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Dandaragan Plateau Shield-backed Trapdoor Spider (Idiosoma dandaragan)

The Dandaragan Plateau shield-backed trapdoor spider is a Western Australian mygalomorph spider known from the eastern margin of the Dandaragan Plateau. Its burrow-based shelter and poorly known ecology make careful checks important before ground disturbance. It is listed as DBCA Priority 2, not as threatened under the information provided.

Conservation status

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

Seasonal planning

Seasonal activity and survey-detection patterns are not known for this species. Plan checks around the project programme and site conditions rather than assuming a species-specific season.

Seasonal activity: Not recorded.

Survey timing: No species-specific survey months are known.

The planning row is not a claim about the spider’s seasonal activity or detectability.

  • Survey and works planning: Planning prompt only: seasonal activity is not known. Arrange checks before disturbance whenever potential habitat or suspected burrows may be affected.

Identification: Appearance and size

The species is a shield-backed trapdoor spider, but field-level identification details are limited.

It is a mygalomorph spider in the shield-backed trapdoor spider group. Its appearance and body size have not been described in detail.

  • Do not identify the species from size or colour, as those details are not known.

Identification: Similar species

The Moora assessment describes Idiosoma clypeatum as closely related to I. dandaragan. Field characters to distinguish the two species are not described.

  • Seek expert confirmation where identification affects a development decision.

Identification: Field signs

Burrows were among the signs sought in a targeted survey for this species. A distinctive burrow shape, door or other diagnostic field sign has not been described.

  • Record the position and condition of any suspected burrow and avoid treating an unverified burrow as a confirmed species record.

Distribution: Known range

The documented range is in south-western Western Australia, along the eastern margin of the Dandaragan Plateau.

The reported range extends from near New Norcia in the south north to at least Watheroo National Park. A 2026 paper reports a substantial range extension for the species, but does not name the new localities.

Distribution: WA regions

The DBCA priority list flags the Midwest, Wheatbelt and Swan regions. The species is Priority 2, meaning it is poorly known and known from few locations, with some locations on conservation lands. This is a DBCA priority category, not a listing under the Biodiversity Conservation Act 2016.

  • No national listing is recorded.

Distribution: Records and limits

Atlas of Living Australia records show 13 Western Australian records at six distinct 0.1-degree locations, between latitudes -31 and -30.2 and longitudes 116 and 116.3. Records outside Western Australia were excluded as likely errors.

  • These record counts and coordinate bounds do not provide precise site locations.

Habitat: Documented habitat context

Potential habitat and survey-site conditions are described, but the species’ habitat preferences are not fully known.

A clearing assessment considered a site near Moora to contain suitable potential habitat. The project area included remnant native vegetation, but the assessment did not establish that the spider was present there.

Habitat: Habitat condition

At the Moora survey area, minor earthworks and rabbit diggings had disturbed parts of the site and were reported to have degraded potential habitat. Preferred soil, vegetation structure and moisture conditions are not known.

Habitat: Limits of knowledge

Habitat requirements are poorly known. Do not assume that all remnant vegetation, or only undisturbed vegetation, is suitable or unsuitable.

Foraging habitat: Diet and foraging

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

No prey, feeding behaviour or foraging habitat has been recorded for I. dandaragan.

Foraging habitat: Precaution on site

Do not infer that a burrow or nearby ground is unimportant because no feeding activity is observed. The species’ foraging ecology is not known.

Breeding habitat: Known information

Breeding biology and breeding habitat are poorly known.

Information on breeding season, mating, egg laying, young and breeding-site requirements is not available.

Breeding habitat: Work planning

Do not schedule works around an assumed breeding season. If suspected burrows are found, seek site-specific ecological advice before disturbance.

Sheltering habitat: Burrow evidence

Burrows are a relevant search target, although their structure and use by this species are not described in detail.

A targeted survey included searches for individuals and evidence of burrows. Whether burrows have a particular form or how deep they extend is not known.

Sheltering habitat: Protective approach

Treat suspected burrows as potentially occupied until assessed. Avoid probing, excavating or blocking them during routine site checks.

