BSG Ecology has worked with otter expert Geoff Liles in addressing complex issues regarding development sites close to Special Conservation Areas for otter, and on other sites where impacts on the species have the potential to occur, for many years. We were therefore delighted when he agreed to provide desk-based training on otter ecology, and how an understanding of this should inform the approach to survey work and the interpretation of results. This initial session will be complemented by a field-based training day later in the year.

Otters are protected under both European and UK legislation. In addition to affording protection to the animals, the legislation extents to both natal sites (which are used for period of approximately three months) and resting places. They move around their home ranges actively using overland travel routes that link the habitats that provide resources for them. Some of these resources will be actively used for short periods, such as when amphibians are spawning, but not at other times of year. Being solitary and territorial, with large home ranges (typically approximately 20 km for females and 40 km for males) otter occur at low density in the landscape. Understanding these basic aspects of their ecology and the large number of features they are reliant on helps start to provide insight into developing survey scope and interpreting results.

The training provided information into field signs, the typical sites otters use for resting (of which they will have many as they range so widely) and breeding. Key points included:

• that the trees which most often develop suitable cavities around their root systems (oak, ash and sycamore) are often used for resting (but that resting sites are very varied in their nature and include bramble scrub and rhododendron thickets);
• resting site entrances can be very small (e.g. one radio tracking study found a dog otter using a resting site with a 100 mm entrance), and locations are typically very close to water (allowing escape if disturbed);
• typical breeding sites are disturbance free, close to food sources and in areas that are not subject to regular flooding;
• suitable breeding sites are very limited in the landscape (and the best are used repeatedly); and,
• overland travel routes are often missed during standard consultancy surveys if no waterbodies are present on site. They tend to be direct, often passing straight across open fields, being used as short cuts and access routes.

The variety of breeding and resting areas otters use and the range of food they take were illustrated through the use of numerous excellent photos and video footage. Typical sprainting locations were also described in detail and shown on photos, and the function of sprainting in marking out home ranges (thereby communicating with other otters) discussed.

During the training Geoff also provided numerous facts and novel insights into otter ecology based on his experience. These included that otters have a relatively catholic diet when foraging in freshwater, but tend to feed on crabs in coastal situations (due to their abundance), that feeding remains cannot be conclusively concluded as being from otter in the absence of spraints (which will typically be present if the remains have in fact been left by an otter), and that otters have up to 60,000 hairs per square centimetre (as opposed a few hundred per square cm on a human scalp) indicating how well insulated they are.

Take away messages from the training included:

• that desk studies often miss readily accessible data on otter (such as the UK-wide road casualty data collated by Cardiff University and provided as an interactive online map)
• where otter are a potential issue with regard to a scheme, numerous surveys can be needed to understand the ecological function of habitats for the species, and these can involve the use of trail cameras, dry suits and canoes; and,
• that opportunities to incorporate straightforward (to conceive) mitigation measures allowing animals to move between features in the landscape, such as habitat corridors and underpasses, are often missed in development schemes if an understanding of how otters use an area has not been achieved.

An excellent and instructive morning of training from an expert with a detailed understanding of legal protection (and interpretation of terminology), huge experience in undertaking otter survey work and mitigation, and in the provision of advice to statutory bodies such as Natural Resources Wales and conservation organisations in the UK and continental Europe.

Emily McVean, Senior Ecologist commented: “Geoff shared (a very enjoyable) presentation of otter behaviour, resting sites, and field signs – accompanied by snippets of wisdom and a bibliography of references. I’ve taken a lot of notes on the importance of Overland Travel Routes and how to identify these. Geoff’s passion is infectious –  I’m eager to put his tips into practice to predict where overland travel routes might be, and hopefully find some ‘juicy’ fresh spraints.”

Natalie Sabin, Senior Ecologist said: “The training was very informative, I took away a lot of really useful information which can now be applied to otter surveys.”