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Southern Brood Frog (Pseudophryne semimarmorata)

The Southern Brood Frog, usually called the Southern Toadlet, is a small terrestrial frog endemic to south-eastern Australia. It uses damp ground cover in forests, woodlands, heathlands and grasslands, and breeds in shallow burrows or depressions that flood after rain. Clearing, altered drainage, fire, drying conditions and chytrid disease can affect both adults and breeding sites on development projects.

Conservation status

Victoria, Flora and Fauna Guarantee Act 1988: Endangered.

South Australia, National Parks and Wildlife Act 1972: Vulnerable.

Breeding season

Southern Brood Frogs breed mainly from autumn to early winter, with calling concentrated from March to May and extending into June after rain. Clearing risk is highest around nest flooding, tadpole development and the emergence of small toadlets in late spring and summer.

Reproductive mode: Egg laying on land, followed by a tadpole stage in water.

Clutch size: 70 to 170 eggs, with up to 200 eggs reported.

Incubation or gestation: Not recorded; males guard eggs for up to 4 weeks.

Size at hatching or birth: Hatchling length is 2.3 mm.

Age at maturity: Not recorded.

Nest or egg sites: Loose egg clutches are laid in shallow burrows, tunnels, muddy holes, shallow depressions and nests beneath moist leaf litter, logs or rocks. Sites are usually in low-lying ground that can flood after rain.

Breeding frequency: One clutch per year is reported.

Confirm timing locally before works, because calling, nest flooding and tadpole development respond to autumn and winter rainfall and to night temperatures.

  • Calling: Males may call from January, call from February to June, and usually call after rain or when water is available. Calling is strongest in March and April, with possible calling in July and August also reported.
  • Egg laying: Eggs are laid during the autumn breeding period, mainly from March to May and possibly into June. Females lay eggs in shallow burrows, tunnels or depressions that can be flooded by rain.
  • Tadpoles: Rain floods the nest and carries hatchling tadpoles into ponds, dams, flooded grassland, drainage lines, creeks or wetlands. Tadpoles have been observed from April to June and may take 6 to 8 months to develop.
  • Froglets: Metamorphosis occurs by late spring and summer. Small toadlets may therefore leave the water from about October to December, depending on when nests were flooded and whether water persists.
  • Active period: The species is nocturnal and is documented as active at night from March to June. Calling and movement may extend from January to August when rain and suitable water are available, with males moving to low-lying nesting sites during breeding.
  • Winter inactivity: Winter inactivity is not specifically recorded for this species. As a fossorial frog, it shelters beneath leaf litter, logs, rocks and in burrows when not active, but calling or activity may continue into June and possibly July or August after suitable conditions.
  • Highest clearing risk: Risk is highest from March to June, when adults call, eggs are present and nests may flood, and from October to December, when late-stage tadpoles and newly metamorphosed toadlets may be present. Retain damp cover and avoid compaction, infilling, drainage changes and dewatering near breeding sites throughout the year.

Identification

This is a small, ground-dwelling myobatrachid with a dark, warty back and a strongly patterned underside. It is most likely to be detected by calling males after autumn rain or by hand searches beneath ground cover.

Adults are about 20 to 30 mm long. The upper body is dark brown to olive green, with black warty blotches. The underside is mainly yellow, orange or red, with broad black and white or black and blue marbling across the chest and upper belly.

The toes are unwebbed and lack adhesive discs. The species has a coloured gland at the base of each hind leg. It generally walks rather than makes long hops.

Body length: About 20 to 30 mm snout to vent length.

Upper surface: Dark brown to olive green with black warty blotches.

Underside: Yellow, orange or red with contrasting black and white or black and blue marbling.

Toe structure: Toes are unwebbed and have no discs.

Identification: Sex and similar species

Females have a smooth underside, while males have a granular underside. The call is very similar to the call of Bibron's Toadlet, Pseudophryne bibronii.

The most reliable distinction from Bibron's Toadlet is the belly pattern. Southern Toadlets have an orange or yellow mottled underside. Confirmatory identification may require close examination of a captured animal by an appropriately authorised person.

