Part 3 - Environment Protection and Biodiversity Conservation (National Recovery Plan for the Pookila (New Holland mouse) Pseudomys novaehollandiae) Instrument 2026 - Threats | Zoe
Environment Protection and Biodiversity Conservation (National Recovery Plan for the Pookila (New Holland mouse) Pseudomys novaehollandiae) Instrument 2026
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The Pookila (New Holland mouse; Pseudomys novaehollandiae) is a small, burrowing, rodent native to south eastern Australia, that is patchily distributed from Tasmania to south-east Queensland. The species has had catastrophic declines that were recorded since the discovery of new populations in the 1970s. Isolated remnant populations are at high risk of extirpation and genetic inbreeding.
Distribution is fragmented across southern Queensland (Qld), the northern and central coastal areas of New South Wales (NSW), central southern coastal Victoria (Vic), and north-eastern Tasmania (Tas) including Flinders Island (Burns et al. 2023a). While the species is typically restricted to coastal areas, it occupies areas up to 300 km inland in Qld and NSW.
Since the species’ description in 1843, more than a dozen known populations have been lost and many more have declined. It has not been live trapped on mainland Tas since 2010 and in Vic, seven of twelve populations have become extinct since the 1970s (Burns et al. 2023b). Encouragingly, the Pookila was rediscovered on Flinders Island, Tasmania in 2021 and was last recorded in southern Qld in 2022. It has now been translocated into Mulligans Flat Woodland Sanctuary in the Australian Capital Territory (ACT), Yiraaldiya National Park feral predator-free area (NSW), reintroduced into the Cranbourne Royal Botanic Gardens (Vic) in 2024, and has numerous ongoing and successful captive-breeding programs.
European colonisation in Australia exposed the Pookila to compounding threats that caused population declines across its range. These threats include the direct destruction and fragmentation of habitat due to land clearing for agriculture, urbanisation, road construction, and forest plantations, as well as predation by introduced cats and European red foxes (DEWHA 2010; Burns 2019a). Introduced rodents may outcompete the Pookila under some conditions, and both introduced rodents and cats are vectors of novel diseases. Infection may also cause mortality and/or increase the Pookila’s susceptibility to predation (for example, toxoplasmosis spread by feral cats) (Lazenby et al. 2019; Burns 2019a).
1.2 Conservation status
The Pookila is listed as Vulnerable under the Environment Protection, Biodiversity and Conservation Act 1999 (EPBC Act), Vulnerable (ACT, Qld, NSW, VIC) and Endangered (Tas) (Table 3).
The Pookila was first listed under the EPBC Act in the Vulnerable category on 11 August 2010. It was reassessed by the Threatened Species Scientific Committee in July 2024 retaining its Vulnerable category status under Criteria 1 and 2 (DCCEEW 2024b).
Criterion 1 (A4b) was met due to the severe declines in population size estimated to have occurred in Tas and Vic and the significant declines suspected to have resulted from the impacts of the 2019 and 2020 bushfires in NSW, with the Committee concluding that the Pookila was subject to a population size reduction of at least 30% (DCCEEW 2024b).
Criterion 2 B2ab(i,ii,iii,iv,v) was met due to the limited Area of Occupancy (AOO), low/very low number of locations (six), and estimated continuing decline in EOO, AOO, area of habitat, number of locations and populations, as well as the number of mature individuals (DCCEEW 2024b).
Table 3: Conservation status of the Pookila
Listing
Conservation Status
Environment Protection and Biodiversity Conservation Act 1999 (Commonwealth)
Vulnerable
Nature Conservation Act 2014 (Australian Capital Territory)
Vulnerable
Nature Conservation Act 1992 (Queensland)
Vulnerable
Biodiversity Conservation Act 2016 (New South Wales)
Vulnerable
Flora and Fauna Guarantee Act 1988 (Victoria)
Vulnerable
Threatened Species Protection Act 1995 (Tasmania)
Endangered
IUCN Red List of Threatened Species
Vulnerable
1.3 Cultural and community significance
The Pookila currently occurs on the Country of the Awabakal, Banbai, Barunggam, Biripi, Bunurong, Boonwurrung, Bundjalung, Burrgati, Daingatti, Darkinung, Dharawal, Dharug, Eora, Geawegal, Gumbainggir, Gunaikurnai, Kuringgai, Gunaikurnai, Ngunnawal, Palawa, Wiradjuri, Wonnarua, Worimi and Yuggera Peoples.
The species has likely been known by numerous names in different Aboriginal languages across its geographic range. The name Pookila is derived from the Ngarigo word for ‘mouse’ – bugila (Braithwaite et al. 1995; Hercus n.d.), deviating somewhat from traditional Ngarigo pronunciation (Braithwaite et al. 1995). The assignation of that name was part of an initiative by the CSIRO to provide Indigenous Australian names for Australian rodents (Braithwaite et al. 1995). This was considered a way to avoid the undesirable associations with introduced vermin often attached to the words ‘rat’ and ‘mouse’, impeding conservation of native rodents due to negative public perception (Braithwaite et al. 1995). An alternative name could have been ‘tuwaranga’ which means ‘mouse’ in palawa kani, the language of the Tasmanian Aboriginal people (Tasmanian Aboriginal Centre, 2023), however, the name Pookila has been associated with this species since 1995 and is included on the Australian Government’s SPRAT database.
1.4 National Pookila Recovery Team
A National Pookila Recovery Team (the recovery team or NPRT) was established in 2021 with the aim of improving recovery efforts for the species at a national scale. A previous Pookila Recovery Team (1995 to 2002) was largely based in Vic. The current recovery team has representation across the species’ entire distribution. Beyond the core recovery team there are three sub-groups: captive breeding, habitat and fire management, and Vic management.
The role of the recovery team is to facilitate and encourage collaborations across jurisdictions, provide advice to partners and land managers, increase engagement, improve the public perception of the Pookila as well as the responsibility of advising and coordinating the implementation of recovery actions. The recovery team also seeks to facilitate opportunities for mutual learning and skill sharing with First Nations people. The membership of the recovery team includes species experts and land managers from relevant government agencies and non-government organisations and draws from a broader network of expertise from First Nations people, researchers, and community groups.
1.5 Key partners
Implementation of recovery planning is a collaborative effort involving a range of key partners and affected interests. The groups likely to have primary interest in recovery planning for the Pookila are listed in Table 4.
Table 4: Groups with primary interest in Pookila recovery
Organisations
Involvement/ interest
ACT Government
Management of the land of the first Pookila translocation site. Ongoing monitoring at the site and potential future releases in the area.
Australian National University (ANU)
Captive-breeding program for NSW individuals. Ongoing monitoring and management in Mulligans Flat Woodland Sanctuary and potential future reintroductions in the ACT and other jurisdictions.
Aussie Ark (AA)
Maintains an insurance population. Potential development of a captive-breeding program for the Pookila and future reintroductions into cat and fox free sites in NSW.
Corangamite Catchment Management Authority (CCMA)
Managers of habitat under threat from P. cinnamomi.
