Conserving water voles - best practice
Because of the population dynamics and dispersal behaviour of water voles, the protection of individual colonies in isolation is unlikely to achieve any lasting conservation benefits. Instead, a strategy that considers a number of nearby populations together is, realistically, the only way likely to ensure long-term persistence. The basic principles for conserving water voles can be summarised thus:-
- Maintain habitat connectivity between individual colonies and minimise the degree of isolation between adjacent vole colonies, such that occupied sites are within a 1.5 km radius of one another
- Maintain abundant herbaceous riparian vegetation (including the management of trees to avoid excessive shading)
- Minimise the opportunity for mink colonisation (including habitat management to reduce the opportunities for denning, targeted mink control and rabbit control, as appropriate)
In the uplands
In upland river systems, conservation effort should be directed at extensive catchment or multi-catchment scale areas.
- Good quality upland water vole habitat comprises sedge-rich areas, including grasses, rushes and heather adjacent to slow flowing, shallow burns with steep peaty banks. These areas are also likely to be favoured by deer and sheep and may, in some cases, be vulnerable to excessive grazing and poaching. Stock reduction may therefore be required to prevent this.
- Where they include areas of suitable water vole habitat new native woodland schemes will need to incorporate suitable riparian corridors.
- Avoid muirburn in areas of suitable water vole habitat. An unburnt buffer strip of at least 10 m on each side of any watercourse used by water voles is required to protect the voles' habitat.
- Constant vigilance is required to prevent mink colonisation of upland river catchments. This could be achieved by targeted and co-ordinated trapping effort concentrated at critical times (February to April) and at critical sites (e.g. the tributaries leading to these upland catchments).
- The presence of rabbits may encourage the spread and establishment of mink in the uplands by providing a reliable food source and potential breeding sites. This can enable permanent rather than transitory colonisation by mink. Measures may therefore be needed to prevent the spread of rabbits into such areas.
In the lowlands
Here, water voles are best protected from excessive grazing of riparian habitats by the creation of a fenced-off buffer strip either side of the water course. Ideally, these strips should be 6 m wide on both sides of the watercourse. Scrub encroachment should be prevented by occasionally cutting all this vegetation back to around 10-15 cm during the autumn/winter. In some lowland river catchments, overgrown field drainage ditches are important refuges for water voles. It is recommended that clearance and dredging of these is undertaken on a 5-10 year rotation. As dredging usually necessitates the removal of bankside vegetation, it is better to cut this in September/October, prior to any excavation work, allowing water voles to move away from the area, prior to the earthmoving operations.
- Avoid re-profiling both banks in any one section.
- Progress upstream leaving sections of untouched habitat at least 250 m in length.
- Keep the length of each dredged section to a minimum; if possible, no longer than 150 m.
- Only operate machinery from one bank (i.e the opposite bank should remain completely untouched).
- Only dredge during the winter months.
Note that the above operations are likely to require a licence from Scottish Natural Heritage, unless the dredging work can be undertaken without risk of damaging a water vole burrow and the operating machinery does not come within 10m of a burrow entrance.
Further detail on this can be found in the Water Vole Conservation Handbook (3rd edition).
Last updated on Friday 2nd September 2016 at 15:09 PM. Click here to comment on this page