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Central Pebble Mouse (Pseudomys johnsoni)

The Central Pebble Mouse is a small Australian rodent associated with stony rises, gravelly plains and pebble mounds in arid inland areas. In project areas, its burrow systems and surrounding pebble mounds can be damaged by clearing, earthworks, vehicle movement and changes to ground cover, although the species is more widespread than early records suggested.

Conservation status

Northern Territory, Territory Parks and Wildlife Conservation Act 1976: Near threatened.

Breeding season

The only direct seasonal evidence supplied is the observation of suckling females in August and September. Other timing, including mating, dispersal and independence of young, is not reported, so the calendar should be treated as a planning guide based on the available breeding observation rather than a complete species calendar.

No information was supplied on mating dates, litter size, gestation, juvenile independence or seasonal dispersal. Confirm timing with local survey data and the relevant Northern Territory, Queensland or Western Australian authority before works.

  • Breeding, mating and births: Suckling females were observed in August and September. The timing of mating and births is not separately reported.
  • Young, dependent in burrows: The August and September suckling-female records indicate dependent young may be present in burrow systems during these months.
  • Highest clearing risk: August and September are the highest precautionary clearing-risk months because suckling females have been recorded then. Clearing at active mounds can injure adults or dependent young and damage their burrow system.

Identification

The Central Pebble Mouse is a small, lightly built Pseudomys with a relatively long tail, pale underparts and a distinctive association with pebble mounds. Live trapping, close examination of burrow entrances and comparison with other small Pseudomys may be needed for reliable identification.

The upperparts are light yellow-brown to reddish-brown, with black guard hairs. The underparts are white. The tail is brown above and white below, and lacks a terminal tuft. The ears are short and lightly furred.

Head and body: 61 to 64 mm in the summary measurements.

Tail: 76 to 95 mm in the summary measurements.

Hind foot: 17 to 18.5 mm.

Ear: 12 to 13 mm.

Weight: 9 to 17 g.

Identification: Distinguishing features

The species can be confused with other small Pseudomys, especially the Pebble-mound Mouse, P. chapmani, the Desert Mouse, P. hermannsburgensis, the Bolam's Mouse, P. bolami, and the Delicate Mouse, P. delicatulus. The original description distinguishes P. johnsoni by its combination of a relatively long hind foot, shorter tail relative to body length than P. chapmani, longer molar rows and a moderately long bulla.

Pseudomys johnsoni has a longer hind foot than P. chapmani, with adult means of about 17.4 mm and 16.0 mm respectively. It is larger than P. delicatulus in overall body size, with an example adult mean weight of 11.7 g compared with 7.6 g for P. delicatulus in the comparative diagnosis.

Sexes were not sexually dimorphic for the characters assessed in the original study. Females have four abdominal teats.

Identification: Field signs

The strongest field sign is a complex burrow system with a mound of small pebbles beside the entrance. The mound may be used to close the entrance later. Pebble mounds are associated with stony ridges, rises and gravelly plains occupied by spinifex and open shrub overstorey.

The supplied documents do not provide diagnostic measurements for tracks or scats, descriptions of calls, or information on eyeshine. Treat an unconfirmed capture or burrow record as a Pseudomys record until an experienced mammal specialist confirms the species.

  • Map every pebble mound and burrow entrance before clearing or ground disturbance.
  • Photograph the mound, entrance, substrate and nearby vegetation, and record the location with an accurate GPS position.
  • Do not rely on a pebble mound alone for species identification because other pebble-mound mice construct similar structures.

Distribution: States and bioregions

The species is known from arid central Australia and from additional records in Queensland and Western Australia. The supplied sources identify three Australian states or territories, but do not provide a complete modern bioregional distribution or a national population estimate.

In the Northern Territory, records are from the Davenport and Murchison Ranges south-east of Tennant Creek, including the Mittiebah Range near Alexandria Station in the Barkly Tableland. The original type locality was Kurinelli Mine on Kurundi Station, at about 150 m elevation.

In Queensland, records are from west of the Great Dividing Range, from near Cloncurry to Camooweal, and from the Mount Isa area. In Western Australia, the species is reported from the Kimberley region.

Northern Territory: Davenport Ranges, Murchison Ranges and Mittiebah Range in or near the Barkly Tableland.

Queensland: Inland areas west of the Great Dividing Range, including the Mount Isa area and the country from near Cloncurry to Camooweal.

Western Australia: Kimberley region.

Known elevation record: The type locality at Kurinelli Mine was about 150 m above sea level.

