Morii & Nakano 2017

Citizen science reveals the present range and a potential native predator of the invasive slug Limax maximus Linnæus 1758 in Hokkaido, Japan.

Morii Y*, Nakano T, 2017. BioInvasions Records, 6: 181–186. doi: 10.3391.

Press releases in English and Japanese.

Introduced on Asia Research News (Website), Excite News (Website) and some other media.


The giant garden slug Limax maximus Linnæus, 1758 (Limacidae, Pulmonata) is considered one of the most widely spread terrestrial molluscs in the world and is a formidable pest of agricultural and horticultural crops. This slug was recently introduced to Japan, where its population is now rapidly increasing and spreading. A naturalised population of L. maximus was first discovered in Hokkaido, Japan, in 2012 in the isolated natural forest of Maruyama Forest Park in Sapporo City, and the species has become common in this area. In the present study, we investigated observations of L. maximus reported by ordinary citizens acting as “citizen scientists” to assess the recent expansion of this invasive slug. We posted an announcement in the local newspaper requesting reports of the occurrence of L. maximus via e-mail and analysed 38 observations provided by local citizens. As a result of these reports, 16 naturalised populations of L. maximus were detected in Hokkaido, several of which were quite far from the original population in Sapporo City. Moreover, a terrestrial macrophagous leech, Orobdella kawakatsuorum Richardson, 1975 (Arhynchobdellida, Orobdellidae), is reported as a potential native predator of L. maximus for the first time.