Arnhem Roundleaf Bat (Hipposideros inornatus)

Conservation status

Commonwealth, EPBC Act 1999: Endangered.

Northern Territory, Territory Parks and Wildlife Conservation Act 1976: Vulnerable.

Breeding season

The supplied documents do not provide a breeding calendar, seasonal movement pattern or period of peak presence in Australia. The species is known from the Northern Territory year-round in the available information, and roost disturbance is a potential risk in any month.

Month-specific breeding, young and movement information is unavailable in the supplied documents. Confirm any proposed timing restrictions with a bat ecologist after site assessment.

• Roosting and foraging: The species roosts by day and forages at night. No seasonal pattern of presence or activity is provided, so potential use should be assumed in all months where suitable habitat is present.
• Highest clearing risk: There is no evidence for a seasonal peak. Disturbance, destruction or reduced access to caves and mine adits may harm the species year-round, particularly if a roost or maternity roost is occupied.

Identification

The Arnhem Roundleaf Bat is a moderately large, light brown to grey-brown insectivorous bat with a well developed nose-leaf. It is known from a restricted part of the Northern Territory and has no similar species in the Northern Territory according to the conservation advice.

Adults have a head and body length of 66 to 77 mm and weigh 22 to 35 g. The upperparts are light brown or grey-brown, occasionally orange, and the underparts are slightly paler.

The species has large, acutely pointed ears and a well developed nose-leaf, which are useful features when examining a captured bat under appropriate handling and identification protocols.

Colour: Light brown or grey-brown above, occasionally orange, and slightly paler below.

Ears: Large and acutely pointed.

Nose-leaf: Well developed.

Identification: Similar species

The conservation advice states that there are no similar species in the Northern Territory. Identification should still be checked against current regional bat keys and confirmed by an appropriately qualified person where a project record may affect approvals or site controls.

Identification: Field signs and handling

The species is a cave and mine roosting bat. Relevant field evidence includes bats observed at cave entrances, mine adits or associated roost areas, particularly in cool, draughty locations close to water.

The supplied documents provide no diagnostic information on tracks, scats, calls, echolocation parameters, nests or eyeshine. Absence of visible bats does not exclude a roost, because the species roosts during the day and may not be visible from an entrance.

• Treat caves, mine adits and other potential roost voids as fauna habitat until assessed by a suitably qualified bat ecologist.
• Avoid entering or blocking potential roosts during inspections unless access is authorised and the inspection method has been assessed for disturbance risk.

Distribution: National range

The Arnhem Roundleaf Bat is endemic to Australia and has one of the most limited distributions of any Australian bat taxon. All confirmed areas described in the supplied documents are in the Northern Territory.

The species is currently known from the Kakadu escarpment and the adjoining western edge of the Arnhem Land plateau, including Deaf Adder Gorge and the upper South Alligator River area.

Large areas in the central and eastern parts of the Arnhem plateau remain unsurveyed. The species should therefore not be assumed to be absent from suitable sandstone country solely because there are no existing records.

Australian state or territory: Northern Territory only in the supplied records.

Estimated extent of occurrence: About 2,100 km².

Estimated area of occupancy: About 12 km² based on maternity roost sites, and possibly less than 4 km² using a 2 by 2 km grid method.

• For project searches, give priority to sandstone escarpments, caves and mine workings in western Arnhem Land and the Kakadu region, with nearby riparian and woodland habitat also considered relevant.
• The supplied documents do not provide a state-by-state bioregion list beyond the Northern Territory locations described above.

Distribution: Known strongholds and subpopulations

Known records are concentrated around the Kakadu escarpment, Deaf Adder Gorge and the upper South Alligator River area. A roost containing 14 adults and eight young was reported by Churchill, and 92 bats were observed flying over a site near Deaf Adder Gorge.

A population of 15 bats was found at Tolmer Falls in Litchfield National Park in 1978. No bats have been recorded there or in the surrounding vicinity since 1983, despite targeted searches, so that subpopulation is treated as lost or no longer detected.

