Biodiversity

Species Profile and Threats Database


For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
 
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 Endangered as Placostylus bivaricosus
Listing and Conservation Advices Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
 
Recovery Plan Decision Recovery Plan required, included on the Commenced List (1/11/2009).
 
Adopted/Made Recovery Plans Lord Howe Island Biodiversity Management Plan (NSW Department of Environment and Climate Change (NSW DECC), 2007b) [Recovery Plan] as Placostylus bivaricosus.
 
Federal Register of
    Legislative Instruments
Inclusion of species in the list of threatened species under section 178 of the Environment Protection and Biodiversity Conservation Act 1999 (37) (26/10/2005) (Commonwealth of Australia, 2005b) [Legislative Instrument] as Placostylus bivaricosus.
 
State Government
    Documents and Websites
NSW:Lord Howe Placostylus Placostylus bivaricus (Gaskoin, 1855) Recovery Plan (New South Wales National Parks and Wildlife Service (NSW NPWS), 2001b) [State Recovery Plan].
NSW:Placostylus bivaricosus (a large land snail) -endangered species listing. NSW Scientific Committee - final determination (NSW Department of Environment, Climate Change and Water (NSW DECCW), 1997e) [Internet].
NSW:Lord Howe Island Placostylus - profile (NSW Department of Environment, Climate Change and Water (NSW DECCW), 2005jh) [Internet].
State Listing Status
NSW: Listed as Endangered (Threatened Species Conservation Act 1995 (New South Wales): December 2013) as Placostylus bivaricosus
Non-statutory Listing Status
IUCN: Listed as Critically Endangered (IUCN Red List of Threatened Species: 2011.2)
Scientific name Placostylus bivaricosus [66769]
Family Bulimulidae:Pulmonata:Gastropoda:Mollusca:Animalia
Species author (Gaskoin, 1855)
Infraspecies author  
Reference ANZECC Threatened Fauna List May 2000
Other names Placostylus cuniculinsulae [86782]
Placostylus bivaricosus bivaricosus [79106]
Placostylus bivaricosus cuniculinsulae [79107]
Placostylus bivaricosus etheridgei [79108]
Distribution map Species Distribution Map

This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.

Illustrations Google Images
http://www.amonline.net.au/invertebrates/mal/endangered/348402.htmhttp://www.femorale.com.br/shellphotos/detail.asp?species=Placostylus+bivaricosus+%28Gaskoin%2C+1854%29

Scientific name: Placostylus bivaricosus.

Common name: Lord Howe Flax Snail.

Other names: Lord Howe Placostylus.

Three subspecies of the Lord Howe Flax Snail are currently recognised on the basis of shell morphology (Australian Museum 2001); Placostylus bivaricosus bivaricosus, P. bivaricosus cuniculinsulae and P. bivaricosus etheridgei.

The Lord Howe Flax Snail is a large land snail. It has a pointed, conical shell up to 8 cm long, is medium to dark brown in colour (weathering to white in older specimens) and has a thickened lip in mature adults. The soft body parts are black (New South Wales National Parks and Wildlife Service 2006).

The Lord Howe Flax Snail is endemic to Lord Howe Island. The species was formerly widespread and common on the island, but has declined significantly in range (Brazier 1889; Smithers et al. 1977; Sutherland & Ritchie 1977). The species is currently restricted to two fragmented locations (comprising a total of 26 sites) in the Settlement area and around North Bay (Ponder & Chapman 1999).

Placostylus bivaricocus bivaricosus was formerly common over the northern end of Lord Howe Island, from sea level to about 200 metres (the top of Malabar Hill). P. bivaricosus cuniculinsulae occurred on Blackburn (Rabbit) Island in the lagoon. However, this subspecies is presumed extinct as no specimens have been collected there for over a century (Australian Museum 2001). P. bivaricosus etheridgei occurred in the mountains at the southern end of Lord Howe Island, including the Erskine Valley, to an altitude of 350 metres and is thought to persist in lower densities (NSW National Parks & Wildlife Service 2001a).

The extent of occurrence of the Lord Howe Flax Snail is less than 15.2 km² and the current area of occupancy for the species is approximately 8 km² (Ponder & Chapman 1999).

The total population of the Lord Howe Flax Snail is estimated to be less than 1000 mature individuals. The abundance of dead snail shells provide an indication of the historical widespread abundance of the Lord Howe Flax Snail in the mid-island lowlands. In some areas, shells occur in densities of up to 30 shells/m² in many parts of the Settlement area (Ponder & Chapman 1999).

