The diet of otters was studied by the means of spraint analysis in the Bieszczady Mountains, in southeastern Poland. The study area extended over 25 km long stretch of the River San, about 1 km above Solina dam reservoir. Spraints were collected on seven 2 km long sections in 1993, and on three sections in 2010. In both study periods, otter spraints were collected in August, when the weather conditions were similar. The study revealed high contribution of mountain fish species such as Phoxinus phoxinus,Cottus spp., and Barbatula barbatula in otter diet. Diet composition along the River San showed little variation in 1993, except from the section closest to dam reservoir where it was characterised by the highest frequency of occurrence of perch Perca fluviatilis, cyprinids and amphibians. The share of perch in otter diet decreased, while that of noble crayfish Astacus astacus increased with the distance from Solina reservoir.
Changes in otter diet between 1993-2010 were characterized by an increase of the consumption of perch and cyprinids on the one hand,
and a decrease of the consumption of crayfish, on the other. Both spatial and temporal changes in otter diet reflected the effect of Solina
reservoir on the river community and the availability of prey to otters. The results indicate the ongoing changes in fish community influenced by the construction of Solina reservoir.
The seasonal diet composition of otters (Lutra lutra) living by an eutrophic fish pond system, a wetland alder forest, and a slow-flowing stream located in south-west Hungary was investigated by spraint analysis (n = 801, 116 and 234 samples respectively). Both percentage relative frequency of occurrence (O%) and biomass (B%) of food items (calculated by coefficients of digestibility) were estimated. The food composition of the otters living by the three areas differed significantly (PAstacus spp.) was dominant (54 O% and 62 B%). Close correlation was found between relative frequency of occurrence and biomass of food items.
Diet composition and feeding habits of Eurasian otters (Lutra lutra) living on three moors (Baláta, Nagyberek and Fehérvíz) in Hungary were studied over two years using spraint analysis (n = 199, 503 and 315 samples from the three moors, respectively). The food and presence of otters in the first moderate and second drought year, when the moors dried during the summer period, generally differed. Area-dependent variations in the diet were also found. The primary food source was fish (biomass estimation for the first and second year: Baláta 94.4% and 99.9%; Nagyberek 93.9% and 71.5%; Fehérvíz 66.4% and 82.1%). Most fish (mean: 94.6–99.9%) were small-sized (below 100 g in weight), and the most frequently taken species was Carassius spp. On moors, which are dependent on rainfall and ground-water only, during or after periods of drought otters temporarily changed their diet from optimal prey (fish) to sub-optimal prey (e.g., waterfowl) and they often left the habitat entirely. On moors with small canals, during periods of drought otters kept fish as the dominant food source, and weathered out extreme environmental local conditions.
In early spring of 2007, unusual feeding behaviour was observed for the Eurasian otter (Lutra lutra) when a cache of toads (n = 18), black bullheads (n = 2) and great diving beetles (min. 58 ind.) were found in a hollow tree-trunk on the shores of an oxbow lake near the River Danube. Spraint analysis identified the primary food of otters in the area to be fish, with non-fish (buffer) prey of very low importance. As the otter consumed almost exclusively fish, and appeared to store mainly buffer food items, this may indicate that either preferred fish were less available (limited) or that non-fish items were relatively more abundant for a short period during the mild ‘cold’ winter and spring period. The otter had abandoned this particular cache. Food caching is an important dietary adaptation for many species, providing readily available food during periods when fresh food may be difficult to find.
Eucoleus schvalovoj Kontrimavichus, 1963 (Nematoda: Capillariidae) is redescribed. The original description of this species was brief and inadequate in thal it was based on just a few specimens removed from the Eurasian otter, Lutra lutra (Linnaeus, 1758) in the Khabarovsk region, USSR. Detailed morphological study of several specimens of E. schvalovoj from the oesophagus of L. lutra from Spain revealed new characters, above all in males, and allows for a better characterisation of this species. Since its original description £. schvalovoj has only been recorded in Spain.
Understanding the diets of predators, prey selection and their impact on prey populations is pivotal to investigations on the ecology of predator and prey species. In this study, we observed a hand-reared European otter (Lutra lutra) foraging in the wild, in order to identify the type of prey captured by the predator. The study was carried out between March and June 2001 in a diverse range of natural otter habitats in Białowieża Forest (NE Poland). We found that tadpoles represented an important part of the otter's diet in June, when their frequency of occurrence and biomass reached 38% and 11%, respectively. During spring, tadpoles were less common than other types of prey, such as adult amphibians, fish, or aquatic Coleoptera. Otter diet varied among months and there were differences in the main prey type captured among water body types. Our results highlight the need to develop methods that enable the identification of tadpoles and other cryptic seasonal food items in riparian predator diets.
The construction of dams is a significant environmental issue due to its impacts on native fish populations and riparian animals and habitats. The response of otters Lutra lutra Linnaeus, 1758 to such disturbances was evaluated using the Aguieira reservoir (Central Portugal) and its associated tributaries as a model. Visiting rates suggested the presence of resident otters, both in the reservoir and in two of the tributaries. There was a significant negative influence of water level and precipitation in the number of spraints found around the reservoir. Nevertheless, marking behaviour was positively related to substrate and negatively related to vegetation cover, though these variables explained only a small amount of variation in otter signs. In the tributaries, although precipitation also negatively affected the number of otter signs found, the availability of rocks in the riverbed and the presence of refuge had a positive influence in marking behaviour. Prey composition and abundance differed between reservoir and tributaries, but the main otter prey in both systems was the pumpkinseed, which is very abundant in the reservoir. Results demonstrate that otters regularly use the Aguieira reservoir, which provides a good prey base, and the associated tributaries, which provide shelter.