TALES OF THE RIVERBANK
Discover the secrets behind the elusive water vole’s comeback
In 1929, American minks – relatives of weasels and otters – were brought over to Britain from North America for the fur trade, but it wasn’t long before some escaped and others were illegally released. This invasion was absolutely disastrous for Britain’s water voles, with one mink able to wipe out all the inhabitants along a stretch of riverbank in just a few weeks. While water voles can dive into streams or hide in their burrows to escape from larger native predators, these tactics did little to stop the agile, semiaquatic minks. Adding to the pressures of water pollution and the degradation of riverbanks, the arrival of the minks eventually led to a more than 90 per cent drop in water vole numbers between 1989 and 1998. In fact, water voles have experienced the biggest decline of any British mammal in the last century.
“The mink invasion was absolutely disastrous for Britain’s water voles”
In response to the crash in their numbers, conservation groups have redoubled their efforts to save these endearing animals. The wildlife charity People’s Trust for Endangered Species (PTES) is dedicated to helping water voles and has put more than half a million pounds into dozens of conservation programmes since 1980.
These have involved looking into the best ways to restore riverbank habitat, captive breeding and reintroducing voles to areas they used to inhabit, as well as investigating ways to control mink populations.
Emily Thomas, key species monitoring and data officer for PTES, explains why the charity is working hard to protect these struggling rodents. “Immortalised as Ratty in The Wind in the Willows, water voles are a key part of our natural heritage. They have been in Britain since the last ice age and play an important ecological role along our waterways as an indicator of a healthy environment, providing food for a range of native predators and even affecting the bankside plant diversity through the creation of their burrow networks.”
When water voles dig burrows in a riverbank it dries out the surrounding wet soil. This change promotes the activity of microbes in the soil, which alters the level of nitrogen available for plants to use and determines which species can survive in the area. As prey, water voles also provide an important source of food for birds like owls and herons, mammals including foxes, otters and weasels, and even large fish such as pike. These little critters are absolutely vital to their ecosystems.
In 2015, PTES launched a new scheme to find out how Britain’s water voles were really doing. The National Water Vole Monitoring Programme (NWVMP) invites volunteers from across England, Wales and Scotland to go out each spring and monitor sites for signs of any water vole activity. The chubby little animals are hard to spot, so monitors check for clues like droppings, feeding remains and burrows.
The data from the 2017 survey has now been analysed, and Emily believes that there are some positives to be found in the results. “The NWVMP aims to bring together
“Immortalised as Ratty in The Wind in the Willows, water voles are a key part of our natural heritage”
“It’s only by continually monitoring sites annually that we’ll be able to get a comprehensive idea of how water voles are faring across the country”
all current monitoring, as well as resurvey sites from the previous national surveys so we can find out what the current situation is and detect any future changes. Last year, we received data from 222 sites across Britain, of which 82 had active water vole signs (latrines, feeding signs or sightings) present at them. 130 sites were surveyed in England, 78 in Scotland and 14 in Wales. Of the positive sites, 56 were in England, 15 were in Scotland and 11 were in Wales.
The distribution of these positive sites was very encouraging, with sites ranging from Cornwall and Suffolk up to the Highlands and across to the Isle of Anglesey.”
Many of the positive sightings came from surveys conducted in nature reserves or reintroduction areas.
According to Emily, PTES is still hoping to gather data from volunteers in even more locations, especially in the South West, the West Midlands, southern Scotland and Wales.
“The previous national survey sites were specifically selected to give a good geographical spread across Britain, ensuring all habitats and areas were surveyed. By the 1996–98 surveys, many of them no longer had water voles present, and so it’s unsurprising that water vole
occupancy at these sites is still low. However, we know from the first national survey that many of these sites supported water voles 25 years ago; therefore some should have the potential to support the species in the future.
“Mink control continues and habitat conditions keep improving, therefore the longterm aim of the monitoring programme is to continue to survey these historic sites annually in the hope that water voles will recolonise them. Once again, we’ll be aiming to increase the number of sites surveyed [in 2018] so we can continue to collect robust data to determine yearon-year trends.
“It’s only by continually monitoring sites annually that we’ll be able to get a comprehensive idea of how water voles are faring across the country.”
In previous years the survey has run through May, but PTES are extending the window this year so that data can be collected between mid-April and mid-June. Recent mild winters have encouraged riverbank plants to grow thick earlier than usual, so the earlier start gives volunteers looking for the shy voles a bit of a head start. It’s vital to the programme but, as Emily explains, the surveying isn’t too time consuming.
“Volunteers are asked to survey one of the nearly 900 pre-selected sites across Britain, recording all sightings and signs of water voles along a 500-metre [1,640.4-foot] length of riverbank from mid-April to mid-June. Sites that are already being surveyed can also be registered with the NWVMP. Though no prior experience is required, volunteers will need to learn how to identify water vole field signs.”
To find out more, or to register as a volunteer for PTES’s 2018 National Water Vole Monitoring Programme, visit:
“The programme invites volunteers to monitor sites for signs of water vole activity”
below Water voles are shy creatures, usually vanishing into the water if they hear anyone approaching
If volunteers don’t
spot the voles themselves, they look for signs that they live
in the survey area
Water voles chew their food at an angle, leaving behind distinctive piles of nibbled stems when they feed
Diving into a stream doesn’t protect water voles from minks because the predators are strong swimmers