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Oenpelli Rock Python (Nyctophilopython oenpelliensis)

The Oenpelli Rock Python is a large, rare python endemic to sandstone country in western Arnhem Land, Northern Territory. It uses rock crevices, caves, overhangs, trees and dense vegetation, so clearing, access tracks, blasting, fire regime changes and removal of prey habitat can affect individuals and local subpopulations on development sites.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

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

Breeding season

Mating has been reported in July and egg laying in November. Adult activity is reported to peak from November to March during the wet season, while activity and sightings may decrease through the drier months. Plan clearing controls across the year because eggs, gravid females and animals sheltering in rocks, trees and dense vegetation may be present at different times.

Reproductive mode: Egg laying.

Clutch size: 4 to 9 eggs reported in captivity. Another source reports 15 to 30 eggs.

Incubation: Not recorded.

Size at hatching: Not recorded.

Age at maturity: Not recorded.

Nest or egg sites: Concealed nests, often in hollow logs or dense vegetation. Field nest sites are not confirmed.

Breeding frequency: Not recorded.

Confirm timing locally before works by checking recent rainfall, temperature and wet season onset, and obtain site-specific advice from the project ecologist where breeding or shelter use is suspected.

  • Mating: Mating is reported in July. Other sources describe breeding in the wet season or late dry season to early wet season, so local timing may vary with rainfall and temperature.
  • Egg laying: Egg laying is reported in November. Another source places breeding in the wet season but does not provide additional laying months.
  • Active period: Activity is reported to peak during the Australian wet season, from November to March. The species is nocturnal, and sightings may be more likely at night, dawn and dusk.
  • Dry season inactivity: Outside the wet season, from approximately April to October, sightings may become less frequent as animals retreat into rock formations and reduce activity. This is a reported seasonal pattern, not evidence that the species is inactive throughout the dry season.
  • Highest clearing risk: Treat clearing risk as year round because the species uses caves, crevices, overhangs, trees, large stumps and dense vegetation, and breeding timing is not fully resolved. Apply additional checks around the reported July mating and November egg laying periods, and inspect shelters during the drier months when animals may remain concealed.

Identification

This is a very large, slender python with a restricted range in western Arnhem Land. It is most likely to be detected by a direct sighting at night, in rocky habitat or in trees, rather than by distinctive ground signs.

Adults may exceed 4 metres in total length and are unusually thin in proportion to their length compared with other pythons. The dorsal surface is dark olive-brown or pale brownish to olive, with dark blotches in longitudinal rows. The belly is pale cream to yellow.

The species can change colour, tending to be lighter at night and darker during the day. It may occur on the ground or in trees, and may remain motionless for long periods while ambushing prey.

Maximum reported length: More than 4 metres in the wild species accounts; more than 5 metres reported for one captive specimen.

Typical colour: Olive-brown to pale brownish olive dorsally, with dark blotches; pale cream to yellow underneath.

Identification: Distinguishing features

The combination of very large size, a slender body, olive colouration with dark longitudinal blotches, and association with Arnhem Land sandstone country is useful in the field. The species has heat-sensing pits on the rostral, first three supralabial and posterior infralabial scales, and more than 400 ventral scales, but these features are normally unsuitable for an animal that is not being handled.

  • Do not use the historical genus names Morelia, Simalia or Nawaran as evidence that a different species is present. They are names used for the same taxon in different sources.
  • Obtain clear photographs of the head, dorsal pattern, body proportions and habitat, and record the location without attempting to handle the snake.

Identification: Field signs and handling

The supplied sources do not describe diagnostic tracks, scats, calls, sloughs, eyeshine or nest signs. A large shed skin or a sighting in a sandstone crevice, cave, overhang or shady tree may warrant targeted identification by a suitably qualified herpetologist, but these observations are not species-specific on their own.

The species is rare and may be illegally collected. Avoid publicising precise refuge locations and use fauna handling procedures appropriate to a large python.

  • Before clearing or rock removal, inspect sandstone crevices, caves, overhangs, large tree hollows and dense vegetation for a large python or shed skin.
  • Stop work and obtain advice from the fauna spotter catcher or project ecologist if a suspected Oenpelli Rock Python is found.

