Water voles on the wetlands
Seaton Wetlands is a complex of freshwater grazing marsh, salt marsh and a large tidal lagoon, spreading along the western bank of the Axe Estuary, Seaton. The sites are owned and managed by East Devon District Council as a Local Nature Reserve, and attract in the region of fifty thousand visitors a year.
In 2008 a three-year funded project made a small introduction of water voles into the site. Extensive work was carried out by the Project Officer to monitor these animals, and to protect and enhance their habitat through advice given to riparian landowners. Mink control was also undertaken at various sites across the catchment as well as close to the release locations. Water voles quickly became an easily seen species on the nature reserve, and many people enjoyed fabulous close up views of this charismatic mammal in ditches and ponds. However, as with so many of these time-limited projects, once the funding had finished there was disruption to the continuity of the work and, despite efforts, the population of water voles did not flourish as was hoped.
At the time of the first introduction I was employed as the Education Ranger in the Countryside Team. I left this role in 2011 in what turned out to be a five year sabbatical, returning as Countryside Team Leader in the summer of 2016. By this stage, an ecologist’s report suggested that the population of water voles in the area was, at best, 70 individuals: all but two of these were on land neighbouring the reserve. In efforts to improve the situation, we adjusted the mink control strategy, simplifying a network of 12 rafts to four stations distributed evenly through the site. The four rafts are now equipped with traps connected to “Mink Police” units that send an SMS message to my mobile phone if the trap is sprung. This means that trapping effort at these four strategic positions can be constant, safe in the knowledge that there can be a rapid response to any catches — whether of mink or non-target animals — whereas previously trapping was necessarily limited by the availability of people able to physically check the traps on site at regular intervals. The control strategy seems to be working. In 2017, a total of 8 mink were caught and dispatched on the site, whereas so far this year only four have been captured and sightings have been greatly reduced compared to previous years. At the same time, there has been an increase in the frequency of otter signs and sightings. Since spring 2018, regular spraint, footprints and sightings of otter have been made, and it’s my feeling that this presence has led to the site becoming considerably less desirable for mink.
With this efficient predator monitoring in place it was judged that that a two-year phased reintroduction of water voles could go ahead. Derek Gow provided valuable guidance whilst reponsibility for day to day monitoring of the voles and mink is held within my core work programme. Funding for the project therefore consisted solely of the cost of the vole captive breeding, and these costs were split evenly between the site budget and a contribution from the local Axe Vale & District Conservation Society.
The first 213 voles were introduced to the site on September 4th with a soft release process lasting five days. Pens containing 2-6 siblings or adult pairs were distributed through suitable habitat on the site. Getting the pens out onto site, mapped and recorded, took all day and was supported by 12 volunteers; a task where lots of willing helpers was a massive benefit! Each pen measures 60x80x20cm and is hinged in such a way as to fold flat (and trap fingers regardless of which way you carry it) to aid transport. The voles were fed a ration of ¼ sweet apple and a slice of carrot per vole per day. On the fourth day the front of the pen was opened and a wooden baffle with two 10cm holes in the bottom corners fitted so the voles could come and go as they pleased. Feeding continued on day five and then, on day six, the pens were removed from the site.
Most of the pens had vole burrows directly beneath them and when lifted, carefully, there was often a vole or two lurking beneath. While lifting the pens, however, there was a surprising lack of evidence of feeding on vegetation immediately around the area and daily monitoring of the sites is now being conducted to observe feeding evidence increasing.
The voles will be bolstered by a further introduction next year and we will look northward of the nature reserve for suitable areas, in the ownership of sympathetic individuals, to extend the range of the scheme. Between now and then, and stretching on for as long as the need remains, vole numbers will be monitored closely and stringent mink control will be undertaken. Historically mink rafts were checked by volunteers, walking a stretch of riverbank and assessing clay sheets for mink prints, notifying a contractor when mink presence was suspected. Reportedly this became a rather demoralising task for volunteers over time. The revised raft system and Mink Police technology is our most significant departure from the approach used in 2008. Vole numbers will be monitored by volunteers, with transects being plotted to count latrines, feeding stations, burrows and sightings in the months ahead.
I recall just how contentious the introduction of a captive-bred mammal was back in 2008 and, while acceptance has now grown that it is a necessary step for the recovery of many once common animals in our landscape, there remains the same duty of care to ensure these animals are being introduced to an environment in which they can thrive.
With this responsibility falling within my core work programme, aided by new technology, I feel there is reason to be optimistic about this project establishing a sustainable population of water voles on the river. However, perhaps the biggest influence on the success so far has been the constant presence of otters in and around the site: ensuring that they remain here in growing numbers is also something I will be working hard to achieve.
James Chubb
Countryside Team Leader (Sites)
East Devon District Council
Do you have a story to tell about a mammal project which is happening near you? Please contact us at pr@themammalsociety.org to let us know, tag us in your social media post (see below) or contact your local Mammal Group.
To record mammal signs and sightings as you walk/cycle please download the Mammal Mapper app or to find out other ways to record sightings visit our Mammal Records page.
For less than the cost of a cup of coffee a month you can support evidence based conservation by becoming a member of the Mammal Society. Find out more/join us here.