Source and sink dynamics of density-dependent otter (Lutra lutra) populations in rivers of central Finland.

Long-term studies were carried out in central Finland between 1985 and 2003 to examine the temporal and spatial variation in the density of otter populations. Snow tracking was used to estimate the total population and the number of litters in the study area. In total 52 otters, including 16 cubs in 11 litters, lived in the study area (1,650 km(2)) in 2002-2003.