Distribution

The Oenpelli Rock Python has a highly restricted Australian distribution. All documented records in the supplied material are from the Northern Territory, in western Arnhem Land sandstone country.

The known range is centred on sandstone outcrops and massifs around the upper reaches of the Cadell, South Alligator and East Alligator rivers. The type locality is 6.5 kilometres south-west of Oenpelli, at 12°21'S, 133°01'E.

The species is associated with the Kombalgie sandstone gorges and has also been reported from woodland, heathland and open rocky plains. It occurs within Kakadu National Park.

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

Main region: Western Arnhem Land.

Type locality: 6.5 kilometres south-west of Oenpelli, Northern Territory.

Known protected area: Kakadu National Park.

Distribution: Population and subpopulations

The total population has not been adequately surveyed, and the rate of decline has not been established. The available assessment inferred a population of fewer than 10,000 from prey abundance and other factors, rather than from a complete population survey.

The sources do not provide population estimates for individual gorges, catchments, bioregions or subpopulations. The species' inaccessible habitat may reduce disturbance but also limits survey coverage.

Inferred population: Estimated to be below 10,000, with substantial uncertainty.

Population trend: Not quantified in the supplied documents.

  • Treat records from separate sandstone gorges or massif systems as potentially important local subpopulations until connectivity and movement between them are known.
  • Use targeted searches and expert review where works occur near sandstone outcrops, dense vegetation, caves or gorges within western Arnhem Land.

Habitat: Core habitat

The species is closely associated with sandstone landforms and dense vegetation, but it also uses adjoining open and wooded habitats. Specific elevation limits and mapped bioregional boundaries are not given in the supplied documents.

Core habitat includes weathered sandstone massifs, sandstone gorges, rock outcrops with dense vegetation, overhangs and caves. The species is also associated with shady trees and may move between discrete positions within its territory.

Reported surrounding habitats include woodland, heathland, open rocky plains, dry forest and some patches of monsoon forest.

  • Map sandstone gorges, outcrops, caves, overhangs and densely vegetated rocky areas before finalising a clearing footprint.
  • Retain connected vegetation around rocky refuges where practicable, including shady trees used as resting or ambush sites.
  • Include adjacent woodland, heathland and open rocky plains in impact assessments where they connect sandstone refuge areas.

Habitat: Site limits

The supplied documents do not provide an elevation range, temperature threshold, rainfall limit or formal vegetation community classification. The documented range is restricted to western Arnhem Land in the Northern Territory, particularly sandstone massif country around the upper Cadell, South Alligator and East Alligator rivers.

Elevation limit: Not reported in the supplied documents.

Climate limit: Not reported in the supplied documents.

Foraging habitat: Diet and feeding sites

The Oenpelli Rock Python is a nocturnal ambush predator. It forages in trees and rocky habitat, with prey use changing from birds to larger mammals as the snake grows.

The species feeds on birds in fruiting trees and has been suggested to specialise in birds. Adults also prey on medium to large mammals, including possums and large macropods. Captive animals have eaten birds and rodents.

It may remain motionless for long periods while waiting for prey. Reported foraging settings include fruiting trees, shady trees, woodland, rocky plains and sandstone gorge habitat.

  • Retain fruiting and shady trees connected to sandstone refuges where they occur within or beside a work area.
  • Assess removal of woodland and rocky habitat for its likely effect on birds, possums, macropods and other prey, not only on the python's shelter sites.
  • Avoid assuming that an apparently empty rock outcrop is unused, because the species may remain concealed for long periods.

Foraging habitat: Foraging range

The species is territorial and roams between discrete positions, including overhangs, caves in sandstone gorges and shady trees. The supplied documents do not give a home-range area, daily movement distance or seasonal foraging distance.

Home-range size: Not reported.

Movement pattern: Territorial, with movement between discrete rocky and tree refuges.

Breeding habitat: Breeding biology

Breeding information is limited. The species lays unusually large eggs, and the available clutch information comes from captive observations rather than a documented field study.

