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Painted Trilling Frog (Neobatrachus pictus)

The Painted Trilling Frog is a stout, burrowing frog of south-eastern Australia. It spends the dry season underground and emerges after heavy rain to feed and breed in shallow temporary wetlands, making soil disturbance, wetland loss and clearing of woodland or grassland habitat important considerations on development sites.

Conservation status

New South Wales, Biodiversity Conservation Act 2016: Endangered.

Breeding season

Painted Trilling Frogs emerge and breed after heavy rain, mainly from March to October in the southern part of their range. Clearing risk occurs during wet breeding events and also during dry periods, when adults may be underground in soil refuges.

Reproductive mode: Egg laying.

Clutch size: About 1,000 eggs per female.

Incubation: Not recorded.

Size at hatching or birth: Not recorded.

Age at maturity: Not recorded.

Nest or egg sites: Loose egg clusters or chains near the water surface, often in or entwined with submerged aquatic vegetation at temporary ponds, swamps, dams and pool margins.

Breeding frequency: Opportunistic breeding after heavy rain, often involving large numbers. Annual breeding frequency is not recorded.

Confirm timing locally before works, because heavy rainfall triggers emergence and breeding, while temperature, water persistence and soil moisture affect calling, tadpole development and aestivation.

  • Calling: Males call from still or slow-flowing water, often while floating with only the head showing or from aquatic vegetation. Calling is mainly from March to October, with winter activity reported as the peak, but rainfall can shift the timing.
  • Egg laying: Females lay about 1,000 small, pigmented eggs in loose clumps or chains near the water surface and in submerged vegetation. Spawning is mainly from March to October after heavy rain, with winter reported as the peak period.
  • Tadpoles: Tadpoles develop in temporary ponds, swamps and dams and take about 5 to 7 months to become frogs. Because breeding can occur from late summer to spring, tadpoles from different rainfall events may be present in any month, depending on local water persistence.
  • Froglets: Froglets can appear throughout the year because tadpoles take about 5 to 7 months to metamorphose and breeding events may occur from March to October. The documents do not identify peak months for juvenile emergence.
  • Active period: Adults emerge, call, breed and feed after heavy rain, mainly from March to October in the southern range. Activity is rainfall dependent and may occur outside these months after substantial rain.
  • Dry season aestivation: During water shortages, adults burrow into soil and form a cocoon from the outer layer of shed skin. November to February is a practical guide for the dry-season refuge period in southern temperate areas, but the timing is controlled by rainfall and soil moisture rather than fixed months.
  • Highest clearing risk: Risk is highest from March to October when adults may be above ground, calling and spawning, and when eggs, tadpoles or metamorphs may occupy shallow water. Clearing, excavation or soil compaction from November to February can still kill aestivating frogs underground, particularly during dry conditions.

Identification

The Painted Trilling Frog is a medium-sized, stout burrowing frog. It may be encountered above ground only for a short period after substantial rain, so calls and breeding habitat can be as useful as direct sightings.

Adults are 55 to 65 mm long. The head is wider than it is long, the snout is rounded and the hind legs are longer than the front legs. The dorsal surface is variable, with brown, beige, yellow or yellowish-green tones and numerous dark brown to black patches. A cream or yellow stripe commonly runs along the backbone. The belly is smooth and white.

Size: 55 to 65 mm snout to vent

Belly: Smooth and white

Hind-foot feature: Black digging tubercle

  • Check the underside of each hind foot for the black metatarsal tubercle used as a digging structure.
  • The toes are about three-quarters webbed in females and nearly completely webbed in males.
  • Breeding males develop small spines on top of the warts, giving the skin a prickly appearance.

Identification: Distinguishing similar frogs

The Painted Trilling Frog is easily confused with Sudell's Frog, Neobatrachus sudellae, where their ranges overlap. Sudell's Frog is generally smaller, at 35 to 50 mm, and usually has fine to coarse yellow, brown, grey and olive patterning rather than the Painted Frog's larger dark patches and typical pale dorsal stripe.

