Kerry Slug

The Kerry slug or Kerry spotted slug, scientific name Geomalacus maculosus, is a rare species of medium-sized to large air-breathing land slug. It is a terrestrial pulmonate gastropod mollusc in the family Arionidae, the roundback slugs.

An adult Kerry slug generally measures 7–8 cm (2.8–3.2 in) in length and is dark grey or brownish in colour, with yellowish spots. The internal anatomy of the slug shows some unusual features, and some characteristic differences from the genus Arion, which is the type genus of the family Arionidae. The Kerry slug was described in 1843, rather late compared to many other relatively large land gastropods that form a part of the fauna of the British Isles; this is one indication of this slug's rarity and its secretive habits.

Although the distribution of this slug species does include some wild habitats in southwestern Ireland (e.g. in County Kerry), the species is more widespread in north-west Spain and from central to northern Portugal. However, it is not found anywhere between Ireland and Spain. The species appears to require environments that have high humidity and acidic soil (soil with no calcium carbonate in it). The slug is mostly nocturnal or crepuscular, although in Ireland it is active on overcast days. It feeds on lichens, liverworts, mosses and fungi, which grow either on boulders or on tree trunks.

This rare species is officially protected by conservation laws in each of the three countries in which it occurs. However, the survival of the Kerry slug is nonetheless threatened because it lives only in completely wild, unspoiled habitat of a particular type: acidic woodlands and moorlands that support the species of lower plants on which the slug relies for food. This habitat type is itself at risk from a number of different factors, ranging from climate change to the construction of roads. Attempts have been made to establish breeding populations in captivity, to help ensure the survival of this slug species, but with only limited success.