The species is oviparous. Captive clutches of 4 to 9 eggs have been reported, with eggs measuring about 110.5 by 60 millimetres. The supplied documents do not state the mating season, laying months, incubation period, age at maturity or lifespan.

Breeding mode: Egg laying.

Clutch size: 4 to 9 eggs reported in captivity.

Egg size: About 110.5 by 60 millimetres.

Mating season: Not reported.

Incubation period: Not reported.

Age at maturity: Not reported.

Lifespan: Not reported.

Breeding habitat: Breeding habitat

The sources do not identify a specific nest site or field breeding habitat. Because the species uses caves, crevices, overhangs, trees and dense vegetation, these features should be retained and checked before rock removal, tree clearing or blasting in occupied range.

  • Treat caves, deep crevices, overhangs, large tree hollows and dense vegetation near sandstone outcrops as potential breeding habitat until inspected.
  • Schedule pre-clearing searches and fauna management around the uncertainty in breeding timing rather than assuming that no eggs or young are present.

Sheltering habitat: Known refuges

Shelter is centred on sandstone features and shady trees. The species may use several discrete refuges within its territory rather than a single den.

Documented shelter locations include rock crevices, caves and overhangs in sandstone gorges. The species also uses trees, shady trees and large tree stumps, and is associated with sandstone outcrops with dense vegetation.

No dimensions are provided for crevices, caves, tree hollows or stumps. The sources do not describe burrows, constructed nests or communal roosts.

Refuge types: Rock crevices, caves, sandstone overhangs, shady trees and large tree stumps.

Refuge dimensions: Not reported.

  • Inspect rock crevices, caves, overhangs, large tree stumps, shady trees and dense vegetation before clearing or ground disturbance.
  • Use exclusion zones or other site controls around occupied refuges where practicable, with distances set by the project ecologist and relevant approval conditions because species-specific refuge distances are not reported.
  • Do not fill, seal or blast potential refuges without an approved fauna management response.

Sheltering habitat: Detection and response

The species is nocturnal and may be concealed during daytime inspections. Night searches can improve the chance of detection, but the supplied documents do not specify a validated survey method or survey effort.

  • Plan searches with an ecologist familiar with large pythons and western Arnhem Land sandstone habitat.
  • If a python is found, keep people and machinery clear, prevent capture by untrained personnel, and record photographs, habitat and coordinates for the project fauna records.

Threats: Clearing and construction

The main documented threats are altered land use, changed fire regimes, loss of suitable habitat, decline in large prey and illegal collection. The supplied documents do not specifically quantify road mortality, disease or hydrology impacts.

Suitable habitat is limited, and altered land use can remove sandstone refuge sites, dense vegetation, shady trees and prey habitat. Clearing may also separate discrete rock and tree positions used within a territory.

Rock removal, blasting, trenching, access tracks and tree clearing can directly affect caves, crevices, overhangs, stumps and other potential refuges.

  • Complete a targeted habitat assessment before clearing in western Arnhem Land sandstone country.
  • Flag and retain sandstone gorges, outcrops, caves, crevices, overhangs, dense vegetation and shady trees where project design allows.
  • Require a fauna spotter catcher or suitably qualified ecologist to inspect potential refuges before disturbance.

Threats: Fire, prey and introduced species

Changed fire regimes are a documented threat. As a large predator, the species may be particularly affected by declines in available prey. Large mammals are described as susceptible to land-use change and introduced species.

The supplied documents do not identify a particular introduced predator or quantify the effect of fire frequency, intensity or season on Oenpelli Rock Python subpopulations.

  • Assess whether the project changes fire access, fuel continuity or fire management around sandstone refuges.
  • Retain habitat supporting birds, possums, macropods and other potential prey.
  • Manage construction waste and food sources so that introduced animals are not attracted to work areas.

Threats: Collection and other pressures

Illegal collection for private use is known to affect some subpopulations. Inaccessibility limits this threat in some areas, but it also limits survey and monitoring.

Road mortality, disease and hydrology change are not specifically documented in the supplied sources. Assess them where a project introduces roads, altered drainage, water extraction or contact with captive or domestic animals.

