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Kakadu Pebble Mouse (Pseudomys calabyi)

The Kakadu Pebble Mouse is a small native Australian rodent known from the upper South Alligator and Mary River valleys in Kakadu National Park, Northern Territory. It is associated with pebble mounds and stony ground, so clearing, earthworks and disturbance of surface stones can remove both habitat and field signs used to detect it.

Conservation status

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

Breeding season

The supplied documents do not provide seasonal records for breeding, young, movement or dispersal. The calendar below therefore uses an all-year precaution for clearing and disturbance rather than claiming a documented breeding season.

Seasonal information should be updated with local survey results, trapping data and advice from the relevant Northern Territory fauna authority.

  • Highest clearing risk: Use an all-year precaution because the breeding and sheltering seasons are unknown and clearing can remove pebble mounds, surface stones and ground cover at any time.

Identification

This is a small native mouse in the Australian Pseudomys group. Positive identification in the field is difficult without a captured animal, specimen examination or reliable genetic identification, so pebble mounds and the surrounding stony habitat should be recorded carefully.

The supplied documents do not provide measurements, body mass, pelage description, sex differences, tracks, scats, calls, eyeshine or other external field characters for Pseudomys calabyi.

Do not assign an unidentified small native mouse to this species from appearance alone. Record photographs, exact location, habitat, surface stones and any associated mound structures, and refer captures or specimens to an appropriately qualified mammalogist.

Body length: Not provided.

Tail length: Not provided.

Weight: Not provided.

Sexual dimorphism: Not provided.

Identification: Pebble mounds

Pebble mounds are the most useful reported field sign for this species group. The review identifies Pseudomys calabyi as one of Australia's pebble-mound mice and distinguishes pebble-mouse mounds from ordinary piles of stones.

For comparison, the review states that recognised pebble-mouse mounds can be identified by selected stones and are distinguishable from other stone mounds. The supplied extract does not give a verified mound diameter, height, stone size or activity test for Pseudomys calabyi.

  • Photograph each mound with a scale and record its position before vegetation or stones are disturbed.
  • Record whether stones appear deliberately selected, whether the mound is continuous or broken, and whether fresh disturbance or runways are present.
  • Do not treat every pile of stones as a species record, because other pebble-mound Pseudomys species and non-biological stone piles can occur.

Identification: Similar species and field handling

Other pebble-mound mice include the central pebble-mound mouse, Pseudomys johnsoni, the western pebble-mound mouse, Pseudomys chapmani, and other regional species. The review notes that several species occupy similar stony settings and that their taxonomy and relationships have required further work.

A field sign record should therefore be reported as a pebble-mound mouse record unless the species has been confirmed by an accepted identification method. Use low-stress trapping and release procedures under the relevant permit and animal ethics requirements where a species-level record is needed.

Distribution: Known range

The supplied distribution information is restricted to the Northern Territory. No confirmed Western Australian, Queensland, South Australian, Victorian, New South Wales, Australian Capital Territory or Tasmanian range is given for Pseudomys calabyi.

The species has been recorded from Stage III of Kakadu National Park, in the valleys of the upper South Alligator and Mary Rivers.

The supplied documents associate the species with the Arnhem Land and Kakadu region. No mapped national range, site count or occurrence polygon is provided in the extract.

State or territory: Northern Territory.

Known bioregional setting: Arnhem Land, including Kakadu National Park.

Named localities: Upper South Alligator River valleys, upper Mary River valleys and Kakadu National Park Stage III.

Known strongholds or subpopulations: No separate strongholds or subpopulations are identified in the supplied documents.

Population estimate: Not provided.

Population trend: Not provided. Earlier material described the species as insufficiently known.

  • For Northern Territory projects, treat records from Kakadu National Park and nearby suitable Arnhem Land habitat as requiring specialist review.
  • Do not extend the species identification to other pebble-mound mouse records outside the known Northern Territory area without taxonomic confirmation.

Distribution: Project mapping

Map all records at the finest practical scale and retain the distinction between active, inactive and uncertain pebble mounds. A mound record alone may indicate habitat use but does not establish the number of animals present.

The review indicates that several pebble-mound mouse species are separated by unsuitable habitat and that taxonomic treatment has required further work. This makes regional comparison and expert review important when records occur outside the known Kakadu area.

