Roman snail: An introduction to its ecology and legal protection
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122
Heather Mansfield Roman snail: An introduction to
Senior Ecologist
Water & Environment
its ecology and legal protection
Atkins
Abstract
In 2008, the Roman snail Helix pomatia was added to Schedule 5 of the
Wildlife and Countryside Act 1981 (as amended), and it became an offence
to intentionally kill, injure or take individuals of this species (as did possession
and sale). Also known as the ‘edible snail’, the primary reason for its legal
protection in England and Wales (and elsewhere in Europe) was an increasing
trend in collection of large numbers by amateur cooks and for commercial
use in restaurants. However, the legal protection this species is now afforded
has implications for development projects. Distributed throughout south-
east England (but especially the North Downs) and through the Chilterns and
Cotswolds, and occupying a broad range of habitats (where suitable soils
are present), this species could occur on a wide variety of sites. This article
provides an introduction to Roman snail ecology and licensing requirements,
and illustrates these using a case study in Surrey – the M25 Controlled
Motorways Scheme.
Background
Atkins ecologists first came across As a result of these findings, and
Roman snails in early 2009, a need to resolve the issue of the
when working on behalf of the presence of this legally protected
Highways Agency, undertaking an species within proposed construction
Environmental Assessment as part areas for the above scheme, further
of proposals for the installation of surveys have been carried out and
new gantries along a stretch of the appropriate licences sought.
M25 motorway in Surrey (the M25
Controlled Motorways scheme). An
empty Roman snail shell was found
Habitat requirements
during an extended Phase 1 habitat and distribution
survey, at the base of a steep chalk
section of the motorway verge The Roman snail is known to inhabit
between junctions 7 and 8 of the open woodland, rough and tussocky
M25. On a subsequent nocturnal grassland, hedge banks, chalk
Figure 1. Roman snail habitat on M25 quarries and areas of scattered scrub.
survey a live individual was found,
verge
in an area of long, semi-improved Figures 1 and 2 show the areas of
grassland with dense patches of the M25 motorway verge where
bramble, close to junction 8. Atkins Roman snails have been found.
ecologists have also found Roman This species requires loose, friable
snails on another section of the M25 soil for burying into for hibernation
motorway (close to junction 6), when and also for depositing eggs. Lime-
working on a separate project for rich, free draining soil is a habitat
Environment
the Highways Agency. Shells were requirement in the UK and studies
found within plantation woodland have found a preference for south-
on the verge and live individuals have facing slopes1. Roman snails will
been spotted numerous times in the not occur in sandy soil. They will
tussocky grassland situated directly also avoid grazed grassland and very
behind the woodland. open, exposed habitats.
Figure 2. Roman snail habitat on M25
verge
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Figure 3 shows a UK distribution
map for Roman snail2. The species is
not native to the UK and is thought
to have been introduced by the
Romans. Much of its distribution in
the UK is considered likely to be due
to local introductions by humans.
There are documented introductions
elsewhere in England and also in
Scotland and Ireland, and these are
still shown on some distribution
maps, but these introduced animals
rarely survived for very long2. This
was presumably because soil and/or
weather conditions were not suitable.
The main hotspots for populations
of Roman snails in England are
along the North Downs (from Surrey
to Kent), the Chilterns (especially
in Hertfordshire) and throughout
the Cotswolds and Mendip Hills
fringes. There are also documented
populations in Cambridgeshire.
Life history
Many aspects of the Roman
snail’s life history and behaviour
contribute to its vulnerability to Figure 3. Distribution map for the Roman snail, from Kerney (1999)
over-exploitation. In particular,
their tendency to aggregate in high
numbers and disperse only short Identification
distances leaves them vulnerable
to collection. Individual snails may Adult Roman snail shells are typically
spend their entire lives within an area larger than those of other snail
of approximately 30m in diameter species in England, measuring up
and take two to five years to reach to 5 cm across and displaying a
maturity and reproductive success pattern of brown bands (see Figure
may be low, with many British 4). Crucially, the bands on their shell
populations found to have a low lack the zig-zag pattern found on
proportion of young snails3. the garden snail Cornu aspersum Figure 4. Adult Roman snail
(= Helix aspersa- see Figure 5). The (Photograph: Dr Martin Willing)
In England, Roman snails are typically body of the Roman snail is pale grey
active from May to August. The and measures up to 10 cm long on
earliest and latest dates for activity in adults.
an area of the Cotswolds were April
30th and September 1st 3, with peaks Empty Roman snail shells often
in activity most likely in May and appear very pale and lack the brown
June4. colouration shown in Figure 4, as do
juvenile Roman snail shells (shown
Roman snails hibernate in the ground in Figure 6). Empty shells become
by digging down into loose soils, ‘bleached’ and in this state are
pulling vegetation and soil over the usually more than one year old4.
