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 d ifferent habitat factors on otters Lutra lutra (Linnaeus, 1758) and to deve lop a predictive model to better understand the distribution of the otter i n Denmark. During the National Otter Survey in 1991 data were collected on 19 variables which reflected aspects of habitat structure, composition, org anic 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 dep th, presence of trees, bottom substrate and Saprobien-Index) were identifie d. In Denmark, otter habitat typically consists of water courses with depth s > 1 m over a varied bottom, with pH > 7.0, Saprobien-Index on II-III to I II (indicating slight organic pollution) with no trees on the banks. Some o f 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 w ith care.