Notes on the technique of the otter field survey

Abstract

Rom anowski J., Brzeziński M. and Cygan J. P. 1996. Notes on the technique of the otter field survey. Acta Theriologica 41: 1 9 9 -2 0 4 . D ata (2083 sites visited) collected during the otter Lutra lutra (Linnaeus, 1758) survey of Poland in 1 9 9 1 -1 9 9 4 were used to evaluate some of the factors affecting the efficiency of the technique. The success in detecting otter signs was found to be significantly affected by the presence of "spraintable" bridges and other potential sprainting sites on the banks. Decreased efficiency of the technique was noted in specific habitats, eg large rivers, canals surrounded by open fields or meadows, and any aquatic habitats w ith few potential sprainting sites on the banks. It is suggested that modifications: spot checks at additional bridges and extended searches of river banks, could be used to improve the reliability of the survey in areas with low numbers of otter signs. Institute of Ecology IntroductionThe standard field survey method, based on the search for otter Lutra lutra (Linnaeus, 1758) signs, has been succesfully used in many European countries (for references see Macdonald and Mason 1994). The survey is usually carried out based on the system of 10 x 10 km square grid, where around 6 sites are visited in each square (Lenton et al. 1980). The basic assumption of this method is that the 600 m-long walk along the waterside is enough to find spraints (excrements) or tracks of otters inhabiting an area (Macdonald 1983). Finding otter signs indicates the presence of these animals (positive sites), whereas the absence of signs at a series of sites (negative sites) enables to state, with high probability, that otters do not occur in the area, eg along one river.The national otter survey undertaken in Poland in 1991-1994 was based on the modified standard method, with one site visited in each 10 x 10 km square (Brzeziński et al. 1996). Numerous data (2083 sites visited) collected in various habitats enabled us to critically assess the method used and evaluate some of the factors affecting the efficiency of the search.[199] Otter signs under bridgesAt most sites we began the search for otter signs under a bridge. To supplement the main survey we performed spot checks under additional bridges (see Lenton et al. 1980). In most of those 10 x 10 km squares which were negative after the initial search, 1-3 spot checks were conducted. There were two reasons for choosing the bridges: the first one was the ease of approaching the river, the second -the longevity of otter signs under the bridge cover. Otter spraints remain on the banks from several days to several weeks but in sheltered places they can exist as long as 12 months (Jenkins and Burrows 1980, Macdonald and Mason 1988).During our studies otter signs were found under bridges in 56.9% of all posi tive sites. It should be mentioned, however, that not all bridges were suitable for the survey. Bridges which had boulders, natural banks, wooden or concrete ledges underneath were frequently used by otters as sprainting place...

Faecal DNA typing to determine the abundance and spatial organisation of otters (Lutra lutra) along two stream systems in Kinmen

“…Eurasian otters often defaecate at prominent sites along the bank of aquatic habitats, such as rocks, logs, sandy heaps, or under bridges (Foster-Turley et al, 1990;Romanowski, Brzeziński & Cygan, 1996). Due to the ease of collecting faecal samples, molecular scatology may offer a potentially favourable tool for obtaining population data on otters.…”

Use of stream environment by river otters in Hongcheon river, Gangwon Province, Korea

“…Besides previously published data showed that the majority of sings (about 70-80%) Macdonald, 1986, 1987;Romanowski et al, 1996). visually from high resolution satellite images and measured using GIS and remote sensing techniques (Table 1).…”

Habitat correlates of the Eurasian otter Lutra lutra recolonizing Central Poland

“…The surveys were carried out from February till April each year, in the period of high detectability of otter signs (Romanowski 2000). The standard otter monitoring method was used to provide fully compatible results (Romanowski et al 1996; Reuther et al 2000). Searching usually started at a bridge.…”