Department of Climate Change, Energy, the Environment and Water (DCCEEW, Cwlth)
The Pookila is a priority species in the Threatened Species Action Plan 2022-2032, which provides guidance and support in the design and delivery of projects for priority species. Recovery plans inform decision making under the EPBC Act referral and assessment process.
Department of Energy, Environment and Climate Action (DEECA)
Primary agency involved in threatened species management on public and private land in Vic.
Department of Natural Resources and Environment (DNRE)
Primary agency involved in threatened species management on public and private land in Tas.
Department of the Environment, Tourism, Science and Innovation (DETSI)
Primary agency involved in threatened species management on public and private land in Qld.
Flinders Island Aboriginal Association Incorporated (FIAAI)
Traditional Owners of Flinders Island population Tas.
Friends of the Prom (FOTP)
Group established to support the management of Wilsons Promontory National Park.
Gippsland Water (GW)
Manages a significant Vic population.
Gunaikurnai Land and Waters Aboriginal Corporation (GLaWAC)
Joint managers of Lakes National Park, and Gippsland Lakes Coastal Park, and have Registered Aboriginal Party status of Providence Ponds Flora and Fauna Reserve in Vic.
Land holders/Landowners
Consultation and engagement with all types of landowners will play a role in the success in meeting the recovery plan’s actions and objectives.
Local councils
Community involvement projects and cooperation with management actions on a local level.
Monash University (MU)
Storage and research of Pookila cell lines and genetic tissue. Supporting research of the genetic sequencing of the Pookila and subsequent projects surrounding genetic information.
Moonlit Sanctuary Wildlife Conservation Park (MSWCP)
Managing a captive population of Pookila as well as community conservation and engagement activities.
Forestry agencies
Actions and management regarding forestry operations and Regional Forest Agreements.
NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW NSW)
Primary agency involved in threatened species management on public and private land in NSW.
NSW National Parks and Wildlife Service (NPWS NSW)
Implementation of appropriate management actions within parks and reserves in NSW, including reintroduction of the Pookila to establish new populations in NPWS-managed feral predator-free areas.
Parks Victoria (PV)
Implementation of appropriate management actions concerning habitat within Vic parks and reserves.
National Threatened Species Institute (NTSI) Priam Psittaculture Centre (PPC)
Host of a captive breeding program founded from northern ESU individuals.
Royal Botanical Gardens Victoria Cranbourne (RBGVC)
Location for reintroduction to establish a new population.
Tasmanian Aboriginal Land and Sea Council Aboriginal Corporation (TALSCAC)
Traditional Owners of Northeast population Tas.
Trust for Nature (TFN)
Managing properties adjacent to occupied habitat.
Turner Family Foundation (TFF)
Manager of Spicers Peak Nature Refuge south-east Qld habitat.
University of Canberra (UC)
Involved in captive husbandry and dietary analyses.
University of Southern Queensland (USQ)
Collaborative research project with the DETSI and the Turner Family Foundation to refine knowledge of distribution and ecological requirements in south-east Queensland.
University of Sydney (USyd)
Analysis and advice on captive-breeding genetics.
Wadawurrung Traditional Owners Aboriginal Corporation (WTOAC)
Traditional Owners of Anglesea population Vic.
Woodlands and Wetlands Trust (WWT)
Community engagement, education and volunteer programs at Mulligans Flat Woodland Sanctuary.
World Wildlife Fund Australia (WWF)
Potential partner for island translocation.
Zoos Victoria (ZV)
Programs underway for monitoring, management, captive breeding, genetic rescue, reintroductions, research, studbook management and species coordination, community conservation and engagement.
Zoo and Aquarium Association Australasia (ZAA)
Coordination of the NPRT, initial engagement/consultation with First Nations people, and assistance with studbook management and coordination.
2 Species information
2.1 Taxonomy and description
Pseudomys novaehollandiae, family Muridae, is endemic to Australia and was first described in 1843 as Mus novaehollandiae (Waterhouse 1843). It was later transferred to the genus Pseudomys with the new name of Pseudomys (Gyomys) novaehollandiae (Thomas 1910). There is some geographic overlap and occasional evidence of hybridisation with its sister taxon, P. delicatulus (Delicate mouse), in the north of its range (Roycroft et al. 2024). However, the two taxa were found to be both genetically and morphologically distinct (Ford 2003; Roycroft et al. 2024).
The Pookila is a nocturnal, terrestrial, burrowing rodent. It is small, with a head-body length of approximately 65–90 mm and a tail length of 80–105 mm (Menkhorst & Knight 2011). The species’ dorsal coat is sandy brown with black flecks and the ventral coat is white (Figure 1). The tail appears bicoloured with a darker dorsal side and paler pink ventral side, and the feet are pink with fine white hairs (Figure 1).
Individuals in the south of the range are heavier than those further north. Tas individuals are the heaviest, weighing 19–28 g, followed by Vic at 18–25 g, then Qld and NSW at 12–20 g (Hocking 1980; Burns et al. 2023a). The species is most similar in appearance to the delicate mouse, which is generally smaller and more finely featured. It is superficially similar in appearance to the invasive house mouse (Mus musculus). It is distinguishable by its larger prominent eyes, larger rounded ears, lack of ‘mousy’ odour and absence of a notch on the upper incisors (note that examining dentition is not recommended for identifying live animals) (Seebeck et al. 2003; DEWHA 2010; Burns et al. 2023a; DCCEEW 2024b). The Pookila’s body shape is also thicker and more rounded compared to the house mouse, lacking an obvious neck (Burns 2019b).
Figure 1: A Pookila (Pseudomys novaehollandiae) individual showing identifying characteristics: Underbelly of a male Pookila showing the white fur, paler surface of the ventral tail and pink feet with white hairs. The inset top picture shows the darker dorsal side of the tail and the bottom picture showing the white belly with black underfur.
The Pookila has a fragmented distribution across coastal areas of central-eastern and south‑eastern Australia (Figure 2). It occurs in southern Qld, the northern and central coastal areas of NSW, central-southern coastal Vic, and north-eastern Tas including Flinders Island (Burns et al. 2023b; DCCEEW 2024b). A large portion of its distribution occurs within areas with Regional Forest Agreements (RFAs), Indigenous Protected Areas and National Parks. In Qld and NSW, the Pookila occurs in the World and National Heritage Listed Greater Blue Mountains Area and the Gondwana Rainforests of Australia. It is known only from subfossil records in National Heritage Listed areas including the Australian Alps National Parks and Reserves, Ku-ring-gai Chase National Park, Lion, Long and Spectacle Island Nature Reserves and the Great Ocean Road region (Ford 2003; Smith et al. 2023c). While most modern detections of the species exist from coastal areas, it has also been located in areas up to 300 km inland in Qld and NSW. The species’ distribution is believed to have once been continuous, forming one large population throughout these areas.
