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Desert Mouse (Pseudomys desertor)

The Desert Mouse is a small native rodent of arid and semi-arid Australia. It depends on dense ground cover, particularly mature spinifex, tussock grass, sedges and shrubs, so clearing, high-frequency fire, grazing and construction disturbance can remove both food and shelter on development sites.

Conservation status

New South Wales, Biodiversity Conservation Act 2016: Critically endangered.

Breeding season

The Desert Mouse has a flexible breeding cycle and can be active throughout the year. Rainfall and vegetation growth can change local abundance quickly, so the timing of surveys and clearing controls should reflect recent conditions as well as the calendar.

Months are indicative across the species' range. Local rainfall, vegetation growth, fire history and recent survey results should guide project timing.

  • Breeding: Breeding can occur throughout the year. Births have been recorded in March, June and August to December.
  • Young: Young are dependent for about three weeks before weaning. Because breeding is possible year-round, dependent young may be present in any month.
  • Rainfall response and local expansion: Populations can increase and expand into wider habitat after suitable rain and subsequent vegetation growth. No fixed national movement season is provided.
  • Highest clearing risk: Risk is present in every month because breeding and dependent young can occur year-round, and shallow burrows and dense ground-cover refuges may be occupied at any time. Risk can increase locally after rain when abundance and habitat use expand.

Identification

The Desert Mouse is a small, stout rodent with a grizzled chestnut to brown appearance. It is most reliably identified from a combination of coat, eye-ring, measurements, habitat and capture or photographic evidence.

The upper fur is bright chestnut brown with long, dark guard hairs that give an unkempt or spiny appearance. The underfur is light grey-brown. The upper lip and chin are greyish-white, and the eye is surrounded by a distinctive pale orange ring.

The tail is brown above, paler on the sides and below, sparsely furred and scaly in appearance. It is equal to or shorter than the head and body length.

Head and body: 70 to 105 mm

Tail: 67 to 103 mm

Weight: 11 to 35 g

Identification: Distinguishing features

The Desert Mouse overlaps in range with the introduced House Mouse, Mus musculus, and the Dusky Hopping Mouse, Notomys alexis. The supplied survey guidance identifies these as similar species but does not provide a diagnostic feature set for separating them in the field.

Do not rely on habitat or general brown rodent appearance alone. Record photographs, body measurements, tail proportions, the pale eye-ring and the capture or observation location, and obtain specialist confirmation where identification is uncertain.

Identification: Field signs and survey clues

Desert Mice usually use simple, shallow burrows or nests in dense grass tussocks. Complex tunnels have also been observed.

The supplied sources do not describe diagnostic tracks, scats, calls or eyeshine. Dense ground cover, shallow burrows, nests under tussocks and suitable spinifex or shrub habitat are therefore the most useful field clues, but they are not sufficient on their own to confirm presence.

Distribution: National range

The Desert Mouse was formerly widespread across inland and southern Australia. Its present distribution is patchy, with the strongest documented conservation significance in the central deserts and a very small, uncertain NSW population.

Historical records extended from the Murray-Darling region of NSW through the Flinders Ranges, the Gibson and Great Sandy Deserts, the Nullarbor Plain, the western coast and Bernier Island in Western Australia.

The species is now regarded as contracted mainly to the central deserts. Records and habitat information also cover Queensland and South Australia.

States and territories with documented records or range: NSW, Queensland, South Australia, Western Australia and the Northern Territory context around Uluru.

Rainfall context: Reported from areas receiving median rainfall below 600 mm, and from some habitats within a 500 to 750 mm rainfall zone.

Relevant bioregions named in the sources: Greater Sandy Desert, Simpson-Strzelecki Dunefields and Murray Darling Depression

Distribution: Strongholds and subpopulations

Uluru-Kata Tjuta National Park supports a significant population and is an important documented stronghold in the central deserts. The park population occurs within a broader fauna area extending north from Uluru, west of Yulara and west to the Sedimentaries.

In NSW, the species was not confirmed between 1857 and a single male captured at Sturt National Park in September 2008. Intensive survey in that area found no other individuals, indicating a very restricted and poorly understood NSW occurrence.

Distribution: Population size and trend

The total national population is not provided. In NSW, the number of mature individuals was inferred to be extremely low.

