A survey was conducted within the entire land catchment of the Munster River Blackwater where a total of 275 sites was surveyed within 146 squares (5 x 5km), 184 (66.9) proving positive and 91 (33.1) negative for Otter Lutra lutra Linnaeus presence. Just one square was negative and this contained only two small ponds and no running water. Most squares were proved positive at the first, second or third site visited, and only 6.3 required a visit to a fourth or fifth site to prove them positive. The otter was present across the catchment from the estuarine area extending into the foothills of the mountain ranges. Proportionately more positive sites were recorded at altitudes below 100m (71.2, n = 156), there were fewer positive sites on streams of less than 4m in width (64.6, n = 130), and fewer sites containing a bridge were positive (66.4, n = 241). However, it is known from radio tracking studies elsewhere that otters make extensive use of small streams but leave no spraint evidence, and the importance of this habitat might be underestimated here. Although direct comparisons between this and previous surveys are unwise, there is no evidence that the otter has withdrawn from any part of the Blackwater catchment during the last 25 years, and the overall distribution of positive sites is almost identical to that described by O'Sullivan (1991) for the period 1988-90. Although new technologies for research are now available it is likely that spraint surveys, with some modifications, will continue to be used for catchment and national surveys for some time to come.
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