Movements and Establishment of Reintroduced European Otters Lutra lutra

Establishment patterns of reintroduced European otters Lutra lutra are described from a behavioural and a conservation perspective. Thirty-six 1-year-old otters, 11 wild-caught and 25 captive-bred, were released and radio-tracked in Sweden between 1989 and 1992. Movements after release depended on whether the release area was already occupied by other otters. Establishment occurred in areas that were unoccupied or were occupied by otters of the opposite sex. Females established exclusive home ranges and remained in these areas on attaining maturity. There was a tendency among males to expand their home ranges coincident with sexual maturity; no such range expansion was observed among females. Competition for resources largely explains the movement and establishment pattern in released otters. Competition for mates over-rides competition for other resources in adult males. A distance of c. 10 km between the release site and areas occupied by other otters is recommended. Areas occupied by otters were associated with lakes and rivers with high biomass production.