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Ninety Seven Mile Creek Camaenid Land Snail (Westraltrachia subtila)

Westraltrachia subtila is an air-breathing land snail in the family Camaenidae, endemic to Australia. Western Australian records are from the Kimberley, but its habitat and ecology are poorly known. It is classified as DBCA Priority 2, a priority category rather than a listing under the Biodiversity Conservation Act 2016. Works near records should use a precautionary approach.

Conservation status

Western Australia, WA Threatened and Priority Fauna List: Priority 2.

Seasonal planning

Species-specific seasonal information is not known. Use year-round precautionary planning rather than assuming a period of low activity.

Seasonality: Activity, breeding and detectability by season have not been documented for this species.

Month values indicate a general planning window, not known activity or breeding months for this species.

  • Survey and works precautions: Year-round planning window only. No species-specific seasonal activity or breeding period is known.

Identification: Appearance and size

The species is identified taxonomically, but field identification details are limited.

Westraltrachia subtila is an air-breathing terrestrial gastropod in the family Camaenidae. Shell form, colour, dimensions and other diagnostic features have not been described.

Identification: Similar species

There is no comparison with similar species or field key. Other Westraltrachia species are recorded in the region, so do not identify this snail from genus or location alone.

Identification: Field signs

No species-specific field signs are known. As general land-snail practice, crews may encounter live snails or empty shells during careful searches of ground-level material. These signs require expert identification.

Distribution: Known range

Known records indicate a restricted and poorly documented Western Australian distribution.

The species is endemic to Australia. Atlas of Living Australia records show six Western Australian records at three distinct 0.1-degree locations, between latitude -17.8 and -17.6 and longitude 125.1 and 125.2. Records outside Western Australia were excluded as likely errors.

Distribution: Western Australian region

The DBCA priority list flags the Kimberley region. The DBCA common name refers to Ninety Seven Mile Creek, and a fauna survey for the Napier Downs Irrigation Project lists the species as confirmed. Precise site coordinates are not available for either named place.

Distribution: Record limitations

The small number of records does not show that the species is absent elsewhere. Its distribution is poorly known, consistent with its DBCA Priority 2 category.

Habitat: Known habitat

Specific habitat preferences have not been documented.

Westraltrachia subtila is a terrestrial land snail, but the vegetation, landform, soil and ground conditions at its records have not been described.

Habitat: Site assessment

Do not assume that a particular vegetation type or ground feature is suitable or unsuitable. At or near records, assess and document the range of ground-level conditions before clearing.

Foraging habitat: Diet and foraging

The species' diet and foraging locations have not been documented.

Food items, feeding behaviour and foraging habitat are unknown. Do not infer a diet from the species' family.

Foraging habitat: Precaution during searches

As general land-snail survey practice, inspect ground-level material carefully and avoid unnecessarily moving or damaging it. Treat any live snail or shell found as a potential record until an appropriately qualified person has assessed it.

Breeding habitat: Breeding information

Breeding biology and breeding habitat are poorly known.

The breeding season, egg-laying site, clutch size, development period and other reproductive details have not been documented.

Breeding habitat: Works planning

Do not schedule clearing on the assumption that any particular month is outside a breeding period. Apply the same precautionary checks throughout the year unless reliable species-specific information becomes available.

Sheltering habitat: Known shelter

Taxon-specific sheltering behaviour and refuges have not been documented.

Where Westraltrachia subtila rests, shelters or aestivates, and whether it uses particular ground features, are unknown.

Sheltering habitat: General search practice

For land-snail searches generally, look carefully around ground-level cover and sheltered microsites without assuming the species uses them. Return moved natural material to its original position where this can be done safely.

Threats: Known threats

Specific threats to this species have not been identified.

No species-specific threat assessment is available. The Priority 2 category indicates that the species is poorly known and known from few locations.

Threats: Development precautions

As a general precaution for land snails, clearing could harm individuals or ground-level features they use. Avoid unnecessary disturbance around known records and retain suitable undisturbed areas where practicable, without assuming any particular feature is confirmed habitat.

Survey methodology: 1. Desktop assessment

No species-specific survey method or detectability information is known. Use a documented, cautious approach and seek expert identification.

