Each surveyor is allocated a stretch of river. He, (or she), explores this patch to discover the features of interest to and used by the otters. Then he selects a series of sites that are thought to give a good chance of detecting the presence of a passing otter without resurveying the whole stretch. The idea is that this set of sites should be readily accessible and easy to cover in one half-day, so that a morning will suffice to reveal whether an otter has been present or absent, and how much evidence it has created.
The name and grid reference of these sites is then entered on a master copy of the Electronic Monthly Form and forwarded to SERC, giving the state of play at the nominated sites. We record the number of fresh and recent spraints, any evidence such as padding, and the presence of water-related wildlife such as Mink or Water Voles. The sites should not be chopped and changed; in order to identify any trends, it is vital to record a result from a constant effort; in each person’s case, what was found by one visit to the same number of places on one occasion each month. It is of no benefit to our survey, if an otter unexpectedly turns up, to run around frantically after it, recording every last spraint or footprint.
This can be a very interesting and revealing thing to do, especially if there is snow. It will tell you a lot about how the otters use your patch, but basically this exercise should take place in the acquaint phase before the sites to be recorded are nominated.
The choice of date each month is up to the recorder, and does not have to be rigidly the same each month, EXCEPT that in the spring, probably at the end of April, the whole Otter Group undertakes a major, co-ordinated sweep of the whole county on two consecutive days.
A weekend is nominated for the Two-Day Event, and everybody checks their patch on the Saturday as they usually do. On the Sunday a repeat check is made to try to locate evidence that was definitely not there on the previous day. The aim is to freeze the otter picture for that one night, and to cancel out the distortions in our monthly checks from the otters wandering so much and appearing in several people’s results. It is a sort of count. The idea behind it is that at present an otter is constrained in its wanderings by territorial pressure from its neighbours. But should there be a sharp decline in population and the neighbours die, the otter would wander more freely, across several surveyors’ patches, and our survey score would not show any decline. This is what happened in the 1970’s, when the problems were only discernible to the hunts, and even to them only some time after the die-off had started.
The results are recorded on a special Two-Day Event form. On day 2 much less detail is required, just was there an otter present during Saturday night or not. To obtain consistency over the years, each cluster of fresh evidence is counted as the work of one otter only, even if more were seen. It is in fact a record of the number of occupied territories, not of animals, which is about as reliable as it is safe to get with these elusive creatures.
Inevitably, some surveyors have to be absent for this weekend. They are encouraged to let us know in advance, so that a substitute can be arranged.
Several of our surveyors who live handy to the river, or who take a dog for a daily walk, record the activity at one convenient spot every day, usually a sprainting stone. Some have built a pile of prominent stones specially to be able to do this. Over time this builds up a very indicative picture of the changing frequency, and we are trying to encourage as many people as possible to do this; double the number would more than double the value of the information, as it would eliminate some of the vagaries caused by the natural mobility of these animals.
As the result is expressed as a percentage of positive days over the number of days checked each month, periods when the river is too full, or when the observer is on holiday, are cancelled out of the equation. There is a recording form for this.