Populations can increase rapidly after good rain and vegetation growth. A 24-fold increase in trapping success was recorded at two sites near Uluru in less than two years, although population eruptions rather than plagues have been recorded.

NSW area of occupancy estimate: 8 km², based on two 2 km by 2 km grid cells using the available NSW records.

Recent NSW confirmed records described: One male at Sturt National Park in 2008, following no confirmed NSW records since 1857.

Recorded increase near Uluru: 24-fold increase in trapping success at two sites in less than two years

Habitat: Habitat types

Desert Mice use arid and semi-arid habitats where dense, persistent ground cover provides food and shelter. They can occupy several vegetation communities, but open ground with little cover is less suitable.

Most records are from sand dunes or sandplains dominated by spinifex, especially Triodia species. The species has also been recorded in open eucalypt woodland, riparian habitat, acacia shrubland, samphire and nitre bush shrubland, sedgeland, cane-grass habitat, alluvial plains, stony hills, scree slopes, wetlands and bore-drain sedgelands.

Habitat: Required structure

Dense ground cover of mature hummock grass, tussock grasses, sedges or shrubs is an important habitat feature. The species survives in small pockets of preferred habitat and expands into surrounding areas after rain when vegetation growth increases.

A documented NSW example consisted of vegetated, stabilised sand dunes up to 15 m high, alternating with rocky plains, claypans, swamps and other interdunal areas. The dunes carried dense shrub cover including Acacia, Dodonaea, Hakea and Atalaya, with lower shrubs and ephemeral grasses and forbs after rain.

Example dune height in NSW habitat: Up to 15 m

Important ground cover: Mature Triodia hummocks, tussock grasses, sedges or dense shrubs

  • Retain connected patches of dense ground cover during site planning and clearing.
  • Treat spinifex hummocks, tussock grass, sedges and dense shrubs as potential habitat even when no animals are detected.
  • Avoid assuming that recently burnt or heavily grazed open ground is suitable simply because it occurs within the species' broader range.

Habitat: Climate and elevation

The sources describe the species by arid and semi-arid climate and rainfall rather than elevation. No elevation limit is provided.

The documented rainfall context ranges from median rainfall below 600 mm to habitats within a 500 to 750 mm rainfall zone.

Foraging habitat: Diet

The Desert Mouse is mainly a plant-eater that forages within dense vegetation. Food availability and activity can increase after rainfall and subsequent vegetation growth.

Leaves and shoots make up most of the diet. The species is less granivorous than many other desert rodents, but seeds and invertebrates are used in some parts of its range.

The diet changes with local and seasonal availability. It may feed opportunistically on whatever food is available.

Main foods: Leaves and shoots

Additional foods recorded: Seeds and invertebrates in some areas

Foraging habitat: Foraging sites and behaviour

Foraging occurs in or around dense spinifex, tussock grass, sedges and shrubs. The species may be active during both day and night, possibly because regular feeding is needed for its folivorous diet.

Populations expand from small refuge patches into wider areas after rainfall and vegetation growth. The supplied sources do not provide a measured foraging radius or home-range size.

  • Survey dense ground cover as well as nearby recently greened areas after rain.
  • Retain vegetation links between dense refuge patches and surrounding feeding habitat during clearing and construction planning.

Breeding habitat: Breeding biology

Breeding can occur throughout the year, with reproductive activity and population growth linked to rainfall and vegetation availability. Breeding habitat is closely tied to dense ground cover and nearby food.

The oestrous cycle is seven to nine days. Gestation lasts 27 to 28 days, and females can undergo post-partum oestrus soon after giving birth. Births have been recorded in March, June and August to December, but the species can breed throughout the year.

The average litter is about three young. Young are weaned at about three weeks and reach sexual maturity at about 10 weeks.

Breeding season: Throughout the year, with births recorded in March, June and August to December

Oestrous cycle: 7 to 9 days

Gestation: 27 to 28 days

Average litter size: About 3 young

Weaning: About 3 weeks

Age at sexual maturity: About 10 weeks

Lifespan: Not provided in the supplied sources

Breeding habitat: Breeding habitat features

Females require dense vegetation that provides food and concealed nesting or burrowing sites. Mature spinifex, tussock grass, sedges and dense shrubs are the best-supported structural features.

