Spraints have been used to survey otters in the UK since 1979 and a standard methodology has been set up which has been used in Britain and Europe for most survey work. At present data from these surveys is being used to give an estimation of actual population numbers. However, for this to be possible, there must be a correlation between sprainting numbers, active spraint sites, and otter numbers. This paper investigates whether such a correlation exists. There is evidence from previous work that there is seasonal variation in sprainting and this study confirms this. Therefore spraint surveys should be undertaken in the same months for each repeat survey. 1. Introduction Recent reports have stated that otters are increasing in number all over the United Kingdom. However these reports must be treated with some caution because of the methodology of surveys. The standard methodology for otter surveys is to look for spraints (droppings) for a distance of up to 600？m from what is considered to be a suitable sprainting site, such as under a bridge or at the confluence of two streams/rivers. If spraint is found, then the 10？km grid square is marked as positive but this cannot give any idea of actual otter numbers—it simply confirms that an otter has passed that way [1, 2]. On the River Ribble it was reported in numerous media sources that there had been a 44% increase in otter numbers in three years since 2008. This was based on information from the Environment Agency website [3]. However otter populations cannot increase so quickly as they have a very slow rate of reproduction. Otters do not become sexually mature until 18–24 months and there will normally be 1-2 cubs, although occasionally there are three. The young stay with the female for 12–15 months, so she may only breed about every eighteen months. Furthermore, a report from Cardiff University highlighted the fact that out of 110 otters aged from England and Wales only 10 were aged 4 years or older and the maximum age found was only 8 years [4]. This means that otters in England and Wales are dying much younger than in some other European countries. In Germany, for example, otters have been recorded living until 16 years old and the bulk of reproductively active females were 6–8 years old. In Cardiff only two females were older than 6 years. This therefore suggests that either otters in England and Wales reach peak breeding earlier than in Germany or they are dying before they reach this stage. What the Environment Agency actually meant to say was that the number of spraints had increased by 44%. This
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