Identification: Field signs and detection

Males call from small burrows or shallow depressions after autumn rain. Calling is usually concentrated from late March to early May, and males stop calling when night temperatures fall below about 10 degrees Celsius.

Adults and recently metamorphosed toadlets shelter beneath leaf litter, logs and rocks. Eggs may occur in loose clusters in burrows or shallow depressions. There are no documented species-specific tracks, scats, sloughs or eyeshine signs in the supplied sources.

  • Search damp leaf litter, the underside of logs and rocks, and shallow ground depressions.
  • Use repeated searches during April and early May because surveys outside the calling period can fail to detect animals that are present.
  • Treat any small, dark toadlet with a strongly orange or yellow marbled underside as a potential Southern Toadlet until identification is confirmed.

Distribution: National range

The Southern Toadlet is endemic to south-eastern Australia. The supplied sources describe a broad but discontinuous range across South Australia, Victoria, Tasmania and Bass Strait islands.

The range extends from south-eastern South Australia across southern Victoria, mainly south of the Great Dividing Range, to northern and eastern Tasmania and Flinders Island. Victorian records extend as far north as the Little Desert, although most Victorian records are on public land.

The supplied documents do not identify formal bioregion names or provide a national occupancy map. They also do not identify confirmed strongholds or genetically distinct subpopulations.

Reported range size: Approximately 99,400 km² in one supplied source.

Elevation: Generally associated with lower elevations; no numerical elevation limit is given.

  • South Australia: extreme south-east, with no record in the state frog census from 1998 to 2002.
  • Victoria: mainly south of the Great Dividing Range, with records as far north as the Little Desert.
  • Tasmania: northern and eastern areas, including Flinders Island and other Bass Strait islands.

Distribution: Population status

The population is considered to be declining, but the current population size is uncertain. Victorian surveys and historical comparisons indicate losses from areas where the species was previously recorded.

During surveys of areas affected by the 2009 Kilmore East to Murrindindi fires, only one Southern Toadlet was detected across 106 survey sites, including burnt and unburnt sites with previous records. This result should not be treated as a national abundance estimate.

Survey result after the 2009 fires: One detection from 106 survey sites.

Known population trend: Decreasing.

Population size: Unknown.

  • South Australia: the species was not recorded in the frog census over the five-year period from 1998 to 2002.
  • Victoria: monitoring described in the supplied sources indicates a reduction in records and local recruitment failures.
  • No national population estimate or reliable density estimate is provided.

Habitat: Habitat types

The species uses damp terrestrial habitat rather than necessarily living beside permanent water. Suitable sites combine moist ground conditions with leaf litter, logs, rocks or other low cover.

Records come from damp areas in forests, woodlands, heathlands and grasslands. In Tasmanian black gum and Brookers gum forest communities, the species is associated with damp terrestrial sites and vegetative shelter.

Sites do not need to contain permanent water. Temporary wet areas and flow paths can be important because breeding sites flood after rain and transport tadpoles to pools or wetlands.

Vegetation types: Forests, woodlands, heathlands and grasslands.

Water requirement: Damp terrestrial habitat and temporary flooding; permanent water is not always required.

Typical elevation: Lower elevations, with no numerical limit specified.

  • Retain damp ground habitat beneath intact or partly intact vegetation.
  • Assess temporary drainage lines, shallow depressions and wet hollows even where no permanent pond is present.
  • Treat connected patches of leaf litter, logs and rocks as habitat rather than as isolated cover objects.

Habitat: Site condition

Moisture retention is likely to depend on ground cover, shade and natural drainage. Clearing, canopy removal, logging, firewood collection and altered surface flows can dry or disturb the microhabitat.

Project assessments should include nearby wet depressions and downstream pools because breeding success depends on rainwater entering nests and carrying hatchling tadpoles to suitable water.

  • Map damp ground cover, shallow depressions, temporary flow paths and downstream pools before clearing.
  • Avoid unnecessary removal of logs, rocks and deep leaf litter from retained habitat.
  • Maintain natural drainage patterns where practicable and prevent sediment, contaminants or construction runoff from entering temporary breeding pools.

Foraging habitat: Food and feeding sites

The supplied sources provide little information on detailed feeding ecology. They identify small terrestrial invertebrates associated with chemical defence, which supports treating damp litter and ground cover as feeding habitat.