Currently known locations used for listing assessment: Two locations.

Known occupied roost sites: The advice reports no other known currently occupied roost sites beyond the few sites described, while noting that many potential sandstone sites remain unexplored.

Distribution: Population size and trend

There is no reliable total population estimate. The number of subpopulations is unknown, and there is no information on movement between sites or metapopulation structure.

Population size is probably declining, with an inferred loss of the Litchfield subpopulation between 1983 and 1998. The available estimate of decline was considered too imprecise to assess the species under the population reduction criterion.

Estimated mature individuals: 300 to 999, inferred from counts at the few known roosting sites, but not considered a reliable total population estimate.

Generation length: 6 to 7 years.

Trend: Probably declining, with an inferred decline in extent of occurrence, area of occupancy, number of subpopulations and number of mature individuals.

Habitat: Overall habitat

The species uses sandstone escarpment country for roosting and a range of nearby vegetation communities for night-time activity. Roost habitat is more specific than foraging habitat and should be assessed separately on development sites.

Day roosts are in cool, draughty areas of caves in rugged sandstone formations, particularly where caves are close to water. One abandoned mine was also used as a roost.

At night, the species forages in monsoon rainforests, riparian vegetation and eucalypt woodlands, typically where these habitats are close to escarpment areas.

• Map and retain caves, rock shelters, mine adits and other potential roost structures, together with nearby water and connected night-foraging habitat.
• Consider both the roost structure and surrounding vegetation when assessing clearing or construction impacts.

Habitat: Vegetation and structure

Documented foraging vegetation includes monsoon rainforest, riparian vegetation and eucalypt woodland. The documents do not provide minimum patch sizes, tree sizes, canopy densities or elevation limits.

The strongest habitat association reported is with escarpment areas and rugged sandstone formations, rather than with a particular tree species.

Key physical features: Rugged sandstone formations, cool draughty caves, nearby water and escarpment country.

Documented vegetation: Monsoon rainforest, riparian vegetation and eucalypt woodland.

Elevation limit: Not stated in the supplied documents.

Foraging habitat: Diet

The Arnhem Roundleaf Bat is an insectivorous bat that feeds at night in several vegetation types, generally near escarpment country. Species-specific information on feeding height, foraging distance and seasonal prey use is not available in the supplied documents.

The species is described as insectivorous. The diet of related Hipposideros species mostly comprises large insects, including beetles, moths, cockroaches and locusts.

No species-specific list of prey plants, prey densities or dietary proportions is provided.

Primary food: Insects.

Likely prey types from related species: Large insects including beetles, moths, cockroaches and locusts.

Foraging habitat: Foraging setting

The species forages at night in monsoon rainforests, riparian vegetation and eucalypt woodlands, typically close to escarpment areas.

The documents do not state the normal foraging range, feeding height, commuting distance from roosts or response to artificial lighting.

Activity period: Night-time foraging.

Foraging range: Not documented for this species.

• Retain riparian vegetation, monsoon rainforest and eucalypt woodland near known or potential roosts where project design allows.
• Assess lighting, noise and vegetation removal around roost access routes and likely night-foraging habitat as part of the site impact assessment.

Breeding habitat: Breeding biology

Breeding-site requirements are poorly known. The conservation advice refers to maternity roost sites and recommends research into their characteristics, so all suspected maternity roosts require careful protection from disturbance.

A roost containing 14 adults and eight young has been reported, confirming use of roosts by young. The supplied documents do not state the mating period, birth season, litter size, gestation period or duration of dependence.

Age at sexual maturity is estimated at 1 to 2 years and is based on information from other Hipposideros species. Longevity is probably around 12 years, also based on other Hipposideros species.

Breeding season: Not documented.

Litter size: Not documented.

Gestation: Not documented.

Age at sexual maturity: Estimated at 1 to 2 years, based on other Hipposideros species.