Painted Frog call: A long, low-pitched repeated trill

Sudell's Frog call: A rapid or slowly pulsed trill, described as ‘craw-aw-aw-aw-aw-aw’

  • Use several characters together, including size, dorsal pattern, the pale backbone stripe, toe webbing, foot tubercle and call.
  • Do not rely on colour alone. Both species are variable and may be active only after rainfall.

Identification: Field signs and survey cues

The most useful field sign is the male advertisement call. Males call while floating at the water surface with only the head showing, or from aquatic vegetation. Direct searches should focus on recently inundated shallow pools and nearby woodland or grassland after heavy rainfall.

  • Listen for a long, low-pitched repeated trill around shallow temporary pools, dams, slow-flowing creek sections and aquatic vegetation.
  • Inspect damp ground, pool margins and soft soil for recently emerged frogs, but avoid relying on surface searches during dry weather.
  • Treat underground burrows and aestivation sites as likely even when no frogs are visible. No species-specific tracks, scats, sloughs or eyeshine are described in the supplied documents.

Distribution

The species occurs in south-eastern South Australia and western Victoria, with a small number of records in New South Wales. It is difficult to survey because it is active mainly after good rainfall and can be confused with Sudell's Frog.

The documented range includes south-eastern South Australia and western Victoria. In New South Wales, it has been recorded at only a few locations, mainly in the south-west of the state. The species is associated with the Plains mallee box woodlands of the Murray Darling Depression, Riverina and Naracoorte Coastal Plain bioregions, although the supplied material does not define its full distribution within those bioregions.

Bioregions associated in the supplied material: Murray Darling Depression, Riverina and Naracoorte Coastal Plain

New South Wales records: Fewer than 30 individuals recorded in the state, although detection is difficult

Named strongholds or subpopulations: Not identified in the supplied documents

  • South Australia: widespread in the south-eastern part of the state.
  • Victoria: western Victoria.
  • New South Wales: a few locations in the south-west.

Distribution: Population status

The species is Endangered in New South Wales and is not listed under the EPBC Act. The supplied sources do not provide a national population estimate or a confirmed national trend. Low detectability means that absence from a survey, particularly in dry conditions, should not be treated as evidence that the species is absent.

EPBC Act: Not listed

New South Wales: Endangered

National population estimate: Not stated in the supplied documents

National population trend: Not stated in the supplied documents

Habitat: Terrestrial habitat

Painted Trilling Frogs use dry woodland, mallee and grassland habitats for much of the year, then move to shallow waterbodies after heavy rain. The terrestrial and aquatic parts of the habitat should be assessed together.

The species is reported from open forests, shrubby areas, woodlands and grasslands. In south-west New South Wales it is usually found in woodland and grassland, including areas associated with the Plains mallee box woodland ecological community.

  • Retain native vegetation around temporary pools, dams, floodplain depressions and slow-flowing creek sections.
  • Include adjoining soil habitat in impact assessments because adults spend the dry season underground.
  • Inspect both intact vegetation and cleared or grazed areas that retain suitable shallow wetlands.

Habitat: Breeding habitat and physical conditions

Breeding occurs in shallow ephemeral pools, dams, ephemeral claypans, swamps, floodplains and slower-flowing sections of larger creeks and rivers. The species has a dry season and a rainy season, and emergence and breeding are triggered by substantial rainfall.

Elevation limit: Not stated in the supplied documents

Climate setting: Typically a seasonal environment with a dry season and a rainy season

Waterbody types: Ephemeral claypans, swamps, floodplains, dams, shallow pools and slower-flowing creek or river sections

  • Map temporary pools and drainage depressions, including pools that are dry during the initial site inspection.
  • Record aquatic vegetation and the duration and depth of inundation where possible.
  • Assess hydrology changes that could prevent pools from filling, cause premature drying or increase permanent water where temporary conditions are required.

Foraging habitat

The Painted Trilling Frog appears to feed mainly during the wet period, when it is above ground and in or near recently inundated habitat. Species-specific feeding studies are limited in the supplied material.

The species account states that the Painted Trilling Frog probably eats insects and other invertebrates. It apparently does its feeding during the rainy season, after leaving its underground aestivation site.