  • Restrict access to known refuge locations and do not publish precise records publicly.
  • Record and report suspected illegal collection or unauthorised handling through the relevant Northern Territory and project channels.
  • Use project-specific risk assessment for roads, drainage and disease because species-specific evidence is not provided here.

Survey methodology: 1. Nocturnal spotlighting

Survey effort should be targeted to the species' very restricted habitat in western Arnhem Land. The Oenpelli rock python is nocturnal, uses sandstone crevices, caves, trees and overhangs, and may remain motionless for long periods, so searches must cover both rocky refuges and arboreal habitat.

Conduct nocturnal searches when the species is active, with particular attention to sandstone gorges, overhangs, caves, rock crevices, shady trees and dense vegetation around outcrops.

Search fruiting trees, woodland, heathland and open rocky plains where the species or its prey may occur.

Use experienced observers who can identify a long, slender python and distinguish it from other snakes, because motionless individuals may be difficult to detect.

Activity period: Nocturnal

Known adult length: More than 4 m, with one captive report exceeding 5 m

  • Record the start and finish time, weather, search route, habitat searched and visibility conditions for every search.
  • Do not rely on a single night because the population is poorly surveyed and the species can remain motionless for long periods.

Survey methodology: 2. Targeted refuge and habitat searches

Inspect accessible rock crevices, caves, overhangs, sandstone gorges, large trees and dense vegetation associated with sandstone outcrops.

Search discrete resting positions rather than only walking transects, because the species is territorial and may move between overhangs, caves and shady trees.

Treat likely refuges as occupied until they have been assessed by the project ecologist and fauna spotter catcher.

Known habitat: Sandstone massif and outcrops in western Arnhem Land, including areas around the upper Cadell, South Alligator and East Alligator rivers

Associated habitat: Sandstone gorges, dense vegetation, woodland, heathland and open rocky plains

  • Use non-destructive visual inspection and lighting of crevices and hollows where safe and authorised.
  • Do not enter unstable caves, climb trees or disturb rock features solely to improve detection.
  • Map each searched refuge and record signs, sightings, photographs and any evidence of prey use.

Survey methodology: 3. Detection planning and survey records

Base the survey area on mapped sandstone outcrops, gorges, caves, overhangs, dense vegetation and trees connected to those features.

Use repeated targeted searches where initial searches are negative, because the total population and decline rate are poorly known.

Obtain regulator or species specialist advice before using trapping, handling or other intensive methods, as no species-specific trapping effort or trap design is provided in the supplied documents.

  • Record survey nights, observer hours, route length or area searched, habitat type, weather, moon or illumination conditions, detection method and search result.
  • Report both positive and negative results, including the features searched and any areas that could not be accessed safely.
  • Avoid presenting absence from a single survey as evidence that the species is not present.

Survey methodology: Minimum effort and reporting

  • Use a regulator-approved, risk-based survey design because the supplied documents do not specify a minimum number of nights, hours, transects, trap nights or survey area for this species.
  • Complete targeted nocturnal searches of all accessible sandstone refuges and connected trees within the proposed disturbance footprint and nearby retained habitat.
  • Have the project ecologist review all records before clearing or construction starts.
  • Submit confirmed records, including coordinates, photographs and survey effort, to the relevant Northern Territory wildlife database or other relevant state or territory wildlife database.
  • Report the species under the current accepted name used by the relevant regulator and include taxonomic synonyms where they assist database matching.

Before habitat disturbance: Avoid and minimise habitat loss

Avoid disturbance to sandstone habitat wherever practicable. This species has a restricted range, limited suitable habitat and known association with Kakadu National Park and western Arnhem Land sandstone systems.

  • Retain sandstone gorges, caves, overhangs, rock crevices, large trees and dense vegetation associated with sandstone outcrops.
  • Keep connected habitat between rocky refuges, trees and foraging areas wherever practicable.
  • Do not remove or seal caves, crevices or overhangs unless the project approval specifically addresses the feature and a qualified ecologist has assessed it.
  • Avoid clearing in mapped habitat until targeted surveys and the required approvals are complete.
  • Give particular weight to retaining habitat used by medium to large mammals and other prey, because the species is a large predator and may be affected by prey declines.

