In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.
|EPBC Act Listing Status||Listed as Critically Endangered|
|Listing and Conservation Advices||
Commonwealth Listing Advice on Thersites mitchellae (Mitchell's Rainforest Snail) (Threatened Species Scientific Committee, 2002i) [Listing Advice].
|Recovery Plan Decision||
Recovery Plan required, this species had a recovery plan in force at the time the legislation provided for the Minister to decide whether or not to have a recovery plan (19/2/2007).
|Adopted/Made Recovery Plans||
Mitchell's Rainforest Snail Thersites mitchellae recovery plan (NSW National Parks & Wildlife Service (NSW NPWS), 2001u) [Recovery Plan].
Federal Register of
Inclusion of species in the list of threatened species under section 178 of the Environment Protection and Biodiversity Conservation Act 1999 (04/07/2002) (Commonwealth of Australia, 2002b) [Legislative Instrument].
Documents and Websites
|State Listing Status||
|Non-statutory Listing Status||
|Scientific name||Thersites mitchellae |
|Species author||(Cox, 1864)|
|Reference||ANZECC Threatened Fauna List May 2000; NSW National Parks and Wildlife Service (2001). Mitchell's Rainforest Snail Thersites mitchellae recovery plan. NPWS, Hurstville, NSW.|
This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.
Scientific name: Thersites mitchellae
Common name: Mitchell's Rainforest Snail
The genus Thersites belongs to the family Camaenidae. Three species are currently recognised in the genus Thersites: Thersites mitchellae (Cox 1864) from lowland subtropical rainforest and swamp sclerophyll between the Tweed and Richmond Rivers, Thersites novaehollandiae (Gray 1834) from temperate and subtropical rainforest from Barrington Tops to the NSW/Queensland border and Thersites richmondiana (Reeve 1852) from upland temperate and subtropical rainforest between the McPherson Range on the NSW/Queensland border and the Conondale Range in south-east Queensland (Bishop 1978; NSW NPWS 2001u).
Mitchell's Rainforest Snail is a terrestrial gastropod with a shell up to 5.5 cm wide and 5 cm high. The shell has a strongly elevated spire giving it a triangular profile and a thickened, reflected lip. The shell is deep reddish chestnut to black in colour with two prominent yellow bands and has a satin appearance when held close to light. The snail's body colour is black with a thin lighter line on the dorsal midline (NSW NPWS 2001u). Mitchell's Rainforest Snail has an average weight of 25 g (Murphy 2002).
Mitchell's Rainforest Snail is restricted to the coastal lowlands between the Tweed and Richmond Rivers in the New South Wales north coast bioregion (NSW NPWS 2001a). Records indicate the species is distributed along the coastal plain between Banora Point in the north and Lennox Head in the south (Murphy 2002).
Since 1995, the NSW National Parks and Wildlife Service has conducted surveys for Mitchell's Rainforest Snail that targeted suitable habitat (NSW NPWS 2001u). The species was found at five locations: Stotts Island, Banora Point, Byron Bay, Suffolk Park and Lennox Head (TSSC 2002i). The largest known population of Mitchell's Rainforest Snail is in Stotts Island Nature Reserve in the Tweed River near Murwillumbah (NSW NPWS 2001u; Stanisic 2000).
The species' current area of occupancy has been estimated to be less than 5 km² (Murphy 2002).
Mitchell's Rainforest Snail is now restricted to remnant areas of habitat in a highly fragmented urban and agricultural environment. This, along with the limited dispersal ability of the species, means that many of the populations are effectively isolated from others, except where they exist within the same bushland remnant or similar immediately adjacent locations (NSW NPWS 2001a).
Field surveys were undertaken in 1998, 1999 and 2000 to provide additional information on Mitchell's Rainforest Snail (Murphy 2002; Stanisic 1998, 1999, 2000).
The 1998 survey, conducted between the Richmond and Tweed Rivers (NSW), located Mitchell's Rainforest Snail at four sites, three of which were new localities for the species (Stanisic 1998, NSW NPWS 2001u).
The 1999 survey was conducted at two sites in the Wilson Creek valley (NSW) west of Mullumbimby. The survey team could not establish the presence of the species at either site (Stanisic 1999).
The 2000 survey was conducted on Stotts Island at eight sites with Mitchell's Rainforest Snail located at all sites (Stanisic 2000). This study provided information on the distribution and status of the species on Stotts Island, identified potential threats to the population and provided recommendations for management (NSW NPWS 2001u; Stanisic 2000).
