Oregon Forestsnail
Distribution: Elevation: 350 m In B.C. this snail is restricted to the Coast Region in the Fraser Valley Lowlands known from occurrences (mainly on the south side of the Fraser River) in Langley, Chilliwack (Ryder Creek watershed, Little Mountain, Cheam Lake), Mission (Hatzic Prairie) and Abbotsford (McKee Peak and lower Sumas Mountain as well as the City proper). Other locations include Bridal Veil Falls (Durand 2006) and one recent occurrence on southern Vancouver Island (BC Conservation Data Center 2010). Anecdotal occurrence information exists for Point Roberts, indicating the species may occur as far west as Tsawwassen and Delta/Surrey but these populations remain unconfirmed (Forsyth et al 2002).
Description: shell diameter 28-35 mm One of the largest land snails in BC, the round shell is pale brown lightening to amber around the aperture. This species lacks the ‘hairs” found on some land snail species (Durand 2006). This species has 5-6 whorls (shell spirals) with irregular, fine, pale lines and striations. The thick white aperture lip of adult snails is evident when viewing the snail ventrally. As the snail matures the shell can become bleached looking and begin to flake.
Diet: This species has a marked preference for understory herbaceous vegetation, especially stinging nettle and sword fern communities found in association with big leaf maple, salmonberry and red alder.
Looks Like? In general the size of the Oregon forestsnail and the distinct thick white shell aperture distinguish it from other land snails on the South Coast. There is another species of the same genus in BC (Idaho forestsnail), but this is found in the east and the ranges of the two do not overlap. The Puget Oregonian is almost the same size; but unlike the Oregon forestsnail, adults have a tooth-like projection in the shell aperture. As well the Puget Oregonian probably no longer exists in the province (Forsyth 2004, BC Conservation Data Center 2010). The northwest hesperian is smaller (shell diameter <16 mm) and the shell is usually covered with short hairs, which are noticeable when the shell is held up to light. Other large snails within the range of the Oregon forestsnail include the native Pacific sideband, and the introduced grovesnail and brown garden snail. With the exception of the Puget Oregonian, the aperture of these co-occurring species do not have a white, thickened lip.
Puget Oregonian
Distribution: Elevation: <350 m Endemic to the Pacific Northwest, in B.C. this snail is considered extirpated having only been identified from three records between 1895 and 1905 on Southern Vancouver Island and the Fraser Valley Lowlands (BC Conservation Data Center 2010). Recent attempts to locate this species have proven unsuccessful. As well within its known populations in Washington state and Oregon it occurs in a very patchy distribution (Burke 1999, EC 2010).
Description: Shell Diameter 18-26 mm This is the largest species in the Cryptomastix genus. The shell colour is yellowish to brown with a more accentuated flared aperture than that of Oregon Forest Snail. The shells of mature individuals have microscopic bristles. Like Oregon Forest Snail the inside of the aperture is ringed by a pale white thickened lip but Puget Oregonian has a tooth-like structure (“parietal tooth”) within the curve opening of the shell not found in other snail species in its genus (Burke 1999, EC 2010).
Diet: This species has a marked association with mature forests supporting significant stands of mature Western Hemlock, old growth Big Leaf Maple and Sword Fern understory. Little is known however about its actual forage preferences. However there is supposition that it may be dependent on the filamentous bodies of fungi (“mycelium’). Though immature individuals may also exploit herbaceous plants in the understory (Burke 1999).
Looks Like? See Oregon Forest Snail.
Pacific Sideband
Distribution: elevation up to 1220 m. Pacific sideband appears to have a similar range size to Oregon forestsnail, but includes areas to the north of the Fraser River. This species range does overlap with Oregon forestsnail (e.g. Chilliwack, Abbotsford, Mission) and possiblt that of puget Oregonian if isolated populations still persist in BC. Other documented occurrences range from Surrey and Burnaby to the Harrison area (Forsyth et al 2004, Brown and Durand 2007).