Rainfall and subsequent vegetation growth can support rapid population increases. Retaining unburnt refuge patches and dense ground cover is therefore relevant to breeding habitat, not only to shelter.

  • Avoid clearing dense tussocks, spinifex hummocks and shrub patches during any period when occupied habitat cannot be excluded.
  • Plan pre-clearance checks around dense ground cover and shallow burrows, with controls maintained across the wider refuge patch rather than only around an individual animal.

Sheltering habitat: Burrows and nests

Desert Mice shelter close to the ground in simple burrows or nests within dense vegetation. These refuges can be lost through clearing, fire, grazing and machinery movement even when the animals are not visible.

The species usually uses simple, shallow burrows or nests in dense grass tussocks. Complex tunnels have also been observed.

The sources do not provide burrow dimensions, nest dimensions or a standard disturbance buffer. Shallow burrows and dense tussocks should therefore be treated as potential occupied refuges during site inspection and clearing.

  • Inspect dense tussocks, spinifex hummocks and shrub bases for shallow burrow openings, runways or nests before disturbance.
  • Do not enter or collapse suspected burrows with machinery unless this is part of an approved fauna management method.
  • Keep machinery, vehicle parking and spoil placement out of dense ground-cover patches until they have been assessed.

Sheltering habitat: Fire and ground cover

The species prefers vegetation that has not been burnt for a long time. One study cited in the NSW determination found a strong preference for vegetation more than 25 years post-fire, suggesting a need for dense cover.

Fire can reduce populations by removing ground cover. High-frequency fire can therefore remove both shelter and the vegetation needed for recovery.

Post-fire habitat preference reported: Vegetation more than 25 years post-fire

  • Retain unburnt refuge habitat where it occurs within or beside a project area.
  • Avoid broad slashing or burning that removes continuous ground cover around known or potential habitat.

Threats: Clearing and construction

The main project-related risks are removal of dense ground cover, fragmentation of refuge patches, altered fire regimes and increased access for predators or herbivores. The NSW population is especially sensitive because its mature population is inferred to be extremely small.

Clearing shrubs, grasses, spinifex, sedges or other dense ground cover removes feeding and shelter habitat. Fragmentation can leave small isolated pockets that are less able to support animals between rainfall events.

Roads, tracks, laydown areas, trenching and utility corridors can directly remove cover and increase vehicle movement through remaining habitat. The supplied sources do not quantify road mortality for this species, so vehicle risk should be assessed from site conditions and local records.

  • Map and retain dense ground-cover patches before finalising the clearing footprint.
  • Keep access tracks, stockpiles, compounds and spoil outside potential refuge patches where practicable.
  • Use fauna spotter catcher controls for any clearing that could affect dense ground cover, shallow burrows or nests.

Threats: Fire, grazing and introduced herbivores

High-frequency fire reduces ground cover and is associated with lower Desert Mouse populations. The species prefers long-unburnt vegetation, including vegetation more than 25 years after fire in one study.

Domestic stock, feral goats, rabbits and pigs can graze or trample habitat. Stock watering points can attract herbivores and predators and degrade surrounding habitat. Competition with the introduced House Mouse is also identified as a possible threat.

  • Retain unburnt refuge habitat and avoid high-frequency burning in or beside known habitat.
  • Control grazing and trampling around retained habitat, including impacts from domestic stock and feral herbivores.
  • Manage temporary watering points so they do not concentrate herbivores or predators near retained habitat.

Threats: Predators and information gaps

Predation by foxes and feral cats may significantly affect small or restricted populations. The sources also identify insufficient knowledge of distribution and ecology as a conservation threat.

Hydrology change is not identified specifically in the supplied species sources. However, works that alter wetlands, bore-drain sedgelands, claypan swamps or other moisture-supported vegetation should be assessed for loss of dense cover and food plants.

  • Manage fox and feral cat access where the project affects known or potential habitat.
  • Survey potential refuge habitat, particularly after rain when density and distribution may be higher.
  • Record all captures, photographs, burrows and habitat condition so local distribution can be updated.

