Long-haired Rat (Rattus villosissimus)

Conservation status

New South Wales, Biodiversity Conservation Act 2016: Vulnerable.

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

Breeding season

The timing below reflects the documented Western Australian population increase and the species' ability to breed in any month when food is available. Local timing can shift with rainfall, green vegetation, irrigation and population density.

Month values are indicative for the documented Western Australian breeding event, not a fixed national calendar.

• Breeding: Breeding can occur throughout the year when food is suitable. In the 1983 Western Australian increase, breeding occurred from January to July, peaking in April and May.
• Young: Young are born after a gestation of 22 to 24 days, open their eyes at about 17 days and can be weaned at about 21 days. Dependent young may therefore occur during any breeding period.
• Population movement and expansion: Numbers increase after favourable conditions through local reproduction or immigration, and range can extend from northern and arid areas into central and eastern Australia during boom periods. The sources do not define a fixed movement season.
• Dry-period refuge use: When arid conditions return, animals become restricted to refuge areas with food and water, often near bore holes and other wet areas. Exact months vary with rainfall and irrigation.
• Highest clearing risk: Clearing risk is highest during the documented January to July breeding period, especially April and May, when litters and dependent young are most likely. Active burrows and dense cover remain sensitive outside this period whenever food and water support breeding.

Identification

The Long-haired Rat is a large, grey native rat with conspicuous black guard hairs. Identification is most reliable when body size, coat texture, colour and the location of burrows are considered together.

Adults have a body length of 12 to 22 cm, a tail length of 10 to 18 cm and a weight of 50 to 280 g.

The coat is light grey overall, with long black guard hairs that can give the animal a dark grey appearance. It lacks the lateral tan or brown colouration seen in some other native rats.

Identification: Similar species and field signs

Compared with many other native rats, the Long-haired Rat is relatively large and has a distinctly grey, dark-haired coat without obvious tan or brown sides.

The species is usually associated with burrows beneath vegetation or other cover. Two burrow forms have been recorded: a simple tunnel up to 0.5 m deep with two entrances, and a more extensive system up to 0.8 m deep, with multiple entrances and grass bedding.

The available sources do not describe diagnostic tracks, scats, calls, nests or eyeshine. Do not rely on these signs alone for identification.

Identification: Sex and activity

The available sources do not provide reliable external features for separating males and females in the field.

The species is nocturnal. Surface activity is centred on burrows and can be reduced when the moon is above the horizon.

Distribution: National range

The Long-haired Rat occurs mainly in northern Australia, with periodic expansion into arid areas of central and eastern Australia during population increases. Records and strongholds described in the sources are concentrated in the Kimberley and the Ord River irrigation area, with additional occurrences in Queensland.

The species occurs in northern parts of mainland Australia and in the arid region of northern Australia. During boom periods, its range can extend into central and eastern Australia.

In Western Australia it occurs in the Kimberley, including the Ord River irrigation area near Kununurra. In Queensland it can occur in cultivated pastures and other suitable habitats.

Distribution: Strongholds and population pattern

The Ord River irrigation area is a documented stronghold during population increases. In ordinary conditions, animals may be uncommon and restricted to scattered refuge populations near bore holes and other wet areas.

Numbers can increase through local reproduction or immigration. The 1983 Kimberley increase was attributed to local reproduction in the Ord River area rather than immigration.

Population declines follow the return of arid conditions, together with predator effects and possible reductions in rat health. The sources do not provide a national population estimate or a long-term population trend.

Documented Kimberley population increase: 1983, with high numbers also recorded in 1996 in the Ord River irrigation area

Distribution: Project interpretation

On a project site, apparent absence during dry conditions does not rule out use of the area during wetter periods. Wet areas, bore sites, drainage lines, irrigated land and dense vegetation should be treated as potential refuge habitat when assessing clearing.

Habitat: Habitat types

The Long-haired Rat uses a wide range of open and semi-open habitats, but generally needs either dense vegetation or burrows for shelter. Water and green vegetation strongly influence persistence and population increase.

Recorded habitats include subtropical, temperate, desert and hummock grassland areas.

The species can use watercourse margins, farms, pastoral leases, homesteads, outbuildings and cultivated pastures when populations are high.

Habitat: Structural features

Important features include dense grass or other ground vegetation, cover around burrow entrances, burrowable soil and reliable access to green vegetation or water.

In dry periods, refuge populations occur near bore holes and other wet areas. The sources do not provide an elevation limit or a defined upper or lower temperature limit.

