The otter (Lutra lutra) in Tunisia

The otter is common and widespread in northern Tunisia and the Oued Medjerda effectively represents a southern limit for the species. The distribution of otters is largely coincident with dense bankside cover, provided mainly by Nerium oleander. Rivers south of the O. Medjerda offer little shelter for the animals.     

The otter (Lutra lutra L.) in Spain

In a survey of Spain during June 1981, signs of otters were found at seventy (40%) of the 176 stations investigated. Otters were mainly concentrated in the mountainous north and north-west and in the plains and mountains of the south-west. Water pollution appears to be an important limiting factor in some areas.     

The otter (Lutra lutra L.) in western France

In a survey of western France during October-November 1980, signs of otters were found at 46 (15%) of the 315 sites investigated. Otters were largely restricted to four areas, three of these being in the uplands (of Brittany, the Massif Central and the Pyrenees) and one in the coastal lowlands (of the Landes-Gironde). The average number of signs found per successful site was 1 6, significantly lower than for Scodand and Ireland but similar to the figure for England. The percentage of positive sites and the scattered nature of the signs in western France was also broadly comparable witJi the English situation. This is surprising since most of the factors which adversely affect otters appear to be less oppressive there dian in England. Only water pollution is noticeably more extreme and this seems to offer the best, overall explanation for the nature of the decline in the area studied.     

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.

     

Helminth parasites of the Eurasian otter Lutra lutra in southwest Europe

The helminth fauna in 109 Eurasian otters (Lutra lutra L.) from France, Portugal and Spain was analysed, together with 56 faecal samples collected in Portugal and 23 fresh stools from otters included in a reintroduction programme. Seven helminth species were found in L. lutra in southwest Europe: Phagicola sp. (Trematoda), Aonchotheca putorii, Eucoleus schvalovoj, Strongyloides lutrae, Anisakis (third stage larvae) and Dirofilaria immitis (Nematoda), and Gigantorhynchus sp. (Acanthocephala). Eucoleus schvalovoj was the dominant species throughout southwest Europe. Strongyloides lutrae was significantly more prevalent in the Iberian Peninsula than in France. Apart from these two dominant nematodes and A. putorii, the other helminth species were incidental parasites of L. lutra in southwest Europe. The helminth fauna of L. lutra in southwest Europe is, in general, poorer than that reported in eastern Europe and in all other aquatic mustelids in southwest Europe. Phagicola specimens are reported for the first time in a non-marine wild carnivore in Europe. The prevalences of E. schvalovoj and S. lutrae obtained by necropsy were higher than those observed by coprological analysis using a formalin-ether concentration method (Ritchie). Nevertheless, the culture of fresh faeces appears to be the best method to study infection of L. lutra by Strongyloides.     

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.     

Determinants of Eurasian otter (Lutra lutra) diet in a seasonally changing reservoir

Otter diet in reservoirs is known to experience seasonal changes. We selected a reservoir with a large population of exclusively wintering great cormorants and seasonal changes in stored water volume to test the relative influence of abiotic and biotic factors on otter foraging ecology. DNA metabarcoding of otter spraints revealed a dietary change from autumn to winter. Otters had a diet dominated by the exotic goldfish in autumn, but predated intensively on the native northern straight-mouth nase in winter. This change was likely caused by predation of cormorants on goldfish and to fish biology. Secondly, macroscopic analysis of spraints revealed that otters shifted from a diet dominated by fish (in terms of biomass) to a diet dominated by red swamp crayfish during spring–summer, when the latter became overabundant. As revealed by modelling, this second shift was most likely influenced by the sudden increase in stored water volume in spring, but also by the cumulative effect of cormorant predation on fish during autumn–winter. Macroscopic analyses of otter spraints collected in a second reservoir with no cormorants revealed a lack of seasonality. Hence, the combined influence of both biotic and abiotic factors explained otter diet seasonality in a lentic-water novel ecosystem.

     

Procedures to genotype problematic non-invasive otter (Lutra lutra) samples

Non-invasive genetics is a powerful tool in wildlife research and monitoring, especially when dealing with elusive and rare species such as the Eurasian otter (Lutra lutra). Nevertheless, otter DNA obtained from scats and anal secretions appears to be exposed to very quick degradation processes, and the success rate in DNA amplification is lower than in other carnivores. We collected 191 samples from April to September 2011 along the river Sangro basin (Italy) which was recently re-colonized by the Eurasian otter. Using two sets of microsatellite loci (six Lut and seven OT loci), we investigated the influence of sample type and age, collection time, storage time, temperature and humidity on genotyping success and amplification success. We also tested the efficacy of different DNA extraction kits and storage buffer mediums. Finally, we compared amplification success rate, allelic dropout and false allele rates for each locus. We obtained a mean amplification success rate of 79.0 % and a genotyping success rate of 35.1 %. Fresh pure jellies yielded the highest amplification success and genotyping rate. Six microsatellite loci should be theoretically sufficient to distinguish the individual unrelated otters (PID?=?0.001), while 13 loci were needed to distinguish sibling otters (PID_sibs?=?0.002) in our population. We identified 11 otters, and molecular sexing ascertained the presence of five males, four females and two uncertain individuals. Generalized linear models highlighted a significant influence of sample type and age, temperature and humidity both on genotyping and amplification success.     

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.     

Effects of sea water on thermal insulation of the otter, Lutra lutra

Otters Lutra lutra L. which feed in the sea in Scotland frequently wash in fresh water. Experiments were carried out with otter pelts and with captive otters, to study the biological function of this behaviour. In vitro , the fur of otters lost much of its thermal insulation after five soakings in sea water and subsequent drying. Otters were fed in sea water or fresh water, with or without simultaneous access to alternative fresh water. When fed in sea water, otters used the alternative fresh water much more than when fed in fresh water, they were more reluctant to enter sea water if no alternative fresh water was present, and without this alternative fresh water they showed signs of hypothermia. After swimming in sea water the animals spent more time grooming and rolling. Without fresh water present the otters' fur lost its capacity for retaining air under water. These observations suggest an explanation for the restricted distribution of otters living along the coast, and for the lack of use of marine habitats by small mammals in general.