Description shell diameter 35 mm+ Diameter shell 1.3 to 1.5 times height; with 6.5 to 7 whorls. Size is one of the key distinguishing factors for this snail, at greater than 35mm it is the largest land snail in BC, deserving the nickname “Giant” Sideband. Unlike Oregon Forestsnail which is somewhat uniform in colour, this species has a strikingly patterned shell with black and yellow bands along the lower periphery of each whorl. The rest of the shell is chestnut and amber and the snail itself is a rich reddish brown with black speckling. Periodically abnormal coloured individuals can be found with a mustard coloured shell lacking any patterning (Brown & Durand 2007), however the body remains the distinct reddish brown.
Diet: As with other land snails this species has a generally vegetarian diet, preferring herbaceous plants in the understory as well as foraging amongst tree trunks and upper branches (has been found up to 6.7 meters above the forest floor – Brown & Durand 2007).
Looks Like? Pacific Sideband’s sheer size distinguish it from other land snails, however the variation in band patterns and colour, and occurrence of a solid yellow coloured shell morph makes mistaken identity possible with the introduced Grovesnail. The striping on Grovesnail however is narrow and the shell is somewhat squat when laid on its side compared to the sideband which is broader from the centre whorl to the aperture. As well Sidebands’ body colour and pebbly flesh distinguish it from the somewhat smoother yellow body of Grovesnail.
Primary Habitat
All three species are found in greatest abundance in broadleaf forests with the Oregon Forestsnail found in moderate canopy closure (33-66%) and Pacific Sideband in higher canopy closure (33-67%+). Both these species show a marked preference for sites dominated by big leaf maple and lesser occurrences of red alder, western red cedar and cottonwood. Puget Oregonian in the U.S. has similar plant association preferences with the addition of mature Western Hemlock (Burke 1999). The preference for shrub cover varies between Oregon Forestsnail and Pacific Sideband with low shrub cover (0-5%) for Oregon Forestsnail, and 5%+ for Pacific Sideband. Shrub species typically were salmonberry, red elderberry and thimbleberry. Both these species tend to prefer slightly sloping topography, with a southwest aspect and sites with a low percent (<5%) mossy groundcover. An association with a thick cover of stinging nettle is common, often in combination with sword fern. Interestingly Oregon Forestsnail prefers sites with high levels of stinging nettle versus sword fern, while Pacific Sideband prefers sword fern being more dominant than stinging nettle (similar to preferences for Puget Oregonian). A thick leaf litter layer (5-10cm) is important for providing essential moisture regimes and development of fungal mycelium (Forsyth et al 2002, Durand 2006, Brown & Durand 2007).
Secondary Habitat: Individuals utilize edge areas along preferred habitats such as drainage ditches, trails and exposed soils. Herbaceous edges along coniferous stands can also provide some forage.
Critical Feature: Little is understood about these species of forest snail distribution or abundance and even less is known about site preferences for egg laying or juvenile dispersal. While these species can adapt to a reasonably high degree of disturbance, proximity to preferred habitat is critical to ensure connectivity and sufficient forage and refugia for local population persistence (Forsyth et al 2002, Durand 2006, Brown & Durand 2007, EC 2010).
Seasonal Life Cycle
Jan / Feb / Mar / Apr / May / Jun / Jul / Aug / Sep / Oct / Nov / DecHabitat Guild: Deciduous forests (immature to mature), mixed forests, herbaceous thickets.
Threats
q Distribution coincides with areas undergoing significant urbanization, industrial agricultural practices and logging leading to natural habitat loss, fragmentation, clearing and infilling.
q Backcountry and passive recreational activities (e.g. ATV and mountain biking) can result in impacts to forage plant communities as well as direct mortality.
q Competition from introduced species such as the Grovesnail and Brown Garden Snail could be impacting native mollusks. Misidentification of native snail species as introduced pest species in gardens as well as slug control may result in direct mortality.
q Colonization of native plant communities by invasive and exotic plant species can reduce and eliminate preferred food plants.
q Use of pesticides and soil contamination from surface runoff
q Predation from raccoons and skunks.
q Harvesting and non-permitted collection by the public.