The estimated total number of mature individuals is less than 500 individuals (TSSC 2002i).
The largest known population of Mitchell's Rainforest Snail and largest remaining single area of habitat is in Stotts Island Nature Reserve in the Tweed River near Murwillumbah (NPWS 2001u; Stanisic 2000). A complex of smaller populations and habitat fragments has also been identified in remnant areas around Cumbebin Wetland at Byron Bay (Murphy 2002).
Stotts Island Nature Reserve has been declared critical habitat for the Mitchell's Rainforest Snail under the NSW Threatened Species Act 1995 (NSW NPWS 2001t). The Mitchell's Rainforest Snail population on Stotts Island faces a number of potential threats, including: accidental fire, feral animal introduction, weed invasion, and habitat disturbance. Declaration of the entire island as critical habitat provides greater scope for the exclusion of potential threats and the integrated management of this species (NSW NPWS 2001t).
Key habitat components for the species are a well-developed leaf litter layer (providing food, shelter and breeding sites) and an intact forest canopy (maintaining a moist microclimate and providing a source of leaf litter) (Murphy 2002; NSW NPWS 2001t).
Mitchell's Rainforest Snail is restricted to lowland subtropical rainforest and swamp sclerophyll forest with a rainforest understorey on alluvial soils with a basaltic influence (NSW NPWS 2001u; Stanisic 1998). It is apparently absent from other rainforest types in the area, such as littoral rainforest (Stanisic 1998). Between 1955 and 1995, Mitchell's Rainforest Snail was recorded at only two to three sites (Stotts Island and Wilsons River) (Stanisic 1998), despite the Queensland Museum extensively collecting for snail species in the littoral (coastal) rainforests of the area. This type of correlation with particular rainforest communities is a trait shared by 90% of eastern Australian land snail species (Stanisic 1994) and suggests a dependence on high moisture levels, low fire frequency and a well developed leaf litter layer (NSW NPWS 2001b).
Most of the sites where Mitchell's Rainforest Snail is known to survive are located on slightly elevated ground on the margins of coastal wetlands. This may be an artefact of land clearing patterns or indicate a real microhabitat preference (NSW NPWS 2001a). Breeding populations of Mitchell's Rainforest Snail can persist in narrow strips of remnant rainforest (Stanisic 1998), although the longer-term viability of populations at such sites is uncertain (NSW NPWS 2001t).
Microhabitat data for Mitchell's Rainforest Snail includes records of live animals found by day sheltering under palm fronds on the ground, inside dead palm frond stems, under leaf litter at the base of trees, and under bark in fig (Ficus spp.) trees (Stanisic 1998). There are also records of Mitchell's Rainforest Snail active at night on the surface of leaf litter (Murphy pers. obs. cited in NSW NPWS 2001t; Stanisic 2000). Stanisic (1998) concluded that Mitchell's Rainforest Snail is probably terrestrial and that juveniles are possibly arboreal (living in trees). The related Thersites novaehollandiae is active at night, foraging on the rainforest floor and up to six metres high on tree trunks being most obviously active on warm, wet nights (Murphy pers. obs. cited in NSW NPWS 2001t).
This species is hermaphroditic (NSW NPWS 2001u). Breeding behaviour has only been observed once, with a clutch of 70 eggs laid below the surface of leaf litter (Murphy pers. obs. cited in NSW NPWS 2001t). Eggs of Mitchell's Rainforest Snail are comparatively large, approximately 3 mm in diameter. The eggs are white and sub-circular with a leathery skin (Stanisic 2000). Juvenile individuals are probably arboreal rather than terrestrial (Stanisic 1998).
Little is known about the feeding habits of Mitchell's Rainforest Snail. It is known to be herbivorous and thought to feed on leaf litter, fungus and lichen (Stanisic 2000).
This species is mainly active at night, particularly during or following rain but no information is available on dispersal patterns or over what distances the species can move (NSW NPWS 2001t).
Mitchell's Rainforest Snail can be easily confused with other land snail species which also occur on the coastal plain of north-eastern New South Wales, such as the common Fraser's Snail (Sphaerospira fraseri). Fraser's Snail can be differentiated by its cream to brown coloured shell, with numerous fine stripes, a rounded profile and a circular, rather than angular, opening (NSW NPWS 2001t).