The species is a small terrestrial frog that feeds in damp ground habitat, but the supplied documents do not give a quantified diet or feeding rate. Ants, beetles and millipedes are identified as dietary sources associated with skin alkaloids in Pseudophryne species.

Likely feeding areas include leaf litter, under logs and around rocks in the small area surrounding the breeding site. The reported home range is about 5 m from the breeding site.

Documented dietary items: Ants, beetles and millipedes are identified as dietary sources associated with skin compounds.

Reported foraging or home range: About 5 m from the breeding site.

  • Retain moist leaf litter, logs, rocks and low vegetation around known or potential breeding sites.
  • Avoid broad-spectrum pesticide use in retained habitat where it could reduce terrestrial invertebrate prey or expose frogs to contaminants.
  • Do not assume that habitat lacking permanent water is unused, because adults forage and shelter in damp terrestrial cover.

Breeding habitat: Breeding biology

Breeding occurs on land in nests that flood after rain. The species depends on a combination of suitable nest sites, autumn rain and nearby temporary pools or wetlands for tadpole development.

Males make burrows in areas likely to flood after rain and call from them. Females lay loose clusters of eggs in the burrows or in shallow depressions. After rain, hatchling tadpoles are washed into larger pools and wetlands.

Metamorphosis occurs from late spring into summer. Recruitment can fail when nests dry before hatching, or when ponds dry while early-stage tadpoles are still present.

Breeding season: Late summer to early winter; calling usually occurs from late March to early May.

Egg clutch: About 50 to 170 eggs.

Egg size: Up to 6 mm in diameter.

Egg placement: Loose clusters in male-made burrows or shallow depressions.

Tadpole pathway: Rain floods the nest and carries tadpoles to pools or wetlands.

Age at maturity: Not stated in the supplied sources.

Lifespan: At least 10 years.

Breeding habitat: Breeding-site features

Suitable breeding sites are damp terrestrial depressions or burrows that can be inundated by rainfall, but are not permanently submerged. They need a hydrological connection to pools or wetlands that retain water long enough for tadpoles to develop.

Autumn rainfall and night temperatures affect breeding activity. In south-west Victoria, ideal conditions were reported when autumn rain began around mid-March and night temperatures remained above 10 degrees Celsius from March to May.

  • Inspect shallow depressions, burrows and damp ground beside temporary drainage features before earthworks.
  • Protect nest sites from drying, compaction, infilling and severed overland flow during the breeding period.
  • Maintain suitable downstream pools and wetlands, while preventing sediment and polluted runoff from entering them.

Sheltering habitat: Refuges

Adults and young shelter at ground level. The species does not require tree hollows, caves or permanent dens, but depends on moist cover close to breeding areas.

Southern Toadlets shelter beneath rocks, logs and leaf litter in damp areas. They may also use male-made burrows and shallow depressions for breeding.

The species has a small home range of about 5 m from the breeding site, so removal of nearby cover can affect the same individuals even when the nest itself is retained.

Shelter types: Leaf litter, logs, rocks, burrows and shallow depressions.

Home range from breeding site: About 5 m.

Known refuge dimensions: Not provided in the supplied sources.

  • Retain logs, rocks, deep leaf litter and low vegetation within and around known breeding areas.
  • Search beneath cover objects by hand rather than relying only on visual searches of open ground.
  • Replace lifted rocks and logs carefully after inspection and avoid leaving animals exposed to drying conditions.

Threats: Clearing and construction

The main project risks are loss of damp terrestrial habitat, disruption of temporary water movement and drying of breeding sites. Disease and altered fire and rainfall patterns add risks across the species' range.

Clearing for housing, roads, infrastructure and agriculture removes forest, woodland, heathland and grassland habitat. Earthworks can crush adults, nests and shelter sites, compact burrows, remove leaf litter and logs, and change the flow of rainwater.

The small reported home range means that retaining only an isolated nest or wetland may not protect the surrounding shelter and feeding habitat.