P. bivaricosus etheridgei has declined in range and abundance. It may survive as a number of small, isolated local populations, based on the identification of hatchling snails collected from leaf litter in the 1970s (Ponder & Chapman 1999).

Given the persistent threats to the species, it is suspected the Lord Howe Flax Snail will continue to undergo a reduction in numbers.

The two populations of the Lord Howe Flax Snail are included in Permanent Park Preserve and Environment Protection areas (Lord Howe Island Board 1986). However, the majority of recent records are outside the island's formal reserve system, with many occurring in the Settlement area where they may be at risk from development (NSW NPWS 2001a).

Brazier (1889) noted that the Lord Howe Flax Snail was abundant under cover in shady, damp situations and on scrubby calcarenite (chalky) hillsides, was sparingly represented at higher altitudes and appeared to avoid open areas.

Ponder & Chapman (1999) found the species sheltering under leaf litter in forest often, but not exclusively, in the vicinity of Banyan trees (Ficus columnaris) and mostly on calcarenite-derived soils and sandy soils. The vegetation at all sites where recent observations have been made is either Kentia Palm (Howea fosteriana) closed-forest or Greybark (Drypetes australasica) - Blackbutt (Cryptocarya triplinervis) closed-forest or a combination of the two (Curtis 1998; Pickard 1983; Ponder & Chapman 1999).

The age of sexual maturity and lifespan of the Lord Howe Flax Snail are unclear, but related Placostylus species in New Zealand reach sexual maturity at three to five years and may live for 20 years or more (Parrish et al. 1995).

The Lord Howe Flax Snail lays small clutches of round eggs in the soil beneath leaf litter, probably during late spring and summer. The eggs hatch into small-shelled snails about 7 mm in length and 5 mm in width. Hatchling and juvenile mortality is high (Ponder & Chapman 1999).

The Lord Howe Flax Snail is believed to feed on the fallen dead leaves of broadleaf trees (Ponder & Chapman 1999).

Adult Lord Howe Flax Snails are readily identifiable due to their large size and pointed, conical shell. However, juvenile snails may be easily confused with other species and generally require expert identification.

Any area supporting evergreen closed-forest on sandy or calcarenite-derived soils on Lord Howe Island should be considered potential habitat for this species, particularly where there is a cover of leaf litter. The presence of the species at a site can most easily be determined by searching for empty shells or shell fragments. The presence of empty shells, particularly fresh shells with an intact periostracum (colouring) should be treated as indicating the likely presence of living individuals. Searches for shells can be undertaken year round. However, surveys to locate active, live animals are best undertaken at night during warm, wet weather. Live animals can also be found during the day by searching in the leaf litter. Search effort will vary according to the size and amount of potential habitat being surveyed. It is suggested that, for small sites (less than 0.5 hectares) at least three hours be spent searching (NSW National Parks & Wildlife Service 2001a).

Access to sites should be by foot to avoid any unnecessary damage to their habitat. Rocks, logs and other potential refuge sites are to be returned to their original position immediately after searching. No repeat collections from populations sampled within five years should be conducted, unless it is part of a specific program approved by the National Parks and Wildlife Service (NSW National Parks & Wildlife Service 2001a).

The main threats to the Lord Howe Flax Snail are the clearing and modification of habitat for development and predation and habitat disturbance by exotic animals (predominantly the Black Rat (Rattus rattus) possibly the Common Blackbird (Turdus merula) and the Song Thrush (Turdus philomelos). Other potential threats include herbicide and pesticide use (including the use of snail baits for introduced European snails and slugs), invasion of habitat by exotic weeds, and trampling and habitat disturbance by domestic stock and poultry (NSW National Parks & Wildlife Service 2001a).

Habitat clearing

Historic habitat clearing would have had a substantial impact on the Lord Howe Flax Snail during establishment of the Settlement area, rural grazing areas and palm plantations (Ponder & Chapman 1999). An assessment of potential habitat for the species indicated that nearly 50% of high quality, potential habitat for the species has been cleared since settlement of the island. The clearing of native forest on Lord Howe Island is now controlled and has largely ceased (Lord Howe Island Board 1986), although it may still be an issue at a smaller scale with respect to development and landscaping works in the Settlement area.