The species’ historic distribution is inferred through the presence of subfossils as well as genetic information (Ford 2003; Breed & Ford 2007; Smith et al. 2023c). Its current distribution is attributable both to longer-term climatic and landscape changes, as well as a large population decline following European colonisation (Breed & Ford 2007; Theden-Ringl et al. 2018; Roycroft et al. 2021). Despite the ACT and surrounding region not being mapped within the current Pookila distribution (Figure 2), there is subfossil evidence of historical occurrence in nearby areas with similar habitat (Ford 2003; Smith et al. 2023c).
The extent of occurrence (EOO) for the species was estimated at 326,000 km2 and the area of occupancy (AOO) for the species was estimated at 694 km2 (DCCEEW 2024b). The AOO may have further contracted since this estimate, as nearly half of the species’ habitat was affected by the 2019 and 2020 bushfires. However, this includes approximately 30% of the species’ habitat that burned at low to medium severity (Legge et al. 2022). The species is likely to survive low to medium severity fires, but high severity fires could greatly reduce survivability (Wilson et al. 2018; Burns & Phillips 2020; DCCEEW 2024b).
The Pookila is associated with early to mid-stage vegetation succession following fire events (Woinarski & Burbidge 2016). Therefore, some recovery after the 2019 and 2020 bushfires is possible due to potential development of suitable habitat post-fire (DCCEEW 2024b).
Figure 2: Modelled distribution of the Pookila
The modelled distribution of the Pookila or the Pookila habitat is known or likely to occur from south east Queensland along the northern and central east coast of New South Wales to costal regions in Victoria, predominantly to the east, all the way to Flinders Island and north and eastern Tasmania. The Pookila is also likely to occur 100-300 km inland in New South Wales. Pookila or Pookila habitat may occur in close proximity to these known or likely regions. Refer to subheading 'Species distribution' for more information.
Note: Source: Base map Geoscience Australia; species distribution data Species of National Environmental Significance database.
Note: Caveat: The information presented in this map has been provided by a range of groups and agencies. While every effort has been made to ensure accuracy and completeness, no guarantee is given, nor responsibility taken by the Commonwealth for errors or omissions, and the Commonwealth does not accept responsibility in respect of any information or advice given in relation to, or as a consequence of, anything contained herein.
Note: Species distribution mapping: The species distribution mapping categories are indicative only and aim to capture (a) the habitat or geographic feature that represents recent observed locations of the species (known to occur) or habitat occurring in close proximity to these locations (likely to occur); and (b) the broad environmental envelope or geographic region that encompasses all areas that could provide habitat for the species (may occur). These presence categories are created using an extensive database of species observations records, national and regional-scale environmental data, environmental modelling techniques and documented scientific research.
2.3 Population size and trends
In 2008, the national population size of the Pookila was estimated at fewer than 10,000 individuals (Menkhorst et al. 2008; DEWHA 2010) and was reported to be 8,000 individuals in the IUCN assessment by Woinarski and Burbidge (2016). In the assessment for listing under the EPBC Act, the maximum plausible population size prior to the 2019 and 2020 bushfires was estimated (using calculations of AOO and density) to be 34,700 individuals, with the post-fire plausible population range of 13,100–26,300 (DCCEEW 2024b). There was a reduction in the number of Pookila populations located in Vic (from 12 to 5; Burns 2019a), and in Tas (from 16 to 2; (Lazenby et al. 2019). However, there is limited information from which to infer similar trends across the NSW and Qld populations (Lazenby et al. 2019; Burns 2019a; DCCEEW 2024b). A study conducted over a 32-year period near the Tomago aluminium smelter in NSW indicated an overall declining population (SMEC 2015). Shorter-term studies conducted over 5 years recorded a possible decline at Wyrrabalong National Park but no evident trend over 7 years at Munmorah State Conservation Area (DCCEEW 2024b).
2.4 Important populations
The Evolutionarily Significant Units (ESUs) concept is used by conservationists to strategically prioritise taxa or populations of a species for recovery purposes (for example, to target for captive-breeding), when resources are limited or when the granularity of genetic diversity is not sufficiently captured in the current overarching taxonomic status (Avise 1989; Moritz 1994). There are two recognised ESUs of Pookila, separated by more than 200,000 years of divergence (Burns et al. 2023b). The Southern ESU (Vic populations) is rarer, both genetically and geographically fragmented, and more threatened than the Northern ESU (NSW and Qld populations), which is comparatively genetically healthy and not at immediate risk of extinction (Burns et al. 2023b). Tas populations were not included in the Burns et al. (2023b) analysis due to the lack of data. However, these populations are expected to place either independently or within the Southern ESU and are considered to be at extremely high risk of extinction (Burns et al. 2023b). Given the Tas populations are likely closely related to the Vic populations, until further information is available these populations should be managed as part of the Southern ESU (Burns et al. 2024).
Populations in Vic and Tas are severely fragmented and are thought to make up less than 5% of Pookila numbers nationally (DCCEEW 2024b). In Tas, the species was known from 16 separate sites in 1998, but its status on the Tas mainland is in doubt with no recent records (Lazenby et al. 2019; DNRE Tas 2023). However, it was rediscovered on Flinders Island in 2021 (DNRE Tas 2023). In Vic, extensive surveys found the species in only 5 of the 12 parks and reserves in which it had previously been recorded (Burns 2019a; Burns et al. 2023b). The remaining populations are spatially isolated and at high risk of genetic issues without assisted migrations to support genetic rescue (Burns 2019a; Burns et al. 2023b).
The connectivity and extent of populations in NSW and south-east Qld is poorly understood. Genetic evidence indicates the isolation of these populations has occurred relatively recently compared to the isolation of populations in Vic (Burns et al. 2023a; Burns et al. 2023b; DCCEEW 2024b). The extant populations are in sites that are geographically distinct and unlikely to be connected by gene flow, as were the now locally extinct populations.
There is evidence that Pookila populations are strongly affected by rainfall. In NSW, the length of the breeding season, and thus reproductive output, has been shown to increase during times of above-average rainfall (Kemper 1976, 1980). Abundance in the Anglesea (Vic) population had a strong positive relationship with cumulative monthly residual rainfall (Lock 2005). Densities of this population peaked following 4 years of above-average rainfall and declined during below-average rainfall and drought conditions (Lock 2005; Wilson et al. 2017). There are also data to suggest that population fluctuations at Wilsons Promontory (Vic) were influenced by rainfall patterns (Wilson et al. 2005). All populations are considered important for the long-term recovery and survival of the species (Table 5).
Table 5: Populations of Pookila
Region
Population
Status
Year of last detection
Year of last survey
Known or expected decline?
