Snailing on Skye

The middle of September brought a week of fine weather and three conchologists to the “Misty Isle”. Since a Conchological Society marine meeting had been planned for 18th–21st September, it seemed a good idea to do some non-marine recording on the Isle of Skye as well, so three members – Rosemary Hill, Ron Boyce and Adrian Sumner – got together and did some recording before the marine meeting started.

The marine conchologists were going to be based at Broadford, in the south-east of the island, and this was also a good base for non-marine conchology, as the area is geologically the most favourable part of Skye. Although most of the Highlands and Islands of Scotland are based on ancient igneous rocks such as granite, and covered with acid peaty soils, there are extensive areas of both Cambrian and Jurassic limestone to the south-west of Broadford (see Map, page 2). The Cambrian limestone is part of the Durness limestone, which forms a band running down the west of Scotland from the north coast of Sutherland to Argyll. Such basic soils promised to support a richer fauna than the more acid soils found over much of Skye.

Over 60 species of non-marine molluscs are recorded for Skye in the Atlas of Land and Freshwater Molluscs of Britain and Ireland (Kerney, 1999), and Chris du Feu has done a lot of recording on the island over the last few years and added a few more species, concentrating particularly on slugs (see his article in this issue). In general, however, recent records have not been obtained for many parts of the country since the Atlas was published, and it was hoped to get some really up-to-date information on the slugs and snails of Skye. In particular, it would be nice to know which species of Balea, of which two species have recently been recognised in Britain (Gittenberger et al., 2006), occur in Skye.

Adrian had already been on the island for several days and done some desultory recording before joining up with Ron and Rosemary. Zenobiella subrufescens was a nice find in the grounds of Armadale Castle in the south. Arion owenii also turned up here and in Broadford, but didn’t seem to be as widespread and common on Skye as in many places in the west of Scotland; Chris du Feu had already recorded its presence on Skye, but regards it as a very recent immigrant. In the north-west of the island by Claigan coralline sands, where a small trickle ran across the grassland and into the sea, Potamopyrgus antipodarum was an interesting find. Although this little freshwater snail has spread to almost every corner of the British Isles, it appears to be very local on Skye, and we found it nowhere else; however, Ancylus fluviatilis, which occurred in the same trickle as P. antipodarum, was common and widespread. A day trip to the small island of Raasay, off the east coast of Skye and reached by a small ferry (Figure 1) from Sconser, produced a list of 14 species. Nearly half of these were slugs, so it was quite exciting to find several specimens of the snail Clausilia bidentata in a small patch of deciduous wood after finding so many shell-less species. The area around the ruins of the old ironstone mine up in the hills proved to be quite productive, but also had a good population of midges, which curtailed examination of the site!

Ron and Rosemary had also done some preliminary reconnaissance, and near Loch Cill Chriosd in Strath Suardal, which runs south-west from Broadford towards Torrin, they discovered a real curiosity – a “land limpet”. This was a fine specimen of Ancylus fluviatilis that for some reason was attached to a rock completely away from the water (Figure 2)!

Serious recording began on 14th September, when Ron, Rosemary and Adrian met in the large car park at Broadford and headed south to Tokavaig Wood, near Ord. Some hard searching produced only 12 species in this mixed deciduous wood with a predominance of hazel. We soon found specimens of Balea heydeni (Figure 3), and the first ones were attached to bark on the ground. Although Balea spp. are reported to be found only rarely on the ground (Boycott, 1934; Kerney, 1999), these were only the first of several that we found there. Obviously if a piece of bark or a branch to which a specimen of Balea is attached should fall to the ground, the snail will fall with it. No doubt they subsequently climb up another tree, and thus the species becomes dispersed. Another highlight of the site was a young specimen of the slug Limax cinereoniger. Large Arion spp. were also here: A. flagellus, quite common on the island, and some specimens of A. cf. rufus, one of which was enjoying a meal of puffballs that were growing out of the moss on a tree trunk (Figure 4).

After lunch we returned to the tiny settlement of Ord (Figure 5) where, however, examination of the beach revealed little, although a watercress-choked stream running across it produce Lymnaea truncatula and Pisidium personatum.