Invasive species

The Black Rat was accidentally introduced to Lord Howe Island in 1918, and became prolific across the island by 1930 (Billing 1999). Within 25 years of their arrival, the Lord Howe Flax Snail was in noticeable decline (Iredale 1944). The Black Rat preys extensively on this species, particularly on juvenile snails, and are considered a significant threat to its survival (Ponder & Chapman 1999). Predation by the Black Rat on Lord Howe Island was listed as a key threatening process under the Threatened Species Conservation Act 1995 (NSW) in 2000.

New Zealand Placostylus species are preyed upon by the introduced Song Thrush and Common Blackbird (Parrish et al. 1995; Sherley et al. 1998), so it is likely that they would also prey upon the Lord Howe species. Both of these bird species had colonised Lord Howe Island by 1953 (Hutton 1991). Local island residents have observed these bird species preying upon the Lord Howe Flax Snail (G. Wilson Lord Howe Island Board 2001, personal communciation).

The feral Pig (Sus scrofa) and the Goat (Capra hircus) were established on Lord Howe Island by 1851 (Pickard 1983). Predation and habitat disturbance by the Pig and habitat disturbance by the Goat were considered serious threats to the species survival (Smithers et al. 1977). However, the Pig has been successfully eradicated from the island and eradication of the Goat commenced in 1999.

Other threats

Ponder and Chapman (1999) identified habitat disturbance and trampling of snails by domestic cattle, and habitat disturbance and predation of eggs and hatchlings by domestic fowl, as possible localised threats to the Lord Howe Flax Snail.

Introduced weeds such as exotic grasses, Asparagus Fern (Asparagus spp.), Guava (Psidium spp.) and Crofton Weed (Ageratina adenophora), are invading some areas of Lord Howe Flax Snail habitat. The potential effect of these species on habitat suitability for the snail is unknown but is likely to be adverse (Ponder & Chapman 1999).

The potential effect of herbicides on the Lord Howe Flax Snail is unknown. Snail baits, used by local residents to control the introduced Garden Snail (Cantareus aspersus) are likely to be fatal to the species.

The Lord Howe Flax Snail does not seal the shell opening (aperture) with a mucous seal during dry conditions, as the introduced Garden Snail does and is, therefore, prone to desiccation (Sherley 1994). Large juveniles and adults may gain some protection from desiccation by pushing the front of their shell shallowly into the soil to cover the aperture (Sherley et al. 1998). The shells of recently deceased Lord Howe Flax Snails were noted in areas where the forest canopy had been damaged by drought or storms, allowing higher light penetration and, therefore, a hotter, drier microclimate (Ponder & Chapman 1999).

The Lord Howe Island Biodiversity Management Plan (NSW DECC 2007b) identifies a number of actions taken from the Lord Howe Placostylus (Placostylus bivaricosus) Recovery Plan (NSW National Parks & Wildlife Service 2001a), which have already been completed, including:

  • mapping potential habitat for the species across Lord Howe Island;
  • carrying out ongoing Black Rat control in areas of known Lord Howe Flax Snail habitat;
  • carrying out surveys to improve knowledge of population numbers and behaviour of the species; and
  • carrying out regeneration of suitable habitat on Blackburn Island.

The Lord Howe Island Biodiversity Management Plan (NSW DECC 2007b) also identifies further actions, which are yet to commence or have commenced but are not yet completed, including:

  • studying the impact of the Blackbird and the Song Thrush on the Lord Howe Flax Snail and investigate the feasibility of eradicating these bird species from Lord Howe Island;
  • supporting further research on the threats to the species and assess the success of actions to control these agents;
  • supporting research into the genetics of the Lord Howe Flax Snail; and
  • preparing and distribute educational brochures and erect signage to inform the local community and tourists about the species.

A captive breeding program for the Lord Howe Flax Snail has commenced, which engages the help of the local school on Lord Howe Island. The program involves the construction of a number of rat-proof pens, which are provided with shade and appropriate leaf litter, in which breeding populations of the Lord Howe Flax Snail may be established and maintained. Adult snails reared in the program are released back into natural populations to maintain genetic diversity (Ponder & Chapman 1999).