  • Before clearing, survey damp ground, cover objects, shallow depressions, temporary flow paths and nearby pools.
  • Stage clearing outside the main calling and breeding period where practicable, and use an authorised fauna spotter catcher during works where animals may be present.
  • Keep machinery, stockpiles, access tracks and spoil out of retained damp habitat and temporary drainage features.
  • Avoid removing logs, rocks and leaf litter from retained habitat unless the action is part of an approved fauna management procedure.

Threats: Hydrology, drying and fire

Roads, tracks, groundwater use and other works can alter natural flow or lower the water table. These changes may stop nests from flooding or cause ponds to dry before tadpoles complete development.

Fire, logging and firewood collection can damage shelter and breeding habitat. More frequent or severe fire, late autumn rain and cold nights may reduce breeding success.

  • Keep natural overland flow to suitable nest sites and temporary pools where possible.
  • Prevent drainage works from diverting water away from breeding depressions or concentrating erosive flow through them.
  • Plan fuel reduction and fire operations around pre-fire surveys, preferably in April and May, with repeated visits where practicable.
  • Monitor retained breeding sites after major rainfall and during dry periods for nest desiccation and pond drying.

Threats: Disease and other pressures

Chytrid fungus is identified as a major threat to frog populations and can spread through infected frogs and water. It affects tadpole feeding structures and the skin function of adult frogs.

Other reported pressures include habitat fragmentation, overgrazing, salinity, agricultural pesticides and climate change. The effect of some of these pressures on this species is uncertain, but they should be considered where relevant to a project.

  • Apply current amphibian hygiene procedures to footwear, equipment, containers and water used between sites.
  • Do not move frogs, tadpoles, soil, water or wet organic material between catchments unless authorised and managed under the project hygiene plan.
  • Limit pesticide drift and contaminated runoff into damp habitat, breeding depressions, pools and wetlands.
  • Record all detections and non-detections with survey date, weather, rainfall, habitat condition and survey effort.

Survey methodology: 1. Call surveys and active searches

Survey effort should target damp, low elevation habitat with leaf litter, logs, rocks and seasonal flow paths. The Southern Brood Frog, also known as the Southern Toadlet or Marbled Toadlet, is most detectable during calling and breeding activity after autumn rain.

Survey during the breeding period from late summer to early winter, with the strongest focus on late March to early May when males commonly call after rain.

Visit after suitable autumn rainfall, when males are calling and temporary flow paths, pools and wetlands are likely to hold water.

Search damp areas under leaf litter, logs and rocks in forests, woodlands, heaths and grasslands, including sites that are not beside permanent water.

Use repeated visits during the season, or visits over consecutive seasons, because surveys outside April and early May may fail to detect animals that are present.

Record calling males, adults, juveniles, eggs, tadpoles, empty nest sites and suitable breeding depressions separately.

Survey methodology: 2. Habitat and refuge searches

Inspect leaf litter, logs, rocks, shallow depressions and damp terrestrial shelter during daylight searches, taking care to replace every cover object in its original position.

Search the upper and lower parts of the site, including areas where runoff could flood male nest burrows and carry tadpoles into pools or wetlands.

Map damp habitat and likely breeding flow paths even when no toadlets are detected, because the species has a small home range of about 5 metres from the breeding site.

Survey methodology: 3. Wetland and tadpole checks

Inspect temporary pools, drainage lines, wet depressions and connected wetlands after rain for tadpoles and recently metamorphosed toadlets.

Repeat checks from late spring into summer where breeding habitat has received follow-up rain, because tadpoles develop into small toadlets during this period.

Treat a failed tadpole or egg search cautiously, as nests can desiccate and ponds can dry while early-stage tadpoles are still present.

Survey methodology: Minimum effort and reporting

  • Undertake repeated targeted surveys during late March to early May, with visits after suitable rain and additional checks from late spring into summer where breeding habitat is present.
  • Use the same mapped search areas and survey conditions on repeat visits so that changes in detection are interpretable.
  • Record date, start and finish time, rainfall and recent weather, temperature where available, surveyors, search area, habitat features, breeding evidence, locations and photographs.
  • Have records verified by the project ecologist and submit confirmed records to the relevant state wildlife database, including the Victorian Biodiversity Atlas where the work is in Victoria.
  • Report negative results with the same detail as positive results, including the area searched, search conditions and number of repeat visits.