Before habitat disturbance: Approvals and work planning

Common conservation listing in the supplied material: Northern Territory Vulnerable; IUCN Vulnerable is also reported

Known protected area: Kakadu National Park

  • Check whether the proposed action requires an EPBC Act referral because the species is nationally listed as Vulnerable.
  • Obtain all Northern Territory or other relevant state and territory permits for clearing, fauna handling, relocation and wildlife rehabilitation.
  • Prepare a fauna management plan that identifies exclusion areas, survey methods, fauna spotter catcher responsibilities, stop-work triggers, handling arrangements and reporting requirements.
  • Stage clearing so retained habitat remains connected and fauna can be managed progressively rather than exposed across a large cleared area.
  • Schedule works to avoid the species' nocturnal activity period where practicable, while recognising that daytime works can still disturb animals sheltering in crevices, caves and trees.

Before habitat disturbance: Pre-clearance preparation

  • Complete the approved targeted survey before finalising the clearing boundary.
  • Mark no-go areas around occupied or potentially occupied sandstone refuges, caves, overhangs, trees and dense vegetation.
  • Install exclusion fencing only where it will not block movement between retained rocky refuges and trees, and inspect fencing for trapped or displaced fauna.
  • Brief all machinery operators and contractors on the species' appearance, habitat, stop-work procedure and reporting requirements.
  • Confirm that an authorised fauna spotter catcher, suitable containment equipment, a wildlife veterinarian and an approved wildlife carer are available before disturbance begins.

During habitat disturbance: Daily controls and machinery interface

Clearing should proceed slowly and under active fauna spotter catcher supervision. The main field risks are crushing or blocking animals in rock refuges, trees and dense vegetation, and removing connected shelter before an animal can be safely managed.

  • Inspect the work area each day before machinery enters, including rock crevices, caves, overhangs, trees, dense vegetation and recently exposed ground.
  • Use a fauna spotter catcher with authority to stop machinery immediately when a snake, suspected refuge or unexpected habitat feature is found.
  • Clear in short stages from retained habitat towards the approved clearing boundary, allowing the spotter catcher to inspect each area before machinery advances.
  • Keep machinery away from marked no-go areas and maintain the approved exclusion distances around occupied or potentially occupied features.
  • Do not allow workers to handle, chase, corner or kill a snake.

During habitat disturbance: Habitat feature handling

  • Treat sandstone caves, overhangs, crevices and large trees as potential refuges and inspect them before disturbance.
  • Do not break, collapse, fill or seal a rock refuge while it is occupied or before the fauna spotter catcher has cleared it.
  • Retain suitable rocks, logs, trees and dense vegetation in retained habitat where they form part of connected shelter or foraging areas.
  • Use a staged process for any tree or rock feature that must be removed, with the spotter catcher checking the feature before, during and after removal.
  • Do not move a large rock feature or destroy a cave to search for an animal unless the action is authorised and directed by the project ecologist.

During habitat disturbance: If an Oenpelli rock python is found

  • Stop work immediately within the animal's potential movement area and keep people and machinery back.
  • Photograph the animal from a safe distance and notify the project ecologist and fauna spotter catcher.
  • Allow the animal to move away naturally into nearby retained habitat when this can occur safely.
  • Use handling or relocation only when it is necessary to protect the animal or enable approved works, and only by a person authorised under the relevant permit and fauna management plan.
  • Relocate the animal only to suitable nearby retained habitat that is connected to sandstone refuges, trees and dense vegetation, unless the regulator directs otherwise.
  • Place an injured animal in an appropriate secure container and arrange prompt assessment by a wildlife veterinarian or approved wildlife carer.
  • Never attempt to restrain a large python without trained personnel, suitable equipment and a safe handling plan.

During habitat disturbance: Stop-work triggers and records

  • Stop work if an Oenpelli rock python is found, if a suspected occupied refuge is exposed, or if clearing moves outside the approved boundary.
  • Stop work if exclusion fencing traps an animal or blocks movement between retained habitat features.
  • Record the date, time, coordinates, habitat feature, animal condition, photographs, people involved, action taken, relocation destination and recommencement approval.
  • Record all injuries, mortalities, escapes, unauthorised clearing and breaches of exclusion areas and notify the relevant regulator as required.
  • Resume work only after the project ecologist or other authorised person confirms that the fauna risk has been controlled.