Distribution: Strongholds and population status

The original description considered the species to have a very restricted distribution in arid central Northern Territory. Geological mapping records cited in that work located only four pebble-mound sites in the Murchison and Davenport Ranges.

Later work in Queensland, the Northern Territory and Western Australia indicated that the species was more common than first thought. The supplied sources describe the distribution as fragmented and the population as stable, but do not give an abundance estimate, density, home range or total population size.

Population size: Not reported in the supplied documents.

Trend: Described as stable in the supplied summary.

Distribution condition: Fragmented, with additional records showing that the species is more widespread than initially recognised.

Habitat: Habitat types

The Central Pebble Mouse occupies dry, stony country where pebble mounds and burrows can be constructed. Habitat descriptions consistently emphasise rocky or gravelly ground combined with spinifex and a variable shrub overstorey.

Recorded habitats include open woodland, wooded valleys, dense shrubby understorey and spinifex grassland. In central Northern Territory, captures were made on stony ridges, rises and gravelly plains with Plectrachne pungens or Triodia longiceps, with variable shrub cover.

The type locality was a rocky outcrop with large boulders on a stony rise vegetated by Triodia longiceps. Associated shrubs included Acacia spondylophylla, Acacia hilliana and Grevillea wickhamii.

  • Prioritise inspection of stony rises, rocky outcrops, gravelly plains and pebble-covered ridges.
  • Search both spinifex grassland and open woodland or shrubland where pebble mounds occur.
  • Retain the ground surface, stones, spinifex clumps and shrub cover around mapped mounds where practicable.

Habitat: Structural features and limits

Pebble mounds are a key habitat feature and may indicate long-standing use because similar mounds made by lithophilous rodents can persist. The supplied sources do not provide a minimum mound density, vegetation height, patch size, home range or upper and lower climate limits.

The species was originally described from arid central Northern Territory. The available elevation information is limited to the type locality at about 150 m.

Climate context: Arid central Australia is the best-supported environmental context.

Elevation: Only a type-locality elevation of about 150 m is given.

Mound density and patch size: Not reported in the supplied documents.

Foraging habitat: Where to assess foraging habitat

The supplied documents do not state the diet, food plants, prey types, feeding times or foraging range of Pseudomys johnsoni. Field assessment should therefore focus on protecting the habitat structure associated with its burrows rather than assuming that feeding areas can be separated from shelter areas.

Potential foraging habitat occurs within the recorded vegetation types, including spinifex grassland, open woodland, shrubby valleys, stony ridges and gravelly plains. The documents do not identify particular food plants or describe how far animals forage from their burrows.

The species is a small murid rodent, but the supplied sources do not provide species-specific evidence for whether plant material, seeds, fungi, invertebrates or other foods dominate its diet.

Diet: Not reported in the supplied documents.

Foraging range: Not reported in the supplied documents.

Named vegetation associated with records: Plectrachne pungens, Triodia longiceps and shrubs including Acacia spondylophylla, Acacia hilliana and Grevillea wickhamii.

  • Inspect the area around each burrow system for continuous spinifex, ground cover, leaf litter, shrubs and undisturbed stony surfaces.
  • Record habitat condition across the full area proposed for clearing, not only at the mound entrance.
  • Avoid presenting food availability or foraging distance as known species facts unless supported by site-specific survey evidence.

Breeding habitat: Breeding features

Breeding information is limited. Suckling females have been observed in August and September, but the supplied sources do not provide litter size, gestation length, age at maturity or lifespan.

Breeding habitat is likely to be within the complex burrow systems associated with pebble mounds, because suckling females have been recorded and the species constructs burrows in stony habitat. The supplied documents do not describe nest material, nest chambers or the distance between breeding burrows.

Breeding season evidence: Suckling females recorded between August and September.

Litter size: Not reported in the supplied documents.

Gestation: Not reported in the supplied documents.

Age at maturity: Not reported in the supplied documents.

Lifespan: Not reported in the supplied documents.

Breeding shelter: Complex burrow systems associated with pebble mounds.

  • Treat active burrow systems and nearby pebble mounds as breeding habitat during August and September.
  • Avoid collapsing entrances, removing mound material or driving over stony rises where active burrows are present.
  • If clearing cannot be avoided, obtain project-specific advice on capture, exclusion and release from the relevant wildlife authority or fauna specialist.

Sheltering habitat: Burrow systems

The species shelters in complex burrow systems in stony or gravelly ground. Pebbles piled beside the entrance are the most distinctive shelter sign described in the supplied sources.