Diet: Probably insects and other invertebrates

Feeding period: Apparently during the rainy season

Foraging range: Not stated in the supplied documents

  • Search for feeding habitat in damp woodland, grassland, pool margins and other areas occupied after rainfall.
  • Retain ground cover and native vegetation around temporary wetlands because these areas may support the frog's invertebrate prey.
  • Do not assume that dry-season absence indicates a lack of foraging habitat.

Breeding habitat: Breeding habitat and behaviour

Breeding is opportunistic and can involve large numbers following heavy rain. Males call from shallow water or aquatic vegetation, while females deposit eggs near the water surface.

Painted Trilling Frogs breed after heavy rainfall from late summer to early spring. In the south-west New South Wales region, breeding sites include shallow ephemeral pools, dams and slower-flowing sections of larger creeks and rivers. Males float with only the head showing or call from aquatic vegetation.

  • Protect shallow pools and their margins during and after rainfall events.
  • Retain aquatic vegetation and avoid disturbing egg deposition areas near the water surface.
  • Survey calling frogs at night or during suitable wet conditions, because breeding activity is rainfall dependent.

Breeding habitat: Breeding facts

The supplied documents do not provide species-specific information for gestation, incubation period, age at maturity or lifespan.

Breeding trigger: Heavy rainfall

Typical breeding period: Late summer to early spring

Eggs: Up to about 1,000 small eggs per female

Egg placement: Loose clumps near the water surface or in vegetation, sometimes joined by thin strands

Tadpoles: May grow to about 90 mm from snout to tail tip before metamorphosis

Gestation or incubation: Not stated in the supplied documents

Age at maturity: Not stated in the supplied documents

Lifespan: Not stated in the supplied documents

Sheltering habitat

The main dry-season refuge is underground. The species uses a specialised cocoon of shed skin during aestivation, so clearing can affect frogs that are not visible at the surface.

At the beginning of the dry season, the Painted Trilling Frog digs into soil in open forests or shrubby areas. It forms a cocoon from the outer layer of shed skin and remains underground in a deep sleep-like state until the rainy season begins.

Refuge type: Underground soil shelter

Dry-season strategy: Aestivation inside a cocoon formed from shed skin

Burrow or refuge dimensions: Not stated in the supplied documents

Hollows, dens and roosts: Not applicable or not described for this species

  • Treat suitable soil beneath woodland, mallee, shrubland and grassland as potential refuge habitat, even when no frogs or burrow openings are visible.
  • Avoid broad-scale soil excavation, grading, ripping and compaction in areas connected to breeding pools.
  • Where clearing cannot be avoided, plan searches and fauna handling around rainfall and emergence conditions rather than relying only on daytime surface searches.

Threats: Clearing and fragmentation

The main documented risks are loss and fragmentation of terrestrial habitat, over-grazing and loss of suitable wetlands. Project activities can also affect frogs hidden underground or breeding in temporary pools.

Clearing woodland, mallee, shrubland or grassland can remove underground aestivation habitat and isolate breeding pools from surrounding terrestrial habitat. The species account also identifies future conversion to farmland as a potential risk.

  • Avoid clearing native vegetation around ephemeral pools, dams, floodplain depressions and creek margins.
  • Retain connected terrestrial habitat between breeding sites and nearby woodland or grassland.
  • Treat dry soil as occupied potential habitat where suitable breeding waterbodies occur nearby.

Threats: Grazing and wetland loss

The New South Wales guide identifies over-grazing and loss of suitable wetland habitat as likely threats. Grazing can alter vegetation and soil around temporary wetlands, while wetland loss removes breeding opportunities after rain.

  • Manage stock access to shallow pools and their margins during breeding periods.
  • Prevent sediment, spoil and construction runoff from entering temporary wetlands.
  • Maintain the filling and drying pattern of ephemeral waterbodies where practicable.

Threats: Disease, fire and roads

Chytrid fungus is identified as a major cause of decline among threatened frogs in south-west New South Wales, but the supplied documents do not establish its specific effect on Painted Trilling Frog populations. The documents do not give species-specific evidence for fire or road mortality.