Survey methodology: 1. Habitat assessment and targeted searches

Survey effort should target dense ground cover on sandy plains, dunes, spinifex, tussock grass, sedgeland and shrubland. Desert Mouse activity and numbers increase after rain and vegetation growth, while fire can remove the cover it needs. Use suitably authorised methods and obtain animal ethics and wildlife permits before trapping.

Map sandy plains, dunes, spinifex hummocks, dense tussocks, sedges, shrubs, samphire, chenopod, nitre bush and wetland or bore-drain sedgeland before selecting survey locations.

Inspect shallow burrows, nests in dense tussocks, runways, tracks and other signs in suitable ground cover.

Search during and after periods of rain when vegetation growth is likely to increase activity and distribution.

Record recent fire, grazing, trampling, clearing, watering points and the condition and continuity of ground cover.

Survey methodology: 2. Live trapping

Use live trapping only under the relevant animal ethics approval, wildlife authority approval and project method statement.

Where trapping is required, use the Australian Government threatened mammal survey guideline method that matches the habitat and species group, including the stated trap type, placement, checking and recommended effort.

Place traps through dense ground cover and along likely runways, rather than on bare inter-dune surfaces, and protect them from exposure, predators and weather.

Check traps at the frequency required by the approval and method, and release non-target animals promptly at the point of capture unless an authorised veterinarian or wildlife officer directs otherwise.

Record trap locations, trap nights, weather, rainfall, fire history, ground-cover condition, captures and trap failures.

Survey methodology: 3. Camera, hair and sign detection

Use motion-sensing cameras or other non-capture methods where trapping is unsuitable, placing them beside dense tussocks, burrow entrances, runways and other retained cover.

Use hair sampling only where the device and laboratory method can distinguish Desert Mouse hair from house mouse and other rodents.

Treat burrow, nest and camera observations as detection evidence, but do not infer absence from a non-detection where cover is sparse, conditions are dry or survey effort is low.

Retain photographs, images, sample identifiers and the exact location of each record.

Survey methodology: 4. Local knowledge and survey timing

Consult Traditional Owners and local people about records, habitat use and suitable survey locations, following applicable cultural information protocols.

Speak with graziers and farm staff where relevant, particularly during dry periods when animal densities may be low.

Repeat or extend surveys after suitable rain if initial surveys occur during dry conditions, because populations can expand after rainfall and vegetation growth.

Consider both day and night observations because the species has been recorded as partly diurnal and is also described as nocturnal.

Survey methodology: Minimum effort and reporting

  • Use the effort, equipment, checking intervals and weather conditions specified in the approved survey guideline or project method, and explain any departure from that method.
  • Survey all areas that could be cleared or disturbed, plus adjoining retained habitat that could support relocation or continued movement.
  • Record survey dates, start and finish times, rainfall, temperature where available, fire history, habitat condition, search effort, trap nights, camera effort, personnel, permits and all detections or non-detections.
  • Have a suitably qualified ecologist verify species identification, especially where house mice or other native rodents occur.
  • Submit confirmed records and associated location, date and survey method information to the relevant state wildlife database, including the NSW BioNet Atlas where the record is in New South Wales.
  • Report any threatened species incident, injury, death or unexpected concentration to the relevant wildlife authority and the project approval holder.

Before habitat disturbance: Avoid and minimise

Avoid clearing dense ground cover wherever practicable. The species uses small pockets of mature vegetation and shallow burrows or nests, so apparently open or disturbed ground can still connect occupied habitat.

  • Retain sandy plains, dunes, spinifex hummocks, tussock grass, sedgeland, shrubland, samphire, chenopod and nitre bush habitat with dense ground cover.
  • Avoid clearing areas with mature, unburnt ground cover, because the species has been associated with vegetation that has not been burnt for more than 25 years after fire.
  • Keep connected strips of ground cover between retained habitat patches and avoid isolating small refuge areas with roads, pads, trenches or fences.
  • Keep stock, rabbits, pigs, goats and other herbivores out of retained habitat where practicable, and do not establish new watering points beside retained habitat.
  • Avoid unnecessary disturbance around known burrows, nests, runways and dense tussocks.