Genetic diversity (relative heterozygosity a)
ACT
Mulligans Flat Woodlands Sanctuary
Not persisting, translocated
2021
2023
Known
Translocation trials with individuals from the Australian National University (ANU) captive-breeding colony (using NSW founders)
NSW
Barcoongere State Forest
Unknown
2016
2016
Unknown
Unknown
Barrington Tops State Forest
Extant
2001
2025
Expected decline
Unknown
Booti Booti National Park
Extant
2022
2022
Unknown
Unknown
Broadwater National Park
Extant
2024
2025
Known
Low
Bunjalung National Park
Unknown
2002
2024
Known
Unknown
Bylong
Unknown
Unknown
Unknown
Unknown
Moderate
Carrai National Park
Unknown
2020
2023
Unknown
Unknown
Chaelundi State Forest
Unknown
2013
2013
Unknown
Unknown
Dalmorton State Forest
Unknown
2013
2013
Unknown
Unknown
Doyles River State Forest
Unknown
1984
1984
Unknown
Unknown
Ellis State Forest
Unknown
2022
2022
Unknown
Unknown
Gibraltar Range State Forest
Unknown
2015
2015
Unknown
Unknown
Goobang National Park
Extant
2025
2025
Unknown
Moderate
Goulburn River National Park
Extant
2025
2025
Unknown
Unknown
Kiwarrak State Forest
Unknown
2019
2019
Unknown
Unknown
Malara State Forest
Unknown
1999
Unknown
Unknown
Moderate
Malara State Forest
Unknown
1993
1993
Unknown
Unknown
Manobalai Nature Reserve
Extant
2024
2024
Unknown
Unknown
Marara State Forest
Unknown
2014
2014
Unknown
Unknown
Marengo State Forest
Unknown
2022
2022
Unknown
Unknown
Mernot State Forest
Unknown
2008
2008
Unknown
Unknown
Mount Royal National Park
Extant
2023
2023
Unknown
Unknown
Mummel Gulf National Park
Unknown
2020
2023
Unknown
Unknown
Munmorah/Chain Valley
Extant
2025
2025
Unknown
Unknown
Myall Lakes
Extant
2022
2022
Known
Unknown
Nymboida National Park
Unknown
2015
Unknown
Unknown
Moderate
Olney State Forest
Unknown
2004
2004
Unknown
Unknown
Port Stephens
Extant
2022
2022
Unknown
Moderate
Ravensworth State Forest
Unknown
2016
2016
Unknown
Unknown
Royal National Park
Extant
2022
2022
Expected decline
Unknown
Styx River State Forest
Unknown
2000
2000
Unknown
Unknown
Watchimbark Reserve
Unknown
2011
Unknown
Unknown
High
Werrikimbe National Park
Unknown
1984
2020
Unknown
Unknown
Wollemi National Park
Extant
2025
2025
Unknown
Unknown
Wyrrabalong National Park
Unknown
2013
2013
Unknown
Unknown
Yiraaldiya National Park feral predator-free area
Translocated, persistence to be determined by post-release monitoring
2025
2025
Known
Translocation trials with individuals from the captive-breeding colonies at ANU and NTSI (PPC) using NSW founders
Yuraygir National Park
Extant
2024
2025
Expected decline
Unknown
QLD
Crows Nest/ Ravensbourne/Helidon Hills
Unknown
2022
2025
Known
Moderate
Emu Creek (private property)
Unknown
2022
2024
Known
Unknown
Main Range National Park/Spicers Peak Nature Refuge
Unknown
2022
2025
Known
Unknown
Numinbah Valley
Unknown
2005
2005
Unknown
Unknown
TAS
Beaconsfield
Unknown
1978
2002
Known
Unknown
Flinders Island
Extant in the north of the island, undetected in the south
2025
2025
Expected decline
Unknown
Freycinet
Unknown
2003
2025
Known
Unknown
St Helens
Unknown
2009
2025
Expected decline
Unknown
Waterhouse Conservation Area
Unknown
2010
2025
Known
Unknown
Wukalina/Mt William
Unknown
2004
2025
Known
Unknown
VIC
Anglesea
Locally extinct
1999
2021
Known
Very low (from historic samples)
Cranbourne
Locally extinct
1976
Unknown
Known
Unknown
Dutson Downs
Extant
2024
2025
Known
Low
Gippsland Lakes
Extant
2025
2025
Known
Low
Hummock Island
Locally extinct
1977
Unknown
Known
Unknown
Langwarrin
Locally extinct
1984
Unknown
Known
Unknown
Mullungdung
Locally extinct
1976
2017
Known
Unknown
Providence Ponds
Extant
2025
2025
Known
Low
Reeves Beach
Locally extinct
1978
2017
Known
Unknown
The Lakes National Park
Extant
2025
2025
Known
Low
Tyabb
Locally extinct
1975
Unknown
Known
Low (from historic samples)
Wilsons Promontory
Extant
2025
2025
Known
Very low
Note: a - Heterozygosity measures from Burns et al. (2023b).
Note: Source: Lazenby et al. (2019), Burns (2021a), DCCEEW (2024), NSW BioNet and unpublished data from members of the recovery team and Recovery Network.
2.5 Habitat
Pookila habitat includes open heathland, tall open forest with a grassy understorey, open woodland with a grassy or heathy understorey, and vegetated sand dunes (Keith & Calaby 1968; Posamentier & Recher 1974; Fox & Fox 1978; Hocking 1980; Fox & McKay 1981; Pye 1991; Wilson 1991; Van Dyck & Lawrie 1997; Lock & Wilson 1999; Sparshott & Sparshott 2003; Wilson & Laidlaw 2003; Lazenby et al. 2007; Dixon 2014; DNRE Tas 2022) (see Figure 3). Historically, the species has been found across a broader array of habitat types (DCCEEW 2024b), and it does not occupy all plausibly suitable habitat at present (Burns et al. 2020; Smith et al. 2023a). Sandy soils suitable for burrowing are common across most occupied habitats and soft sandy substrates, while deep topsoils are thought to be optimal (Abicair et al. 2020). Within the northern parts of the species’ range, it also occupies sites up to 300 km from the coast and in subcoastal locations at higher elevation, where soil composition differs (Martin 1995; Van Dyck & Lawrie 1997; Vernes et al. 2006; Dixon 2014; Churchill et al. 2023).
The species is often, although not exclusively, found in areas with high floristic diversity with leguminous perennials (Wilson 1991; Seebeck et al. 2003; Wilson & Laidlaw 2003; Lazenby et al. 2007; DEWHA 2010). For example, the heathland element of the species’ habitat is represented by dry heathlands that are floristically diverse and even (a high number of plants that are all relatively abundant compared to each other) that grow on sandy soils with a high percentage of bare ground (Seebeck et al. 1996).
The species has been identified as preferring early successional habitat, at some sites with peak abundance approximately 3–7 years post-fire and 7–9 years post-sand mine rehabilitation (Braithwaite & Gullan 1978; Fox & Fox 1978; Fox & Fox 1984; Twigg et al. 1989; Wilson 1991; Wilson et al. 2018). However, research in Vic suggests that the relationship between the Pookila and fire is complex, and local densities may be high in areas that have not been affected by fires for over 60 years (Burns and Phillips 2020). Similarly, surveys conducted on the NSW central coast have found high densities in long-unburnt vegetation (F Ford 2023, personal communication 8 August). Season, fire severity and extent, predation pressures, and climatic conditions following fire, all affect habitat suitability more strongly than a linear effect of time-since-fire (Burns & Phillips 2020). Furthermore, it is likely that it shelters in burrows during times of fire. This behaviour may be one of the attributes that allows the Pookila to persist in situ through some fire events (Friend 1993; Burns & Phillips 2020).