Key Conservation & Management Objectives
q Assess and inventory through criteria set-out in: Draft Gastropod Best Management Practices Guidebook Oregon Forestsnail and Other Land Snails at Risk in the Coastal Lowlands. BC Ministry of Environment. In draft 2007 (Available by request from the regional Species at Risk Biologist).
q Determine the full range extent and potential presence/habitat suitability of these species within BC, especially in areas under pressure from development or clearing on the South Coast and Vancouver Island by expanding habitat suitability mapping as done for Big Leaf Maple distribution for Puget Oregonian (EC 2010). Ensure these species continue to persist in historic (e.g. for Puget Oregonian), existing, and newly located sites through habitat securement and land management partnerships.
q Little is known about carrying capacity of preferred plant communities, land use decisions which lead to a need to salvage and relocate populations should be avoided or closely monitored to prevent competition impacts.
q Assessments should not discount or solely rely on existing scientific literature when scoping study areas for the potential presence of Pacific sideband or other species at risk. It is apparent that due to natural variation, geographic location and isolation, and species adaptability (e.g., adapting to an urbanized area), more than a single habitat type may be suitable (Brown & Durand 2007).
q Land snails and slugs are not highly mobile and tend to move usually only to find food or reproduce. Smell is considered the primary sensory behavior utilized to find and move toward a food item (which may be only in the range of centimeters to meters over a terrestrial mollusks lifetime). Oregon Forestsnail has been shown to utilize variable patch sizes from as little as 4m2 to as large as 70m2 (Durand 2006). Home range size however does not necessarily equate to the size and complexity of habitats needed to support a given population or populations of snails ( MoE 2007)
q Where seasonal habitats, such as hibernation or summer dormancy sites, are widely separated, or where habitat is of lower quality, individual snails may require large areas of connectivity and maintain larger home ranges. Minimum size of areas that can support a viable population of snails is unknown but must contain habitat features required for all seasonal activities and developmental stages. (MoE 2007). In general, land snails have a low tolerance to drying and exposure, are not extensively mobile, and are slow to disperse. This leaves them extremely vulnerable to activities that impact microclimate conditions, or decrease food supplies available in populated sites.
q Habitat alteration by either human or natural means (including fire, herbicide use, recreation development), over-collecting, and disturbance during summer dormancy should be avoided (Oregon State University 2007).
q Sightings, specimens, or observations of activities threatening its habitat should be reported to the regional Species at Risk Biologist at the Ministry of Environment office.
References & Citations:
Durand, Ryan,. 2006. Habitat Assessment of the Endangered Oregon Forestsnail, Allogona townsendii, In the Lower Fraser Valley of British Columbia (in publication).
Brown, Darren and Ryan Durand. 2007. Habitat Assessment of the Pacific Sideband (Monadenia fidelis) In the Lower Fraser Valley British Columbia (in publication).
BC Ministry of Environment. 2007. Draft Gastropod Best Management Practices Guidebook Oregon Forestsnail and Other Land Snails at Risk in the Coastal Lowlands. (In draft)
Environment Canada. 2010. Recovery Strategy for the Puget Oregonian Snail (Cryptomastix devia) in Canada. Species at Risk Act Recovery Strategy Series. Environment Canada, Ottawa. iv pp. + Appendix.
COSEWIC 2002. COSEWIC assessment and status report on the Oregon forestsnail Allogona townsendiana in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 20 pp.
Burke, T.E. 1999. Management recommendations for terrestrial mollusk species. Cryptomastix devia, Puget Oregonian snail. V. 2.0. Prepared for Oregon Bureau Land Manage.
Land Snails of British Columbia. Robert Forsyth. 2004. UBC Press.
Oregon State University - Oregon Natural Heritage Information Center: Status factors for Monadenia fidelis ochromphalus (and other threatened and endangered land snails)
International Forest Products Limited and Ministry of Water, Land and Air Protection. 2003. A Field Guide to Species at Risk in the Coast Forest Region of British Columbia:
BC Species & Ecosystems Explorer (BC Conservation Data Center Summary Report) http://www.env.gov.bc.ca/atrisk/toolintro.html
NatureServe Explorer - http://www.natureserve.org
Committee on the Status of Endangered Wildlife in Canada: http://www.cosewic.gc.ca/
Image credits:
Oregon Forest Snail: Ryan Durand & Gord Gadsden
Puget Oregonian: William P. Leonard/Green University
Pacific Sideband and Grovesnail – Pamela Zevit
Habitat – Ryan Durand
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Draft 2010
Disclaimer: This species account and related conservation recommendations are draft only and presently under review and subject to change.