Chytrid fungus: A documented major threat to threatened frogs in south-west New South Wales; species-specific effects on this frog are not stated

Fire response: Not stated in the supplied documents

Road mortality: Not stated in the supplied documents

  • Apply hygiene controls between wetland sites, including cleaning and disinfecting footwear, vehicles and handling equipment according to current amphibian disease procedures.
  • Do not move frogs, soil, water or aquatic vegetation between sites without appropriate biosecurity controls.
  • Assess fire intensity, timing and repeated soil disturbance where these could remove ground cover or alter refuge soil, while recognising that species-specific fire thresholds are not provided.
  • Treat temporary access tracks and vehicle movements near breeding pools as potential risks and use normal amphibian exclusion and speed controls where appropriate.

Threats: Hydrology change

Because breeding follows heavy rain and depends on shallow temporary or seasonal water, changes to drainage, runoff, floodplain connectivity or pool drying can reduce breeding opportunities. The supplied sources do not quantify required water depth, hydroperiod or flow.

  • Map natural drainage lines, claypans, depressions and seasonal pools before works begin.
  • Prevent diversion of runoff away from breeding pools and prevent prolonged inundation where it changes the temporary nature of the habitat.
  • Schedule earthworks and drainage changes outside wet periods where practicable, and inspect sites after rainfall for breeding activity.

Survey methodology: 1. Rainfall triggered call and visual surveys

Painted frogs are burrowing and are most detectable after heavy rain, when they emerge to breed in shallow temporary or permanent water. Surveys should target calling males, wetland breeding habitat and suitable burrowing areas, particularly in woodland and grassland.

Plan targeted night surveys after substantial rainfall, from late summer to early spring where those conditions apply. Painted frogs may emerge in large numbers after heavy rain, but they can be difficult to detect at other times.

Listen for the species call, described as a long, low pitched repeated trill. Search shallow pools, ephemeral claypans, dams, slow flowing creek sections and aquatic vegetation for floating males and egg clumps.

Use a head torch and conduct a slow visual search around the full accessible wetland margin, checking water edges, emergent vegetation and nearby damp ground. Follow the approved project survey guideline for the number of nights, survey duration, transect length and area coverage, because the supplied documents do not specify a numeric effort standard.

Record rainfall, start and finish times, air and water conditions, waterbody type, observers, call detections, visual detections and the position of each observation.

  • Do not rely on a single dry night, because the species is mainly active after good rainfall and may remain underground during dry periods.

Survey methodology: 2. Breeding habitat and egg searches

Inspect shallow ephemeral pools, dams, floodplain depressions, slow flowing creek sections and wetland margins during and after rainfall. These are documented breeding settings for the species.

Search for loose egg clumps near the water surface, in aquatic vegetation and around the edge of the waterbody. Eggs may be attached to one another by thin strands.

Walk each accessible wetland margin systematically and map the wetland, adjacent damp ground, access route and any areas that cannot be safely inspected.

Avoid entering soft claypans or wetlands where access could damage eggs, tadpoles or the wetland bed. Use observations from the edge or an approved low impact access method.

Survey methodology: 3. Daytime habitat and burrow assessment

Map woodland and grassland within and next to the disturbance footprint, including areas with heavier or clay soils and depressions that could hold water after rain.

Inspect suitable loose soil, cracks and ground cover for signs of burrowing frogs, but do not excavate soil or disturb suspected aestivation sites solely to search for the species.

Use night call surveys and post rain searches as the primary detection methods, because the species spends the dry period underground and is difficult to find when inactive.

Record nearby retained woodland, grassland, wetlands, dams, creeks and other areas that could receive an animal moved from the work area.

Survey methodology: Minimum effort and reporting

  • Use a qualified ecologist to set survey timing and effort under the applicable state survey guideline and project approval conditions, as the supplied documents do not provide a species specific numeric effort standard.
  • Schedule repeat targeted surveys after suitable rainfall where the first survey occurs in dry conditions or produces no detection.
  • Include the method, dates, rainfall trigger, conditions, coverage, observers, call and visual results, breeding evidence, photographs and spatial data in the survey report.
  • Submit confirmed records to the relevant state wildlife database and notify the project approval authority where required.
  • Treat a call or frog that cannot be separated confidently from Sudell's frog as an identification issue requiring expert confirmation, because the two species can look similar and share much of their range.