Lifespan: Probably around 12 years, based on other Hipposideros species.

Young recorded at a roost: Eight young were reported with 14 adults at one roost.

Breeding habitat: Maternity habitat

The species is presumed to use caves and mines as roosts, and the estimated area of occupancy was calculated from maternity roost sites. Specific maternity-roost temperature, humidity, dimensions and access requirements are not provided.

Potential maternity roosts should be managed as high-sensitivity habitat until their use has been assessed.

• Do not seal, gate, modify or excavate a cave or mine adit without first assessing whether it is a maternity or other bat roost.
• Schedule inspections and works to minimise human visitation and disturbance at occupied or suspected maternity roosts.

Sheltering habitat: Natural roosts

Day shelter is provided by cool, draughty caves in rugged sandstone formations, especially near water. Abandoned mine adits may also provide roosts, and the loss of access to these structures is a recognised threat.

The species roosts during the day in cool, draughty areas of caves in rugged sandstone formations. Roosts are particularly associated with caves close to water.

The documents do not provide roost chamber dimensions, entrance dimensions, colony density, preferred height or temperature and humidity thresholds.

• Inspect caves, rock fissures and sandstone shelters that could provide cool, draughty roost spaces, especially near water and escarpments.
• Maintain roost entrances and airflow, and prevent construction activity from blocking access or changing the internal conditions of a roost.

Sheltering habitat: Artificial roosts

One abandoned mine was found to be used as a roost. Destruction or reduced accessibility of old mine adits is therefore relevant to project planning, although only one mine adit record was available in the advice.

Human visitation may have contributed to abandonment of the former Tolmer Falls roost, so repeated entry and inspection can itself be an impact.

Known artificial refuge: An abandoned mine adit.

Roost dimensions: Not documented.

• Assess abandoned mine adits before closure, stabilisation, gating or other structural works.
• Constrain human visitation at known or suspected roosts and retain safe bat access where this is compatible with mine safety requirements.

Threats: Roost disturbance and loss

The main project-related concern is disturbance or loss of roosts. Fire may affect prey availability across the range, while feral cat predation is possible but has not been demonstrated for this species.

Disturbance at roost sites is rated as a moderate threat. The species is considered highly likely to be sensitive to disturbance, and human visitation may have contributed to abandonment of the Tolmer Falls roost.

Destruction or reduced accessibility of roosts, including old mine adits, is also rated as a moderate threat. Works that block entrances, alter airflow, destabilise chambers or increase visitation may affect roost use.

Roost disturbance consequence rating: Moderate.

Roost disturbance extent: Minor, based on the conservation advice.

Roost destruction or reduced access consequence rating: Moderate.

• Establish exclusion zones and access controls around known or suspected caves and mine roosts before clearing or construction begins.
• Obtain specialist advice before blasting, vibration-generating works, excavation, stabilisation, gating or sealing near a potential roost.
• Do not rely on a single daytime inspection to determine that a roost is unused.

Threats: Fire and habitat change

Inappropriate fire regimes operate across the species' entire known range. The conservation advice states that the habitat now has a very high fire frequency and that changes in fire season and intensity could affect prey abundance.

The documents do not demonstrate a direct clearing, fragmentation or hydrology effect for this species. However, clearing or altering riparian vegetation near escarpment roosts can reduce documented foraging habitat, and changes to nearby water availability should be assessed.

Inappropriate fire consequence rating: Minor.

Fire threat extent: Entire known range.

• Retain monsoon rainforest, riparian vegetation and eucalypt woodland near roosts where practicable.
• Incorporate species-beneficial fire planning around known habitat and assess how construction access, linear infrastructure and altered drainage may change fire frequency, intensity or water availability.

Threats: Predators and other pressures

Predation by feral cats has not been demonstrated, but predation at roosts or entrances is possible. The conservation advice recommends assessing feral cat abundance and its effect on population viability.