  • Search and map stony ground, surface pebble concentrations and connected suitable patches before clearing design is finalised.
  • Submit unusual records, isolated occurrences and records outside Kakadu to the relevant Northern Territory fauna authority or a mammal taxonomist.

Habitat: Stony ground and surface structure

The available information points to stony ground in the wet dry tropics of northern Australia, especially within Kakadu and the upper South Alligator and Mary River valleys. Detailed vegetation associations, elevation limits and climate thresholds are not provided.

The species belongs to a group of mice associated with pebble mounds. Surface stones and the soil beneath or between them are therefore important habitat features to retain during site planning.

The supplied review describes pebble-mound mice generally as occupying stony surfaces in Australian upland or elevated settings, but that description is not a species-specific habitat model for Pseudomys calabyi.

Vegetation community: Not specified for Pseudomys calabyi in the supplied documents.

Elevation range: Not provided.

Climate limit: Associated broadly with the wet dry tropics of the Northern Territory, but no numerical climate limits are provided.

  • Retain intact pebble fields, shallow stony soils, natural stone concentrations and connected ground cover wherever practicable.
  • Avoid grading, stripping, burying or stockpiling surface stones before a fauna assessment has checked for pebble-mound mouse signs.

Habitat: Habitat connectivity

The review notes that pebble-mound mouse species are separated from one another by extensive unsuitable areas. This indicates that isolated suitable patches may have limited connectivity and should not be treated as interchangeable habitat.

No home-range size, dispersal distance or minimum patch size is available for Pseudomys calabyi.

  • Keep stony habitat patches connected where possible, especially along natural ground corridors between recorded mound areas.
  • Include indirect effects such as access tracks, temporary work areas, drainage changes and material storage in the habitat assessment.

Foraging habitat: Evidence available

The supplied documents do not describe the diet, food plants, prey, feeding method or foraging range of Pseudomys calabyi. Field assessment should therefore focus on retaining the intact ground layer and surface structure associated with its pebble-mound habitat.

No species-specific diet or feeding observations are included in the supplied material. No food plant, seed, invertebrate prey or foraging distance is identified.

Because the species is a small ground-dwelling Pseudomys associated with pebble mounds, clearing controls should protect the ground layer and the soil and stone matrix around mound areas rather than retaining isolated stones only.

Diet: Not provided.

Foraging method: Not provided.

Foraging range: Not provided.

Key food plants or prey: Not provided.

  • Do not remove surface stones, litter or low ground cover from recorded mound areas unless an approved fauna management measure requires it.
  • Keep vehicle movements, spoil placement, laydown areas and repeated pedestrian traffic away from mapped mound concentrations.
  • Record flowering, seeding, fruiting and ground invertebrate conditions during surveys, but do not use these observations as a species-specific diet profile.

Breeding habitat: Breeding information

No breeding observations or reproductive measurements for Pseudomys calabyi are included in the supplied documents. The breeding information below should be treated as unavailable for this species, not as evidence that breeding does not occur at a site.

The available material does not identify a breeding season, litter size, gestation period, age at maturity, lifespan, nest type or breeding location.

Until local information is available, retain suitable stony ground and ground cover around active or suspected pebble mounds throughout the year. Do not assume that clearing outside a presumed breeding season is low risk.

Breeding season: Not provided.

Litter size: Not provided.

Gestation: Not provided.

Age at maturity: Not provided.

Lifespan: Not provided.

Breeding habitat features: Species-specific nest or breeding-site features are not provided. Retain intact pebble-mound habitat, soil and ground cover as the best-supported precaution.

  • Request local records and advice from the Northern Territory fauna authority when breeding risk affects clearing timing.
  • Where clearing cannot avoid suitable habitat, use a targeted fauna survey and an approved management plan rather than relying on a calendar exclusion period.

Sheltering habitat: Pebble mounds and ground refuge

Pebble mounds are the only shelter-related field feature identified in the supplied documents. The documents do not confirm whether Pseudomys calabyi uses burrows, nests, hollows, rock crevices or other refuges.

The species is one of the recognised Australian pebble-mound mice, and pebble mounds are the principal sign requiring protection during site works.

The supplied material does not provide mound dimensions, burrow dimensions, nest construction, refuge depth, den occupancy or the distance animals travel from mounds.

