containing very low levels of saxitoxin [37±9 µg STX (100 g)−1] to highly toxic clams [226±96 µg STX (100 g)−1]. Feeding rates returned to pretreatment levels when the otters were again switched to low‐toxicity clams, but siphon discard frequency remained high. Paralytic shellfish poisoning symptoms were observed only in an otter calculated to have consumed the most STX (154 µg kg−1 d−1), a dosage within the range of oral LD50s reported for other nonprimate mammals. None of the other otters displayed symptoms, and all subjects were eventually released in good health. These findings suggest that otters are not immune to paralytic shellfish poisoning toxins (PSPT) and that they have the ability to detect and avoid consumption of lethal amounts of toxic prey. This behavioral response is highly adaptive given the importance of butter clams in sea otter diets, and the chronic toxicity of butter clams in areas where toxic dinoflagellate blooms occur. A comparison of the distributions of otters and toxicity levels of butter clams in southeast Alaska suggests that the sequestering of PSPT may protect some clam populations from otter predation and limit the distribution of otters to the exposed outer coast where toxic clams are rare.