Fen Management Handbook - Scottish Natural Heritage

Sensitive periods
Species breed within this habitat from February to August, so disturbance should be minimised
within this period which includes avoidance of damaging mechanical operations, e.g. coppicing and
scrub clearance.
Reptiles
Grass snake
As grass snakes occupy a large home range, maintaining a healthy population may depend on
suitable management over a fairly large area of land, which for a population of snakes may cover
several square kilometres. General maintenance of fen vegetation and open waters (rotational
cutting and / or grazing) to prevent excessive scrub encroachment) will maintain suitable grass
snake habitat. Surveys should where possible aim to identify likely hibernation sites so that these
can be protected. Possible locations include rabbit warrens in banks or other areas above the flood
level. Searching for snakes early in the season after emergence from hibernation may reveal likely
hibernation sites. Artificial hibernacula can be provided in the form of part-buried rubble mounds in
areas free from risk of flooding.
Egg laying sites, such as compost heaps and manure heaps should be provided. In the case of
compost heaps, arisings from management activities can be used. Manure from grazing livestock can
also be used if present.
Heaps should be positioned in a sunny position and close to cover, such as hedgerows or long
grass. Heaps can be constructed by placing a criss-cross pattern of branches on the ground (which
provides ventilation and a means of access to the heap), topped with bark chippings, cut grass,
manure etc. Heaps should be replenished annually as the material rots down.
Amphibians are a major prey item for grass snakes and therefore need to be maintained on sites
where snakes are present.
Sensitive periods
Mowing of habitat likely to support grass snakes, especially sunny banks adjacent to water, should
be avoided between March - October. If mowing during this period is unavoidable, unmown
sanctuary areas should be left, and the vegetation should be cut no shorter than 10cm. Undertake
mowing on warm days when snakes will be more active, and do not mow early in the morning when
the animals will be more sluggish. Heaps should not be disturbed between early May and late
September when grass snakes will be using the heap to lay eggs.
Amphibians
Common frog
Frogs occur in a variety of habitats provided that there are suitable breeding ponds nearby, so
general vegetation fen management techniques will ensure that suitable terrestrial habitat persists.
They are at greater risk of predation in close-mown or close-grazed vegetation, so refuges should
be left when cutting large areas of grassland around breeding ponds. Size, shape and depth of
breeding ponds is not critical to breeding success; warm breeding areas are more important, so
ponds should be located in unshaded locations. Frogs may hibernate in ponds, so prefer permanent
waterbodies. Frog tadpoles are eaten by fish, so permanent waterbodies should be located where
they are not at risk of being colonised by fish during flood events. Fish should be removed from
breeding ponds if colonisation occurs (removal of fish would need to take account of relevant
legislation, and a licence from the appropriate authority (e.g. EA, SEPA) would be required to transfer
fish into another waterbody).
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