Refuge type: Pebble mounds are documented as the characteristic field sign, but their shelter function for Pseudomys calabyi is not described in the supplied extract.

Burrow size: Not provided.

Nest size: Not provided.

Mound dimensions: Not provided for Pseudomys calabyi.

  • Fence or otherwise clearly mark mapped mound areas before vegetation clearing, earthworks and vehicle access begin.
  • Keep spoil, fill, water flow, vibration and machinery away from mounds and the surrounding stone and soil matrix.
  • Treat apparently inactive mounds as potentially important until a suitably qualified person has assessed them, because the supplied documents do not provide a reliable inactivity period.

Sheltering habitat: Other potential refuges

No evidence is supplied for use of tree hollows, fallen timber, rock crevices, dense grass tussocks or artificial structures. These features should not be described as confirmed refuges for this species.

During a fauna inspection, record all ground-level cover and natural cavities near mound areas because their use may be clarified by local trapping or camera data.

Threats: Clearing and earthworks

The supplied documents provide limited species-specific threat information. The main project concern is the loss or disturbance of stony habitat and pebble mounds, combined with the uncertainty created by a poorly known distribution and population status.

Clearing can remove the surface stones, soil, ground cover and possible shelter structures associated with pebble-mound habitat. Grading, excavation, trenching, stockpiling and access tracks can also destroy or bury mounds.

The species has a restricted known distribution in the Kakadu region, and no population estimate is available. Avoidance and early mapping are therefore preferred to relying on post-clearing relocation.

  • Survey and map pebble mounds before finalising the clearing footprint.
  • Exclude mapped mound concentrations from clearing, laydown, spoil and repeated vehicle access wherever practicable.
  • Use a clearly marked no-go buffer determined by the project ecologist and relevant authority, because the supplied documents do not provide a species-specific buffer distance.

Threats: Fragmentation and roads

The review states that pebble-mound mouse species are separated by extensive areas of unsuitable habitat. New roads and infrastructure can further divide suitable stony patches and increase vehicle access through them.

No road mortality rate, crossing distance or movement corridor width is provided for Pseudomys calabyi.

  • Place new tracks and permanent infrastructure outside connected stony habitat where possible.
  • Limit night driving and enforce low-speed controls near confirmed or suspected habitat.
  • Prevent informal access tracks from spreading through mound areas.

Threats: Fire, predators and other pressures

The supplied documents do not identify a species-specific fire response, predator list, disease, hydrology sensitivity or impact from introduced animals for Pseudomys calabyi.

Fire can alter ground cover and the condition of stony habitat, while changed drainage can erode, bury or expose mound areas. These are practical project risks requiring local assessment, rather than documented species-specific effects in the supplied material.

Fire response: Not provided.

Predation impacts: Not provided.

Disease: Not provided.

Hydrology change: Not provided.

  • Keep fire management, erosion control and drainage design from removing or burying surface stones and ground cover around mapped habitat.
  • Do not assume that a burnt or apparently inactive mound area is unoccupied without follow-up assessment.
  • Record foxes, cats, dogs, feral pigs and other predators during site surveys, but seek local evidence before assigning a species-specific predation impact.
  • Record disease or unusual mortality observations and report them through the relevant Northern Territory wildlife channels.

Survey methodology: 1. Habitat assessment and mound search

The supplied documents provide limited species-specific survey guidance. They identify the Kakadu pebble-mound mouse as a pebble-mound mouse recorded in Stage III of Kakadu National Park, including valleys of the upper South Alligator and Mary Rivers, and indicate that mound-building mice use stony ground.

Before selecting detection methods, inspect the proposed disturbance area and nearby retained habitat for shallow stony ground, pebble mounds and connected areas of suitable cover.

Treat suspected pebble mounds as potential fauna habitat until they have been photographed, mapped and assessed by a suitably qualified ecologist.

Record the mound dimensions, pebble size and condition, and photograph the surrounding ground surface because pebble mounds can be distinguished from unselected stone piles by their construction features.

Survey methodology: 2. Targeted searches and trapping

Use a combination of systematic searches, remote cameras, spotlighting and live trapping where the risk assessment indicates that the species could be present.

The supplied documents do not specify a species-specific number of nights, trap nights, transect length, survey area or spotlighting duration, so set effort in consultation with the relevant Northern Territory wildlife authority and the project ecologist.

