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Nature in Wales

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N.s. Vol. 4, no. 1/2 1985

Reduction in the distribution of the land snail Theba pisana in the Tenby area, Dyfed

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greatest numbers close to the fort, although
scattered individuals were seen elsewhere. The
presence of T. pisana on only these south and
south-west slopes, combined with the apparent
suitability of parts of the north and east slopes
suggests that its distribution here is restricted largely
by aspect. Cowie (1982) showed that variation in
vegetation cannot account for this restriction.
There was little suitable habitat for T. pisana along
the South Cliff, where the gardens of the houses on
the cliff-top extend right to the edge. However, a
few specimens and one or two small colonies were
found, particularly between the public gardens
beneath the Esplanade, and the edge of the cliff. The
most extensive area inhabited by T. pisana in Tenby,
and the area where its population density appeared
highest (up to about 200 adults per sq m in summer
Cowie 1982), was around the western end of the
Esplanade and the sloping tarred path leading from
it down to the beach. This included the areas Stubbs
(1900) indicated as the 'Jubilee Gardens' and the
'Wreck Field'. ('Wreck' was presumably a mis-
spelling of 'Rec', short for 'Rectory' the Rectory
Field is now a metalled car park which retains this
name.) The largest single part of this area inhabited
by T. pisana is the bank between the Rectory Field
car park and the sloping path to the beach, an area of
about 30 x 8 m. The dominant plant of this bank is
alexanders. T. pisana was also found in large
numbers in patches alongside the path down to the
beach, again associated largely with alexanders.
From this centre its distribution extended inland
around the edges of the car park, along Battery
Road, and down the road to the 'Fundrome', which
was demolished during the course of the survey.
Fig. 2 Map of Stackpole Warren showing the area inhabited by
T. pisana at present.
Most of this area is now short turf. The paths and
roads are metalled, and some of the paths have
railings along their seaward sides. T. pisana was
found stuck to these railings or in the uncut
vegetation at their bases. Elsewhere it was found in
the few areas of rough vegetation remaining,
particularly behind the small amusement arcade and
shop towards the bottom of the cliff near the beach.
Further inland, a small colony (about 100 m2) was
found on the seaward side of the railway bank at the
bottom of the unsurfaced track leading from the
inland end of Queen's Parade down to the golf
club-house and Burrows. The vegetation was uncut,
and the snails were associated largely with fennel
(Foeniculum vulgare Mill.).
The half of the Burrows nearer to Tenby was
covered with sea buckthorn (Hippophae rhamnoides
L.) and was devoid of T. pisana. A few individuals
were found by the large rocky outcrop beside the
railway about half way along the Burrows (no doubt
the 'Black Rock' of Stubbs). A few were also found
near the track which passes over the railway line,
alongside this outcrop, and onto the Burrows. From
here, T. pisana was found in small numbers
scattered over the remaining south-western half of
the Burrows, often associated with sea radish
(Raphanus maritimus Sm.). This area does not carry
sea buckthorn, the dominant plant being marram
(Ammophila arenaria (L.) Link.). However,
nowhere was a large area covered with vast numbers
of T. pisana.
Both sides of the Narberth Road were searched
from where it joins the Norton (a road running
Fig. 3 Detailed map of Tenby showing the present distribution
of T. pisana.
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