INTRODUCTION
There is a direct correlation between the decline in amphibian
populations with pond loss and habitat deterioration in Herefordshire
as elsewhere in the UK. Smooth, palmate and great crested
newts have all declined in the countryside. However, the
growth in the popularity of garden ponds and demand for fishing
pools has helped to compensate for these deficiencies, allowing
for a small increase in the frog population, whilst smooth
newt numbers have remained at a stable level.
This guide outlines the methods by which both keen amateur
and professional managers of the countryside can help to
increase local amphibian populations by creating new ponds
and modifying and maintaining existing ponds and their associated
habitats. The methods are mainly directed towards encouraging
amphibians. However they are also complementary towards other
aquatic flora and fauna.
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POND DESIGN
Pond shape and dimensions
A butyl liner installed in
a new pond showing shelves and central depth
©W.Watson
An amphibian pond should have the following basic characteristics.
They should have shallow sloping sides for the growth of
marginal vegetation. Preferably at least two different depths
of shelving should be created to cater for the varying requirements
of emergent aquatic vegetation and to allow for variations
in rainfall patterns (see photo above). There should be a
deeper area in the centre of the pond which will retain water
during periods of drought. The ideal depth for an amphibian
pond is about 2 metres. However, a pond depth of a metre
may be sufficient to retain water throughout an average year.
If you want to create a smaller shallower pond, bear in mind
that evaporation will occur more rapidly. If a pond dries
up in the breeding season any remaining tadpoles that have
failed to develop into metamorphs will die. You can compensate
for this by filling up the pond with tap water or by providing
some form of regular inflow. There is no great benefit in
constructing very deep ponds because amphibians, with the
exception of our common toad Bufo bufo, tend to confine themselves
to the vegetated margins. Studies have revealed that the
optimum breeding site size for palmate and smooth newts is
100 m2, great crested newt frequently thrive in ponds between
250 m2 and 400 m2 but may found in larger ponds.
You must decide on what size the pond should be, whether
the pond should be lined and if so what material should be
used. If you can rely upon the natural geology to hold water
then that will be the preferable option, both from the cost
point of view and for the amphibians. Natural clay is common
in many regions of the UK, but make sure you get down to
natural levels. Digging a pond by hand is very laborious
work and serious consideration should be given to hiring
a small mechanical excavator. Always bear in mind your water
source and how you are going to conserve water.
Pond restoration
A biological survey should be conducted before you undertake
any restoration work to find out what amphibians are present
and in what numbers. The survey work should be carried out
by a suitably qualified person. HART members can undertake
amphibians surveys on your behalf, but they will usually
request travel expenses or Additional expenses may be charged
when giving advice on pond management or creation.
Desilting with an excavator
©W.Watson
It may be necessary to modify your management practices
according to what is found in your pond. For example, ponds
containing the specially protected great crested newt which
are silted should have management priority over ponds where
no amphibians were recorded. If protected species are present
do seek further advice (see
protected species advice section below). Restoration
work should be carried out in amphibian dormant season although
work can commence in summer if the pond is totally dry. It
is also important to establish whether any other key aquatic
species are present and adapt the management to benefit rare
or protected species. It is normally advisable to de-silt
half the pond one year and complete the task the following
year as this assists natural re-colonization by existing
pond flora and fauna. In poorly vegetated ephemeral ponds
this practice may not be necessary.
Planning Permission
Ponds excavated for agricultural purposes do not require
planning permission. However ponds excavated for other purposes,
such as wildlife conservation, may require permission, even
if they are to be located on agricultural land. Local planning
offices will be able to advice, and should always be contacted
prior to pond construction. It may also be necessary to consult
planning offices regarding disposal of spoil.
Before undertaking construction or restoration you are advised
to consult some of the pond literature. There are some free
leaflets and information is also given on how to obtain these
publications (see Book
List).
