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Mt Lesueur Shield-backed Trapdoor Spider (Idiosoma gardneri)

The Mt Lesueur shield-backed trapdoor spider, Idiosoma gardneri, is a poorly known Western Australian spider described in a taxonomic revision of the Idiosoma nigrum-group. It is known from very few records, so site checks and careful soil-disturbance practices are appropriate. It is a DBCA Priority 2 species in Western Australia.

Conservation status

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

Seasonal considerations

Species-specific activity, breeding and movement months are unknown. Plan surveys and clearance around project requirements rather than assuming a season is low risk.

Known timing: No seasonal timing has been recorded for this species.

Planning: Arrange survey and avoidance measures before disturbance. The row below is a planning prompt, not a biological season.

No species-specific seasonal information has been found.

  • Survey and clearance planning: Planning window only. Species activity and breeding timing are unknown, so complete checks before works and do not infer that any month is free of risk.

Identification: Appearance and size

Identification information for this species is limited. Confirm suspected records with a suitably experienced spider taxonomist.

Idiosoma gardneri is a shield-backed trapdoor spider in the nigrum-group. No body size or field description sufficient for reliable identification has been recorded.

The taxonomic paper describes enlarged, hardened third abdominal sigilla as a feature of shield-backed spiders in this group. This group-level feature is not sufficient on its own to identify I. gardneri.

Identification: Similar species and field signs

Other Idiosoma species occur in Western Australia, but no field comparison reliably separates I. gardneri from them.

No species-specific burrow or other field sign has been described. As general trapdoor-spider survey practice, inspect the soil surface carefully for possible burrow entrances. Treat any sign as unconfirmed until assessed by an expert.

Distribution: Known range

The known distribution is very poorly documented and may not represent the full range.

Atlas of Living Australia records show one Western Australian record at one distinct 0.1-degree location, with coordinates rounded to latitude -30.1 and longitude 115.2. Records outside Western Australia are excluded as likely errors.

The taxonomic paper reports that the species was known from a single specimen collected in 1989. It is not known whether additional records have since been made.

Distribution: WA regions

The DBCA priority list does not specify a region for this species. The DBCA common name refers to Mt Lesueur, but no fuller named locality is given.

Habitat: Habitat evidence

Species-specific habitat information has not been documented.

The vegetation, soils, landform, moisture conditions and disturbance history at occupied sites have not been described. Do not infer habitat requirements from the species' common name or from information about other Idiosoma.

Habitat: Site assessment

For project planning, treat suitable habitat as unknown until a site assessment has been completed. Record soil and vegetation conditions at any suspected detection without presenting them as established species preferences.

Foraging habitat: Foraging information

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

No prey types, foraging distances, activity periods or foraging microhabitats are recorded for I. gardneri. Do not transfer diet or behaviour descriptions from other species to this taxon.

Foraging habitat: Precaution on site

As general practice for ground-dwelling spiders, avoid unnecessary soil disturbance in areas being assessed. Record observations of prey, webs or burrow-associated signs as unconfirmed context rather than species-specific evidence.

Breeding habitat: Breeding information

Breeding habitat and reproductive timing have not been documented.

The species' breeding location, reproductive timing and number of eggs or young are unknown.

Breeding habitat: Precaution

Do not schedule disturbance on the assumption that a particular season is free of breeding activity. Where possible, complete surveys and protective planning before ground works begin.

Sheltering habitat: Shelter information

Shelter locations and burrow characteristics have not been documented for I. gardneri.

Burrow structure, depth, entrance features and use of alternative shelter are unknown.

Sheltering habitat: General search practice

As general practice when surveying for trapdoor spiders, examine the ground surface and soil carefully for possible burrow openings and associated signs. Do not excavate or open suspected burrows to confirm occupancy.

Threats: Known pressures

Threats specific to this species have not been identified.

The taxonomic paper notes the conservation significance of the Idiosoma nigrum-group generally, but does not identify or assess particular threats to I. gardneri.

Threats: Works-site implications

Because the species is known from very few records, do not assume it is absent because no detections have been made. Treat unassessed ground disturbance as a potential risk and apply the project's fauna and clearing controls.

Survey methodology: 1. Desktop assessment

The species' detectability and effective survey methods are not established. Survey design should account for this uncertainty.

Check current DBCA information and occurrence records before works. Atlas of Living Australia records show one record at one Western Australian 0.1-degree location, while the taxonomic paper reports a single specimen collected in 1989.

Survey methodology: 2. Ground inspection

As general trapdoor-spider survey practice, walk the proposed disturbance area systematically and inspect the soil surface for possible burrow entrances. Record the search area, conditions, effort and any signs. This method has not been validated for detecting I. gardneri.

Survey methodology: 3. Identification and records

Photograph and accurately map suspected signs or specimens where this can be done without harm. Seek expert identification and follow relevant permits and handling requirements. Record non-detections alongside survey effort and limitations.

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. Set out controls

Plan for uncertainty because the species' habitat and detectability are not documented.

Ensure clearing crews know the species' name, its Priority 2 status and the limits of current distribution information. Mark approved disturbance boundaries clearly and brief crews to stop work if a suspected spider or burrow is found.

Before habitat disturbance: 2. Survey and avoid

Arrange a suitably qualified fauna survey before ground disturbance where required by project approvals or risk assessment. Avoid disturbing suspected burrows and retain undisturbed ground around detections while advice is obtained.

During habitat disturbance: 1. Work to limits

Use staged, controlled works and respond cautiously to any suspected detection.

Keep machinery and personnel within approved disturbance areas. Use the project's standard fauna spotter-catcher controls and avoid unnecessary soil stripping or compaction outside those limits.

During habitat disturbance: 2. Stop and assess

If a suspected spider or possible burrow is found, stop work in the immediate area, protect the location from further disturbance and notify the environmental lead or fauna spotter-catcher. Do not excavate, damage or relocate a suspected burrow without expert direction and any required approvals.

During habitat disturbance: 3. Record the event

Document the location, date, photographs, work activity and action taken. Seek expert confirmation before recording the detection as I. gardneri.

After habitat disturbance: 1. Review and report

After works, retain records and follow through on any detection or avoidance commitments.

Provide survey and incident records to the project environmental lead and relevant agencies where required. Clearly distinguish confirmed identifications from unverified signs and include survey effort and limitations.

After habitat disturbance: 2. Maintain protected areas

Keep any agreed exclusion areas intact and check that barriers, signs and access controls remain effective. Do not disturb suspected shelter sites during clean-up or follow-up works.

Rehabilitation actions: 1. Restore site conditions

The species' rehabilitation requirements are not documented.

Where rehabilitation is required, follow the approved site plan. Avoid introducing unverified habitat features or moving soil from suspected occupied areas. Record the materials and methods used.

Rehabilitation actions: 2. Monitor and adapt

If a detection was made, seek advice from a suitably qualified ecologist on appropriate follow-up checks. General rehabilitation success does not demonstrate that the species has recolonised or persisted without targeted assessment.

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