The supplied documents do not identify disease, vehicle strike, road mortality, artificial lighting or collision as demonstrated threats for this species.

Feral cat consequence rating: Minor.

Feral cat threat extent: Minor.

• Record feral cat activity around important roosts and include practical cat-control measures where monitoring shows a project-related risk.
• Treat road, lighting and disease risks as site-specific matters requiring assessment rather than as established species threats.

Survey methodology: 1. Inspect potential roosts

Survey must focus on nocturnal activity, cool roosting places and foraging habitat near sandstone escarpments and water. The species is difficult to assess because its distribution, population size and number of roosts are poorly known, so survey design should be set by a suitably qualified bat ecologist and adapted to the site.

Before night survey, inspect accessible caves, sandstone crevices, mine adits and other enclosed structures, especially cool, draughty places near water.

Do not enter or substantially disturb a potential roost without the required access approvals and a site safety assessment.

Record evidence of use, including bats, guano, staining, odour and suitable roost conditions, and map each feature.

Survey methodology: 2. Nocturnal bat detection

Survey around sandstone escarpments, caves, mine adits, monsoon rainforest, riparian vegetation and nearby eucalypt woodland.

Use bat detectors to identify and map activity because increasing use of bat detectors has helped define the species' distribution and abundance.

Sample likely flyways and foraging areas close to escarpments and water, and include the entrances and approaches to potential roosts.

Conduct surveys at night when bats are active, with the timing, number of nights and detector placement determined by a bat ecologist from the size and habitat complexity of the site.

Survey methodology: 3. Targeted observation and trapping advice

Use dusk emergence observation at potential caves and mine adits where this can be done without approaching or blocking the roost.

Treat any echolocation identification as requiring suitable reference calls or confirmation by an experienced bat ecologist, because the conservation advice does not provide a species-specific call library or diagnostic call parameters.

Do not use harp traps, mist nets or other capture methods unless the survey is designed, supervised and permitted by an appropriately authorised person.

Survey methodology: Minimum effort and reporting

• Set and document survey effort before fieldwork, including the number of nights, survey hours, detector locations, weather, moon conditions, habitat sampled and any access limitations.
• Survey all accessible potential roosts and representative nocturnal foraging habitat within the proposed disturbance area and retained areas that may be used by displaced bats.
• Record all detections with coordinates, date, time, method, call files or photographs where available, habitat, roost condition and the number of bats observed.
• Report the species, likely roosts and survey limitations to the project ecologist and relevant approval authority.
• Submit verified records to the relevant state or territory wildlife database and the Australian Government threatened species records system where requested.
• Retain raw detector files, field sheets, photographs, maps and clearance records with the project environmental records.

Before habitat disturbance: Avoid and minimise

Avoid disturbance to roosts first, then reduce the area and duration of habitat disturbance. Treat every cave, mine adit and suitable sandstone feature near water as potentially important until survey and approval requirements have been addressed.

• Retain known and potential caves, mine adits, sandstone crevices and the vegetation linking them to nearby water and escarpments.
• Retain foraging habitat that includes monsoon rainforest, riparian vegetation and eucalypt woodland near escarpment areas.
• Keep works, lighting, vibration, blasting, dust and vehicle access away from roost entrances wherever practicable.
• Maintain connected movement routes between retained roosting places, water and foraging vegetation rather than isolating individual habitat patches.
• Do not seal, gate, fill, stabilise or otherwise alter a mine adit or cave until its use by bats has been assessed and the required approval is in place.

Before habitat disturbance: Approvals and work planning

• Check the EPBC Act requirements because the species is listed as Endangered nationally.
• Check Northern Territory or other relevant state and territory threatened species requirements before works, noting that the source material records the species as Vulnerable in the Northern Territory.
• Obtain any permits required for handling, capture, release, cave access, mine access or disturbance to wildlife and roosts.
• Prepare a fauna management plan that maps potential roosts, foraging habitat, exclusion areas, survey results, stop-work triggers, contacts and reporting requirements.
• Stage clearing so that retained roosts and nearby foraging habitat remain available while the work area is being completed.
• Schedule noisy or intrusive work outside periods identified by the bat ecologist as likely to cause roost disturbance, and avoid night works near known or potential roost entrances.