The Pookila has been considered a ‘habitat specialist’ (Braithwaite & Gullan 1978), but fossil record observations, and a strategic translocation and assessment of microhabitat use, suggests that it had broad habitat preferences (Smith et al. 2023c). Remains of the species are common in most bone deposits in south-eastern Australia that has been examined, and these deposits occur across a broad range of historical vegetation types and altitudes (Ford 2003). The species’ perceived habitat specialisation may have been further challenged by the Pookila translocation into a predator exclusion zone in the ACT as part of the Mulligans Flat-Goorooyarroo Woodland Experiment. The box gum and grassy woodlands comprising the predator exclusion area are not the type of coastal habitat often associated with contemporary records of the species (Abicair et al. 2020). However, recent detections of the species in grassy open forests and woodlands in Qld means that these non-coastal habitat types are still represented in the Pookila distribution.
The currently skewed occurrence (and perhaps specificity) of the Pookila towards coastal areas may in part be due to the interaction among threats, such as habitat clearing, altered fire regimes and predation pressures by introduced species such as cats (Felis catus) and European red foxes (Vulpes vulpes). However, it is worth noting that individuals sourced from the ANU breeding colony in the Mulligans Flat population are significantly underweight compared to their founding populations (13.6 g vs. 17.5 g) (Abicair et al. 2020), and that the population may not be self-sustaining. Together, these attributes may indicate that the habitat there may now be suboptimal for the Pookila. However, it may be important to pursue translocations in a diversity of habitats (including those that may be suboptimal) to build the species' resilience to environmental change and to restore ecological functions (Smith et al. 2023a).
Figure 3: Photographs of contemporary Pookila habitat
These grouped 6 images demonstrate the diversity in the Pookila's habitat throughout the species' range. Refer to the footnote of this collective image for descriptions on habitat per image in addition to subheading 'Habitat' for more information.
Note: Contemporary habitat in which the Pookila has been detected. Depicted are: a) grassy woodlands at Cunninghams Gap in Qld (photo: Ian Gynther); b) woodland with a grass and sedge understorey at Mt Hyland, NSW (photo: Anna Lloyd); c) coastal heathland at Munmorah in NSW (photo: Barbara Wilson); d) woodland with a heath understorey at Anglesea in Vic (photo: Barbara Wilson); e) coastal heathland at Loch Sport in Vic (photo: Phoebe Burns); and f) coastal heathland with a woodland overstorey on Flinders Island in Tas (photo: Rosemary Gales) (Source: DNRE Tas 2022).
2.5.1 Habitat critical to the survival of the Pookila
All potential habitat should be considered important to the Pookila’s persistence and recovery, this includes any:
Areas within the species’ modelled distribution;
Areas where the species previously occurred but has since become locally extinct;
Patches of suitable habitat that may not be currently occupied by the species but have the potential to be occupied by natural dispersal; and
Areas that could be restored for reintroduction.
All areas that contain habitat that serves one or more of the following ecological functions have the potential to be habitat critical to the survival of the Pookila:
Foraging habitat: vegetation with appropriate density and diversity to be able to support a population, such as native vegetation with seasonal abundance of edible flowering, fruiting, and seeding plants. Vegetation cover is important for the species to be able to forage without increased risk of predation. This habitat includes open heathland, tall open forest with a grassy understorey, open woodland with a grassy or heath understorey and vegetated sand dunes (Keith & Calaby 1968; Posamentier & Recher 1974; Fox & Fox 1978; Hocking 1980; Fox & McKay 1981; Pye 1991; Wilson 1991; Van Dyck & Lawrie 1997; Lock & Wilson 1999; Sparshott & Sparshott 2003; Wilson & Laidlaw 2003; Lazenby et al. 2007; Dixon 2014; DNRE Tas 2022).
Breeding habitat: substrate for the species to be able to create burrows, or alternatively, ‘surface nests’ in low-lying vegetation that is suitable for successful reproduction and rearing of young. Soft sandy substrates, with deep topsoils are thought to be optimal (Abicair et al. 2020) but not exclusive. The Pookila mostly occupies coastal areas that provide this substrate. However, it also occupies sites 100–300 km from the coast and areas with higher elevation where soil composition varies. For example, the presence of sandy soils is highly likely in Goobang National Park (NSW NPWS 2001), whilst in the NSW ranges and Northern Tableland areas, soil may vary with a more dominant loamy or quartz soil base where the Pookila occurs or may be present (NSW OEH 2023. pers comm 22 November).
Habitat for the long-term maintenance of the species: including areas that are not subject to prolonged drought or at risk of extreme droughts in future (such as potential climate refugia), and habitat that is maintained through periodic small-scale burns to provide appropriate foraging habitat and connectivity for the species.
Habitat for the maintenance of genetic diversity: includes all current habitats where the species is extant as they contain populations necessary to achieve maximum genetic diversity and increase resilience of the species against future threats. There are two recognised ESUs: the Southern ESU (Vic populations) and the Northern ESU (NSW and Qld populations). Tas may yet be identified as a third ESU or may cluster within the Southern ESU. Therefore, habitat across the species’ range is necessary to maintain the national genetic diversity of the species.
Habitat for translocation: can be identified using habitat modelling followed by ground-truthing at the local-scale and can include locations that have accounted for future changes due to climate change regimes as well as the exclusion of invasive predators.
Refining what constitutes habitat critical to the survival of the Pookila is a priority action in this recovery plan. Until those key characteristics are further clarified, all areas that contain habitat that serves any of the above five ecological functions have the potential to be habitat critical to the survival of the Pookila. Habitat that supports multiple ecological functions and/or a higher number of the ecological attributes identified within the descriptions provided above, increases the likelihood that the habitat may be critical to the survival of the Pookila.
Given that the species has declined markedly in parts of its range and populations may rapidly change in size, failure to detect the species during surveys does not indicate the absence of potential habitat critical to its survival.
2.6 Ecology
The Pookila often nests underground in communal burrow systems in well-drained soils. Individuals have also been recorded sheltering under low growing shrubs in surface nests (Kemper 1980, Lazenby et al. 2007). Burrows vary in length, depth, and complexity, ranging from shallow surface nests to intricate tunnel systems (Kemper 1981). Of three burrows that have been excavated, the largest was 5 m in length with a maximum depth of 60 cm (Kemper 1981). The species is nocturnal, and with a significant proportion of its time spent foraging above ground, it is exposed to a high risk of predation by native predators including owls and introduced predators such as the cat and the European red fox.
Ten individuals were radio-collared in one area of Tas for approximately 2 weeks, yielding information on nightly movements (Lazenby 1999; Lazenby et al. 2007). Over a 2 ha grid, 9 individuals moved up to 206 m in one night, and up to 37 m in one hour (Lazenby 1999; Lazenby et al. 2007). Pookila home ranges have been known to overlap (Lazenby 1999; Lazenby et al. 2007). The species’ home range is approximately 0.5–1.8 ha, increasing as habitat quality decreases (Lock 2005; Burns et al. 2023a).