Guidelines for research involving the collection of threatened land snails have been developed by the National Parks and Wildlife Service in consultation with professional malacologists (NSW NPWS 2001a). These guidelines are designed to assist those required to prepare or review assessments of likely impacts on Mitchell's Rainforest Snail, and include information concerning field survey methods, habitat assessment, and consideration of significance of likely impacts on the species (NSW NPWS 2001a; Murphy 2002).
NSW NPWS recommends that any bush remnant containing lowland subtropical rainforest in particular, but also other lowland moist forest communities, in the NSW north coast area be considered as potentially harbouring Mitchell's Rainforest Snail. This recommendation covers all areas, no matter how small or degraded they might appear, especially if there is any sort of leaf litter layer present (NSW NPWS 2001t).
The shell of Mitchell's Rainforest Snail can remain in the leaf litter for extended periods following the death of an animal. Current or previous presence of the species at a site can most easily be determined by searching for empty shells or shell fragments. Accumulation of shell material can sometimes be found around feeding sites (anvils) used by the Noisy Pitta (Pitta versicolor) (NSW NPWS 2001a). The presence of empty, especially fresh shells with an intact periostracum (colouring), should be treated as confirmation of the presence of living individuals (NSW NPWS 2001t). Searches for shell material can be undertaken year round.
Surveys to locate active live animals are best undertaken at night during warm, wet weather. Searches for live animals can also be be undertaken by day by identifying and investigating potential shelter sites such as fallen palm fronds, leaf litter and loose bark on tree trunks (NSW NPWS 2001a).
The minimum time required to search for shell material or live animals will depend on the size and amount of potential habitat present within the site being assessed. However, it is suggested that for small sites (less than 0.5 ha) at least three hours be spent searching and then scaled up appropriately for larger areas (NSW NPWS 2001a).
The major cause of the decline of Mitchell's Rainforest Snail is habitat destruction (NSW NPWS 2001a, Stanisic 2000). Mitchell's Rainforest Snail has been a consideration in a number of early 2000s development proposals, particularly in the Cumbebin Wetland/Suffolk Park area of Byron Shire, which is a significant area for the species. The occurrence of Mitchell's Rainforest Snail on development sites indicates that the loss of habitat continues to be a significant threat to the species (NSW NPWS 2001a). Land clearing for agriculture and urban development across the species' range has been extensive, and many of the small areas of surviving habitat remain at risk of clearing and development (NSW NPWS 2001a).
Lowland rainforest on floodplain in the NSW North Coast bioregion, including the habitat of Mitchell's Rainforest Snail, was listed as an Endangered ecological community under schedule 1 part 3 of the NSW Threatened Species Conservation Act 1995 in August 1999 (NSW Scientific Committee 1999).
Mitchell's Rainforest Snail is preyed upon by the Noisy Pitta (Pitta versicolor) in Stotts Island Nature Reserve (Stanisic 2000). This conclusion is based on the percentage of shells found with tell-tale Pitta damage. Pitta predation of land snails is a widespread natural occurrence among land snail populations throughout eastern Queensland (Stanisic 2000).
The majority of known remaining populations occur in small areas of remnant rainforest including narrow strips of rainforest bordering coastal wetlands. These small remnant areas are at risk from effects such as loss of moisture, habitat disturbance, frequent fire and invasion by exotic weeds and feral animals (NSW NPWS 2001t). Introduced Rats (Rattus spp.) are known to feed on land snails (Ponder & Chapman 1999; Sherley et al. 1998) and may prey on Mitchell's Rainforest Snail (NSW NPWS 2001u).
Disturbance of the litter zone would pose a serious threat to the species' survival. Increase in public usage of Stotts' Island would increase the risk of such disturbance (Stanisic 2000).
Several introduced weed species were recorded on the southern edges of the Stotts Island during a 2000 survey (Stanisic 2000). These weeds have the potential to considerably alter the quality of the ground strata and leaf litter, and consequently the living space and food sources of Mitchell's Rainforest Snail (Stanisic 2000). Increased public usage would exacerbate the spread of these weeds through the distribution of seeds and the trampling of native species. The presence of weed species needs to be carefully monitored and outbreaks effectively controlled (Stanisic 2000).
The effects of chemical pollution from agricultural chemicals on Thersites mitchellae may be significant however, there is no quantifiable information (Stanisic 2000).
