Friday 10 Oct 2014
Lack of local information on native species allows major pest slugs and snails to become established in Sri Lanka  

Problem Statement: Introduced slugs and snails are currently the most serious agricultural and horticultural pests in several areas of Sri Lanka but their recent arrival has passed unnoticed and largely unrecorded. Because it has not been possible to identify many of the native species in Sri Lanka, exotic pest species had been mistakenly assumed to be native to Sri Lanka and the agricultural authorities had not been alerted to their presence. Sri Lanka is a global biodiversity hotspot with the greatest category of threat to biodiversity owing to high human population density. It possesses a species rich and highly endemic land snail fauna with several ancient relict groups. Much of the original forest in Sri Lanka has been degraded or converted to plantations and other forms of agriculture and it is in these habitats that exotic gastropod species have become established.

Methods: Addressing the problem of a lack of taxonomic resources in Sri Lanka to allow identification of land snails was the focus of the Darwin Initiative Project Land snail diversity in Sri Lanka (1999-2002). Nearly all of the taxonomic resources for the region such as specimen reference collections, particularly type material, and specialist literature are concentrated in The Natural History Museum, London and a primary objective of the project was to provide access to such resources. In Sri Lanka the project focussed on a national survey of terrestrial molluscs to allow the establishment of specimen reference collections and a database on distributions.

Outcomes and Impacts: The survey established that, particularly in the Central Highlands, the most damaging species of exotic pest gastropods were firmly established in very high densities. We now have a good knowledge of what pest species are present and have produced identification guides to the native fauna which will allow a speedy response to the arrival of new exotic slugs and snails, making it possible to prevent further damage to both agriculture and biodiversity.

Lessons: Lack of knowledge of what species are native to an area can allow exotic pest species to become firmly established without any attempts at their eradication or control being put in place. Identification guides prepared by taxonomists are essential tools in the prevention of epidemics of invasive species.


1. Naggs, F. 2002. Molluscan pests in Sri Lanka: voracious exotics having a major and rapidly increasing impact on agriculture. Zoology Department, The Natural History Museum, London. Land snail diversity in Sri Lanka: Darwin Initiative project information leaflet. 2. Naggs, F., & Raheem, D. 2002. Sri Lankan Snails. Department of Zoology, The Natural History Museum, London. 3. Mordan, P. et al. A guide to the pest and exotic snails and slugs of Sri Lanka. Department of Zoology, The Natural History Museum, London. 4. Naggs, F. et al. (In Preparation). Ancient relicts and contemporary exotics: faunal change and survivorship in Sri Lanka’s snail fauna. Slugs & snails. Agricultural, veterinary & environmental perspectives. British Crop Protection Council.


Fred Naggs, Biodiversity & Conservation Officer, Mollusca Group, Department of Zoology, The Natural History Museum, London SW7 5BD |




invasive alien species

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