The generation length of the Pookila is between one and two years (Kemper 1980). Females reach sexual maturity at approximately 13 weeks and live 2–3 years (Kemper 1976; Kemper 1980). Males reach sexual maturity at approximately 20 weeks and longevity remains unclear (Kemper 1976; Kemper 1980). During good conditions in NSW, the average litter size for the species has been previously recorded as 4.6, with a range of 1–6 young, and with females usually producing 1–2 litters per year, or 3–4 in exceptional conditions (Kemper 1976; Kemper 1980). The gestation period is around one month (32 days) and young are weaned at 3–4 weeks of age (Kemper 1976; Kemper 1980).
The breeding season varies depending on location and rainfall, with breeding occurring in NSW from late winter to early summer, while in Vic and Tas the breeding season begins in mid-spring and ceases in late summer (Kemper 1980; Burns et al. 2023b). The impact of rainfall is likely related to its influence on resource availability, which influences variation in birth rates, recruitment, and adult survival (Woinarski et al. 2014). Energy requirements are likely to be high during breeding, particularly for females, and if dietary resources are inadequate during this time, females or their young may perish (Lock & Wilson 2017). Hence, the Pookila demonstrates fluctuating population dynamics where extended breeding seasons follow periods of higher rainfall (Lock & Wilson 2017; Burns 2021). Pookila abundance reduces during periods of drought due to resource shortages and likely failed litters (Lock & Wilson 2017; Burns 2021).
2.6.1 Diet and foraging
The Pookila is an omnivore and feeds on a variety of seeds, leaves, fungi, and invertebrates, exhibiting seasonal and locality-dependent dietary variation (Cockburn 1980; Norton 1987; Wilson and Bradtke 1999; Braithwaite and Gullan 1978). The species plays an important ecological role in dispersing seed and fungi in scats (Wilson & Bradtke 1999; Seebeck et al. 2003; Burns et al. 2023b).
3 Threats
3.1 Historical causes of decline
The distribution of subfossils and the genetic structure of extant populations indicate that the historic distribution of the Pookila extended more continuously throughout parts of coastal eastern Australia, from south-east Qld extending down to the northern parts of Tas and up to 300 km inland on the Australian mainland (Ford 2003; Breed and Ford 2007; DEWHA 2010; Burns et al. 2024; Smith et al. 2023c). The species has since experienced significant declines in distribution and population size and is now distributed in fragmented patches across this area (Figure 2).
3.2 Current known and suspected threatening processes
Current threats and their prevalence and intensity are described for the national Pookila population below. It is important to note that different populations may be experiencing different combinations of threats in varying intensities. There is significant interaction between threats.
3.2.1 Habitat loss, disturbance and modification
Habitat clearing
Land clearing for agriculture, infrastructure, road, and housing development continues to place Pookila habitat at risk of further loss and fragmentation. As very little targeted and systematic monitoring of Pookila populations has occurred across the range in NSW (DCCEEW 2024b), the species is at particular risk of losing habitat where presence has not yet been confirmed.
In 2019, 87% of the Australian population lived within 50 km of the coast (cited in Clark et al. 2021). Coastal development is a continuing, increasing pressure with very high impacts on coastal environments (Clark et al. 2021) that is sprawling beyond established urban areas to regional coastal areas (Infrastructure Australia 2020).
When habitat is cleared, disturbed, or modified, the risk and magnitude of impact to adjacent extant habitat patches increases, along with the interactive capability of threats (Fischer & Lindenmayer 2007; DNRE Tas 2022). For example, land clearing for agriculture can increase the carrying capacity of native and introduced herbivores within the landscape, leading to increased grazing and soil impact pressures on adjacent habitat. This is exacerbated when fire results in a further increase in grazing pressure and movement as herbivores actively seek to consume newly emerging vegetative shoots (DAWE 2022). With an increasing trend of habitat loss due to land clearing, the likelihood that fragmentation has occurred and will continue to occur is very high.
Habitat modification due to Phytophthora cinnamomi infestation
Phytophthora dieback – caused by the root-rot pathogen Phytophthora cinnamomi – is listed as a Key Threatening Process under the EPBC Act (DOEE 2018) and has been observed across the national range of the Pookila (Liu et al. 2013; Wilson et al. 2015; Burns et al. 2020; DCCEEW 2024b). The pathogen is spread through the movement of soil – including on footwear, tools, vehicles and machinery – and in water (DOEE 2018). While the impacts of P. cinnamomi on Pookila populations and habitat have not been investigated directly, the species is likely to be at significant risk. A range of plant species within Pookila habitat have been identified as susceptible to infection by P. cinnamomi (see McDougall 2005).
Phytophthora dieback causes the loss of plant species richness (including keystone species), reduction of structural complexity (Wilson et al. 1994; Garkaklis et al. 2004; Laidlaw & Wilson 2006; Annett 2008; Armistead 2008; Dundas et al. 2013, 2016; Davis et al. 2014; Wilson et al. 2020), loss of food resources (for example, seeds, leaves, nectar, pollen) and suitable refuges from weather and predation (Laidlaw & Wilson 2006). The impacts of Phytophthora dieback can also extend to invertebrate communities and thus impact insectivorous fauna (Cahill et al. 2008), reducing availability of this food resource.
Significant negative impacts from Phytophthora dieback on small mammals and their habitat has been previously documented (Newell & Wilson 1993; Lilith 2002; Laidlaw & Wilson 2006; Swinburn et al. 2007; Annett 2008; Armistead 2008; Dundas et al. 2013; 2016), and long-term studies have identified localised extinctions of species and mammal community declines (Zhuang-Griffin 2015; Wilson et al. 2017; 2020).
Priority Protection Areas for Phytophthora dieback management have been identified for the Otway Ranges, which was informed by habitats occupied by EPBC Act listed species, including the Pookila (Walshe et al. 2021; 2022; Wilson & Garkaklis 2023a; 2023b).
Habitat modification due to native and introduced weeds
Changing grazing and fire regimes have led to habitat loss by encroachment of coast tea tree (Leptospermum laevigatum) in some Pookila habitat (Burns 2019a; Seebeck et al. 2003). This is particularly evident at Wilsons Promontory National Park and in other coastal Vic sites along Ninety Mile Beach where dune succession has given rise to dense thickets of coast tea tree, such as at Reeves Beech. Weed species are of growing concern in other Pookila habitat, for example, in Lakes National Park. Invasive weeds include Asparagus asparagoides (bridal creeper) and Lycium ferocissimum (boxthorn).
3.2.2 Fire regimes that cause declines in biodiversity
‘Fire regimes that cause declines in biodiversity’ is listed as a Key Threatening Process under the EPBC Act (DAWE 2022). Altered fire regimes, such as those resulting from changes to seasonality, frequency and severity of fire weather conditions, are causing declines and loss of biodiversity and ecosystem function (DAWE 2022). The Pookila and the habitat the species relies on have a complicated relationship with fire.