Before habitat disturbance: Avoid and minimise

The main pre clearance risk is removal or isolation of woodland, grassland, burrowing areas and temporary breeding water. Plan the work around rainfall driven breeding activity and retain usable wet habitat wherever practicable.

  • Redesign the footprint to retain shallow wetlands, ephemeral claypans, dams, slow flowing creek sections and wetland margins used for breeding.
  • Retain connected areas of woodland and grassland around breeding water, including suitable burrowing soil and ground shelter.
  • Avoid placing temporary access tracks, stockpiles, spoil or sediment controls on wetland beds, drainage lines or damp ground used by the species.
  • Keep retained breeding habitat connected to nearby woodland and grassland so frogs can move between aestivation areas and breeding water.
  • Fence and clearly mark no go areas before machinery enters the site.

Before habitat disturbance: Approvals and timing

  • Confirm the species status in the project jurisdiction and obtain any required state threatened species permits, survey approvals, handling authorities and wildlife rehabilitation arrangements.
  • The supplied records identify the species as endangered in New South Wales and not listed under the EPBC Act. Check the current EPBC list and obtain advice on referral requirements if the project or another listed matter may be affected.
  • Schedule clearing outside the rainfall driven breeding period where practicable, particularly the period from late summer to early spring identified for south west New South Wales.
  • If works must occur after heavy rain or during active breeding, stage the work and obtain ecologist approval before entering wetland or breeding areas.

Before habitat disturbance: Site preparation

  • Complete a pre clearance survey after suitable rainfall where practicable, and inspect the footprint, access routes and retained habitat for frogs, calls, egg clumps and wetland habitat.
  • Mark wetlands, damp depressions, burrowing areas, access limits and relocation habitat on site plans and in the field.
  • Prepare a fauna management plan that defines survey triggers, stop work points, authorised handlers, relocation arrangements, injured animal treatment and reporting.
  • Install exclusion fencing only where it will not block movement to retained breeding habitat, trap frogs in the work area or damage wetland edges.
  • Brief machinery operators and the fauna spotter catcher on the species appearance, call, burrowing behaviour and wet weather response.

During habitat disturbance: Daily controls and machinery coordination

A fauna spotter catcher should control the immediate work area, check habitat before disturbance and have authority to pause machinery. Wetland and ground disturbance require particular care because frogs may be underground or breeding in shallow water.

  • Inspect the active work area, wetland margins, access tracks, spoil areas and retained habitat at the start of each shift and after rainfall.
  • Require the fauna spotter catcher to walk ahead of machinery and maintain clear communication with the operator by radio or agreed hand signals.
  • Use staged clearing, with machinery working only in the area checked and released by the fauna spotter catcher.
  • Stop machinery immediately when a frog, egg clump, wetland breeding activity, unexpected burrow or other fauna hazard is found.
  • Keep sediment, fuel, concrete washout, dewatering discharge and spoil away from retained wetlands and waterbodies.

During habitat disturbance: Habitat feature handling

  • Do not excavate suspected burrowing areas as a routine search method.
  • Do not drive through shallow pools, claypans, wetland margins or aquatic vegetation unless the approved method specifically allows it.
  • Retain logs, rocks, leaf litter and ground shelter within retained habitat, because these features can provide cover for frogs and other ground fauna.
  • If a wetland, creek section or temporary pool must be disturbed, isolate the work area, inspect it under the approved fauna management plan and obtain ecologist clearance before proceeding.
  • Prevent vehicles and personnel from spreading sediment, weeds or contaminated water between wetlands.

During habitat disturbance: If a painted frog is found

  • Stop work in the immediate area and keep people, vehicles and machinery back from the animal.
  • Only a person authorised under the project fauna management plan and relevant state requirements should capture or handle the frog.
  • Minimise handling, keep the animal cool, shaded and moist, and do not apply chemicals, sunscreen, insect repellent or disinfectant to the frog.
  • Place the frog in an appropriate clean, ventilated container only for the shortest time needed to move it to nearby retained habitat selected by the ecologist.
  • Relocate the frog to suitable retained woodland or grassland with burrowing soil and access to appropriate breeding water, following the approved relocation plan.
  • Do not move eggs or tadpoles unless the relevant authority and fauna management plan specifically authorise that action.
  • Send injured, diseased or lethargic animals to the nominated wildlife carer or veterinarian and record the handover.
  • Treat uncertain identifications as requiring expert confirmation, particularly where Sudell's frog is also present.

