Radnorshire Wildlife Trust - Protecting Wildlife for the Future

About Water Voles and the signs to look out for!

Water voles are almost rat-size but have blunt noses, rounded bodies, shorter furry tails, little round ears hidden in their fur, and are really quite cute! They can be remarkably prolific, producing 2-5 litters each year of 5-8 young, but unfortunately over-winter mortality is very high with the loss of up to 70% of individuals, particularly the young. Adults themselves rarely survive a third winter.

Water vole swimming (photo by M Haylock)

Being near the bottom of the food chain, they are predated on by quite a range of species, even when the American mink is taken out of the equation - stoats, weasels, polecats, house cats (someone told me their cat brought a water vole in once, but that was the last time...), otters, heron, pike, barn owls. Water voles can escape from many of their predators by diving into the water and swimming into bolt holes or burrows in the bank. Unfortunately the female American mink is especially deadly as she will squeeze into the burrows and kill adults and young alike.

During the breeding season, female water voles hold territories that are between 30m and 150m long, depending on habitat quality, population density and time of year. A male's territory overlaps with the females. Populations are therefore strung out along the riverbank and they need contiguous stretches of well vegetated riparian corridor to maintain viable populations. It's easy to understand how colonies can become fragmented and vulnerable if long lengths of the river banks are built on or grazed very tightly.

Suitable Habitat

Water voles are classically found in slow-moving rivers and ditches with swathes of bankside vegetation to provide food and shelter, and soft penetrable banks. Often there are runs and latrine sites along the edge of the water and holes in the bank. They tend not to be found where the river banks are wooded because the shade does not allow the growth of lush vegetation, and also harbours predators!

The photograph on the right shows a well-used pond/wetland habitat and the photo below shows a suitable slow-moving river with soft penetrable banks with plenty of overhanging bank vegetation (photo's by Darylle Hardy).

Ponds and pond complexes can make good habitat, and may be particularly useful when a river is in spate. Areas of reed bed are also favoured, and because of their patchy rather than linear nature, they seem to provide an effective refuge from predators in many places.

Survey work by rangers in the Elan Valley indicates that many of our remaining populations are hiding away in the uplands, using slow-moving narrow water channels clad with rushes and hiding out amongst tussocks of purple moor grass. This terrain is sub-optimal for mink and the widespread habitat would make it difficult for them to find all the water vole clusters.

Keep an eye out for signs if you are walking near the mountain road between Rhayader and Aberystwyth! Another good place is the Wildfowl and Wetland Centre at Llanelli.

Upland stream habitats (photo's by Darylle Hardy)

Listen out for the "Plop!"

Water voles are buoyant and float like a cork when swimming, unlike rats which swim with their heads out the water. Listen out for the ‘plop' as the water vole dives into the water, warning others and escaping into a bolt hole away from a potential predator.

Water Vole droppings (photo by Darylle Hardy)

Droppings are 8-12mm long and blunt-ended (like a tic-tac), very distinctive and the clearest sign of water vole presence. During the March to October breeding season (shorter in colder climes), piles of droppings are laid in latrines, which are used to mark female territories along the water course. Over the winter, water voles are much less active so droppings may be scattered or underground and are much less visible. The colour of dropping varies from olive green to dark brown, depending on how fresh they are or what water voles have been eating.

Field voles make latrines too, often by the water, but their droppings are small, more like grains of rice. Try looking for signs inside a grassy tussock away from a water course so that you can be clear about the difference. Rat droppings tend to be slightly larger than water voles but ragged at the ends, and foul-smelling.

Food

Water voles are mainly herbivorous, eating a wide variety of lush bankside vegetation and consuming about 80% of their body weight every day. In upland areas, they feed on rushes, sedges and mosses. They often make food piles at favoured feeding stations, sometimes very neatly stacked, with stems typically up to 10cm long (a palm's width). Field voles will also do this too but tend cut them into shorter chopped lengths, though recent research has shown that field vole, bank vole and water vole food clippings can look pretty much the same! Always look for supporting evidence, ideally droppings.

Burrows and Tunnels

Water voles are really quite big creatures (rat-size) and tend to leave an obvious tunnel through vegetation, generally staying between 2m and 5m from the waters edge, though in tussocky wet habitat in the uplands, signs may be seen 10m from the water. Burrows tend to be wider than high, about 4-8cm in diameter and are generally found along or close to the waters edge. On a grassy bank they may have lawns grazed around them, or where the water table is high and banks are scarce, they may build a grassy nest in a tussock. Runs are often on a ledge along the waters edge, where the vegetation hangs over and protects them.

Have I got water voles or is it something else?

Water voles are sometimes mistaken for rats which also live and swim along watercourses, but their habits are different so a search for water vole signs will quickly help you establish which you have. Rats don't make leafy food piles and their burrows won't have a ‘lawn' grazed around them. Their droppings are different - being dark and ragged at one end. Rats tend to stay near human habitation and barns.

Look at this document 'Know your vole' to see a good comparison and to find out how to control rats without hurting water voles.

Rat (photo by Darylle Hardy)

Another sign you may find on the bank where the water quality is clean and clear, is piles of caddis larvae cases and shells - this may well be water shrew food piles although I suspect water voles might supplement their diet on these too.

Field voles leave signs which you are most likely to confuse with water voles. They also inhabitat the banks of water courses, paddle around marshy ground, make nests and food piles in Molinia tussocks and even take a swim. Look for their droppings, which are like grains of rice left in a pile. Field vole food piles tend to be shortly chopped - though not always!

Look here for more information, pictures and videos on the Arkive website.