Sloane's froglet (Crinia sloanei) - vulnerable species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a FINAL DETERMINATION to list Sloane's Froglet Crinia sloanei Littlejohn 1958 as a VULNERABLE SPECIES in Part 1 of Schedule 2 of the Act. Listing of vulnerable species is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Sloane's Froglet Crinia sloanei is a small ground-dwelling frog belonging to the family Myobatrichidae. In appearance this species superficially resembles other frogs of the genus  Crinia, but it can be readily identified by its call (Frogs Australia Network) and specific physical characteristics (Robinson 1998, Cogger 2000). The taxonomic status of  C. sloanei is stable (Read  et al. 2001).

2. Crinia sloanei has been recorded from widely scattered sites in the floodplains of the Murray-Darling Basin, with the majority of records in the Darling Riverine Plains, NSW South Western Slopes and Riverina bioregions in New South Wales ( sensu Thackway and Cresswell 1995). It is typically associated with periodically inundated areas in grassland, woodland and disturbed habitats.

3. Crinia sloanei was first described in 1958. Since then it has been recorded only 45 times in NSW (Atlas of NSW Wildlife) with each record comprising an observation of the species at a site (median of 1.5 individuals per record; range 1-20). In several instances, uncertainty exists over records attributed to  C. sloanei that are not accompanied by a lodged specimen. In the past decade numerous broad-scale surveys have been conducted within the range of  C. sloanei. Of the approximately 750 surveyed sites,  C. sloanei was detected at just three (five individuals). In the northern part of its range, the species was notably absent during the Darling Riverine Plains Biodiversity Surveys of 2000-01, which recorded 9230 individual frogs of 17 species from 73 sites (Gosper 2002). Similarly, surveys during the Western Regional Assessment Brigalow Belt South Bioregion Stages 1 and 2 (1999-2001) recorded 252 individual frogs of 18 species from 195 sites, yet did not detect  C. sloanei (Pennay 2002). At a number of sites where records are verified by museum specimens, the species has not been subsequently detected during more recent frog surveys in the vicinity (e.g. Holbrook, Nyngan, Wagga Wagga and Tocumwal) (Atlas NSW Wildlife). The low number of sites, low number of recorded individuals per site, and the low proportion of records of this species in regional surveys all indicate that a moderately low number of mature individuals exist.

4. The scarcity and potential decline of C. sloanei can be assessed by comparing the records of  C. sloanei with the similar Plain’s Froglet  C. parinsignifera. Both frogs are small, primarily located and identified by the male advertising call, breed during spring and occupy floodplain habitats. The ratio of records for  C. sloanei/C. parinsignifera (within the range of  C. sloanei) in the decades 1977-86, 1987-96 and 1997-2006 has decreased from 4/12 (33%), to 15/74 (20%) and 17/339 (5%), respectively. There is no indication  C.  parinsignifera has increased over this period. In addition, compared to records for all frog species in NSW, the recording rate of  C. sloanei has declined by 44% between the decades 1977-86 to 1997-2006 (DECC  in litt. 2007). The apparent loss from previous recorded sites and decline of recording rates indicates at least a moderate reduction in population size of the species.

5. The specific threats to C. sloanei are not well understood. Chytridiomycosis, an infectious disease caused by the amphibian chytrid fungus  Batrachochytrium dendrobatidis, has not been recorded in  C. sloanei or any other  Crinia species in eastern Australia, but is known to infect four other  Crinia species from the same phylogenetic group as  C. sloanei in Western Australia (Read  et al. 2001, DEH 2006). Other threats include degradation of habitat quality through clearing, overgrazing and changes in flooding regimes, predation and climate change. ‘Infection of frogs by amphibian chytrid causing the disease chytridiomycosis’, ‘Alteration to the natural flow regimes of rivers, streams, floodplains and wetlands’, ‘Clearing of native vegetation’, ‘Predation by the plague minnow ( Gambusia holbrooki)’ and ‘Anthropogenic climate change’ are listed as Key Threatening Processes under the Threatened Species Conservation Act 1995.

6. Crinia sloanei Littlejohn 1958 is not eligible to be listed as an endangered or critically endangered species.

7. Crinia sloanei Littlejohn 1958 is eligible to be listed as a vulnerable species as, in the opinion of the Scientific Committee, it is facing a high risk of extinction in New South Wales in the medium-term future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:

Clause 14

The species has undergone, is observed, estimated, inferred or reasonably suspected to have undergone or is likely to undergo within a time frame appropriate to the life cycle and habitat characteristics of the taxon:

(c) a moderate reduction in population size,

(d) an index of abundance appropriate to the taxon,

(e) geographic distribution, habitat quality or diversity, or genetic diversity.

Clause 16

The estimated total number of mature individuals of the species is:

(c) moderately low,

and:

(d) a projected or continuing decline is observed, estimated or inferred in:

(ii) geographic distribution, habitat quality or diversity, or genetic diversity;

(e) the following conditions apply:

(i) the population or habitat is observed or inferred to be severely fragmented;
(ii) all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations.

Professor Lesley Hughes
Chairperson
Scientific Committee

Exhibition period: 28/03/08 – 23/05/08

References:

Cogger HG (2000) ‘Reptiles and Amphibians of Australia, Sixth Edition’ (Reed Books, Sydney).

Department of Environment and Heritage (2006) ‘Threat abatement plan for the infection of amphibians with chytrid fungus resulting in chytridiomycosis.’ Canberra, ACT.

Frogs Australia Network.  Accessed on 19.06.07.

Gosper C (2002) ‘Darling Riverine Plains Biodiversity Survey Technical Report.’ National Parks and Wildlife Service, Western Regional Assessment, Dubbo.

Pennay M (2002) ‘Vertebrate fauna survey, analysis and modelling projects. NSW Western Regional Assessments, Brigalow Belt South Bioregion (Stage 2).’ Planning NSW, Sydney.

Read K, Keogh JS, Scott IAW, Roberts DJ, Doughty P (2001) Molecular phylogeny of the Australian Frog Genera Crinia,  Geocrinia, and allied taxa (Anura: Myobatrachidae).  Molecular Phylogenetics and Evolution 21, 294-308.

Robinson M (1998) ‘A Field Guide to Frogs of Australia’ (Reed New Holland, Sydney).

Thackway R, Cresswell ID (1995) (Eds) ‘An interim biogeographic regionalisation for Australia: a framework for setting priorities in the National Reserves System Cooperative Program.’ (Australian Nature Conservation Agency: Canberra).