Threats: Habitat disturbance

Land disturbance and clearing are relevant considerations, but the species’ threats are not fully assessed.

At the Moora site, earthworks and rabbit diggings were reported to have degraded potential habitat. The clearing assessment considered whether the proposed works would affect habitat and noted that nearby suitable habitat would remain.

Threats: Landscape context

The 2018 revision discusses population decline and local extinction in severely fragmented landscapes as concerns for the Idiosoma nigrum-group. This is group-level context, not a complete, species-specific account of threats to I. dandaragan.

Threats: Status distinction

Survey methodology: 1. Desktop assessment

A targeted survey at the Moora project area used active searches, including searches of soil and leaf litter, and found no individuals or burrow evidence.

Review current species records, the proposed disturbance footprint and nearby remnant vegetation. Check whether records are precise enough to inform site planning; broad coordinate summaries do not identify exact burrow locations.

Survey methodology: 2. Field searches

The 2020 targeted survey used active searches of soil and leaf litter and looked for individuals and burrow evidence. Use careful, non-destructive searches and record search coverage, site condition and any suspected signs.

Survey methodology: 3. Interpret results

No individuals or burrow evidence were found in the Moora survey area, which had disturbed areas. A negative search at one site does not establish that the species is absent elsewhere or that all potential habitat has been checked.

Survey methodology: 4. Escalate uncertainty

The species’ ecology is poorly known, and no detection season is stated. If suitable potential habitat or suspected burrows occur within the disturbance footprint, consult a suitably experienced invertebrate ecologist before works.

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. Review the footprint

Plan works to avoid unnecessary disturbance to potential habitat and resolve uncertainty about suspected burrows before clearing begins.

Map proposed clearing and earthworks against remnant vegetation and available species records. Arrange a site inspection where potential habitat overlaps the footprint.

Before habitat disturbance: 2. Check and mark

Have an ecologist inspect relevant ground for suspected burrows using careful, non-destructive methods. Mark any features requiring avoidance or further assessment and brief the clearing crew on the agreed boundaries.

Before habitat disturbance: 3. Set controls

Where practicable, minimise the disturbance footprint and retain adjacent remnant vegetation identified as potential habitat. Confirm who will stop work and who will assess a suspected find.

During habitat disturbance: 1. Work to marked limits

Use staged, controlled work practices so unexpected burrows or spiders can be assessed before the affected ground is disturbed further.

Keep vehicles, stockpiles and ground disturbance within approved and clearly marked areas. Avoid unnecessary traffic over retained remnant vegetation.

During habitat disturbance: 2. Stop and assess

If a suspected spider or burrow is found, pause work in the immediate area, prevent further disturbance and contact the project ecologist. Do not excavate or handle the animal as a routine response.

During habitat disturbance: 3. Record observations

Record the location, date, site condition and photographs where safe and appropriate. Keep the observation distinct from a confirmed identification until an expert has assessed it.

After habitat disturbance: 1. Inspect controls

After works, retain records of searches and findings and check that agreed avoidance areas have not been disturbed.

Check that marked avoidance areas and retained vegetation remain intact and that access or spoil placement has not extended beyond the approved footprint.

After habitat disturbance: 2. Document outcomes

Keep survey effort, negative results, suspected signs, confirmed records and any work stoppages in the project record. Report negative results with their survey limits.

After habitat disturbance: 3. Seek follow-up advice

Refer new records or unresolved identification to an appropriately experienced ecologist and follow relevant approval conditions. Do not infer that a population is absent from an area based only on a limited search.

Rehabilitation actions: 1. Restore disturbed ground

Species-specific rehabilitation methods are not documented. Use a cautious approach guided by site conditions and approvals.

Where rehabilitation is required, use the approved site plan and avoid introducing unapproved soil or materials, or disturbing retained potential habitat.

Rehabilitation actions: 2. Protect retained habitat

Keep access, spoil and follow-up works out of retained remnant vegetation where practicable. Planting species and soil treatments for I. dandaragan are not known.

Rehabilitation actions: 3. Monitor and report

Record rehabilitation actions and any later observations of suspected burrows or spiders. Seek ecological advice before altering ground where such signs are found.

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