Foraging habitat: Natural food

The Long-haired Rat is an omnivorous herbivore that feeds mainly on plant material, with insects forming a smaller part of the natural diet. It forages at night around burrows, vegetation and cultivated areas.

Natural foods include the roots of desert grasses, herbs, succulent plants, seeds and some insects.

The species moves across open areas but stays close to cover, so feeding habitat is likely to include vegetated ground near shelter rather than exposed open ground alone.

Foraging habitat: Agricultural and disturbed areas

In agricultural areas, the species feeds on crops including rockmelons, maize and sunflowers. It can also occur in cultivated sorghum and oat pastures.

The source records crop damage of 2 to 15 percent in the Ord River valley in 1983. Sunflower damage included climbing stalks and eating soft stem tissue below the flowers.

Foraging habitat: Foraging range

The available sources do not provide a measured nightly foraging distance or home-range size. During field checks, inspect vegetation and ground cover around burrows, water points, crop edges and drainage features rather than surveying only the burrow entrance.

Breeding habitat: Breeding biology

Breeding can occur whenever food is suitable, and reproduction can be rapid when conditions are favourable. Breeding habitat is centred on burrows with nearby green vegetation, food and water.

Breeding season: Can occur throughout the year when suitable food is available. In the 1983 Western Australian population increase, breeding occurred from January to July, with peak breeding in April and May.

Litter size: Usually 5 to 10 young, increasing to an average of 12 during population outbreaks. Litters of up to 20 were recorded during the 1983 outbreak.

Gestation: 22 to 24 days

Postpartum mating: Females can mate directly after giving birth.

Eyes open: Approximately 17 days after birth

Weaning: Approximately 21 days after birth

Age at maturity: Breeding can begin at approximately 62 days, with usual sexual maturity at about 70 days.

Lifespan: Not reported in the supplied sources.

Breeding habitat: Breeding habitat features

Breeding areas require a burrow or dense vegetation for shelter, with access to green vegetation or water. Burrows may contain grass bedding and several entrances.

During project works, active burrows and dense cover should be checked before clearing, particularly near wet areas, bore holes, watercourses, irrigated land and uncropped grass.

Sheltering habitat: Burrows

Burrows are the main daytime refuge. The species also uses dense vegetation and shelter around water points, crop margins and other covered areas.

One recorded burrow type is a simple tunnel up to 0.5 m deep, linking two entrances and lacking bedding.

A second type is up to 0.8 m deep, with multiple entrances, an extensive tunnel system and grass bedding.

Burrow entrances are usually under vegetation or other cover. Activity is centred on these burrows, with surface movement occurring at night.

Simple burrow depth: Up to 0.5 m

Extensive burrow depth: Up to 0.8 m

Sheltering habitat: Refuge habitat

The species generally needs dense vegetation or burrows for shelter. In dry conditions, refuge populations are associated with bore holes and other wet areas.

Clearing, grading, burning or removing vegetation around burrows can remove both the shelter and the food resources used by the species.

Threats: Clearing and construction

The Long-haired Rat can be locally abundant, but populations also contract sharply when dry conditions return. Project impacts are most likely where works remove burrows, dense ground cover, green food plants or access to water.

Clearing dense vegetation can remove burrow cover and food plants. Excavation, trenching, grading and compaction can damage burrows up to at least 0.8 m deep.

Before disturbance, inspect vegetated ground near watercourses, bore holes, irrigated areas, uncropped grass, crop edges and other covered locations for entrances, spoil and bedding.

Threats: Drought and hydrology change

The species can survive for only about 13 days without green vegetation or water, according to the Western Australian fauna note.

Loss of wet refuges, reduced bore or drainage water, altered irrigation and prolonged dry conditions can reduce food availability and shelter use. These conditions are followed by population declines.

Threats: Fire, predators and control

The available sources do not quantify the effect of fire on this species. Burning or repeated removal of grass cover can nevertheless remove shelter and should be assessed as a habitat disturbance.

Predators recorded responding to population increases include Letter-winged Kites, Black Kites, dingoes, cats and snakes. Predation is identified as one factor associated with population decline after wet-period increases.

Rodenticide use can affect native Long-haired Rats and non-target predators. Any control on project or agricultural land must follow applicable approvals and wildlife requirements.

Threats: Fragmentation, roads and disease

The supplied sources do not provide species-specific measurements for fragmentation, road mortality or disease. Assess these risks where works divide dense cover, isolate wet refuges or require vehicle movement through areas with active burrows.

Avoid assuming that a dry site is unused. Population expansion can bring animals into farms, roadsides, homesteads and other disturbed areas.