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CREATING
THE RIGHT CONDITIONS
Plants
A healthy zonation of plants in and around a pond is important
for amphibians as plants provide the right habitat for invertebrate
prey, cater for oviposition and provide the necessary cover
for protection and the means to ambush prey. The choice of
plants is partly dependent upon the size of the pond. In
the submerged zone you should establish native plants such
as hornwort Ceratophyllum demersum, water
crowfoot (Ranunculus
aquatilis) and water-starwort
Callitriche stagnalis. In semi-natural ponds these plants
always seem to provide niches for a myriad of invertebrates
and should be selected in preference to curly
water-weed (Lagarosiphon major) or
Canadian pondweed (Elodea canadensis) because these latter
species quickly produce dense growths of vegetation that
will require frequent
thinning out. On the shallow shelves you should establish
plants for oviposition by newts. Newts will select specific
species of plants in preference to others; the most popular
plants used by great crested newts are float-grass
(Glyceria fluitans) and water
forget-me-not Myosotis scorpioides. Watercress Nasturium
officinale, Water
Mint (Mentha Aquatica) and great hairy willow-herb Epilobium
hirsutum are also commonly selected. In small ponds (less
than 10m x 15m) avoid using aggressive colonizers such as
reedmace Typha latifolia, reed sweet-grass Glyceria maxima
and common reed Phragmites australis, as they are easy to
establish but hard to control. If you want create a floral
screen to your pond it is recommended that you plant Yellow
Flag (Iris pseudacorus)which is less aggressive and also
provides welcome colour.
Predation
Fish predation has a great impact upon amphibian populations.
Under most circumstances, introduction of fish into a newt
pond will eventually lead to the elimination of the newts.
See
picture of 3-spined stickleback, a typical predator.
It is the newt tadpoles that fall easy victim to fish. The
presence
of fish
imposes
a critical limitation on the ability of newts to exploit
larger water bodies and restricts newts to smaller water
bodies. So, if you want to establish a thriving population
of amphibians make sure that there are no fish present! On
the other hand, toads are not particularly affected by fish
predation because their skin contains distasteful toxins
and as a consequence large populations can coexist with fish.
Fish management and control is complicated and governed by
several laws. For further advice please refer to the Countryside
Council for Wales contract services report 476.
Herons feed on amphibians usually in an opportunistic manner,
some birds may develop a preference for newt tadpoles; includes
those of great crested newts. Ducks directly affect amphibian
populations by preying on eggs and tadpoles. They also have
an indirect effect; their dabbling uproots plants on which
eggs are laid, prevents plant re-growth and disturbs water
sediments. On small ponds you would be advised not to encourage
ducks; on larger ponds numbers should monitored and, if necessary,
regulated. It is possible to discourage herons and ducks
by erecting cane and strands of string around the edge of
the pond. See the RSPB guide to discouraging
herons.
Adult great crested newts frequently prey upon tadpoles
and will readily make a meal out of their own tadpoles. Invertebrate
predation is also common although it is not normally at the
level which would cause a serious decline in a population.
Great diving beetles and dragonfly nymphs are the most significant
in this respect.
Food Availability
Most aquatic invertebrates are good colonizers of new sites,
so if you have created a well-balanced pond with a good range
of aquatic flora they'll find it. It does take time, though,
for new ponds to settle. It may take two years or more before
invertebrate levels approach a similar density to those in
established ponds. However, there are various ways in which
invertebrate populations may be encouraged to establish more
rapidly. Inoculation of pond silt, containing invertebrate
eggs and larvae will help provide the right micro-environmental
conditions for invertebrate development. Removal of silt
should occur in the dormant season (from September to January).
Ideally silt should be taken from an existing amphibian site.