The species lives in a complex system of burrows with a mound of pebbles beside the entrance. The entrance may later be sealed with the excavated stones or mound material.

Records include burrows in hard, stony ridges and in rocky outcrops with large boulders. Pebble mounds are also associated with stony rises, gravelly plains and spinifex vegetation.

Shelter type: Complex burrow system.

Entrance sign: A mound of pebbles beside the entrance.

Burrow or mound dimensions: Not reported in the supplied documents.

  • Mark the full visible burrow system, not only the entrance or mound.
  • Maintain a buffer around entrances and mounds during planning because the documents do not define the underground extent of the burrow system.
  • Prevent stockpiling, vehicle access, grading and vibration over mapped burrows where practicable.

Sheltering habitat: Other cover

The supplied sources identify spinifex, shrubs, woodland and boulders as associated surface cover, but do not state whether the mouse uses hollow logs, tree hollows, rock overhangs or leaf litter as separate refuges.

Threats: Clearing and earthworks

The supplied documents do not quantify threats or report species-specific impacts from roads, fire, predators, disease or hydrology change. The main project concern supported by the habitat information is damage to stony ground, pebble mounds and burrow systems, together with loss and fragmentation of recorded habitat.

Clearing, grading, excavation and infrastructure footprints can remove the stony rises, gravelly plains, spinifex and shrub cover associated with the species. Direct crushing or burial of pebble mounds can destroy the visible entrance and damage the connected burrow system.

The distribution is described as fragmented. Further clearing of isolated habitat patches may reduce local occupancy and make it harder for animals to move between suitable stony areas.

  • Complete a targeted search for pebble mounds and burrow entrances before clearing or earthworks.
  • Fence or flag retained mound areas and prohibit access by machinery, vehicles and laydown areas.
  • Keep access tracks, drainage works and temporary disturbance out of stony rises and gravelly plains where active signs occur.
  • Rehabilitate temporary disturbance by replacing the original surface stones and retaining spinifex and shrub cover where feasible.

Threats: Other project risks

Road mortality, altered fire regimes, introduced predators, disease and hydrology change are not discussed specifically for Pseudomys johnsoni in the supplied documents. They should be assessed at the project level where roads, fire management, drainage, artificial water points, waste or domestic and feral animals may affect retained habitat.

Because the species uses burrows in stony ground, altered runoff, erosion, sediment deposition and water concentration around infrastructure may damage entrances or change the surface structure of mound sites.

Species-specific threat data: Not reported in the supplied documents.

Documented habitat concern: Loss or disturbance of stony ridges, gravelly plains, pebble mounds, burrows and associated spinifex or shrub cover.

  • Inspect retained mounds after intense rainfall, flooding, fire and nearby earthworks for collapse, erosion or sediment burial.
  • Manage waste and food sources so they do not attract cats, foxes or other predators to retained habitat.
  • Record road sightings and any carcasses during construction and operation, even though a species-specific road mortality rate is not available.

Survey methodology: 1. Nocturnal searches and spotlighting

Survey should target the species’ distinctive pebble mounds, stony rises, gravelly plains and spinifex habitats. The available documents do not provide a prescribed survey effort, so the project ecologist should document the risk-based method, effort and weather conditions used.

Use nocturnal searches and spotlighting as a general small-mammal method because the species is a small rodent that uses burrow systems and may be difficult to detect during daytime searches.

Search stony ridges, gravelly plains, pebble-covered rises, spinifex grassland and areas with visible pebble mounds, including around the Davenport and Murchison Ranges and the Mittiebah Range where relevant.

Record the start and finish time, observers, transect length, search area, weather, moon conditions, wind, rainfall and all detections or signs.

Walk searches slowly and quietly, and avoid collapsing or blocking burrow entrances and pebble mounds.

Survey methodology: 2. Trapping and identification

Use an appropriately approved small-mammal trapping program where presence cannot be confirmed by observation or sign alone.

Set traps along stony ridges, gravelly plains, spinifex margins and beside active-looking burrow systems or pebble mounds, while avoiding damage to the mound and burrow structure.

The available documents do not specify trap type, trap density, number of trap nights or checking intervals, so the ecologist must set these in the approved survey design and fauna ethics documentation.

Identify captured animals using external measurements, weight, pelage, tail and foot characters, and photographs, because the species can be confused with other small Pseudomys species.

