Observations on an Otter Population in Decline

The distribution of otter signs on the catchment of the River Teme, United Kingdom, over a ten year period indicated that the range of the species, already limited at the start of the study in 1977, de-clined further over subsequent years. Otters became restricted to the upper reaches of the catchment. Evidence is presented that contami-nation with organochlorines (which can be extracted from spraints) may have been responsible for the decline. Reasons for a possible increase in otter distribution during the final years of the study are discussed. Regular observations of sprainting sites on the River Clun (a Teme tributary) showed that otter signs showed a negative expo-nential loss rate with time, 90°/o still surviving two weeks after depo-sition. The level of marking on the Clun suggested a low otter pop-ulation and the clear seasonality tin sprainting activity typical of thriving populations was not detected. Sprainting activity declined during the study period. There was, however, a seasonal pattern in the deposition of different types of signs. Most signs of otters on the Clun were located in the central reaches of the river, which had the greatest amount of bankside cover