Check DBCA records, project records and available spatial data for known Kimberley records and the named localities Ninety Seven Mile Creek and Napier Downs. Confirm the search area and record any limits in coverage.

Survey methodology: 2. Field inspection

As general land-snail survey practice, inspect the ground carefully for live snails and shells, including among ground-level cover. Record the search area, conditions, effort and locations of findings. No season or method is known to ensure detection of this species.

Survey methodology: 3. Identification and records

Photograph findings in place where possible and obtain expert identification before assigning them to Westraltrachia subtila. Record coordinates, date, observer, evidence type and the extent of the search; do not collect specimens unless authorised.

Vegetation associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific vegetation association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Ecosystem associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific ecosystem association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Soil and substrate associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific soil association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Water and wetland associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific water association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Fauna records and mapped habitat: Not yet analysed

Record locations can be overlaid with mapping, but record frequency alone does not measure habitat preference. No species is excluded from desktop assessments by this analysis.

No quality-controlled record-to-map analysis has been completed for this species. The existing generalised distribution dots and indicative range polygons have not been treated as precise occurrence coordinates.

A defensible run needs dated, independently attributable records, coordinate uncertainty, duplicate and captive-record checks, layer versions and regional scope. Preference and absence require additional survey-effort and detection evidence.

Habitat limitations and contrary evidence: No supported exclusion recorded

Not recorded is not the same as cannot occur. Low suitability, resident habitat, breeding habitat and occasional movement are different conclusions.

This library has not established a vegetation, ecosystem or soil-type exclusion for this species. This does not mean all habitat is suitable; the evidence needed to justify an exclusion has not been assembled.

Habitat limitations and contrary evidence: Before using a negative association

  • Confirm the taxon, geographic region, life stage and habitat function covered by the evidence.
  • Check survey methods, season, repeated effort and detectability before interpreting non-detection.
  • Investigate credible contradictory records and microhabitats absent from broad mapping.
  • Do not convert a missing map class, low record count or failed data request into species absence.

Before habitat disturbance: 1. Check records and constraints

Records are few and habitat requirements are unknown, so plan works to avoid unassessed disturbance near records.

Review known species records and survey results with the project ecologist and relevant DBCA contacts. Confirm whether proposed clearing overlaps a record or nearby ground that has not been adequately checked.

Before habitat disturbance: 2. Survey and brief crews

Arrange a suitably timed and scoped pre-disturbance inspection by a qualified person, recognising that no species-specific survey season is known. Mark no-go areas, agree a stop-work and reporting process, and brief clearing crews on the possibility of live snails or shells.

During habitat disturbance: 1. Control clearing

Use staged, supervised work near records and respond cautiously to any potential find.

Keep disturbance within approved limits and retain marked exclusion areas. Use a fauna spotter catcher or ecologist to inspect the active work area and ground-level material where practicable.

During habitat disturbance: 2. Respond to a find

If a possible live snail or shell is found, pause work in the immediate area, protect the find from further disturbance and notify the project ecologist. Photograph and record it, and obtain identification and direction before work resumes. Do not handle or relocate it unless authorised and guided by an appropriately qualified person.

After habitat disturbance: 1. Report and review

Maintain records and use findings to review the remaining works and site controls.

Document search effort, observations, any specimens or shells, identification outcomes and areas disturbed or retained. Report confirmed or suspected records through the project and relevant regulatory processes.

After habitat disturbance: 2. Update controls

Review exclusion areas and work methods if a potential or confirmed record is found. Keep undisturbed areas protected and communicate any revised controls to all crews before work continues.

Rehabilitation actions: 1. Restore disturbed ground

No species-specific rehabilitation requirements are known, so restoration should avoid assumptions about habitat.

Where rehabilitation is required, follow the approved site plan and reinstate ground surfaces and retained natural material as practicable. Avoid introducing materials or making changes beyond the approved rehabilitation design.

Rehabilitation actions: 2. Monitor and adapt

Record rehabilitation works and any subsequent snail observations. Describe the site as suitable habitat or successful species habitat only when supported by appropriate survey and ecological assessment.

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