Before habitat disturbance: Site preparation

• Complete the pre-clearance bat survey before finalising clearing limits and machinery access.
• Mark no-go areas around known or potential roosts, roost entrances, riparian vegetation and retained escarpment habitat.
• Install exclusion fencing where it can protect a roost or retained habitat without blocking bat flight paths or access to water.
• Brief all supervisors, operators and fauna spotter catchers on the species' appearance, roost habitat, reporting chain and stop-work procedure.
• Confirm an authorised wildlife handler, suitable holding equipment, a nearby veterinarian or wildlife carer and a release location in retained habitat before clearing starts.

During habitat disturbance: Daily controls

The fauna spotter catcher must keep roosts and retained habitat outside the work area, watch for bats and stop work when the approved controls are not being followed. Work must not proceed on the assumption that an apparently empty cave or mine adit is unused.

• Inspect exclusion fencing, no-go markers, access controls and roost protection measures before work starts each day.
• Keep machinery, generators, lighting and personnel out of marked roost exclusion areas unless the approved management plan expressly allows access.
• Use the fauna spotter catcher to maintain direct communication with the operator and to stop the machine before a protected feature or animal is approached.
• Keep night lighting away from roost entrances and retained flight paths, and avoid directing lights into caves, mine adits or sandstone crevices.
• Recheck the site after heavy rain, flooding, fire or other events that could change access to a roost or retained habitat.

During habitat disturbance: Handling habitat and animals

• Do not enter, block, collapse, seal or alter a cave, mine adit or sandstone roost feature during clearing unless authorised under the approved method.
• Treat a bat found in machinery, on the ground, in a structure or near a roost entrance as a stop-work event until the fauna spotter catcher has assessed it.
• Do not handle the bat unless the person is legally authorised, trained in bat handling and equipped to manage zoonotic disease risks.
• Keep people and machinery away from the animal and allow it to leave naturally where safe and practicable.
• If relocation is authorised and necessary, place the bat in nearby retained habitat that is suitable for the species and as close as practicable to the capture site, following the approved wildlife protocol.
• Send an injured, grounded or compromised bat to an appropriately equipped veterinarian or licensed wildlife carer, and do not release it until its condition and release location have been assessed.

During habitat disturbance: Stop work and records

• Stop work immediately if a bat is found, a previously unknown cave, crevice or mine adit is exposed, a roost is disturbed, or exclusion controls fail.
• Stop work if clearing enters mapped retained habitat, if vibration or lighting affects a roost, or if the approved fauna management method cannot be followed.
• Notify the project ecologist and approval contact, and do not restart until the fauna spotter catcher and authorised decision-maker have cleared the area.
• Record the date, time, location, species identification, number of bats, condition, action taken, handler, release or treatment details, photographs and any work delay.
• Record all disturbance to roosts, near misses, incidents and corrective actions in the project environmental register.

After habitat disturbance: Post-clearance checks

Post-clearance checks should confirm that no bat or roost feature was missed and that retained habitat remains functional. Monitoring is particularly important because the number of occupied roosts and the total population are not well known.

• Inspect the cleared area, retained habitat edges, access tracks and work compounds for grounded, injured or trapped bats.
• Reinspect exposed caves, mine adits and sandstone features where works occurred near potential roost habitat.
• Check that no spoil, fencing, lighting, infrastructure or erosion has blocked access to retained roosts, water or connected foraging vegetation.
• Remove temporary fauna controls only when the project ecologist confirms that they are no longer needed and their removal will not expose retained habitat to further impact.

