Water voles have repeatedly been shown to be Britain’s most declining mammal, having decreased by 88% over the last seven years, and are under a huge threat from predation by invasive American mink. Approximately 40% of the UK water vole population is believed to occur in Scotland, with a large proportion of these in upland sites. These populations should be considered of prime conservation importance.
Photo by Laurie Campbell
In 2011, Becky Priestley carried out a water vole survey of Coignafearn Estate, just outside the Cairngorms National Park. She walked all burns that were considered to constitute suitable potential water vole habitat and signs of presence were recorded. Classic signs of water vole habitation include rounded burrows up to 7cm in diameter, droppings or latrine sites, star-shaped tracks, cutlengths of cut grass or reeds and a cropped ‘lawn’ outside burrow entrances, although these are less common in upland sites.
A classic upland colony
Droppings are 8-12mm long and 4-5mm wide
Cut lengths of vegetation outside a burrow
Water vole habitation of Coignafearn Estate. Yellow = occupied burns. Red = unoccupied burns
Coignafearn was found to support a flourishing water vole population, with all suitable areas of habitat appearing to be occupied. Signs of presence were found on 186 burns. Aside from burrow entrances, under-snow tunnelling was the most frequently found sign of water vole presence, and was seen at 53.2% of sites. In upland sites such as Coignafearn, water voles mainly occupy underground burns and so although burrow entrances can be found, signs of feeding and latrine sites are predominantly underground.
Several factors were found to influence distribution: a) Slope – 98.4% of sites were on a flat-slight incline; b) Speed of water flow – 64.3% of sites were on static-slow-flowing courses, although speed of flow appears to be less important in underground courses than overground, with a number of sites found on medium-fast-flowing underground streams; c) Vegetation – colonies were only found in well vegetated areas with an abundance of grasses for foraging. Altitude did not appear to directly influence water vole distribution within the estate, with colonies found from 370m to 881m.
Water vole colonies were found in a number of different types of environment on Coignafearn Estate:
a) On the banks of slow-flowing overground water courses
b) In flat upland areas on underground water courses
c) Around static ponds, especially in upland areas
Although upland burns were extensively occupied, there are a number of lowland ponds which are unoccupied and which we believe would make excellent water vole habitat. We are interested in transferring some water voles from upland areas to bolster the lowland populations.
Our survey showed that, in terms of conservation of a rapidly declining species, Coignafearn Estate supports a critically important water vole population.