Documents relevant to the management of the Lord Howe Flax Snail can be found 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:Livestock Farming and Grazing:Habitat alteration (vegetation, soil, hydrology) due to trampling and grazing by livestock Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Climate Change and Severe Weather:Habitat Shifting and Alteration:Habitat loss, modification and/or degradation Lord Howe Island Biodiversity Management Plan (NSW Department of Environment and Climate Change (NSW DECC), 2007f) [State Recovery Plan].
Ecosystem/Community Stresses:Indirect Ecosystem Effects:Loss and/or fragmentation of habitat and/or subpopulations Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Ecosystem/Community Stresses:Indirect Ecosystem Effects:Restricted geographical distribution (area of occupancy and extent of occurrence) Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or habitat degradation by weeds Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation Rattus rattus (Black Rat, Ship Rat) Lord Howe Island Biodiversity Management Plan (NSW Department of Environment and Climate Change (NSW DECC), 2007f) [State Recovery Plan].
Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation by birds Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition, predation and/or habitat degradation Turdus merula (Common Blackbird, Eurasian Blackbird) Lord Howe Island Biodiversity Management Plan (NSW Department of Environment and Climate Change (NSW DECC), 2007f) [State Recovery Plan].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition, predation and/or habitat degradation Turdus philomelos (Song Thrush) Lord Howe Island Biodiversity Management Plan (NSW Department of Environment and Climate Change (NSW DECC), 2007f) [State Recovery Plan].
Invasive and Other Problematic Species and Genes:Invasive and Other Problematic Species and Genes:Slashing and herbicide application for weed control Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Invasive and Other Problematic Species and Genes:Invasive and Other Problematic Species and Genes:pest animal control Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Residential and Commercial Development:Housing and Urban Areas:unspecified Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].
Species Stresses:Indirect Species Effects:Low numbers of individuals Commonwealth Listing Advice on Lord Howe Placostylus (Placostylus bivaricosus) (Threatened Species Scientific Committee, 2005bq) [Listing Advice].

Australian Museum (2001). Threatened and endangered land snail species. Page(s) 2001. Australian Museum Invertebrate Zoology Internet site.

Billing, J. (1999). The management of introduced rodents on Lord Howe Island. Unpublished report by Lord Howe Island Board.

Brazier, J. (1889). Mollusca. The general zoology of Lord Howe Island; containing an account of the collections made by the Australian Museum collecting party, Aug.-Sept., 1887. Etheridge, R., ed. Memoirs of the Australian Museum. 2:3-42.

Curtis, H.S. (1998a). Snail collection - Lord Howe Island. Unpublished report to Lord Howe Island Board.

Hutton, I. (1991). Birds of Lord Howe Island: Past and Present. Coffs Harbour, NSW: author published.

Iredale, T. (1944). The Land Mollusca of Lord Howe Island. Australian Zoologist. 10(3):299-330.

Lord Howe Island Board (1986). Lord Howe Island Regional Environmental Plan 1986.

New South Wales National Parks and Wildlife Service (NSW NPWS) (2001a). Lord Howe Placostylus Placostylus bivaricosus (Gaskoin 1855) Recovery Plan. Hurstville, New South Wales: New South Wales National Parks and Wildlife Service.

NSW Department of Environment and Climate Change (NSW DECC) (2007b). Lord Howe Island Biodiversity Management Plan. [Online]. Sydney, NSW: NSW Department of Environment and Climate Change. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/recovery/lord-howe/index.html.

Parrish, R., G. Sherley & M. Aviss (1995). Giant Land Snail Recovery Plan Placostylus spp., Paraphanta sp. Threatened Species Recovery Plan Series No. 13. New Zealand: Threatened Species Unit, Department of Conservation.

Pickard, J. (1983). Vegetation of Lord Howe Island. Cunninghamia. 1:133-265.

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. (1994). Translocations of the Mahoenui Giant Weta Deinacrida n. sp. and Placostylus land snails in New Zealand: what we have learnt?. In: Reintroduction Biology of Australian and New Zealand Fauna. Serena, M:57-63. Surrey Beatty and Sons, Chipping Norton, New South Wales.

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.

Smithers, C., D. McAlpine, P. Colman & M. Gray (1977). Lord Howe Island. Special Issue of Australian Natural History. Page(s) 23-26. Sydney: The Australian Museum.

Sutherland, L. & A. Ritchie (1977). Defunct volcanoes and extinct horned turtles. In: Smith, N., ed. Lord Howe Island. Page(s) 7-12. Australian Museum, Sydney.

Wilson, G. (2001). Personal communication.

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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). Placostylus bivaricosus in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Fri, 18 Apr 2014 22:47:20 +1000.