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MAMMAL CONFERENCE

A WATER VOLE SPECIES RECOVERY PLAN FOR THE EASTERN REGION DARREN TANSLEY (Dedicated to the memory of Rob Strachan) Until the late 1980s the Eastern Region was considered a UK stronghold for the water vole Arvicola amphibius. The first national survey by Rob Strachan in 1989–90 showed that water voles were present at nearly 75% of sites surveyed. However, the repeat survey in 1998 revealed a catastrophic decline to 30% occupation, a trend that continued into the early twenty-first century when positive sites dropped below 10% for the first time. This earned the water vole the unenviable title of Britain’s fastest declining mammal. Despite full protection under the Wildlife and Countryside Act in 2008, deliberate habitat destruction still occurs on private land, Local Wildlife Sites (formerly known as County Wildlife Sites) and rivers including St Osyth Priory (2010), River Ingrebourne (2011) and the River Brett at Thorington Street (2014). Flooding in the summer of 2012 also wiped out generations of young voles still in their breeding nest chambers when the rivers overtopped their banks, despite water vole attempts to plug their burrows with soil to stop the water getting in. But the worst impact on water voles at a landscape scale has been the increasing distribution of North American mink Neovison vison. Mink can now be found in virtually all river systems in the Eastern Region and controlling the species at a reserve level has proved impossible. In Essex, for example, the Wildlife Trust only manages 0.02% of the land in the county, so even if this is entirely cleared of mink, it will have no more than a negligible impact on the problem. Employing professional trappers across the region would have been a prohibitively expensive, open-ended prospect so it was important to devise a landowner based model of tackling the issue at a landscape scale. One of the first pilots was co-ordinated by Penny Hemphill (Water for Wildlife Advisor, Suffolk Wildlife Trust) on the River Deben where water voles declined from 78.5% of sites in 1997 to 46.8% in 2003. Landowners along the river were given equipment and training to operate a series of trapping stations, the result of which was catchment scale removal of mink. In 2004, a repeat water vole survey found voles in 80% of sites. The advantages of this type of project, now co-ordinated across the region, are that it is relatively cheap to instigate, invests people in their local area and wildlife, gives demonstrably positive results where water vole colonies have not been entirely eradicated and provides potential benefits for agri-environment applications, university studies and training. The goodwill generated by interaction with a wide range of stakeholders has been a vital help in subsequent projects to monitor the rivers. The main problems occur when participants drop out, either through lack of interest or, more often, complacency after initial success. Also chasing volunteers for records of mink or water voles is very time-consuming and confirming that animals are being correctly dispatched in a humane way can be problematic.

Trans. Suffolk Nat. Soc. 51 (2015)

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Suffolk Natural History, Vol. 51

Despite these issues, the Eastern Region Mink Control Group has grown from a handful of small projects, mostly coordinated by county Wildlife Trusts, to a wide-ranging group of organisations and individuals that meet each November to offer advice, assistance and co-ordination, especially in areas where county boundaries bisect catchments. Maps of the Project’s expansion are generated centrally from participant’s records, along with areas where projects have ceased, or gaps in monitoring require attention. With mink control in place, and where pockets of water voles still existed, progress has been extremely encouraging. At this stage, habitat creation, such as new ditch networks at on the Crouch Estuary and at Wivenhoe Ferry Marsh, have provided new areas for water vole colonies to expand. The removal of mink in the landscape around coastal reserves, such as RSPB’s Old Hall Marshes, has also resulted in annual mink captures being reduced to virtually zero, completely reversing the annual trend of increasing mink populations. But on Rivers such as the Essex Colne, water voles had been entirely eradicated before the Essex part of the Project was instigated. Here, a catchment scale reintroduction, involving a 9 km long release site, has been the solution. Funded entirely by developers of the DP World port on the Thames, and involving the trapping and release of nearly 600 water voles and removal of more than 100 mink, this was one of the largest water vole reintroductions in the UK. Five years later, water voles occupy more than half of the river catchment and are still expanding their range. Three landowners have also benefited from Higher Level Stewardship agreements, partly supported by their work with the water vole releases. In the long term, a centrally co-ordinated, local response to mink and water vole monitoring is the only viable strategy. Funding for projects is volatile and the Environment Agency, that has long been supporting this work, now has little or no budget to continue. So volunteer River Wardens are being trained to take over where the professionals have left off. A network of these enthusiasts, working alongside supportive landowners, is delivering increased water vole occupancy at a landscape scale as well as benefits for the habitat and other species. While this strategy is unlikely to result in complete eradication of mink, it has drastically reduced their impact on our native wildlife. The Eastern Region Water Vole and Mink Project continues to enable tiny pots of funding to have a much larger positive impact on the environment. Darren Tansley The Wildlife Trusts’ representative on the UK Water Vole Steering Group Water for Wildlife Officer at Essex Wildlife Trust darrent@essexwt.org.uk

Trans. Suffolk Nat. Soc. 51 (2015)