Fen Management Handbook - Scottish Natural Heritage

Appendix VII – Fen management for vertebrates
Mammals
Water Vole summarised from Strachan & Moorhouse (2006).
Dredge ditches without interfering with the banks; use appropriately sized machinery and do not tip
dredgings onto adjacent vegetation.
Work from one bank only and progress upstream, working in short stretches.
For dredging and cutting, leave gaps of 10m-20m in length as untouched refuge areas for Water
Voles
At least one third of a ditch should remain undisturbed.
Vegetation removal or cutting should be carried out on a 3-5 year rotation
Where bank reinforcement is required use softer options such coir, willow hurdles etc.
Bank profile should be stepped or with a steeper incline on the upper half of the bank to facilitate
burrowing.
Implement management of water levels where infrastructure allows, to prevent flooding or drying out
of ditches.
Sensitive periods
Mowing and weed cutting should not take place during April, May and June inclusive
Weed raking shall not commence before the 1st of August
Tree and bush management works shall only take place between October and March
Cutting of reeds is better left until mid-August (the later the better).
Water Shrew
Recommended management
There is a positive association between water shrew presence and presence of reed/grass/sedge
tussocks and dense bankside ground cover. Shrews tend to be less associated with streams
characterised by dense bankside tree and shrub cover and short grass. Presence of aquatic
vegetation is also preferred.
There is also a positive association between water shrew presence and the abundance of aquatic
crustaceans, aquatic snails and caddis-fly larvae, and they prefer good water quality (high dissolved
oxygen, low Biological Oxygen Demand and low nitrate levels).
Management should therefore aim to keep ditches and watercourses unchoked with vegetation and
prevent scrub encroachment along banks. To maintain aquatic plants and invertebrate communities,
regular dredgings are required. Sections of ditch should be left undredged as a recolonisation
source for aquatic plants and invertebrates. Management of sites should therefore be implemented
as for Water Voles above. Maintenance of good water quality should be considered (e.g. through
vegetative treatment of water sources to remove nutrients). Regular dredging of ditches also assists
in preventing the build-up of nutrients and organic matter in the water.
Sensitive periods
Water shrews breed between April and September, so management actions should be implemented
outside these times.
Harvest Mouse
Recommended management
Ensure areas of long grass are maintained by phased rotational cutting. Do not cut entire area of
habitat in one operation. Retain mosaic of patches of different ages up to 3-5 years between cutting.
Remove arisings to prevent nutrient build-up.
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