The fourth national otter survey of England was carried out from january 2000 to February 2002. Signs of otters were found at 34 per cent of the 3327 sites visited. The results are expressed as the percentage of survey sites found to have signs of otters within alternate 50-km squares of the National Grid and within 12 "regions" of the country. To allow direct comparison these "regions" generally follow the boundaries used in previous surveys. They are the 10 regions of the then water authorities and National Rivers Authority, although two of the regions (Severn-Trent/Midlands and Welsh regions) have been further split into their constituent catchments (the Severn and Trent catchments and the Wye and Dee catchments) for reporting purposes.
For the baseline survey of England in 1977-79 (Lenton et al, 1980) 2940 sites were examined, and signs of otters found at 170 (5.8 per cent) of these. For the second otter survey of 1984-86 (Strachan et al, 1990) 3189 sites were examined, including all those in the 1977-79 survey, and 284 sites (8.9 per cent) were found to be positive. In the third survey of 1991-94 (Strachan & jefferies, 1996), the same 3189 sites were examined and 706 (22.2 per cent) found to be positive. A direct comparison of the 2940 sites examined in all four surveys shows 170 (5.8 per cent), 282 (9.6 per cent), 687 (23.4 per cent) and 1066 (36.3 per cent) respectively were positive. There was a 67 per cent increase in positive sites between 1977-79 and 1984-86, a 142 per cent increase between 1984-86 and 1991-94 and a 55 per cent increase between 1991-94 and 2000-02. This is a 527 per cent increase between 1977-79 and 2000-02, based upon the original 2,940 sites of the first survey.
The 2000-02 survey confirms that the increase in otter distribution seen since the first survey in 1977-79 is continuing. Every one of the 12 regions and catchments, into which England was divided for the survey, shows an increase in the number of positive sites.
Otters were found in 35 of the 38 50-km squares or partial squares surveyed. Only in squares SK n/w (Trent Catchment) and TR n/w (Southern Region) were otter signs found during the 1991 -94 survey, but not during the 2000-02 survey. This was probably because of high water in the period just before the 2000-02 survey, and in both these squares otter signs have been found during subsequent independent surveys. Square NX s/e (North West Region) with only five sites had not been surveyed during previous surveys and no signs were found during the present survey. ln all the other five partial 50-km squares added for this survey, otter signs were found. In square SX s/e (SW Region) 91 per cent of the new sites were positive.
The scale of the increase varies considerably but it is significant that the leading edge of the recovering population is continuing to expand. This appears to be creating large areas with otter populations at low density followed by consolidation which seems to occur some years after the leading edge has passed.
Otters were present in 73 per cent of the 105 LEAP areas surveyed in whole or part. An increase in otter distribution cannot be directly translated into an increase in otter numbers; nevertheless, the expansion in (range must reflect a significant increase in the number of otters on England's rivers and wetlands.
The 2000-02 otter survey of England provides an opportunity to assess the current status of the otter in England and to recommend priorities for action to identify trends in distribution, identify possible barriers to the full recovery of otter populations and the actions needed to remove those barriers.