Make sure that the pond that you take the silt from does
not contain fish. Even if you ensure no adult fish are present
you may inadvertently be introducing fish eggs. Dragonfly
nymphs over-winter in silty mud, if they are known
to be present in the donor pond extra care will have to be
taken as odonata populations can be damaged during this type
of operation. After hatching newt tadpoles are thought to
feed on protozoa (single celled animals) whilst frog and
toad tadpoles in their early stages of development show a
greater preference for algae. Daphnia and Cyclops are important
dietary constituents for tadpoles of all species in their
mid-stages of development. Adult frogs and toads are relatively
catholic in their diet. All three species of newt show similar
dietary requirements with certain populations developing
preferences for selected invertebrate prey. The following
invertebrates regularly fall victim to newts; water snail,
water hoglouse, and various aquatic fly larvae; blood worm
and the like. Whilst on land newts forage for worms, slugs,
snails and other invertebrates. Smooth and palmate newt will
take relative small prey items whilst great crested newts
will tackle larger items. Many of the larger invertebrate
prey items can be specifically selected for translocation.
Water snails are easy to establish in new ponds and will
not only benefit newts as a food source but also keep the
water in good conditions by removing surface algae and unwanted
plant remains.
Hibernation sites
Most species of amphibian spend the majority of their lives
on land. This is certainly the case with our native amphibians.
However the palmate newt is more aquatic, and may spend much
of the spring and summer in water. In the case of the great
crested newt its dormancy may start from June and last until
March; strictly speaking they aestivate from June to October.
All amphibians in the United Kingdom hibernate during the
winter. They normally seek frost-free conditions. Ease of
access to suitable conditions is an important factor. Newts
are known to select holes by the bases of live and dead trees,
light loamy soil, and rubble and rocks with plenty of voids
. It is also normal for newts to move around within hibernacula
in response to changes in temperature.
The lack of availability of adequate hibernacula may restrict
the expansion of amphibian populations. On sites which have
poor terrestrial habitat structure, it is therefore well
worth providing artificial hibernacula. The specifications
below have been devised to replicate these semi-natural conditions.
Hibernacula specifications
Sunken hibernacula are more likely to protect newts from
frost penetration. Ideally you should aim to contract a trench
about 40cm in depth by 1 metre wide; the length depends on
the size of your pond. It is recommended that the hibernacula
are situated parallel to the pond to intercept amphibians
when leaving the water. (In particularly boggy conditions
with a high water table it will be necessary to construct
a raised hibernacula).
The hibernacula trench should be filled with 10 sheets of
correx fluted board (plastic estate agent board) approximately
0.75m2. Old slates or large tiles of similar dimensions could
also be used. Pea gravel should be liberally distributed
one layer thick, between each of the sheets to provide a
consistent depth of 3 to 4mm. Additional infill should consist
of loose loam, soil conditioner and sand, whose proportions
should vary between the different layers. Stacks of 10 correx
sheets 0.75m2 can be placed in line. However it is important
that a gap is left between the stacks to create the access
voids. The gap should be 10cm wide between the correx sheets
and also the vertical cut of the excavation. The gaps should
be filled with a combination of clean hard-core, wood and
soil, which will provide voids to enable the newts to reach
the layers. The presence of such layers provides the newts
with protection from predators whilst enabling them to move
within the hibernacula and locate the right micro-environmental
conditions. Finally the hibernacula should be capped with
stone. Large stones can be used for maximum visual attraction.
A minimum stone diameter of about 100 mm should provide adequate
voids for access.
Hibernacula capped with stone
©W.Watson
Other Terrestrial Requirements
Frogs and toads regularly forage on land. Newts make periodic
sorties on land, foraging for worms and other invertebrates.
Great crested newts regularly wander 250 metres away from
the water in search of food. Frogs and toads wander considerably
further. Ideally a buffer zone should be created around the
pond to provide for the amphibians terrestrial requirements.
On leaving the water adult newts and emerging metamorphs
readily seek out any available flat refuges around the pond
as these provide protection and contain prey. You can provide
these sites by strategically placing items such as planks
of wood, old carpet, brick and rocks around the edge of the
pond, for greatest effectiveness they should be placed close
to water's edge where ground level conditions are permanently
moist. It may be possible to utilize discarded rubbish scattered
for this purpose. Strategically
placed wood piles are a useful addition to pond habitat.