Survey methodology: 1. Burrow and refuge searches

Survey effort should reflect the species’ patchy occurrence, nocturnal activity and boom and bust population cycles. The supplied documents do not provide a species-specific survey guideline or standard effort, so the project ecologist should apply the relevant state survey guideline and increase effort where suitable habitat, recent records or wet conditions indicate a higher detection likelihood.

Search suitable habitat during daylight for burrows, tracks, runways, grass bedding and fresh spoil around burrow entrances.

Give priority to dense vegetation, grassland, wet areas, watercourses, bore holes, uncropped areas and cultivated margins, because the species uses burrows for daytime refuge and needs vegetation or burrows for shelter.

Record each burrow cluster with coordinates, photographs, entrance condition, surrounding vegetation and whether fresh signs are present.

Do not collapse, fill or handle burrows during the survey.

Burrow depth reported: Simple tunnels up to 0.5 metres deep; larger systems up to 0.8 metres deep

Burrow structure: Burrows may have two entrances, or multiple entrances and extensive tunnels with grass bedding

Survey methodology: 2. Nocturnal spotlighting

Conduct spotlighting after dark along the edge of suitable vegetation, around burrow clusters, near water and across open areas used for movement.

Record the start and finish time, route length or area searched, weather, moon conditions, observers and all detections, including animals seen away from burrows.

Include nights with low ambient light where safe to do so, because activity in one study was reduced while the moon was above the horizon.

Keep observers close to cover and avoid driving through burrow areas or dense refuge vegetation.

Activity period: Nocturnal

Detection consideration: Surface activity may be influenced by ambient light and moon position

• Repeat visits when the first survey is negative but suitable habitat or recent records are present.
• Use the same routes and observation points on repeat visits so that results can be compared.

Survey methodology: 3. Trapping and supplementary detection

Use live trapping only where it is authorised by the relevant state authority and conducted under the project’s animal ethics and fauna handling arrangements.

Place traps near burrow systems, dense vegetation, water or other shelter identified during the habitat search, rather than randomly across unsuitable open ground.

Specify the number of traps, trap nights, trap lines, spacing, checking schedule, weather limits and release procedure in the approved survey plan before work starts.

Do not trap during conditions that could expose animals to heat, cold, flooding, dehydration or predation.

Reported breeding season: Breeding can occur throughout the year when suitable food is available

Reported population pattern: Numbers can increase after suitable conditions and decline when arid conditions return

• Treat trapping as supplementary to burrow searches and nocturnal searches, because the species may be uncommon between population increases and can occur in small refuge areas during dry periods.
• Record captures, trap effort, sex and age class where this can be done safely, body condition, release location and any injuries.

Survey methodology: Minimum effort and reporting

• Use the current survey guideline for the state or territory and document the rationale for the selected number of nights, transects, search area and trap nights.
• Survey all suitable habitat within the disturbance footprint and accessible suitable habitat immediately adjacent to it.
• Repeat surveys after substantial rain or when fresh signs, recent records or high food availability indicate that abundance may have increased.
• Map habitat, burrows, detections, search effort, weather, moon conditions, negative results and access constraints.
• Submit verified records to the relevant state wildlife database and provide the project authority with the survey report, spatial data and photographs.
• Report any suspected population concentration or rapid increase to the relevant state wildlife and land management agencies.

Before habitat disturbance: Avoid and minimise

Plan the works around the species’ dependence on vegetation, water and burrows. Retain refuge areas wherever practicable, particularly where burrow clusters or recent records occur.

Redesign the disturbance footprint to retain dense vegetation, grassland, uncropped margins, wet areas, watercourses, bore surrounds and burrow clusters.

Retain connected vegetation between refuge areas and avoid creating isolated patches where practicable.

Keep machinery, stockpiles, spoil and access tracks out of retained burrow areas and vegetation used for cover.

Avoid removing green vegetation or water access during periods when animals are concentrated in small refuge areas.

• Mark retained habitat, burrow clusters, water points and no-go areas before machinery enters the site.
• Use the smallest practicable clearing footprint and confine vehicle movement to marked access routes.

Before habitat disturbance: Approvals and fauna planning

Confirm the current Commonwealth and state or territory conservation status before work starts, because the supplied profile identifies state listings that may trigger additional requirements.

Check whether the project needs an EPBC Act referral, state approval, wildlife permit, damage authority, animal ethics approval or fauna relocation authorisation.

Prepare a fauna management plan that names the fauna spotter catcher, authorised handlers, stop-work authority, release locations, veterinary contacts and reporting pathway.