Use live trapping only under the required permit and animal ethics arrangements, with suitable shelter, food and weather protection, and check traps at the frequency required by the permit.

Species-specific survey effort in supplied documents: Not specified

Species-specific survey season in supplied documents: Not specified

Survey methodology: 3. Timing, conditions and detection records

Plan targeted surveys when weather and ground conditions allow safe access and reliable detection, and document rainfall, temperature, wind, moon phase, start and finish times and any conditions that could reduce detection.

Give priority to the mapped habitat in the valleys of the upper South Alligator and Mary Rivers and other areas identified by the ecologist as comparable suitable habitat.

Record positive and negative results separately, including the location of each animal, mound, camera detection, track or other sign, and retain photographs and coordinates.

Survey methodology: Minimum effort and reporting

  • Obtain advice from the relevant Northern Territory wildlife authority before finalising survey effort because the supplied documents do not provide a Kakadu pebble-mound mouse survey guideline.
  • Use qualified personnel who can distinguish pebble mounds from ordinary stone piles and identify small native rodents in the field.
  • Submit confirmed records, including zero records where required by the project approval, to the relevant Northern Territory wildlife database.
  • Keep the survey design, permits, raw data, photographs, coordinates, weather records and identification decisions with the project environmental records.

Before habitat disturbance: 1. Avoid and minimise

Avoid disturbance to suitable stony habitat wherever practicable. The main known location information in the supplied material is for Stage III of Kakadu National Park, including the upper South Alligator and Mary River valleys.

  • Redesign or narrow the disturbance footprint to retain areas of stony ground, suspected pebble mounds and links between retained habitat patches.
  • Do not use a suspected pebble mound as a spoil area, vehicle turning area, access track or materials storage location.
  • Map all confirmed and suspected mounds, stony habitat and nearby retained habitat before finalising the clearing boundary.
  • Use a qualified ecologist to assess whether a suspected mound is consistent with a pebble-mound mouse mound rather than an unselected pile of stones.

Before habitat disturbance: 2. Approvals and planning

  • Check the current EPBC Act list and determine whether the proposed action requires referral for any nationally listed matters.
  • Check Northern Territory threatened species, wildlife handling and clearing requirements before works because the species is identified in the project information as Near Threatened in the Northern Territory.
  • Prepare a fauna management plan that identifies survey methods, exclusion zones, stop-work triggers, fauna handling authority, release sites, injury response and reporting responsibilities.
  • Stage clearing so that surveyed and controlled areas are completed progressively rather than opening the entire disturbance area at once.

Before habitat disturbance: 3. Site preparation

  • Complete the pre-clearance survey immediately before works, with the timing set by the approved fauna management plan and any permit conditions.
  • Clearly mark no-go areas, retained stony habitat, suspected mounds, access routes and fauna release areas on plans and on the ground.
  • Install exclusion fencing where it can direct fauna away from machinery without trapping animals inside the work area.
  • Brief machinery operators and supervisors on the species identification features, exclusion zones, stop-work process and contact details for the fauna spotter catcher.

During habitat disturbance: 1. Daily controls and machinery coordination

Clearance should proceed under direct fauna supervision in small, controlled stages. The fauna spotter catcher must have authority to pause machinery whenever an animal or suspected habitat feature is encountered.

  • Inspect exclusion fencing, access controls, retained habitat and marked mound locations before work starts each day.
  • Keep the fauna spotter catcher within effective viewing distance of the active clearing face and between machinery and uncleared habitat where safe to do so.
  • Direct machinery to work slowly from the cleared edge towards retained habitat so animals have an opportunity to move into safe areas.
  • Stop machinery immediately when the spotter catcher identifies an animal, suspected mound, burrow, log, rock feature or other fauna risk.

During habitat disturbance: 2. Handling and habitat features

  • Do not handle the mouse unless the person is authorised under the relevant permit and trained in native mammal handling.
  • Do not dismantle, crush or move suspected pebble mounds until they have been assessed and cleared by the fauna spotter catcher or ecologist.
  • Inspect rocks, logs, ground cover and other shelter features before they are moved, and move them only under the approved fauna management plan.
  • Relocate a captured or displaced animal only to nearby retained habitat that has been assessed as suitable and is outside the active work area.
  • Do not release an animal into an isolated artificial refuge unless that action is authorised by the relevant wildlife authority.

