In Search of Water Voles

On learning about the field signs of water voles and the hidden value of these “micro-beavers”

A Water Vole eating (Photo by Jonathan Ridley on Unsplash)

We must have looked a strange sight, about a dozen of us walking slowly along the riverbank peering down at the ground and occasionally scanning the opposite bank with binoculars. What we were searching for were signs of the presence of water voles – the entrance holes to their burrows, their droppings (which are about the size and shape of a tic tac apparently) or their food stores (small, neat piles of short lengths of grasses and reeds with a diagonally cut end). This early in the year we were only likely to find the first of these.

It was mid-March – before the recent spell of warmer weather - a day of blustery sunshine and occasional blasts of wintery rain and we were next to the River Cray where it runs through the grounds of Hall Place, a former stately home now run as a visitor attraction complete with butterfly house, miniature steam railway and large café. Canada Geese honked at us in expectation of being fed or pursued each other along the stream sending up shoots of water. There were Greylag Geese, Mallards and Moorhens too. And above it all the constant roar of several lanes of traffic on the A2 a couple of hundred metres away.

We were all here peering hopefully at the muddy riverbanks as part of a training session for volunteers organised by the London Water Vole Recovery Project which aims to develop a better understanding of the distribution of water voles across the capital. The Cray is one of four rivers – along with the Hogsmill, the Crane and the Roding – which have been selected for inclusion in the project either because water voles have been reintroduced there in recent years or there is reason to believe that the animals are already present or could return soon.

River Hogsmill (Ruth Bradshaw)

As well as learning about the field signs for water voles, we’ve been taught how to distinguish them from a brown rat, the creature they’re most likely to be mistaken for. I now realise that the few times I’ve seen what I convinced myself was a water vole, it was almost certainly a rat. In future I shall know if the creature I’m looking at has pink ears, feet and tail and scurries away through the vegetation it’s a rat but if it has ears that barely show up against its brown fur and a short furry tail and dives into the water with a ‘plop’, it’s a water vole. Hopefully it will be that simple!

Another distinguishing feature – although one that I suspect is not that easy to spot in the wild - is that some of the water voles’ teeth are orange as their incisors are coated in an iron oxide which makes them very strong. This enables them to chew through bark which they generally only do in winter when there’s less other food available. These teeth are essentially a smaller version of the ones beavers have meaning water voles are sometimes described as “micro-beavers”.

Like beavers they are ecosystem engineers whose activities play a vital role in shaping the environment. They help improve bankside plant diversity by dispersing seeds and rhizomes during the creation of their underground burrows and they are also a great source of food for other native species including herons and birds of prey. The presence of water voles is generally an indicator of healthy habitat. However, unlike beavers there is rarely any controversy associated with their activities, as the impact of water voles is smaller-scale and less visible than that of the larger rodents.

There have now been a number of successful reintroductions of water voles around the country, including in London. They are pretty adaptable creatures who eat a wide range of different plants and can make their home anywhere the banks are suitable for digging their burrows – slow-moving streams, ponds, lakes and reedbeds.

Of course, the reason those reintroductions are needed is because we lost so many water voles in the first place. The water vole’s story is among the saddest of the many stories of species loss in this country. But it is also a story that shows we can turn things around if we try hard enough. Once these small, brown rodents would have been found living around pretty much every stream and pond in Britain. But over the course of the twentieth century, their numbers tumbled. The causes of this decline include the familiar ones of habitat loss, pollution and agricultural intensification but in the case of the water vole there is another culprit – the American Mink.

American Mink (Photo by Alexandre Daoust on Unsplash)

Mink were imported to this country for fur farms but many escaped or were released by animal rights activists who clearly hadn’t thought through what their actions would mean for the water voles’ right to life. Numbers had already been falling but during the 1980s and 90s when most of the mink releases took place the size of the water vole population plummeted even further and it’s believed we had lost 90% of our water voles by the end of the 1990s. The tactics water voles use to evade their native predators – diving under water or hiding away behind the small entrance holes of their burrows – are not sufficient defence against the mink. Female minks are small and agile enough to be able to get right inside a water vole burrow and once they discover a water vole colony, they can wipe it out completely.

The need to deal with this threat has long been recognised and there has been a mink trapping programme in place in the UK for several decades now. Advances in technology and the development of smart traps which can be monitored remotely allow many more traps to be laid as each one needs to be visited less frequently. A comprehensive trapping programme in parts of the country, such as the East of England, has proved very successful, and there is now hope that mink could be completely removed from the UK, significantly increasing the water vole’s chances of recovery. Bur in the meantime we’ll be keeping a lookout for signs of mink when we do our water vole surveys.

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To finish….

…a few things I’d like to share:

1. Black Ops and Beaver Bombing: Adventures with Britain’s Wild Mammals by Fiona Mathews and Tim Kendall: This book provides a fascinating overview of some of the attempts to reintroduce, or support the recovery of, our most threatened mammals. There are individual chapters on different species including wild boar, red squirrels and beavers as well as water voles and lots of interesting insights into the challenges associated with species reintroductions.

2. The benefits of reintroducing wolves – Researchers at the University of Leeds have modelled the potential impacts of reintroducing wolves in the Scottish Highlands and found this could deliver substantial benefits for both climate and biodiversity. By reducing the red deer population, the reintroduction of wolves would allow the natural regeneration of native woodland capable of storing significant amounts of carbon and deliver other benefits such as a reduction in Lyme disease.

3. Learning to live alongside bears: This is a lovely piece from The Guardian about a small mountain town in Italy where the people have chosen to love the bears that live alongside them rather than treat them as a threat. This has attracted tourists and brought new residents to an area where the population had previously been declining.