Under certain circumstances, the species can peak in abundance in the years following a fire as resources become more readily available due to regeneration of vegetation, with such areas described as ‘early successional’ (Fox & McKay 1981). Furthermore, the Pookila has been reported to have relatively high survival during and immediately following bushfires, which is also presumably attributed to its ability to shelter in burrows (Friend 1993; Burns & Phillips 2020). However, this response appears to be more common following small-scale, patchy, low-severity burns and is likely reliant on above-average rainfall in the months and years following the fire (Burns & Phillips 2020).
Large-scale, high-severity fires have the capacity to extirpate entire populations, as occurred in 1983 on Ash Wednesday at Anglesea (Wilson et al. 2018). Fires being too frequent, too large, too severe, or poorly timed may lead to direct loss of individuals and/or sudden or gradual loss of habitat through reduction of habitat patches of suitable successional age, size, distribution, and plant diversity that the Pookila requires for availability of food and shelter from predators.
Similarly, prolonged exclusion or poorly timed application of fire may encourage coast tea tree encroachment and loss of favourable food and habitat species. Also, introduced predators may target recently burnt areas, compounding the increased risk of predation from loss of vegetative cover (Hradsky et al. 2017). Planned burning may also threaten the species if conducted during or immediately prior to drought, at too high an intensity, or across a widespread area (Wilson et al. 2018).
The increasing scale, severity, and frequency of fires under a changing climate pose a risk to the Pookila and its habitat. In 2019 and 2020, catastrophic bushfires impacted a large area of eastern Australia with varying severity (Legge et al. 2021). It was estimated that over 45% of the Pookila distribution was burnt, with a third of this area burning with high severity (Legge et al. 2021). The overall population of Pookila was predicted to have declined by 24% by 2021 (one year after fire), with the species suffering an estimated 75% decrease in abundance in severely burnt areas in that same period (Legge et al. 2021).
3.2.3 Climate change: Increasing number of hot days, prolonged drought and changes to precipitation patterns
Increasing frequency, intensity, and duration of drought across much of the species’ range (CSIRO & BoM 2020) may lead to further catastrophic declines and local extinctions. Extreme heat events may exacerbate the effects of drought and could lead to mass mortality events as individuals dehydrate and fail to thermoregulate but this would require further research to confirm whether behaviours would mitigate this threat. The projections for the NSW climate by 2050 include an increase in minimum and maximum temperatures, an increase (double) in the number of hot days per year (days greater than 35°C), and longer fire seasons, with around a 40% increase in ‘very high’ fire danger days (CSIRO & BoM 2021).
Extended periods of low rainfall reduce food availability for Pookila. Recent periods of drought have caused demonstrable crashes in Pookila populations. The local extinction of the Anglesea population is in part attributed to the Millennium Drought (Lock & Wilson 2017), and the species is yet to recover from the 2019 Gippsland drought (Burns 2021).
Fire–drought interactions may have a significant impact on the Pookila with potential compounding effects. This is evident from the 2019 and 2020 bushfires, which followed a period of significant drought in 2017 to 2019 (BoM 2020; DPIE 2020).
3.2.4 Invasive fauna species
Predation by cats and European red foxes
Feral predators can have rapid and catastrophic impacts on populations of threatened rodents (Tuft et al. 2021). While there is limited direct evidence of the consumption of Pookila by feral predators (records in dog scats; Hoskins 1997; Davis et al. 2015; Lock & Wilson 2017; MidCoast Council NSW 2024. pers comm 13 February), it is recognised in the Threat Abatement Plan for Predation by Feral Cats 2024 that the Pookila is likely highly susceptible to predation by cats (and/or in some cases by foxes) (DCCEEW 2024a) and that cats and foxes can significantly impact population numbers (Seebeck et al. 2003; Burns 2019a).
Like many other Pseudomys species, Pookila are docile and display poor awareness of exotic predators (P. Burns, pers. obs.). In such species, selective predation can occur (as reported, for example, on the broad-toothed rat, Mastacomys fuscus; Green 2002), leading to a disproportionate impact of predation on the vulnerable species even when co-occurring species (for example, the house mouse) are at greater abundance. Furthermore, communal burrowing and small local population densities mean that predation events at burrow entrances can cause rapid local declines (Burns 2019a).
The relative impact of predation by feral cats and foxes on the Pookila is not yet understood. Based on factors such as small body size, lower breeding output, and occupation of open habitat, some researchers have identified the Pookila as having a high threat rating from feral cat predation (Dickman 1996; Stobo-Wilson et al. 2021). Radford et al. (2018) reported the cat and fox threat to Pookila to be approximately the same based on expert opinion, although with weak evidence. While foxes are currently absent from the Tas mainland and Flinders Island (DNRE Tas 2022), and fox control is in place in other parts of the species’ range, effective cat control in open, non-insular systems beyond the local scale is not yet possible and potentially counterproductive (Lazenby et al. 2015; Lazenby et al. 2021; see Predator management).
The density and predatory impact of cats and foxes can be altered by competitive interactions with other predators. For example, reduced numbers of foxes via fox control can increase cat density, alter cat behaviour, and ultimately increase the impact of predation by feral cats (Risbey et al. 2000; Rees et al. 2023). Tasmanian devils have been shown to alter the behaviour and abundance of feral cats (Hollings et al. 2014; Lazenby & Dickman 2013), and cats have a much higher predatory impact on small mammals compared to devils (Hollings et al. 2014). The decline of devils caused by Devil Facial Tumour Disease (DFTD) is likely to have increased the predatory impacts of feral cats in Pookila habitat on the Tas mainland.
Impact of hooved feral animals including deer, goats, horses, and pigs
The negative impacts of hooved feral animals on vegetation health and soil erosion are well documented (Keith & Pellow 2005; Bengsen et al. 2017; Wills et al. 2023; Burns et al. 2021). This is also recognised within the Draft threat abatement plan for competition and land degradation by unmanaged goats (DCCEEW 2024c), the Threat abatement plan for predation, habitat degradation, competition and disease transmission by feral pigs (Sus scrofa) (DOEE 2017), and the National feral deer action plan (Government of South Australia 2023). Where these species co-occur with the Pookila, there are risks of habitat degradation through trampling, wallowing, and overgrazing (Burns 2021). Overgrazing pressures may increase in post-fire environments, particularly in heathy vegetation types preferred by the Pookila (Heaton et al. 2022), compounding post-fire food shortages and predation risk, while impeding regrowth of suitable habitat and food species (DAWE 2022). The effects of hooved feral animal control programs on Pookila occurrence and abundance have not been directly studied, but based on vegetation response studies, control programs are expected to benefit the Pookila and its habitat, particularly around fire events.