Before habitat disturbance: Approvals and planning

  • Check the current EPBC Act status before works commence; the supplied records identify the species as not listed under the EPBC Act, but state approval requirements still apply.
  • Check the threatened species legislation, scientific licence, animal ethics and fauna handling requirements for each state or territory in which the project occurs.
  • In New South Wales, treat the species as Critically Endangered and obtain any required approvals for survey, capture, handling, relocation and disturbance.
  • Prepare a fauna management plan that maps habitat, no-go areas, access routes, pre-clearance survey results, fauna handling procedures, stop-work triggers and reporting responsibilities.
  • Stage works so that habitat is cleared in small sections and retained habitat remains available while adjoining areas are checked.

Before habitat disturbance: Site preparation

  • Complete the approved pre-clearance survey shortly before disturbance, with timing adjusted for rainfall, fire history and the condition of ground cover.
  • Mark no-go areas, dense ground-cover refuges, known burrows, nests, runways and relocation areas on plans and on the ground.
  • Use exclusion fencing only where it will not block movement between retained habitat patches or trap animals within the work area.
  • Brief machinery operators, supervisors and fauna spotter catchers on the species' appearance, shallow burrows, dense tussock refuges and the project stop-work procedure.
  • Inspect and manage machinery, spoil areas, materials storage, lighting and access routes so they do not attract predators or remove adjoining ground cover.

During habitat disturbance: Daily controls

The fauna spotter catcher should control the sequence of clearing and retain dense ground cover until it has been inspected. Work should proceed in short stages, with clear authority to stop machinery when an animal, burrow or occupied refuge is found.

  • Complete a daily pre-start inspection of the work area, retained habitat, exclusion fencing, access routes and machinery before clearing begins.
  • Keep the approved fauna management plan, permits, contact list and relocation instructions available at the work front.
  • Clear progressively towards retained habitat where this is safe and approved, giving animals an opportunity to move into connected cover rather than trapping them against machinery or barriers.
  • Prevent domestic animals, food waste and unnecessary lighting from entering retained habitat, and control access by workers and vehicles.
  • Stop work during conditions that increase risk, including excessive heat, fire, flooding or any condition specified in the fauna management plan or approval.

During habitat disturbance: Spotter catcher and machinery interface

  • The fauna spotter catcher should inspect the next clearing section immediately before machinery enters it and remain able to see the active clearing face.
  • Use a defined exclusion zone around the spotter catcher, animals, burrows and dense tussocks, and do not allow machinery to enter until the area is released.
  • Remove vegetation in stages under the direction of the spotter catcher, avoiding sudden collapse of dense tussocks, burrows and nests.
  • Do not allow workers to handle the animal unless they are authorised and trained under the project approval and fauna management plan.
  • If safe inspection is not possible, suspend clearing and use an approved alternative method, such as additional searching or camera observation.

During habitat disturbance: Animal found, injured or trapped

  • Stop work immediately when a Desert Mouse is seen, captured, injured or found in a burrow or nest within the disturbance area.
  • Keep people, machinery and dogs away, and allow the fauna spotter catcher or other authorised wildlife handler to assess the animal.
  • Do not chase, grab, feed or provide water unless directed by the authorised handler, veterinarian or wildlife authority.
  • If relocation is approved, release the animal into nearby retained habitat with dense ground cover and suitable sandy substrate, at a location selected in the fauna management plan and close enough to avoid unnecessary transport.
  • Place an injured animal in a secure, quiet container and transfer it as soon as practicable to an approved veterinarian or wildlife carer.
  • Record the location, date, time, condition, sex and age class where known, handling method, destination, handler, photographs and outcome.

During habitat disturbance: Stop-work triggers and records

  • Stop work if a Desert Mouse is detected in the active clearing area, if an occupied refuge cannot be safely inspected, or if exclusion fencing directs an animal into the work area.
  • Stop work if clearing departs from the approved footprint, if the fauna spotter catcher loses visual control of the clearing face, or if a permit or approval condition cannot be met.
  • Notify the site supervisor, project ecologist and approval holder before restarting work after a stop-work event.
  • Maintain daily records of cleared area, habitat type, weather, rainfall, machinery hours, personnel, searches, detections, incidents, relocations, injuries, deaths and release locations.
  • Report any death, injury, unauthorised handling or unauthorised clearing to the relevant wildlife authority within the timeframe required by the approval.