Set out survey results, habitat controls, clearing limits, weather limits, incident procedures and record forms in the plan.

• Do not rely on the species being treated as an agricultural pest to authorise killing, capture or relocation during project works.
• Obtain written approval before any lethal control, trapping, handling or relocation is proposed.

Before habitat disturbance: Timing and site preparation

Stage clearing so that the smallest area is opened at one time and retained refuge remains available while each stage is checked.

Schedule works outside periods of high food availability or population increase where practicable, using local records and seasonal conditions to set the timing.

Complete a pre-clearance survey close to the start of works and repeat it if clearing is delayed or conditions change substantially.

Fence or otherwise exclude machinery from retained habitat and burrow areas where this can be done without blocking animal movement into the work area.

• Brief all operators on the species’ appearance, nocturnal behaviour, burrow use, exclusion areas and stop-work procedure.
• Place clear signs at exclusion fencing and inspect the fencing before each work shift.

During habitat disturbance: Daily controls and machinery coordination

Use a controlled clearing sequence with a fauna spotter catcher present whenever suitable habitat or burrows are being disturbed. Stop work when an animal, occupied burrow or unassessed habitat feature is found.

Inspect exclusion fencing, retained habitat, access tracks, machinery and the day’s clearing area before work starts.

The fauna spotter catcher should walk the clearing boundary and inspect the active work area before machinery begins, then remain able to see the clearing face and stop machinery immediately.

Clear from the least disturbed edge towards retained habitat where this is safe and approved, giving animals an opportunity to move into nearby cover.

Use slow, staged clearing around burrows and dense vegetation, with pauses for the spotter catcher to search exposed ground.

• Keep the spotter catcher in direct communication with the machine operator and supervisor throughout clearing.
• Do not allow night works in suitable habitat unless they are specifically assessed, approved and supervised under the fauna management plan.
• Keep cleared vegetation, spoil and machinery away from retained burrows and escape routes.

During habitat disturbance: Burrows and habitat features

Treat every burrow cluster as occupied until it has been inspected and cleared by the authorised fauna handler.

Do not fill, collapse, poison, smoke or excavate a burrow without approval and a documented fauna procedure.

Inspect dense grass, bedding, logs, rocks, debris piles, drains, culverts, wet depressions and vegetation at the edge of watercourses before removal.

The supplied documents do not identify a dependence on tree hollows, so do not assume hollow-bearing trees are the primary shelter feature; still inspect any hollow, log or cavity that will be removed.

• Pause machinery when a new burrow, fresh sign, animal or previously unassessed refuge feature is exposed.
• Retain suitable vegetation and burrow habitat beside the work area wherever the design allows.

During habitat disturbance: Animal found, injury and stop-work response

Stop work in the immediate area when a long-haired rat is seen, captured, injured or found in a burrow being disturbed.

Only an appropriately authorised person may capture, handle, identify or relocate the animal.

Avoid chasing the animal through open ground, and keep people, vehicles and dogs away from it while the fauna handler assesses the situation.

Relocate an uninjured animal only where the approval and fauna management plan allow it, using nearby retained habitat with vegetation, shelter and access to water.

Take an injured animal to an authorised wildlife carer or veterinarian as soon as practicable, following the approved transport and reporting procedure.

• Record the time, location, condition, action taken, release or treatment location, handlers and any interruption to works.
• Stop work until the fauna handler confirms that the animal has moved or that the approved response is complete.
• Escalate repeated detections, multiple animals, a breeding group or a concentrated burrow system to the project ecologist and relevant authority before restarting.

After habitat disturbance: Post-clearance checks

Completion of clearing does not end the fauna controls. Check the disturbed area, maintain retained refuge and document whether the approved controls worked.

The fauna spotter catcher should inspect the cleared area, burrow edges, vegetation piles, drains, excavations and retained habitat at the end of each clearing stage.

Check that no animals, trapped individuals, open excavations or damaged exclusion fences remain before the site is handed back to construction crews.

Search for fresh burrows, tracks, carcasses, injured animals and signs of movement between the cleared area and retained habitat.

Keep any remaining trenches, pits or other fauna hazards covered, ramped or checked at the frequency required by the fauna management plan.

• Do not leave cleared vegetation or spoil piled against retained burrows or movement routes.
• Repair damaged fencing and reinstate exclusion controls before the next work shift.

After habitat disturbance: Monitoring and reporting

Monitor retained habitat and nearby refuge areas for burrow use, nocturnal activity and changes in animal numbers after each clearing stage.

