Changes in otter Lutra lutra distribution in Central Spain in the 1964-1995 period

Surveys carried out in 1964, 1984 and 1995 of otter Lutra lutra distribution were compared in order to analyze its changes in distribution in Central Spain. These changes were studied from different areas defined by their physiognomy and human population density. During the 1960s, the species was well distributed throughout the study area but this was followed by a decline and a more recent recovery. Several negative factors (i.e. pollution, human disturbance, habitat destruction, hunting) extinguished or fragmentated some populations. During the last period (1990s) some populations have recovered, probably through recolonization from neighbouring areas supporting healthy populations. Variations in a water quality index and human density were considered to be potential explanatory causes of changes in otter distribution. The current otter distribution is probably very influenced by movements between different areas. High human population density and physical barriers (mainly mountains) can be considered as the principal factors limiting otter movements. This paper emphasizes the importance of studying local population dynamics in order to plan an effective long-term conservation strategy. (C) 1998 Elsevier Science Ltd. All rights reserved.