After habitat disturbance: Monitoring and reporting

• Monitor known or potentially affected roosts and representative nearby foraging habitat using the same methods and locations used before works where practicable.
• Use detector records, emergence observations and roost inspections to compare activity before and after disturbance.
• Continue monitoring for a period set by the approval, management plan and bat ecologist, taking account of the species' estimated generation length of 6 to 7 years where longer-term effects are being assessed.
• Report all detections, incidents, injuries, mortalities, roost changes and management responses to the relevant approval authority.
• Update state or territory wildlife databases with verified records and provide spatial data for retained roosts and habitat where required.

After habitat disturbance: Corrective action and offsets

• Maintain roost protection, lighting controls, erosion controls, fencing and access restrictions for as long as they are required by the approval or management plan.
• Investigate reduced bat activity, roost abandonment, repeated injuries or loss of foraging vegetation and implement corrective actions recommended by the bat ecologist.
• Apply any approved offset or compensatory habitat measure in addition to, not instead of, avoiding and minimising impacts to known roosts and habitat.

Rehabilitation actions: Restore habitat structure

Rehabilitation should restore safe roost access and connected nocturnal foraging habitat near water and escarpments. Planting and fire measures must use local advice because the source material identifies habitat types but does not specify plant species, planting densities or a rehabilitation timeframe.

• Reinstate local native vegetation communities that match the affected monsoon rainforest, riparian vegetation or eucalypt woodland habitat.
• Restore vegetation links between retained sandstone escarpments, caves or mine adits and nearby water.
• Stabilise disturbed ground and drainage so sediment does not enter riparian areas or affect access to roosts.
• Do not create, fill, gate or modify caves and mine adits as a rehabilitation measure without assessing their potential use by bats and obtaining approval.

Rehabilitation actions: Roosts and fauna features

• Protect retained caves, sandstone crevices and mine adits from people, machinery, vibration, inappropriate lighting and unauthorised entry.
• Use a bat ecologist to assess whether any proposed gate or other roost treatment will preserve airflow, access and safe bat movement.
• Do not install nest boxes as a substitute for caves or mine adits unless monitoring and expert advice show that the design is suitable for this species.
• Retain natural rocks, logs and other habitat features where they support the reinstatement of the surrounding native vegetation, while recognising that the conservation advice does not identify them as roost sites for this bat.

Rehabilitation actions: Fire and predators

• Develop fire management with the land manager so that fire regimes support insect prey and retain the structure of nearby rainforest, riparian and eucalypt foraging habitat.
• Monitor the effects of fire season, frequency and intensity on vegetation and prey habitat, because inappropriate fire may reduce prey abundance.
• Assess feral cat presence and predation risk at roosts and entrances, and apply approved control measures if monitoring shows that cats are affecting the species.
• Keep rehabilitation areas free of invasive weeds that reduce the quality or continuity of native foraging vegetation.

Rehabilitation actions: Monitoring and success measures

• Monitor survival and cover of planted native vegetation, riparian stability, connectivity to retained habitat and the condition of roost entrances.
• Repeat bat detector surveys and roost inspections at affected and reference sites using comparable methods.
• Treat successful rehabilitation as retention or recovery of safe roost access, connected native foraging habitat near water and escarpments, and no evidence of work-related roost abandonment or injury.
• Adjust fire, weed, predator and access management when monitoring shows that habitat quality or bat activity is declining.

Sources

• Conservation Advice Hipposideros inornatus Arnhem leaf-nosed bat, Australian Government DCCEEW: https://www.environment.gov.au/biodiversity/threatened/species/pubs/86675-conservation-advice-2015123.pdf
• Hipposideros inornatus (Arnhem leaf nosed bat), Australian Government DCCEEW: https://www.dcceew.gov.au/environment/biodiversity/threatened/nominations/comment/hipposideros-inornatus
• Hipposideros inornatus • Arnhem Roundleaf Bat, mammaldiversity.org: https://www.mammaldiversity.org/taxon/1004607/