After habitat disturbance: Post-clearance inspection

Post-clearance checks should confirm that no animal remains isolated in the work area and that retained sandstone refuges and movement links remain functional.

  • Inspect the cleared area, retained edges, rock refuges, caves, overhangs, trees and dense vegetation after each clearing stage.
  • Check excavations, stockpiles, drains, temporary fencing and machinery areas for trapped or sheltering fauna.
  • Remove or modify temporary controls that create entrapment risks, but retain exclusion fencing where it protects approved habitat.
  • Document the condition of retained habitat and any damage caused during works.

After habitat disturbance: Monitoring and reporting

Population information: The total population is poorly surveyed, and the rate of decline has not been established

  • Repeat targeted nocturnal searches in retained sandstone habitat where the project approval or fauna management plan requires monitoring.
  • Compare records by location, habitat feature, search effort and detection method rather than treating raw sighting counts as a population estimate.
  • Report sightings, injuries, mortalities, relocations, habitat damage and unexpected impacts to the relevant regulator and wildlife database.
  • Review monitoring results with the project ecologist and change work controls if animals continue to use areas affected by the project.

After habitat disturbance: Controls, offsets and compliance

  • Maintain no-go areas, erosion controls, weed controls and access restrictions around retained sandstone habitat for the period specified in the approval.
  • Implement approved offsets or rehabilitation commitments where avoidance and minimisation do not prevent residual impacts.
  • Keep survey data, permits, spotter catcher records, photographs, incident reports and monitoring results in the project environmental record.
  • Audit the completed works against the fauna management plan and approval conditions before demobilisation.

Rehabilitation actions: Restore habitat structure

Rehabilitation should recreate connected shelter and foraging habitat around sandstone features. The supplied documents do not identify particular plant species or a species-specific rehabilitation design, so restoration should use local ecological advice for western Arnhem Land sandstone systems.

  • Retain and protect existing sandstone outcrops, caves, overhangs, crevices and large trees during rehabilitation works.
  • Re-establish dense native vegetation around retained sandstone features using local provenance species appropriate to the original woodland, heathland or monsoon forest community.
  • Reinstate suitable logs, rocks and coarse woody debris where they were removed and where their placement will not block animal movement or create erosion hazards.
  • Reconnect rocky refuges with retained trees and vegetated cover so animals can move between discrete shelter and foraging positions.
  • Do not create artificial caves, rock piles or tree hollows without approval from the project ecologist and land manager.

Rehabilitation actions: Fire, weeds and predators

  • Prepare a fire management approach that maintains the habitat structure required by the species and addresses altered fire regimes identified as a threat.
  • Control weeds that reduce dense native vegetation around sandstone outcrops, gorges and trees.
  • Manage introduced predators and other introduced species in accordance with the land manager's approved program.
  • Prevent construction materials, spoil and sediment from covering crevices, caves, overhangs or dense vegetation.

Rehabilitation actions: Monitoring and success measures

Key rehabilitation setting: Sandstone outcrops and gorges with dense vegetation, including connected woodland, heathland or monsoon forest habitat where present

Known threat relevant to rehabilitation: Altered land use and fire regimes, reduced prey availability, introduced species and illegal collection

  • Monitor survival and cover of planted native vegetation, condition of sandstone refuges, connectivity between retained habitat patches and weed cover.
  • Use repeat nocturnal searches of rehabilitated and retained habitat to detect whether Oenpelli rock pythons or their prey use the area.
  • Set monitoring duration, search effort and performance thresholds in the approved rehabilitation or offset plan because the supplied documents do not provide species-specific success criteria.
  • Investigate any injured or dead python, loss of a refuge, fire damage or prey decline and revise management actions where required.
  • Provide rehabilitation results, monitoring data, photographs and corrective actions to the land manager and relevant regulator.

Sources