Before habitat disturbance: Avoid and minimise

Treat damp terrestrial shelter and temporary breeding flow paths as habitat before clearing starts. The species is not listed under the EPBC Act in the supplied material, but state requirements still apply, including the Victorian Endangered listing and the supplied South Australian Vulnerable listing.

  • Retain damp forest, woodland, heath and grassland habitat containing leaf litter, logs, rocks and vegetated shelter.
  • Avoid clearing temporary drainage lines, shallow depressions and wetland connections that can flood nest sites and carry tadpoles to pools.
  • Keep retained habitat connected where practicable, particularly around known records, breeding depressions and damp refuge areas.
  • Avoid removing logs, rocks and deep leaf litter from retained habitat, as these are documented shelter features for the species.

Before habitat disturbance: Approvals and project planning

  • Check the current state threatened-species listing and obtain any required state permits before survey, handling, relocation or disturbance.
  • Confirm the EPBC Act position for the project, noting that the supplied profile identifies the species as not listed under the EPBC Act.
  • Schedule clearing outside the late summer to early winter breeding period where practicable, and avoid late March to early May when calling males are most likely to be detected.
  • Stage clearing so that retained damp habitat, temporary flow paths and refuge features remain available until adjacent works are complete.
  • Prepare a fauna management plan that identifies survey timing, exclusion areas, fauna spotter catcher responsibilities, stop-work triggers, handling arrangements and reporting requirements.

Before habitat disturbance: Pre-clearance preparation

  • Complete a targeted pre-clearance survey after suitable autumn rain, with repeated visits where the habitat is suitable or a previous record is nearby.
  • Mark retained damp habitat, logs, rocks, leaf litter, shallow depressions, drainage lines, pools and wetlands before machinery enters the site.
  • Install exclusion fencing where it can keep machinery and personnel out of retained habitat, while maintaining safe movement routes and avoiding barriers across drainage paths.
  • Brief machinery operators on the species, its small size, walking behaviour, shelter sites and the requirement to stop when directed by the fauna spotter catcher.

During habitat disturbance: Daily controls and machinery interface

The fauna spotter catcher should control the daily sequence of work and keep machinery away from identified habitat. Work should stop when a toadlet, nest, tadpole concentration or unassessed refuge feature is found.

  • Inspect exclusion fencing, retained habitat and access routes before work starts each day and repair damage promptly.
  • Maintain a clear communication method between the fauna spotter catcher, site supervisor and each machine operator.
  • Clear in small stages, allowing the fauna spotter catcher to inspect each work area before machinery enters it.
  • Keep machinery out of retained leaf litter, logs, rocks, damp depressions, drainage lines and wetlands unless the approved fauna management plan specifically allows disturbance.
  • Use the fauna spotter catcher to direct machine movements and stop work before a refuge feature is moved or crushed.

During habitat disturbance: Refuge and habitat feature handling

  • Do not move logs, rocks or leaf litter in a work area until the fauna spotter catcher has inspected beneath and around them.
  • Treat shallow depressions, damp soil and burrows that could flood after rain as potential breeding features until inspected.
  • Prevent sediment, spoil, fuel and concrete washout from entering temporary pools, drainage lines or wetlands used by tadpoles.
  • Do not drain, fill or isolate wet depressions without approval under the fauna management plan and relevant permits.
  • Retain salvaged logs, rocks and suitable leaf litter for placement in nearby retained or rehabilitated habitat.

During habitat disturbance: Animal encounters and stop-work triggers

  • Stop work immediately if a Southern Toadlet, calling male, egg nest, tadpole concentration or uninspected potential nest site is found within the disturbance area.
  • Keep personnel and machinery clear while the authorised fauna handler confirms identification and assesses the animal and its habitat.
  • Only an appropriately authorised fauna handler should capture, handle or relocate the animal, and handling should be limited to what is needed to remove it from immediate harm.
  • Relocate an uninjured animal only to nearby suitable retained damp habitat identified in the fauna management plan, and record the release location.
  • Place an injured animal in a secure, cool container and arrange prompt assessment by a veterinarian or licensed wildlife carer.
  • Resume work only after the fauna spotter catcher and site supervisor have documented the find, completed any approved relocation and confirmed that the area is safe to re-enter.

