final report - People's Trust for Endangered Species

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Factors that are influencing the decline of the species. The main threats to the species are well documented and include habitat degradation and loss, predation, population isolation, persecution, changes in water levels, and pollution. Changes in land-use and riparian management have resulted in increased vulnerability to predation by mink, which is thought to have accelerated the population decline (Strachan & Moorhouse 2006). Habitat degradation and loss Many Watercourses in the UK have been engineered for the carriage and the containment of water using hard bank protection and engineering, and during this process have lost their natural features and habitats. These modifications channel the water at an increased rate and can contribute to erosion, flooding, and effecting channel downstream. Intensification of farming has also attributed to bankside changes with margins being overgrazed leading to a reduction in bankside and marginal vegetation which is a food source and predation cover for the water vole. Predation Unfortunately for the water vole they are prey to many predators which include; brown rats, owls, heron, otters, stoat, weasel, fox, kestrel, domestic cats and the American mink. To escape from predators, water voles take cover in dense vegetation or dive into the water and escape to their burrows. This strategy is ineffective against the mink because they swim well, hunt efficiently and the females can enter water vole burrows. (Strachan and Moorhouse 2006). The presence of mink and absence of high quality habitat are inimical to water voles. In the vast majority of cases, populations can only exist if high quality habitat is present and mink are absent (Strachan and Moorhouse 2006). Isolation Isolated populations are vulnerable to habitat changes and predation. Within urban situations vole colonies may be small, separated by engineered watercourses. Narrow strips of fragmented habitat can isolate extant water vole populations, making them more susceptible to stochastic variables such as drought, floods, disease and American mink predation (Barreto et al 1998a). Persecution The persecution of water voles is often indirect or unintentional. Water voles can be confused with brown rats which have led to the accidental destruction of water vole colonies, particularly in urban areas when control methods using rodenticides are used carelessly. Changes in water levels Water vole habitat can be affected by fluctuations in water levels especially when floods or droughts occur. Excessive fluctuations can cause burrows to flood affecting access to food and cover (Mullard 2007). Reduction in water levels can also be unfavourable to the water vole; leaving burrows exposed making voles more vulnerable to predators. (Strachan 1998). Changes in land use, land drainage and flood control may exacerbate the process although canals are rarely affected by these fluctuations. Pollution Another factor thought to have caused the decline of the Water Vole population is pollution. Contaminants include organochlorine insecticides, heavy metals and organic pollutants maybe harmful although the specific effects on water voles have not been researched in detail.
The survey Survey methodology Study area Initially the study area encompassed 18 Kilometres of the Llangollen Canal although after consultation with a sympathetic landowner, the area was expanded and included a network of ditches and pools adjacent to the canal. Desktop study The Desktop survey involved collecting records of water vole, mink and otter obtained from the county / local recording centres and from the Canal and Rivers Trust GIS data base. This information would identify and locate potential or possible suitable water vole habitats. This was then checked by a walkthrough survey. Walkthrough Survey Due to the amount of concrete and metal piling reinforcing the bank of the canal, a walkthrough survey was carried out, this would identify suitable soft bank which is preferred water vole habitat. This information was recorded on planning maps (size 1:1783) which were generated during the desktop survey and would support more the detailed field surveys. Detailed field surveys Three surveys were undertaken at each site between June 2011 and September 2012 using standard Water Vole Survey Methodology as recommended within Water Vole Conservation Handbook (Strachan and Moorhouse, 2006). The presence of any water vole signs which included sightings, latrines, burrows, footprints, runs, feeding remains, lawns was recorded along with signs of otter or American mink. To avoid confusion other small mammal’s signs were recorded too. Two approaches where used to survey the banks; from the water, wading along the canal and from the bankside. This information was recorded on a standard water vole recording form which is recommended by the Water Vole Conservation handbook (Strachan and Moorhouse 2006). The habitat characteristics information was recorded once the survey had been carried out and included the following; Bordering Land Use - grazed, woodland, bank fenced, urban, and industrial. Bank Profile - flat 45°, Vertical / undercut. Vegetation - recording the presence and absence of trees, bushes, herbs, submerged plants, reeds and sedges, tall grass and short grass. Disturbance – boat accessibility, human accessibility, signs of erosion, grazing or mowed to within the water margins.
Page 1 and 2: THE LLANGOLLEN CANAL WATER VOLE STU
Page 3: Background information Species desc
Page 7 and 8: unsuitable bankside vegetation (mai
Page 9 and 10: Finally I would like to thank The P
Page 11 and 12: Plate 4 Another image of the pool a
Page 13 and 14: Plate 8. This image shows a rabbit
Page 15 and 16: Plate 12 This image is showing volu
Page 17 and 18: Risk assessment Activity assessed B
Page 19: Grid Reference Office contact detai

final report - People's Trust for Endangered Species

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