Our final destination for the day was Lower Breakish, a limestone area near the shore to the east of Broadford. The journey there was not uneventful however; one feature of the Highlands and Islands is numerous single-track roads with a limited number of passing places. These can be a trap for the unwary and inexperienced, and on the way from Ord we had to help push back on to the road a car that had misjudged things when trying to pass. Conchological Society risk assessments don’t cover such eventualities! Lower Breakish itself proved to be goldmine. Initially we looked at a limestone cliff beside a small river that entered the sea at this point (Figure 6), and Ron’s efforts with his vacuum cleaner produced a specimen of Columella edentula here. However, the greatest concentration of snails was in a drystone limestone wall nearby, which hid a large number of specimens within its cracks, of which the most notable were several specimens of Pyramidula pusilla, absent from most of Scotland because of its preference for limestone.

The next day we concentrated on Strath Suardal, which runs between Broadford and Torrin, and is largely on limestone. Our first stop was by the ruined chapel of Cill Chriosd (Figure 7), which itself harboured several species of snails, including more Pyramidula pusilla, as well as the bright pink little woodlouse Androniscus dentiger, another denizen of limey regions. Behind the chapel was Loch Cill Chriosd (Figure 8), where we found, among other species, Lymnaea palustris and Gyraulus crista; some marshy areas by the loch further along the Strath yielded Oxyloma elegans and Euconulus alderi. Across the road from the loch was a hazel wood, not particularly rich in molluscs with the dry weather, but which produced one of the highlights of the expedition, a specimen of Leiostyla anglica. Altogether we found 26 species in this quite small area.

Further along the Strath, where it meets the sea (Loch Slapin) is the little village of Torrin, our final destination of the day. At an abandoned area covered with limestone dust from the nearby marble quarry Ron discovered what he described as the “National Collection of Trochulus striolatus”, but our main goal here was a hazel wood nearby (Figure 9). The 15 species from this wood included Acanthinula aculeata, and a good number of Balea heydeni, both on tree trunks and on the ground, attached to fallen wood and bark.

Altogether we found 46 species of slugs and snails on Skye, a high proportion of the previously reported total. Although only one was new to Skye (Balea heydeni, and that only because it is a newly recognised segregate in Britain), we did extend the recorded ranges of several species. Perhaps most important, we had fine weather for our recording excursions, and had a jolly good time as a result.

Acknowledgements

We thank Ian Killeen for the determinations of the Pisidium specimens.

References

Boycott, AE. (1934) The habitats of land Mollusca in Britain. J. Ecol. 22, 1–38.

Gittenberger, E., Preece, RC. & Ripken, TEJ. (2006) Balea heydeni von Maltzan, 1881 (Pulmonata: Clausilidae): an overlooked but widely distributed European species. J. Conchol., 39, 145–150.

Kerney, M. (1999) Atlas of Land and Freshwater Molluscs of Britain and Ireland. Harley Books, Colchester.

Figure 1. The Raasay ferry, Loch Striven, approaching Sconser on the mainland of Skye, with the island of Raasay in the background (Photo: Adrian Sumner)

Figure 2. The “land limpet” (Ancylus fluviatilis) from Strath Suardal (Photo: Rosemary Hill)

Figure 3. A specimen of Balea heydeni from Tokavaig Wood near Ord (Photo: Rosemary Hill)

Figure 4. Arion cf. rufus eating a puffball growing out of the dense growth of moss on a tree trunk in Tokavaig Wood (Photo: Adrian Sumner)

Figure 5. The beach at Ord, Isle of Skye (Photo: Adrian Sumner)

Figure 6. Rosemary Hill and Adrian Sumner examining the limestone cliff by the Abhainn Ashik watercourse at Lower Breakish for snails (Photo: Ron Boyce)

Figure 7. The ruined chapel of Cill Chriosd, home to Pyramidula pusilla (Photo: Adrian Sumner)

Figure 8. Ron Boyce and Rosemary Hill searching for molluscs by Loch Cill Chriosd (Photo: Adrian Sumner)

Figure 9. Hazel wood near Torrin, Isle of Skye (Photo: Ron Boyce)