Published body weight: 9 to 17 g

Published head and body length: 61 to 64 mm

Published tail length: 76 to 95 mm

Published hind-foot length: 17 to 18.5 mm

Survey methodology: 3. Habitat and sign assessment

Map pebble mounds, burrow entrances, stony rises, gravelly plains, spinifex patches and connected areas of suitable habitat before clearing.

Inspect for complex burrow systems with a pebble mound beside the entrance, noting whether entrances appear open, recently used or closed.

Record dominant vegetation, including spinifex such as Plectrachne pungens and Triodia longiceps, and note associated shrubs such as Acacia spondylophylla, Acacia hilliana and Grevillea wickhamii where present.

Treat the presence of suitable habitat or pebble-mound sign as a trigger for targeted follow-up survey rather than relying only on a general fauna inspection.

Survey methodology: Minimum effort and reporting

  • Use more than one method where habitat is present, because the available documents do not establish a single reliable detection method for this species.
  • State the survey dates, nights, hours, trap nights, transect lengths, search area, weather, observers, equipment, detection results and limitations in the report.
  • Map every record and every area searched, including negative results and the condition of pebble mounds and burrows.
  • Submit verified records to the relevant state wildlife database for the Northern Territory, Queensland or Western Australia, as applicable.
  • Check the current taxonomic treatment before reporting records, because Pseudomys laborifex is treated as conspecific with Pseudomys johnsoni in the supplied material.

Before habitat disturbance: Avoid and minimise

Plan works around the retention of stony habitat, pebble mounds and burrow systems. The species has a fragmented distribution, with records in the Northern Territory, Queensland and the Kimberley region of Western Australia.

  • Retain stony ridges, rocky rises, gravelly plains, pebble mounds and spinifex grassland wherever practicable.
  • Avoid clearing connected patches of suitable habitat, particularly where pebble mounds or burrow systems occur in clusters.
  • Keep retained habitat linked to other suitable stony or spinifex habitat rather than leaving isolated remnants.
  • Keep vehicle access, stockpiles, laydown areas and drainage works out of mapped pebble mounds and burrow systems.

Before habitat disturbance: Approvals and work planning

  • Confirm the current Commonwealth and state conservation status before works commence, including whether an EPBC Act referral or state approval is required.
  • Obtain any required permits for trapping, handling, collection, relocation or other fauna management activities.
  • Schedule clearing outside the period when dependent young are most likely to be present where practicable, noting that suckling females have been recorded between August and September.
  • Stage clearing so that retained habitat remains available while each work area is inspected and released.
  • Prepare a fauna management plan covering survey findings, exclusion areas, spotter catcher authority, stop-work triggers, handling, relocation, injury response and reporting.

Before habitat disturbance: Site preparation

  • Complete a pre-clearance inspection of all areas proposed for disturbance, with targeted searches of stony rises, gravelly plains, spinifex patches, pebble mounds and burrow entrances.
  • Mark retained habitat, no-go areas, pebble mounds, burrow systems and fauna exclusion zones on plans and on the ground.
  • Use exclusion fencing where it can prevent animals entering an active work area without trapping animals inside the exclusion zone.
  • Brief machine operators and supervisors on the species’ appearance, habitat signs, stop-work procedure and the location of no-go areas.

During habitat disturbance: Daily controls

Clearance should proceed under active fauna supervision in suitable habitat. The spotter catcher should have authority to pause machinery whenever a live animal, burrow system or other fauna risk is identified.

  • Inspect exclusion fencing, gates, access tracks and marked no-go areas before work starts each day.
  • Walk the work area before machinery enters it and check pebble mounds, burrow entrances, rocks, logs and dense spinifex for fauna.
  • Keep machinery within approved disturbance limits and prevent unnecessary driving over stony rises, pebble mounds and retained habitat.
  • Maintain a clear communication link between the fauna spotter catcher, machine operator, supervisor and environmental officer.
  • Record the date, work area, machinery used, weather, inspections, fauna observations, incidents, relocations and stop-work events.

During habitat disturbance: Spotter catcher and machinery

  • The fauna spotter catcher should remain able to see the active clearing face, machinery movement and any habitat features being disturbed.
  • Release each work area only after the spotter catcher has inspected it and confirmed that the approved controls are in place.
  • Use staged, slow clearance where practicable so animals can move towards retained habitat and the spotter catcher can inspect exposed ground and burrows.
  • Stop machinery immediately when the spotter catcher identifies a live Central Pebble Mouse, an occupied burrow, a damaged pebble mound or an unsafe fauna handling situation.