Fire can have significant affects on the distribution of land snails through habitat destruction and habitat alteration (Stanisic 2000). The likelihood of fires in moist subtropical rainforest is less than that in sclerophyll and dry rainforest but fires in this vegetation type have occurred in the past (Stanisic 2000). During the survey in 2000 (Stanisic 2000), evidence of fire on the island (most likely through lightening strike) was observed. The threat of fire-related habitat destruction is likely to increase through any change in public usage of the island (Stanisic 2000).
The recovery plan (NSW NPWS 2001u) for this species proposed the following recovery actions:
1. Survey and research:
- survey on coastal plain to identify additional populations
- survey of foothills areas to determine if species occurs outside the coastal plain
- research into ecology and life cycle
- monitoring of populations to observe any change in status
- genetics research to examine level of variation between and within populations
- survey/research guidelines.
2. Protection of extant populations and habitat:
- advice to other agencies on the species' conservation requirements, location and potential habitat
- map potential habitat
- habitat protection
- critical habitat additional to Stotts Island Nature Reserve
- management measures aimed at controlling threats to the Snail at Stotts Island Nature Reserve
- weed control work.
3. Community awareness:
- prepare and distribute a community awareness brochure
- teacher's kit targeting schools in the Tweed, Byron and Ballina Shires
- high profile media publicity covering the Rainforest Snail's conservation and recovery
- community initiatives
- assist Australian Museum by providing up-to-date information for their internet web site.
Byron and Tweed Shire Councils completed shire-wide vegetation mapping projects, including mapping of lowland subtropical rainforest and swamp sclerophyll forest remnants. This information will assist with implementation of recovery actions for this species (NSW NPWS 2001a).
Stotts Island Nature Reserve is a significant area of known habitat (Stotts Island) for Mitchell's Rainforest Snail where the snail is afforded protection (NSW NPWS 2001b). Some additional areas of known habitat and potential habitat are afforded a level of protection through being within or in proximity to wetland areas identified under State Environmental Planning Policy (SEPP) No. 14 (Coastal Wetlands) and/or within environmental protection zones under the relevant Local Environmental Plans. SEPP No. 14 Coastal Wetlands of relevance or potential relevance comprise those between the Tweed and Richmond Rivers in northern NSW (NSW NPWS 2001a). Specific SEPP No. 14 Coastal Wetlands currently known to contain or be in close proximity to extant populations of Mitchell's Rainforest Snail are Wetland numbers 24 (Banora Point), 79, 80a and 81 (Byron Bay) and 87 (Lennox Head) (NSW NPWS 2001a). It is anticipated that populations of Mitchell's Rainforest Snail or areas of potential habitat will be found within or near additional SEPP No. 14 Coastal Wetlands through habitat mapping, scientific surveys and community awareness as outlined in the recovery plan for this species (NSW NPWS 2001a).
Management documentation relevant to the Mitchell's Rainforest Snail are at the start of the profile.
The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.
|Threat Class||Threatening Species||References|
|Agriculture and Aquaculture:Agriculture and Aquaculture:Land clearing, habitat fragmentation and/or habitat degradation||Mitchell's Rainforest Snail Thersites mitchellae recovery plan (NSW National Parks & Wildlife Service (NSW NPWS), 2001u) [Recovery Plan].|
|Climate Change and Severe Weather:Climate Change and Severe Weather:Climate change altering atmosphere/hydrosphere temperatures, rainfall patterns and/or frequency of severe weather events||Border Ranges Rainforest Biodiversity Management Plan - NSW & Queensland (NSW Department of Environment, Climate Change and Water (NSW DECCW), 2010n) [State Recovery Plan].|
|Climate Change and Severe Weather:Habitat Shifting and Alteration:Habitat loss, modification and/or degradation||Border Ranges Rainforest Biodiversity Management Plan - NSW & Queensland (NSW Department of Environment, Climate Change and Water (NSW DECCW), 2010n) [State Recovery Plan].|
|Climate Change and Severe Weather:Sea level rise:Inundation associated with climate change||Inundation study (Environmental Resources Information Network, 2007) [Database].|
|Ecosystem/Community Stresses:Indirect Ecosystem Effects:Loss and/or fragmentation of habitat and/or subpopulations||Border Ranges Rainforest Biodiversity Management Plan - NSW & Queensland (NSW Department of Environment, Climate Change and Water (NSW DECCW), 2010n) [State Recovery Plan].|
|Human Intrusions and Disturbance:Human Intrusions and Disturbance:Human induced disturbance due to unspecified activities|
|Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or habitat degradation by weeds|
|Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation by rats||Commonwealth Listing Advice on Thersites mitchellae (Mitchell's Rainforest Snail) (Threatened Species Scientific Committee, 2002i) [Listing Advice].|
|Invasive and Other Problematic Species and Genes:Invasive and Other Problematic Species and Genes:Predation, competition, habitat degradation and/or spread of pathogens by introduced species|
|Invasive and Other Problematic Species and Genes:Problematic Native Species:Competition and/or predation by birds||Commonwealth Listing Advice on Thersites mitchellae (Mitchell's Rainforest Snail) (Threatened Species Scientific Committee, 2002i) [Listing Advice].|
|Natural System Modifications:Fire and Fire Suppression:Inappropriate and/or changed fire regimes (frequency, timing, intensity)||Commonwealth Listing Advice on Thersites mitchellae (Mitchell's Rainforest Snail) (Threatened Species Scientific Committee, 2002i) [Listing Advice].|
|Residential and Commercial Development:Residential and Commercial Development:Habitat modification (clearance and degradation) due to urban development|
Australian Museum (2001). Threatened and endangered land snail species. Page(s) 2001. Australian Museum Invertebrate Zoology Internet site.
