By Fiona Mathews, Mammal Society Chair and Professor of Environmental Biology, University of Sussex
Sections of this blog appeared in British Wildlife magazine in 2020
The water vole Arvicola amphibius has the unenviable honour of being a leading contender for the title of Britain’s most rapidly declining mammal. Classified as Endangered in England and Wales, and Near Threatened in Scotland, this is a species that needs urgent conservation action. My copy of the 1962 Sunday Times booklet ‘Water Voles’ reads, ‘They are found all over England, North Wales and on the mainland of Scotland…. They abound along many of the waterways of England, and wherever there is good water contained in firm banks, there you may be sure to find signs of water vole habitation’ (Roden Ryder, 1962). Not any more you won’t. By the time the Vincent Wildlife Trust undertook the first national water vole survey in 1989-90, the species was already in decline (Strachan and Jefferies 1993), and the repeat survey in 1996-8 showed that the situation had gone from bad to worse (Strachan et al. 2000). The current population size is estimated at 132,000 individuals (99,000-329,000), and the expectation for the future is one of continued decline (Mathews et al. 2018).
Why is this? The water vole faces a combination of pressures. There are long-term issues of water quality and riparian vegetation management. The poaching of banks by cattle is a major cause of habitat loss; the re-engineering of waterways as part of flood-management strategies has often acted against the interest of water voles; and the relocation of water voles away from development sites to new locations can be complex and less effective than anticipated. Water flows in many rivers also fluctuate more than they did historically, with spates scouring bankside vegetation and flooding burrows. Finally, there is predation. A wide range of species, from herons to otters, can and do eat water voles. The 1962 Water Vole Pamphlet cites the brown rat as by far the most important predator and does not mention at all the American mink — which was only recorded to be breeding in the wild in in 1956. There has been surprisingly little research on the ongoing impact of brown rats on water voles (indeed, our knowledge of brown rats as a whole is so poor it is currently not possible to estimate trends in their abundance, or even put plausible limits around their population size (Mathews et al. 2018)). At least in urban and peri-urban areas, it would be surprising if they had no effect, and there is also an ongoing risk of accidental poisoning from bait intended for rats. In contrast, the major impact of mink is clear. It is also clear that water voles are more vulnerable to predation amidst poor habitat. Having a network of alternative ponds and streams and wetlands, rich with vegetation, rather than a single, poorly vegetated channel is important. Recent work from Poland shows that water voles can persist — even despite the presence of mink — in a network of mid-field ponds adjacent to a river (Brzeziński, 2019). The availability of such habitats was improved owing to the activities of beavers, which leads one to wonder about the possible opportunities that might be created for Britain’s water voles by beaver reintroductions.
Despite the generally dismal picture, there are some notable exceptions where the fortunes of the water vole appear to be turning around. The Scottish Mink Initiative aims to remove mink from around 30,000km2 of Scotland. Following a highly successful eradication programme in the Cairngorms National Park, led by Xavier Lambin at the University of Aberdeen, it builds on a detailed understanding of the population ecology of water voles and mink in the area. Huge numbers of local volunteers are using footprint rafts to survey for mink, and are participating in the control programme. In England, Essex Wildlife Trust’s water vole recovery programme, led by Darren Tansley, has used a combination of habitat improvement, targeted mink control, and water vole reintroductions to restore the species to more than 500km2. However, most other restoration efforts are much smaller. In the late 1990s and early 2000s, many regions had local water vole and rivers project officers. Sadly, many of those posts were supported only by short-term funding; once local co-ordination disappeared, so did the water voles. As with so much in conservation, restoring the water vole is a marathon, not a sprint, and needs strategic investment over a prolonged period.
We are therefore delighted to be starting a new project in collaboration with Natural Resources Wales leading to an action plan for their recovery. Based on detailed analysis, we aim to direct interventions where they are most likely to deliver the maximum benefits to water vole conservation. We are keen to find out about any current or planned mink control projects going on in Wales, and also to receive any records of mink or water voles (as with all data sent to the Mammal Society, these records will be shared with Local Biological Records Centres).
Brzeziński M, Jedlikowski J, Komar E. Space use, habitat selection and daily activity of water voles Arvicola amphibius co-occurring with the invasive American mink Neovison vison. Folia Zoologica. 2019 68(1):21-8.
Mathews F, Kubasiewicz LM, Gurnell J, Harrower CA, McDonald RA, Shore RF. 2018. A Review of the Population and Conservation Status of British Mammals. Natural England Joint Publication JP025.
Roden Ryder, S. 1962. Water Voles. Animals of Britain 4. Ed L Harrison Matthews. Sunday Times, London.
Strachan R, Jefferies DJ. 1993. The water vole Arvicola terrestris in Britain 1989-90: Its Distribution and Changing Status. London: The Vincent Wildlife Trust.
Strachan C, Strachan R, Jefferies DJ. 2000. Preliminary Report on the Changes in the Water Vole Population of Britain as Shown by the National Surveys of 1989-1990 and 1996-1998. London: The Vincent Wildlife Trust.
Title slide image by Phillip Braude.