KEELED SNAIL
Tasmaphena lamproides
Status
Rare (Tasmanian Threatened Species Protection Act 1995), because its area of occurrence is less than
2
2000 km and its population densities are usually very low (i.e. five to ten live adults/hectare).
Description
A land snail with a heavy shell, which is a yellow to chestnut-red colour and flattened with four to
four and a half whorls. Adults have a shell width of 16–29 mm. The whorls are low-spired and have a
bluntly angular lateral edge, hence the common name 'keeled snail'. The animal is long and slender
with a bright yellow stripe down its neck.
Distribution and habitat
The keeled snail, occupies a range (extent of occurrence) of at least 1150 km2 in the extreme northwestern corner of the Tasmanian mainland. The eastern-most confirmed population is on The Nut,
Stanley, and the southern-most at the junction of the Arthur and Frankland Rivers. There is an
outlying population on Three Hummock Island, 30 km north of the Tasmanian mainland distribution.
The species is also recorded from southern Victoria (Smith & Kershaw 1979) but more study is
needed to determine whether the Victorian population is the same species.
The keeled snail is most common in wet eucalypt forest over 60 years old (Bonham & Taylor 1997)
but can be absent from these forests if the substrate is sandy. It has also been found in rainforests
and swamp forests that are not permanently inundated, and in regrowth as young as 20 years
(though not usually younger than 30 years). In very rare cases it occurs in other habitat types, such
as eucalypt scrub or coastal shrubbery (TSS 2007).
The keeled snail occurs beneath decaying wood and in deep damp litter in forest and some scrub.
Potential habitat for the keeled snail is all land within the current known range of the species with
vegetation cover of mature, regrowth and regenerating forests, predominantly wet eucalypt but also
including some rainforest and blackwood. The species also occurs in some rainforest types.
Blackwood and wet eucalypt forest containing fallen logs, thick scrub and understorey for shelter
and varying topography appears most suitable. The Togari block (west of Smithton) represents prime
habitat. The species sometimes occurs in scrub on good soil (e.g. The Nut at Stanley; the northern tip
of Woolnorth) (FPA 2008).
Biodiversity Values Database This version current at August 2011
Page 1
Little is known of the life history of this snail except that it is a carnivore feeding predominantly on
native land snails and earthworms. Life history attributes used in modelling (e.g. Regan et al. 2001)
were inferred and may be inaccurate (TSS 2008).
The keeled snail, occurs in very low population densities in many parts of its range. Estimated
densities (e.g. Bonham & Taylor 1997) have typically been around five to six mature adults per
hectare, but in some areas have been as high as 20 mature adults per hectare. Usually there are
about half as many live juveniles as live adults. It is possible that these densities were
underestimated, as surveying based on searching smaller areas has produced higher average
densities. The extant population is likely to total several hundred thousand specimens (TSS 2007).
Reading
Bonham, K.J. (1999). Range Boundary Survey for the Keeled Snail Tasmaphena lamproides.
Unpublished report to Forestry Tasmania.
Bonham, K.J. (2000). Distribution and Habitat Characteristics of Tasmaphena lamproides (Keeled
Snail) on Private Land. Unpublished report to the Forest Practices Board, and the Threatened
Species Unit (DPIWE).
Bonham, K.J. (2003). Biogeography of Tasmanian Native Land Snails. PhD thesis. University of
Tasmania.
Bonham, K.J. & Taylor, R. (1997). Distribution and habitat of the land snail Tasmaphena lamproides
(Pulmonata: Rhytididae) in Tasmania. Molluscan Research 18: 1-10.
Forest Practices Board (FPB) (1999). Fauna Technical Note 7. Forest Practices Board, Hobart.
Regan, T., Bonham, K., Regan, H., Taylor, R., Tuson, D. & Burgman, M. (1999). Forest Management
and Conservation of Tasmaphena lamproides in North-west Tasmania: Use of Population
Ciability Analysis to Evaluate Management Options. Final report to Forestry Tasmania, Hobart.
Regan, T.J., Regan, H.M., Bonham, K.J., Taylor, R.J. & Burgman, M.A. (2001). Modelling the impact
of timber harvesting on a rare carnivorous land snail (Tasmaphena lamproides) in northwest
Tasmania, Australia. Ecological Modelling 139: 253-264.
Regan, T.J., Taylor, R.J. & Burgman, M.A. (2000). Investigation of Harvest Scheduling Options for
Forest Management: Implications for the Carnivorous Land Snail, Tasmaphena lamproides in
Northwest Tasmania. Report to Forestry Tasmania.
Smith, B.J. & Kershaw, R.C. (1991). Tasmanian Land and Freshwater Molluscs. University of
Tasmania, Hobart.
Taylor, R.J., Regan, T., Regan, H., Burgman, M. & Bonham, K. (2003). Impacts of plantation
development, harvesting schedules and rotation lengths on the rare snail Tasmaphena
lamproides in northwest Tasmania: a population viability analysis. Forest Ecology and
Management 175: 455-466.
Threatened Species Section (TSS) (2007). Draft Fauna Recovery Plan: Threatened Tasmanian Land
Snails 2006-2010. Department of Primary Industries and Water, Hobart
Biodiversity Values Database This version current at August 2011
Page 2