During habitat disturbance: 3. Injured animals, stop work and records

  • Place an injured animal in a secure, quiet container using the approved handling procedure and arrange prompt assessment by a veterinarian or authorised wildlife carer.
  • Keep work stopped in the immediate area until the animal has been safely removed or the ecologist confirms that the risk has been resolved.
  • Use a stop-work trigger for any live animal, fresh sign suggesting current use, suspected mound, injury, trapped fauna or breach of an exclusion zone.
  • Record the date, time, location, habitat feature, species identification, action taken, release location, injury outcome, personnel involved and machinery affected.
  • Notify the project environmental officer and the relevant wildlife authority of any confirmed capture, injury, death or permit breach within the required timeframe.

After habitat disturbance: 1. Post-clearance checks

Post-clearance work should confirm that retained habitat and fauna controls remain intact and that all observations have been reported. The supplied documents do not provide a species-specific post-clearance monitoring schedule.

  • Inspect the cleared area and retained edges for stranded, injured or dead fauna before demobilising the fauna team.
  • Recheck exclusion fencing, access controls, retained stony habitat and marked mound locations after each clearing stage and after heavy rain or construction changes.
  • Confirm that no suspected pebble mound or retained habitat feature was damaged outside the approved footprint.
  • Complete a final search of temporary stockpile, trench, pipe, culvert and machinery areas before they are closed or removed.

After habitat disturbance: 2. Monitoring and reporting

Species-specific post-clearance monitoring period in supplied documents: Not specified

  • Monitor retained habitat and any known or suspected mound locations at the frequency specified in the approval or fauna management plan.
  • Use the same mapped locations and recording methods during follow-up monitoring so that changes in mound condition, animal detections and habitat disturbance can be compared.
  • Report confirmed records and significant incidents to the relevant Northern Territory wildlife database and wildlife authority.
  • Review the results with the project ecologist and update controls if animals, mounds or suitable habitat are detected after clearing.

After habitat disturbance: 3. Ongoing controls and offsets

  • Maintain no-go areas, fencing, signage and access controls for as long as construction activity could affect retained habitat.
  • Apply any approved offset or compensatory habitat requirement where impacts cannot be avoided or mitigated under the project approval.
  • Keep evidence of completed controls, monitoring results, incidents, corrective actions and database submissions in the project close-out file.

Rehabilitation actions: 1. Recreate suitable ground habitat

Rehabilitation should recreate connected, undisturbed ground habitat and protect the stony features associated with pebble-mound mice. The supplied documents do not identify plant species, nest-box requirements, fire intervals or rehabilitation success thresholds for this species.

  • Reinstate natural ground levels and drainage without burying or removing retained stony surfaces.
  • Use locally appropriate native groundcover and shrub species selected by the project ecologist for the Kakadu area and the original vegetation community.
  • Retain or return locally sourced stones only where the rehabilitation design has been approved, and do not construct artificial pebble mounds that could be mistaken for natural fauna habitat.
  • Reconnect rehabilitated areas with nearby retained stony habitat wherever the project footprint allows.

Rehabilitation actions: 2. Protect habitat features

  • Retain natural rocks, logs and ground cover that provide shelter, subject to weed and bushfire safety requirements.
  • Do not install nest boxes as a substitute for the species' known ground habitat unless the relevant authority specifically approves them for another fauna matter.
  • Control weeds, introduced predators and unauthorised vehicle access where they threaten the recovery of rehabilitated habitat.
  • Develop fire management measures with the land manager and ecologist because the supplied documents do not provide species-specific fire requirements.

Rehabilitation actions: 3. Monitoring and success measures

Species-specific rehabilitation targets in supplied documents: Not specified

Species-specific monitoring period in supplied documents: Not specified

  • Monitor survival of plantings, ground stability, weed cover, predator activity, stony ground condition and any new or maintained pebble-mound mouse signs.
  • Set measurable project-specific success criteria with the regulator and ecologist because the supplied documents provide no numerical rehabilitation targets or monitoring period.
  • Use fixed photographs, mapped plots and repeat fauna searches to document rehabilitation progress.
  • Submit confirmed post-rehabilitation records to the relevant Northern Territory wildlife database and revise weed, predator, access or fire controls if monitoring shows declining habitat condition.

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