Bishop, M.J. (1978). A revision of the genus Thersites Pfeiffer (Pulmonata: Camaenidae). Journal of the Malacological Society of Australia. 4(1-2):9-21.
Masters, M. (2013). Personal Communication. Department of Sustainability, Environment, Water, Population and Communities.
Murphy, M.J. (2002). Mollusc conservation and the New South Wales Threatened Species Conservation Act 1995: the Recovery Program for Mitchell's Rainforest Snail Thersites mitchellae. Australian Zoologist. 32:1-11.
NSW National Parks & Wildlife Service (NSW NPWS) (2001u). Mitchell's Rainforest Snail Thersites mitchellae recovery plan. [Online]. NPWS Hurstville, NSW. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/recovery/t-mitchellae/index.html.
NSW National Parks and Wildlife Service (NSW NPWS) (2001t). Mitchell's Rainforest Snail in Stotts Island Nature Reserve - critical habitat declaration. [Online]. Available from: http://www.environment.nsw.gov.au/criticalhabitat/EastBanksiaScrubCriticalHabitatRec.htm.
NSW Scientific Committee (NSW SC) (1997). Mitchell's Rainforest Snail - endangered species listing - final determination. [Online]. Available from: http://www.environment.nsw.gov.au/determinations/MitchellsRainforestSnailEndSpListing.htm.
NSW Scientific Committee (NSW SC) (1999). Final determination to list Lowland Rainforest on Floodplain in the NSW North Coast Bioregion as an endangered ecological community on Schedule 1, Part 3 of the Threatened Species Conservation Act 1995.
Planit Consulting (2002). Survey for Land Snail Thersites mitchellae. Section 95(2) report to NSW NPWS.
Ponder, W. & R. Chapman (1999). Survey of the Land Snail Placostylus bivaricosus on Lord Howe Island. Unpublished report to New South Wales National Parks and Wildlife Service.
Sherley, G., I.A.N. Stringer, G.R. Parrish & I. Flux (1998). Demography of two land snail populations (Placostylus ambagiosus, Pulmonata, Bulimulidae) in relation to predator control in the far north of New Zealand. Biological Conservation. 84:83-88.
Stanisic, J. (1994). The distribution and patterns of species diversity of land snails in eastern Australia. Memoirs of the Queensland Museum. 36:207-214.
Stanisic, J. (1998). Survey for Land Snail Thersites Mitchellae in northern New South Wales. Unpublished report for the NSW National Parks and Wildlife Service.
Stanisic, J. (1999). Survey for Land Snail Thersites mitchellae in Northern New South Wales. II. Investigation of Wilsons Creek Locality. Report to NSW National Parks and Wildlife Service.
Stanisic, J. (2000). Survey for Land Snail Thersites Mitchellae in northern New South Wales III. Investigation of Stotts Island Locality. Unpublished report prepared for the NSW National Parks and Wildlife Service.
Threatened Species Scientific Committee (2002i). Commonwealth Listing Advice on Thersites mitchellae (Mitchell's Rainforest Snail). [Online]. Available from: http://www.environment.gov.au/biodiversity/threatened/species/thersites-mitchellae.html.
This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.
Citation: Department of the Environment (2014). Thersites mitchellae in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Sat, 15 Mar 2014 12:42:14 +1100.