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Dispersal, home-range size, and habitat use of an endangered land snail, the Oregon forestsnail (Allogona townsendiana)

Edworthy, A.B., Steensma, K.M.M., Zandberg, H.M., Lilley, P.L.
Canadian journal of zoology 2012 v.90 no.7 pp. 875-884
Urtica dioica, adults, forests, habitat destruction, habitat preferences, habitats, meadows, snails, British Columbia, Oregon
Terrestrial molluscs have declined globally, often as a result of habitat loss and fragmentation. Many land snails are poor dispersers and exist in isolated habitat patches. The Oregon forestsnail (Allogona townsendiana (I. Lea, 1838)) coincides with the most densely populated region of British Columbia and is listed as endangered in Canada. To investigate the dispersal distances and habitat-use patterns of Oregon forestsnails, we tagged and tracked 21 adult snails at Langley, British Columbia, for up to 3 years (2005–2008). The maximum daily dispersal distance for a snail was 4.5 m and the maximum displacement that we observed for a snail was 32.2 m during 3 years. Snails occupied home-range areas of 18.4–404.4 m², often overlapping both forest and meadow habitat. Their home-range sizes were smaller in habitats with high availability of stinging nettle (Urtica dioica L.), which may be an indicator of high-quality habitat. Our results suggest that the Oregon forestsnail is a relatively sedentary species with limited dispersal ability in its adult stage. Although Oregon forestsnails are likely unable to colonize suitable habitat independently, remnant forest–meadow mosaic patches such as our study site provide valuable habitat for Oregon forestsnail, which are supplementary to large tracts of intact forest where most of their populations are found.