top to close the top of the entrance
to their chamber. They remain in
Figure 5. Roman snail shell (left), garden
hibernation until spring. snail shell (right)
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122 Roman snail: An introduction to its ecology and legal
protection
Figure 6. Adult Roman snail shell (left),
juvenile Roman snail (right)
Surveying for Roman
snails
Whilst no standard published
survey technique for Roman snails
currently exists, it is considered that
the combination of careful hand
searches and one or two nocturnal Figure 7. Hand searching for Roman snails
torch surveys in suitable weather
conditions, as described below, will In larger areas of habitat, attention hours or be humid and it should also
allow an assessment of presence or would best be focused on log piles be warm.
absence of Roman snail at a site. and areas that could provide refuge
A juvenile Roman snail was found
(see Figure 7). This is best carried
during the torch survey for the M25
Daytime hand searches out during the snail’s active period
Controlled Motorways project.
(May to August), after recent rainfall,
Two survey techniques were used
especially in warm, humid conditions.
by Atkins for the M25 Controlled Legislation and
Individuals will bury into the topsoil
Motorways scheme, once the
presence of the species had
during prolonged hot/dry spells. At licensing
sites with well-established colonies,
been confirmed, following the
evidence of Roman snail presence Roman Snail was added to Schedule
identification of an old shell during
can be found at anytime of the year, 5 of the Wildlife and Countryside Act
the initial extended Phase 1 habitat
in the form of empty shells. in April 2008. It is not a European
surveys in 2009. Hand searches of
areas of habitat to be affected were The tendency for Roman snails to Protected Species, although it does
carried out. This involved searching aggregate in high numbers and the receive legal protection in other
through areas of long grass and longevity of their shells means that European countries. In the UK, it
scrub by hand, looking for Roman hand searching over relatively small is protected in relation to Section
snails and old shells. Particular areas is an effective way to search for 9(1), (2) and (5) of the Wildlife and
attention was paid to searching evidence of this species. Countryside Act only. This means
underneath logs, brash and artificial that it is an offence to intentionally
refuges present on the verge of the Torch surveys kill, injure or take this species. It is
motorway. Some gantry locations In areas deemed potentially suitable also an offence to possess a live or
were ruled as not suitable for the for Roman snails, a nocturnal survey dead Roman snail (possession is only
species due to the presence of sandy was also carried out in June, in order an offence if it has been illegally
taken from the wild) and it is also
Environment
soils. This hand searching technique to look for active Roman snails. Ideal
was effective because each of the timing for torch surveys is late April protected against sale. It is not an
footprints for gantry construction to early June. This involved searching offence to disturb Roman snail or to
were relatively small; the working areas with a powerful torch at least damage or destroy breeding places
area for each gantry footing (i.e. one hour after sunset. This survey or resting places of this species.
total vegetation clearance) was a technique relies on appropriate However, although disturbance is
maximum of ten metres by fifteen weather conditions; it must be not an offence, a licence is needed
metres (150m²). raining, have rained in the last 24 to handle Roman snails, however
briefly, because it is protected against
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‘taking’. This has implications for • This included details about surrounding suitable habitat
consultants carrying out surveys for the scheme and how it would (not more than 20 - 30m from
this species. It is necessary to obtain deliver safety improvements to where they were found). This
a licence from Natural England the relevant section of the M25 would take place outside of the
for the purposes of science and motorway. Background to the hibernation period.
education to allow to you to pick up Roman snail surveys and the
• Fencing would be erected around
and examine Roman snails. habitats to be affected were
each of the works areas at each
provided. Across the 18 new
Furthermore, where Roman snails new gantry location. This fencing
gantry locations, vegetation
occur within areas that are to be would be designed to deter
clearance equalled 0.27ha with a
affected by development proposals, Roman snails from re-entering
permanent habitat loss of 0.11ha.
such that there is a need to move areas prior to works commencing.
them to avoid killing or injuring • Details of the population, i.e. Fencing would be 13 mm
of individuals, any intentional locations and numbers involved diameter chicken wire netting
movement of Roman snails must be and context in the wider area. with metal stakes used at the
licensed or should be covered by a corners for support. This sized
• The locations for each of the
relevant defence in the legislation, mesh is small enough to prevent
new gantries were provided,
because moving Roman snails, even Roman snails getting through,
along with a brief description of
short distances, constitutes ‘taking’. due to the size of their shells,
habitat within each area. The
whilst containing holes large
Licences can only be issued for results of the Roman snail surveys
enough to discourage movement
specific purposes under the Wildlife were set out. The location of
of snails up the fence. The fence
and Countryside Act. There is no this scheme, close to the North
would be buried in the ground
licensing purpose for development Downs (a hotspot for Roman
to a depth of approximately 30
works. However, Natural England snail in England) and within an
cm to prevent snails burrowing
will consider issuing a licence for area of well-connected habitat
beneath. The top of the wire
conservation purposes in certain (the motorway verge) meant
netting would be folded outward
circumstances. Any conservation that populations were likely to
to create a ‘lip’ on the outside to
licence application for Roman snails be more robust than smaller
further deter snails from entering.
will need to demonstrate that the populations elsewhere.