Wood piles attract many invertebrates and amphibians will
readily exploit these situations. They also provide opportunities
for amphibians to aestivate. Ideally these should be situated
in damp locations but above draw-down zone. Amphibians are
prone to getting trampled underfoot around the pond edge.
If visitor pressure or human interference is posing problems
then it is worth establishing areas of non-intervention.
It may be necessary to erect a fence to deter access from
sensitive areas. You can also anchor flat refuges such as
planks of wood with a metal brace attached to plank and driven
into ground, but ensure that there are still gaps underneath.
The best terrestrial habitats have been shown to contain
some long grass, bushes and shrubs and plenty of damp areas,
so aim to maintain the site in an informal method.
Water quality
Great crested newts and smooth newts prefer ponds to be
slightly eutrophic (rich in nutrients) and slightly basic.
Frogs and toads also show preference for slightly eutrophic
water, although the frog is tolerant of a wide range of conditions
and, like the palmate newt, are quite at home within oligiotrophic
water bodies that are low in nutrients. However, since these
conditions support fewer invertebrates population densities
are lower. Small amounts of tap water can be used to top
up ponds with no adverse effect upon amphibians. Undiluted
chlorinated tap water irritates amphibians, therefore it
is wise to leave chlorinated water to stand for 24 hours
which allows the majority of chlorine to evaporate. Ponds
that are regularly disturbed by ducks or other wildfowl or
people and dogs will be cloudy with sediment. Such activity
will restrict feeding and courtship during daylight hours.
As prey items are also disadvantaged by the turbidity it
is not normally a serious problem provided water remains
opaque. However, if water is constantly very cloudy this
will restrict amphibian ability to catch prey, limit courtship
behaviour and restrict or eliminate submerged aquatics plants.
Ideally ponds should be left settle after disturbance.
Shading & Leaf litter
Shading by trees casts shadows which restricts the growth
of aquatic plants. Most aquatic plants require a lot of light
and even moderate shading will frequently result in partial
elimination of aquatic flora. Leaves contribute to the silting-up
of ponds and as they decompose they release substances that
are maybe toxic to amphibians. Oak and willow leaves are
more detrimental in this respect. You can reduce the effects
leaf deposition by systematically removing leaves and silt
each winter. On small garden ponds the placement of netting;
obtainable from garden centres can be quite effective at
catching leaves. Shading has a greater effect on smaller
ponds even ponds up to 400 square metres can almost completely
be cast in shade. Plants are particularly vulnerable from
shading from the south.
On the plus side in large ponds a certain amount of shading
can be useful as a means of controlling excessive vegetation
and thereby maintaining some areas of open-water for amphibians.
On large water bodies surrounding trees act as windbreaks
limiting the effects of temperature loss. However, in smaller
ponds such shading causes a reduction in temperature due
to the lack of sunlight penetration. As a general rule the
level of shading around a pond should not be allowed to increase
to 50%, anything less than that is fine.
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PROTECTED
SPECIES ADVICE - AMPHIBIANS & THE LAW
All UK native amphibians are listed under schedule V of
the 1981 Wildlife & Countryside Act. The great crested
newt and the natterjack toad Bufo calamita are given greater
protection under Section 9 (1) such that it is an offence
intentionally kill, injure, catch, possess or handle these
species. The smooth newt, palmate newt, frog and common toad
are only protected with respect to their sale. It is necessary
to obtain a licence from English Nature if you intend to
handle or disturb great crested newts. If you want to carry
out management work to an existing great crested newt pond
you should refer to the advice given by Natural England on
conservation licences for pond management (see link). For
any other guidance about the law please check out the Natural England website or contact the Herefordshire, Warwickshire & Worcestershire
Team on 01905 763355.
Will Watson November 2003
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BOOK LIST
and REFERENCES
Anon (1981). The Wildlife & Countryside Act 1981. The
Stationery Office.
Anon (1992) Dig a Pond for Dragonflies. British Dragonfly
Society.