During habitat disturbance: Records and incident reporting

  • Record every encounter, including the date, time, exact location, identification, condition, action taken, release location, photographs and names of authorised personnel.
  • Record all stop-work events, habitat features inspected, animals not captured, injuries, deaths and breaches of exclusion controls.
  • Notify the project environmental officer and relevant regulator or wildlife authority when required by the permit, approval or fauna management plan.
  • Submit verified occurrence records to the relevant state wildlife database.

After habitat disturbance: Post-clearance checks

Post-clearance work should confirm that no animals or breeding features remain in the disturbed area and that retained habitat has not been damaged. Continue controls until the site is stable and rehabilitation is established.

  • Inspect the cleared area, retained edges, stockpiles and access tracks for stranded toadlets, disturbed nests, tadpoles and damaged refuge features.
  • Recheck temporary pools, drainage lines and wet depressions after rain where works could have changed flow or caused animals or tadpoles to become trapped.
  • Remove fauna exclusion fencing only after the project ecologist confirms that it is no longer needed and that it will not direct animals into machinery areas.
  • Repair sediment controls, drainage controls and habitat exclusion fencing after storms or construction changes.

After habitat disturbance: Monitoring and reporting

  • Repeat targeted call and habitat searches during the next suitable breeding period where habitat was cleared, disturbed or retained beside works.
  • Monitor retained damp habitat, temporary flow paths and rehabilitated areas for calling males, eggs, tadpoles and metamorphosed toadlets.
  • Compare post-work results with pre-clearance records, noting that detection is affected by rainfall, temperature and survey timing.
  • Provide the final fauna report to the approval holder and relevant authorities, including maps, effort, encounters, relocations, mortalities, rehabilitation actions and database submissions.

After habitat disturbance: Offsets and residual impacts

  • Assess residual habitat loss, hydrological change and disturbance against the relevant state approval and project conditions.
  • Apply any required offset, restoration or threatened-species condition identified by the relevant regulator.
  • Do not treat an absence of detections as evidence that suitable habitat was absent, particularly where surveys were outside the April to early May calling period.

Rehabilitation actions: Restore habitat structure

Rehabilitation should restore damp terrestrial shelter and the seasonal water movement needed for breeding. The supplied documents support habitat and hydrology actions, but do not specify a species-specific planting list or numerical rehabilitation targets.

  • Re-establish locally appropriate native vegetation from the original forest, woodland, heath or grassland community.
  • Restore a continuous layer of leaf litter and retain or replace locally sourced logs and rocks in damp, shaded positions.
  • Reinstate shallow depressions and natural drainage patterns where they were altered, while preventing concentrated flows that scour or dry breeding areas.
  • Keep rehabilitated habitat free of construction spoil, excess mulch, rubbish, fuel and chemical contamination.

Rehabilitation actions: Breeding habitat and connectivity

  • Design temporary wet areas and flow paths so that rain can flood suitable terrestrial nest sites and carry tadpoles into pools or wetlands without stranding them.
  • Maintain links between damp refuge areas, breeding depressions, pools and retained vegetation.
  • Avoid relying only on permanent water, because the species breeds in terrestrial burrows or shallow depressions that flood after rain and is not necessarily found beside permanent water.
  • Do not install nest boxes as a substitute for this species’ documented ground-level shelter requirements.

Rehabilitation actions: Weeds, predators, fire and monitoring

  • Control weeds and prevent dense exotic growth from replacing the leaf litter, log and rock shelter used by the species.
  • Manage rubbish, domestic animals and other avoidable sources of predation around retained and rehabilitated habitat.
  • Plan fire management with pre-fire surveys where practicable, and avoid burning occupied damp refuge or breeding habitat without a species-specific assessment.
  • Monitor rehabilitated sites during late March to early May after suitable rain, then check pools and flow paths from late spring into summer for tadpoles and newly metamorphosed toadlets.
  • Use calling males, egg nests, tadpoles, juveniles and repeated occupancy as success measures, together with survival of logs, rocks, leaf litter, native vegetation and functioning seasonal flow paths.

Sources