The fences would be 1m high.
work proposed is essential and the
• Setting out the conservation aims
impacts to the species cannot be • One monitoring survey for
and how these will be achieved.
avoided in any way. It would also Roman snails would take place
need to demonstrate that the work • The conservation aim of the in the year following completion
will have some conservation benefit proposal in the licence application of the works. This would take
for the species. There is no standard was to ensure the future longevity place within habitats around all
methodology currently available for of the population of Roman snails of the new gantries and also
dealing with Roman snails and each in the area and help to maintain immediately adjacent to the new
licence application will be considered the conservation status of this gantries. The results of the survey
by Natural England on a case-by-case species in the local area. would be assessed to ensure that
basis. The licence application for the the existing distribution of Roman
• Five new log piles would be
M25 Controlled Motorways scheme snail within the local area has
created in areas outside of the
is presented below as a case study been maintained and would be
gantry locations, in areas of
example, to highlight the main issues used to inform further mitigation,
habitat suitable for Roman snails
for consideration. if appropriate.
to provide an enhancement to
Case study: licence application these species. Locations would • Results of the monitoring
for the M25 Controlled be targeted at areas where woody survey would be passed to the
Motorways scheme cover is sparse. Log piles would Conchological Society national
be made from trees cut down non-marine recording scheme
A licence application for this scheme as part of the gantry clearance and the local biodiversity records
was made to Natural England and would be created under centre.
in August 2010 and included supervision by the ecologist.
information on four key areas, Delivering habitat enhancements
summarised below. • Areas of vegetation clearance for Roman snails will depend on the
would be hand searched for conditions at the site, but as well
• Background to the project and Roman snails and any individuals as creating log piles, could also be
details of why the work needed found would be moved to the achieved by creating or introducing
to go ahead.
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122 Roman snail: An introduction to its ecology and legal
protection
a base-rich, friable topsoil. In more
open areas, creating more cover Acknowledgements
through planting of scattered
scrub, or relaxation of management Thanks to colleagues John Box FIEEM and Jules Wynn MIEEM for providing
regimes could deliver enhancements. constructive reviews of the script. Constructive comments from Martin
Woodland edge could be improved Willing, Conservation Officer of the Conchological Society on a draft of this
through the creation of ecotone paper are gratefully acknowledged, as is assistance with field study techniques
habitat where this does not already and habitat recognition on the M25 project. A version of this paper was
exist. originally published in In Practice (2011, 72, 26-29) and their permission to
reproduce it here is gratefully acknowledged.
The above application was granted
by Natural England. However,
subsequently a decision was taken References
by the Highways Agency not to build
1. Pollard E (1975) Aspects of the Ecology of Helix pomatia L. Journal of
new gantries in this part of the M25
Animal Ecology, 44: 305-329.
Controlled Motorways scheme and,
therefore, this licence will not now 2. Kerney M P (1999) The Atlas of the Land & Freshwater Molluscs of
be implemented. Britain and Ireland. Harley Books, Colchester
3. Alexander K N A (1994) The Roman Snail Helix pomatia L in
Summary Gloucestershire and its conservation. The Gloucestershire Naturalist
7: 9.
The Roman snail is a relatively easy
species to identify once familiar with 4. Dr Martin Willing, Conchological Society, (pers. comm.)
its characteristics. Identifying the
potential presence of the species can
be achieved through understanding
of its habitat requirements and will
be aided by the fact that, broadly, its
distribution is quite well understood
and likely to be relatively unchanging
in England due to its inability to
colonise new areas quickly. However,
increased surveying and reporting
for the species, now it is legally
protected, could lead to amendments
to the distribution map and it would,
no doubt, be beneficial to send
records to local biological record
centres and to the Conchological
Society of Great Britain and Ireland.
Dealing with Roman snails on
development sites is relatively
new and mitigation and habitat
enhancement measures are currently
largely untested. Collation of
information from future projects will
enable ecologists and stakeholders
to refine techniques and test
Environment
new approaches. As with habitat
enhancements for other species,
measures to improve habitats for
Roman snails are likely to lead to
benefits for other species in the local
area.
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