Arnold, E.N. & Ovenden, D.W. (2002) Reptiles & Amphibians
of Britain & Europe. Collins Field Guide. ISBN 0-00-2199645
Arnold, H. R. Atlas of amphibians and reptiles in Britain
(1995). ITE research publication no. 10. HMSO Publications
ISBN 0 11 70182 4.
Bardsley, L (2003), The Wildlife Pond Handbook. New Holland
ISBN 1 84330 11 3
Beebee, T.J.C. (1985). Frogs and Toads. Whittett Books,
Oxford. ISBN 0 905483 38 3
Boothby, J. (ed.) (1997). British pond Landscapes. Action
for protection and enhancement. Proceedings of the UK conference
of the Pond Life Project, Chester, Liverpool John Moores
University.
Bray, R. & Gent, T. (1997) Opportunities for amphibians
and reptiles in the designed landscape. English Nature Science
Series No. 30. English Nature. ISBN 1 85716 265 X.
Brian, A. & Harding, B. (1996). A Survey of the Herefordshire
Ponds and their value for Wildlife 1987-1991. Transactions
of the Woolhope Naturalists Club. Vol. XLVIII, Part 3.
Brooks, A. Agate, E. (1981) Waterways and Wetlands. British
Trust for Conservation Volunteers. Oxford.
Drake, M. et al. (1998) Managing ponds for wildlife. English
Nature. ISBN 1 85716 25 3. Available free from English Nature
at Peterborough
Fitter, R. Manuel, R. (1986) Collins Guide to Freshwater
Life. Collins. ISBN 0 00 219143 1
Gent, A.H., & Gibson, S.D., editors (1998). Herpetofauna
workers’ manual. Joint Nature Conservation Committee.
Peterborough.
Great Crested Newt Species Action Plan Steering Group (1998).
Great Crested Newt Biodiversity Action Plan Work Programme
(1998-2002) Version 1.1 Froglife, Halesworth.
Hilton-Brown, D. & Oldham, R.S. (1991) The Status of
the widespread Amphibians and Reptiles in Britain, 1990,
and changes during the 1990's. Nature Conservancy Council.
Available from English Nature, Northminster House, Peterborough.
Hine, A. (Ed.) (1994). Woodland Pond Management. The Corporation
of London. ISBN 0 95016438 0
Kabisch, K. & Hemmerling, J. (1984) Ponds and Pools.
Croom Helm.
Langton, T.E.S., Beckett, C.L., and Foster, J.P. (2001),
Great Crested Newt Conservation Handbook. Froglife, Halesworth.
Available free from Froglife – but usually given out
to great crested newt pond owners or those people recording
the species.
Olsen, L.H., Sunesen, J. & Pederson, B.V. (2001) Small
Freshwater Creatures. Oxford University Press. ISBN 0 19
850798 4
Probert, C. (1989) Pearls in the Landscape The Conservation
and Management of Ponds. Farming Press. Ipswich. ISBN 0 85236
198 X
Sansom, A. (1997). Ponds and Conservation, a guide to pond
restoration, creation and management. Environment Agency.
Slater, F. (1992) The Common Toad. Shire Natural History.
ISBN 0 7478 0161 4
Thompson, Bernard & Coldry. (1985) The Pond. Collins
Watson, W., Datlen, R., & Hollis D. (2000) Aqua Vitae
21. A Best Practice guide for Pond Restoration. Worcestershire
County Council, Countryside Service, Worcester.
Watson, W.R.C. (2002). Review of Fish Control Methods for
the Great Crested Newt species action plan. CCW contract
Science Report 476. On the CCW website as a pdf file
Whitehurst, J. Great Crested Newt mitigation guidelines.
(2001). English Nature. ISBN 1 85716 568 3.
Williams et al. (2000). The Pond Book. A guide to the management
and creation of ponds. The Ponds Conservation Trust, Oxford.
Wisniewski, P.J. (1989) Newts of the British Isles. Shire
Natural History. ISBN 0 7478 0029 4
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