Competition/predation from introduced rodents
While experimental trials have shown the Pookila to be competitively superior to the invasive house mouse (Fox & Twigg 1991; Haering & Fox 1997), there is growing evidence that house mouse plagues may supress Pookila recovery following periods of drought where resources are subsequently scarce (Burns 2021). Rattus rattus and R. norvegicus (black and brown rats, respectively) may also out-compete the Pookila for resources and prey on adults and juveniles, although this requires further research.
Baiting of rabbits and invasive rodents
The susceptibility of the Pookila to 1080, Pindone, and rodenticide has not been tested. However, such poisons are lethal at low doses to some other Pseudomys species and are expected to be lethal to the Pookila (McIlroy 1982; Eisler 1995; Fisher 1999). Running a lethal dose trial on the Pookila is not appropriate given the species’ threatened status and ethical considerations, so it is safest to apply the Precautionary Principle and assume the species is likely susceptible to 1080, Pindone and rodenticide. Rabbit poison baiting is usually conducted with a carrot or oat bait, both foods readily consumed by the Pookila (Prosser et al. 2007), and it is possible that rabbit-baiting programs have contributed to the decline of the species in some areas (Fisher 1999; Burns 2019a). When finding the balance between protecting Pookila habitat by controlling rabbits and potentially poisoning individual Pookila, it is recommended to entirely avoid poison baiting in areas where Pookila presence is known. This is particularly important for at-risk populations; however, it may also apply to locations where Pookila presence is uncertain but these areas are adjacent to suitable habitat and/or a known population (within a 5 km radius). Rabbit and invasive rodent population control measures should use alternative methods. Control measures should be carefully considered depending on the area of control and the potential side effects for native species. Currently, this threat is considered to be high in Wilsons Promontory in Vic, not applicable in Qld or Tas, and unknown in NSW (DNRE Tas 2023).
3.2.5 Small and fragmented populations: Low genetic diversity and inbreeding
Historical and contemporary habitat degradation and destruction, and the species’ very low dispersal ability have left the Pookila highly fragmented across its distribution, with some populations genetically isolated. This severe fragmentation leaves populations at higher risk of extinction, as a single catastrophic event can more easily impact the total area occupied by a population (Garner et al. 2020).
Furthermore, genetically isolated populations are at higher risk of inbreeding depression. Inbreeding reduces genetic diversity, which reduces adaptability to changing environments and anthropogenic impacts. Inbreeding depression also increases species’ vulnerability to disease while also allowing potentially detrimental traits to surface in the population (Keller 2002). Furthermore, inbreeding depression can cause reduced fecundity and further genetic health issues (for example, chromosomal abnormalities) (Keller 2002).
Vic populations (Southern ESU) of the Pookila have relatively low heterozygosity (genetic diversity) and are at risk of inbreeding, with no natural gene flow possible between localities given lack of dispersal (Burns et al. 2023b). Therefore, the Southern ESU is considered an ‘at-risk ESU’. Populations across NSW retain greater heterozygosity and are genetically distinct from those in Vic, although animals in Broadwater National Park appear to have undergone a genetic bottleneck (Burns et al. 2023b). At the time of publishing this recovery plan, two historic mainland Tas samples and a small number of contemporary samples from Flinders Island have been sequenced and are being analysed. Additional Tas samples are being sought through survey work. Genetic mixing within Vic populations has been recommended and is being pursued, whereas no immediate action is required in the Northern ESU (NSW and Qld) (Burns et al. 2023b; Burns et al. 2024) since it is more genetically healthy than the Southern ESU. The recovery team has developed a National Pookila genetic management strategy (Zoos Victoria) and will continue to update it when new information is forthcoming.
Disease
There is limited understanding of the potential prevalence or impact of disease on the Pookila. In general, screening of native rodents for pathogens has been very limited and little information is available on symptomology (Thompson et al. 2010). However, feral cats and invasive rodents carry diseases that could impact the Pookila. In particular, Toxoplasma gondii, a virulent parasite spread by cats, is likely present through much of the species’ former range (Dickson 2018). Previous experimental trials in other Pseudomys species demonstrated rapid, high mortality rates after infection with T. gondii, hence this parasite is likely to also increase the mortality of the Pookila (Burns 2019a).
3.3 Threat prioritisation
Each of the threats outlined in this recovery plan has been assessed to determine the risk posed across the national distribution of the Pookila using a risk matrix (see Table 6). The risk matrix considers the likelihood of an incident occurring and the consequences of that incident and uses a qualitative assessment drawing on both peer-reviewed literature and expert opinion.
Table 6: Risk matrix
Consequence (x) / Likelihood (y)
Not significant
Minor
Moderate
Major
Catastrophic
Almost certain
Low risk
Moderate risk
Very high riskPredation by European red foxes
Very high riskHabitat clearing (past/present)Fire regimes that cause declines in biodiversityIncreasing number of hot days, prolonged drought and changes to precipitation patternsPredation by cats
Very high risk
Likely
Low risk
Moderate riskImpact of hooved feral animals including deer, goats, horses, and pigs
High riskHabitat modification due to Phytophthora cinnamomi infestationHabitat modification due to native and introduced weeds
Very high riskHabitat clearing (future)
Very high risk
Possible
Low risk
Moderate riskCompetition/predation from introduced rodentsBaiting of rabbits and invasive rodents
High riskLow genetic diversity and inbreedingDisease
Very high risk
Very high risk
Unlikely
Low risk
Low risk
Moderate risk
High risk
Very high risk
Unknown
Low risk
Low risk
Moderate risk
High risk
Very high risk
Risk matrix key
Low risk
Moderate risk
High risk
Very-high risk
Definition of likelihood and consequence categories
Consequence is a measure of the severity of the impact of the threat on the survival of the species.
Catastrophic – affecting survival, reproduction or essential movement of individuals in >80% of the population or across >80% of the distribution within the next 3 generations or 10 years, whichever is longer.
Major – affecting survival, reproduction or essential movement of individuals in 50-80 % of the population or across 50-80% of the distribution within the next 3 generations or 10 years, whichever is longer.
Moderate – affecting survival, reproduction or essential movement of individuals in 20-50% of the population or across 20-50% of the distribution within the next 3 generations or 10 years, whichever is longer.
Minor – affecting survival, reproduction or essential movement of individuals in 5-30% of the population or across 5-30% of the distribution within the next 3 generations or 10 years, whichever is longer.
Not significant – affecting survival, reproduction or essential movement of individuals in <5% of the population or across <5% of the distribution within the next 3 generations or 10 years, whichever is longer.
Likelihood is a measure of how regularly the threat impacts the species.
Almost certain – >90% chance that threat will have an impact on the species within the next 3 generations or 10 years, whichever is longer.
Likely – 66-90% chance that threat will have an impact on the species within the next 3 generations or 10 years, whichever is longer.
Possible – 33-66% chance that threat will have an impact on the species within the next 3 generations or 10 years, whichever is longer.
Unlikely – <33% chance that threat will have an impact on the species within the next 3 generations or 10 years, whichever is longer.
Unknown – probability that threat will have an impact on the species within the next 3 generations or 10 years, whichever is longer, could be 0-100%.