Increase monitoring when wet conditions or food availability are followed by fresh signs or a rapid increase in sightings.

Compare post-work records with the pre-clearance map, including habitat removed, habitat retained, burrows affected, animals handled and any mortality.

Provide incident reports to the relevant authority where required by the permit, approval or fauna management plan.

• Maintain a complete register of survey effort, sightings, captures, relocations, injuries, deaths, veterinary outcomes, complaints and corrective actions.
• Submit verified post-work records to the relevant state wildlife database.

After habitat disturbance: Ongoing controls and offsets

Maintain retained vegetation, water access, exclusion fencing and no-go areas until the project ecologist confirms that construction risks have ended.

Remove temporary controls only after checking that they will not expose occupied burrows or isolate retained habitat.

Apply any approved offset, rehabilitation or compensatory habitat measure required by the project approval.

Review the fauna management plan after any detection, injury, mortality, population increase or failure of an exclusion control.

• Do not describe an offset as a substitute for avoiding or minimising direct disturbance.
• Record the location, condition and management actions for any offset or retained refuge area.

Rehabilitation actions: Vegetation, shelter and water

Rehabilitation should restore the shelter, food and water conditions used by the long-haired rat. The supplied documents support habitat-based actions, but do not specify planting mixes, nest-box requirements or quantitative rehabilitation targets.

Re-establish dense grassland or other locally appropriate vegetation around retained and rehabilitated refuge areas.

Use local species suited to the site and include vegetation that can provide green food, cover and root or grass resources, because the species eats grass roots, herbs, succulent plants and seeds.

Reinstate shelter near watercourses, bore areas and other wet refuges without blocking animal movement or concentrating predators at artificial points.

Keep rehabilitation areas free of unnecessary clearing, soil disturbance, stockpiles and vehicle traffic while vegetation establishes.

• Do not specify a planting density or species list unless it is supported by the local reference community and approved rehabilitation plan.
• Control weeds where they reduce native ground cover or alter access to food and shelter.

Rehabilitation actions: Burrows, logs and other features

Retain existing burrow systems wherever safe and protect them from compaction, flooding and machinery traffic.

Do not install nest boxes as a default measure, because the supplied documents describe burrows and vegetation rather than tree hollows as the species’ reported refuges.

Retain or reinstate locally occurring logs, grass cover and other ground shelter where these features are part of the pre-clearing habitat.

Use artificial shelter only where the project ecologist has a documented design, approval and monitoring method.

• Map rehabilitated burrows and refuge features and inspect them for use after works.
• Do not place logs, rocks or mulch over known burrow entrances.

Rehabilitation actions: Predator, fire and agricultural interface management

Manage feral cats and other introduced predators in accordance with approved site and regional control programs, particularly where rehabilitation concentrates animals in refuge areas.

Plan fire management to retain shelter and food resources while meeting legal and asset protection requirements.

Keep rehabilitated refuge areas separate from crop or pasture damage controls unless those controls have been assessed for impacts on this native species.

Use raptor perches or protection of native vegetation only where part of an approved, site-specific management program, because the species’ predators can increase when rats become abundant.

• Do not use rodenticides or other poisons in or next to rehabilitation areas unless specifically approved and assessed for risks to native fauna and predators.
• Coordinate fire, weed and predator actions with the land manager and record each treatment.

Rehabilitation actions: Monitoring and success measures

Monitor vegetation cover, burrow persistence, fresh burrow construction, nocturnal detections, predator activity and access to water at agreed intervals after rehabilitation.

Use the pre-clearing survey as the reference for habitat condition and compare results using the same search areas and methods where practicable.

Set success measures in the rehabilitation plan for establishment of suitable ground cover, protection of burrows, absence of uncontrolled access and use of the area by the species or other native fauna.

Continue monitoring through both wet and dry conditions where the approval requires it, because abundance can change markedly between favourable and arid periods.

• Report failures such as loss of vegetation, flooded or collapsed burrows, weed invasion, predator concentration or renewed unauthorised disturbance.
• Adapt planting, weed, fire, predator and access controls when monitoring shows that refuge habitat is not being restored.

Sources

• The Australian Hydromyine Rodents, Their Interspecific Diversity and Reproductive Biology: A Review, onlinelibrary.wiley.com: https://onlinelibrary.wiley.com/doi/10.1111/1749-4877.70165
• Microsoft Word - Fauna Note 28 Plague Rat.doc, WA Department of Biodiversity, Conservation and Attractions: https://library.dbca.wa.gov.au/static/Journals/082168/082168-28.pdf