During habitat disturbance: Animal and habitat response

  • Do not handle the animal unless the person is authorised under the project approval, permit and fauna management plan.
  • Keep people, vehicles and machinery away from the animal and its burrow while the spotter catcher assesses the situation.
  • Relocate a healthy animal only where relocation is authorised and to nearby retained habitat that provides suitable stony ground, pebble mounds, spinifex and shelter.
  • Do not dismantle a pebble mound or destroy a burrow system to capture an animal unless this is specifically authorised and directed by the fauna management plan.
  • Place an injured animal in a suitable secure container and obtain veterinary or authorised wildlife carer assistance as soon as practicable.
  • Stop work and notify the project ecologist and environmental officer if the animal cannot be safely captured, if dependent young are suspected, or if repeated animals are found in the work area.

After habitat disturbance: Post-clearance checks

Post-clearance work should confirm that no animals remain at risk and that agreed habitat controls are still effective. All records should be retained with the project environmental file and submitted where required.

  • Inspect the cleared footprint, retained edges, access tracks and exclusion fencing after each clearing stage.
  • Recheck exposed pebble mounds, burrow entrances, spinifex clumps, rocks and logs for trapped, injured or displaced fauna.
  • Confirm that machinery, spoil, fencing and temporary works have not entered retained stony habitat or blocked retained burrow systems.
  • Document the cleared area, search effort, findings, incidents, photographs and any corrective action.

After habitat disturbance: Monitoring and controls

  • Monitor retained habitat and any relocated animals using the methods specified in the approved fauna management plan.
  • Repeat targeted searches if animals are detected after clearance, if new pebble mounds are found, or if works expand into mapped suitable habitat.
  • Keep exclusion fencing, no-go markers and access controls in place until the environmental officer confirms that they are no longer required.
  • Investigate any decline in habitat condition, loss of pebble mounds or repeated fauna displacement and revise controls where needed.

After habitat disturbance: Reporting and offsets

  • Report records, injuries, deaths, relocations, permit breaches and stop-work events to the project ecologist and relevant authority in the required format.
  • Submit verified occurrence records to the relevant state wildlife database.
  • Assess whether residual impacts require an offset or other approved conservation measure under the applicable Commonwealth or state approval.
  • Update the project fauna register and final environmental report with maps, effort, outcomes and limitations.

Rehabilitation actions: Rebuild habitat structure

Rehabilitation should recreate the stony, spinifex-dominated conditions used by the species and retain the physical features associated with its burrow systems. Measures should be based on the pre-clearing habitat map and the approved rehabilitation plan.

  • Reinstate suitable surface rocks and small pebbles in areas where pebble-mound habitat has been temporarily disturbed, using clean material that matches the local substrate.
  • Do not place spoil, mulch or dense imported groundcover over stony rises, gravelly plains, burrow entrances or retained pebble mounds.
  • Re-establish spinifex communities using locally appropriate Plectrachne pungens or Triodia longiceps where those species formed part of the original habitat.
  • Retain or replant associated shrubs such as Acacia spondylophylla, Acacia hilliana and Grevillea wickhamii where they occurred before disturbance.
  • Retain natural shelter such as rocks, fallen timber and dense ground cover where these features are present, without blocking known burrow entrances.

Rehabilitation actions: Fire, weeds and predators

  • Manage weeds so that spinifex and native shrub cover can re-establish and vehicle access does not spread weed seed through retained habitat.
  • Plan fire management with the land manager so that burning does not remove all spinifex cover or damage recovering pebble-mound habitat at the same time.
  • Control feral predators and other introduced species where they are identified as a project or site pressure and where control is approved.
  • Keep rehabilitation areas free of unnecessary vehicle traffic, stockpiles and repeated soil disturbance.

Rehabilitation actions: Monitoring and success measures

Known habitat types: Open woodland, wooded valleys, dense shrub understorey and spinifex grassland

Habitat features: Pebble-covered ridges, stony rises, gravelly plains, pebble mounds and complex burrow systems

  • Monitor plant establishment, spinifex cover, weed cover, surface rock condition, soil stability, burrow availability and pebble-mound formation.
  • Compare rehabilitation results with nearby retained stony habitat rather than judging success only by vegetation cover.
  • Use repeat searches, spotlighting, trapping or other approved small-mammal methods to test whether Central Pebble Mouse activity returns to rehabilitated habitat.
  • Record the timing, area and method of each monitoring event, and continue corrective works where habitat structure or fauna use is not returning.

Sources