During habitat disturbance: Stop work and records

  • Stop work if a painted frog, egg clump or active breeding aggregation is found in the disturbance area, or if rainfall creates new breeding water that has not been assessed.
  • Resume only after the fauna spotter catcher and ecologist have applied the approved response, updated the exclusion area and released the work zone.
  • Record every detection, attempted capture, relocation, injury, death, stop work event, weather condition, location, habitat type and final outcome.
  • Photograph the animal or habitat where this can be done without increasing disturbance, and submit records to the relevant state wildlife database as required.

After habitat disturbance: Post clearance checks

Post clearance work must confirm that no frogs or breeding evidence remain in the disturbed area and that retained wetlands and movement routes are still functional.

  • Inspect the cleared area, wetland margins, access routes, spoil areas and exclusion fences immediately after clearing and again after the next suitable rainfall where required by the fauna management plan.
  • Check for live or dead frogs, egg clumps, tadpoles, collapsed burrows, sediment entry and blocked movement routes.
  • Remove temporary fencing, spoil and equipment only after the ecologist confirms that doing so will not cause further harm or cut off retained habitat.
  • Repair damaged wetland edges, drainage paths, exclusion fencing and access controls before the next rainfall event.

After habitat disturbance: Monitoring and reporting

  • Monitor retained wetlands and adjacent woodland or grassland during suitable wet conditions using call listening, visual searches and breeding evidence searches.
  • Compare post construction observations with the pre disturbance survey, including rainfall conditions and survey coverage, rather than treating a dry period with no detections as evidence of absence.
  • Report all detections, injuries, deaths, relocations, wetland impacts, corrective actions and monitoring results to the project owner and relevant approval authority.
  • Maintain controls and monitoring for the period specified in the approval, fauna management plan or offset condition.
  • Apply any required offset or compensatory habitat measure where avoidance and minimisation do not prevent a residual impact.

Rehabilitation actions: Restore habitat and breeding water

Rehabilitation should restore the combination of burrowing ground, woodland or grassland cover and shallow water that the species uses at different times of year. Wetland function and rainfall response are more important than creating permanent open water alone.

  • Reinstate shallow depressions, ephemeral claypans, drainage paths and wetland margins where construction has altered them, using local soil profiles and natural water levels.
  • Design or restore pools with shallow margins and nearby aquatic vegetation, while retaining suitable access for frogs emerging after rain.
  • Revegetate disturbed areas with locally indigenous woodland and grassland species suited to the local soil and water regime.
  • Retain or replace ground shelter such as logs, rocks and leaf litter in non wetland areas without blocking frog movement or creating hazards for machinery.
  • Do not create isolated permanent ponds where they replace the temporary wetland conditions used by the species.

Rehabilitation actions: Manage threats

  • Control weeds that reduce native ground cover or alter wetland structure, using methods that do not contaminate water or expose frogs to chemicals.
  • Keep livestock, vehicles and unauthorised access away from recovering wetland margins and newly established ground cover.
  • Manage sediment, altered drainage and erosion so that restored pools remain suitable for breeding and are not filled with fine material.
  • Use the approved fire regime for the local woodland and grassland community, avoiding burns that remove all ground cover or coincide with wet breeding activity.

Rehabilitation actions: Success measures and monitoring

  • Monitor vegetation establishment, wetland water retention after rainfall, soil stability, ground shelter, weed cover and connectivity to retained habitat.
  • Conduct repeat call and visual surveys after suitable rainfall, recording the same conditions and methods used before disturbance.
  • Use painted frog calls, visual detections, egg clumps and tadpoles as species response measures, with expert confirmation where Sudell's frog cannot be excluded.
  • Set rehabilitation completion criteria in the fauna management plan and continue corrective work until the restored area supports suitable wetland and burrowing habitat.

Sources