After habitat disturbance: Post-clearance checks

Post-clearance work should confirm that no animal or refuge remains in the disturbance footprint and that retained habitat controls are still effective. Monitoring should focus on whether dense ground cover and connected refuge habitat are being maintained.

  • Inspect the cleared footprint after machinery leaves for live animals, injured animals, burrows, nests, tracks and animals trapped against fencing or other structures.
  • Check excavations, trenches, pipes, stockpiles and construction materials before covering, moving or backfilling them.
  • Remove temporary exclusion fencing only after the fauna spotter catcher and project ecologist confirm that no animal remains inside and that removal will not block movement into retained habitat.
  • Confirm that retained sandy habitat, dense tussocks, spinifex, shrubs, sedges and wetland margins have not been damaged by vehicles, spoil, sediment or altered drainage.

After habitat disturbance: Monitoring and reporting

  • Monitor retained and rehabilitated habitat using the approved method, with repeat surveys timed to rainfall and vegetation growth where practicable.
  • Compare detection records, ground-cover condition, fire history, predator activity and disturbance against the pre-clearance baseline.
  • Record any new Desert Mouse detection, evidence of breeding, use of relocation habitat, predator activity, grazing, rabbit damage and changes in ground cover.
  • Provide the regulator and approval holder with the required clearance, incident, relocation and monitoring reports.
  • Submit verified records to the relevant state wildlife database and update the project spatial database with retained habitat, cleared habitat and release locations.

After habitat disturbance: Ongoing controls and offsets

  • Maintain fencing, weed control, feral animal control, drainage controls and access restrictions for the period specified in the approval or fauna management plan.
  • Do not treat an offset as a substitute for avoiding or retaining occupied habitat.
  • Where an offset, conservation agreement or other compensatory measure is required, select and manage habitat that provides dense ground cover and supports the species' sandy plain, dune, spinifex, shrub, sedge or wetland habitat requirements.
  • Document the offset calculation, location, tenure, management actions, performance measures, funding and reporting period required by the approval.

Rehabilitation actions: Rebuild habitat structure

Rehabilitation should rebuild dense, continuous ground cover and shallow refuge habitat. The aim is to provide the vegetation structure used for shelter and feeding, while reducing grazing, predation and damaging fire.

  • Reinstate sandy substrates and natural dune, sandplain and interdune contours where earthworks have altered them.
  • Re-establish locally appropriate spinifex, tussock grasses, sedges, shrubs, samphire, chenopod and nitre bush communities from local provenance seed or other approved material.
  • Protect planted and regenerating areas from grazing, trampling, rabbits, pigs, goats and other herbivores until dense ground cover has developed.
  • Retain or reinstate fallen timber, litter and other natural cover where these occur naturally, without importing material that could introduce weeds or predators.
  • Maintain shallow burrow and nest opportunities in dense tussocks and shrubs, and do not compact or routinely mow rehabilitated ground cover.

Rehabilitation actions: Fire, predators and weeds

  • Use a fire regime that retains unburnt refuge habitat and allows adequate recruitment of dense vegetation.
  • Avoid high-frequency fire in occupied or recovering habitat, because fire reduces ground cover and the species has shown a preference for vegetation more than 25 years after fire.
  • Control foxes and feral cats in accordance with the approved pest management plan, and monitor predator activity near retained and rehabilitated habitat.
  • Control invasive plants and prevent weed-dominated cover from replacing the native ground cover used by the species.
  • Manage stock and introduced herbivores so that grazing and trampling do not remove dense ground cover or degrade burrow and nest sites.

Rehabilitation actions: Monitoring and success measures

  • Set site-specific rehabilitation targets for native ground-cover continuity, spinifex or tussock establishment, shrub recruitment, weed cover, grazing damage, fire history and predator activity before works begin.
  • Inspect rehabilitation after rainfall and during dry periods to assess vegetation response and refuge availability.
  • Use repeat trapping, camera monitoring, habitat searches or other approved methods to test whether Desert Mice use rehabilitated or retained habitat.
  • Treat detection of the species, or sustained improvement in suitable dense ground cover where detection is uncommon, as evidence to be assessed with rainfall and population fluctuations rather than as the sole success measure.
  • Repair erosion, failed plantings, fencing breaches, weed outbreaks and grazing damage promptly, and continue monitoring until the approved performance criteria are met.

Sources