Yellow-spotted Tree Frog (Litoria castanea) - critically endangered species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Yellow-spotted Tree Frog Litoria castanea (Steindachner, 1867), as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to the Yellow-spotted Tree Frog Litoria castanea (Steindachner, 1867) from Part 1 of Schedule 1 (Endangered species) of the Act. Listing of Critically Endangered species is provided for by Part 2 of the Act.
NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Yellow-spotted Tree Frog Litoria castanea (Steindachner, 1867) (family Hylidae), also known as the Yellow-spotted Bell Frog, is an endemic Australian frog, described by Robinson (1996) as follows: ‘This frog can reach a length of 80 mm. It is dull olive to bright emerald green on the back, with varying amounts of irregular bronze spotting and blotches. There is always a pale green stripe down the back. The tympanum is dark and conspicuous, and the dorso-lateral fold is pale cream and also conspicuous. There are scattered black spots on the back. The groin and hind side of the thighs are blue-green, with large yellow or cream spots, and the belly is white. The skin of the back is warty, and it is glandular on the belly. The toes are fully webbed, with tiny toe discs – narrower than the toe itself. The vomerine teeth are between the choanae, and there are maxillary teeth’.
2. The Yellow-spotted Tree Frog is similar to Litoria raniformis Southern Bell Frog but is distinguished by its fully webbed toes and yellow spots on the groin and the back of the thighs (Cogger 2000).
3. The Yellow-spotted Tree Frog occurs in two separate highland areas, one on the New England Tableland, around Guyra and another on the southern highlands around Lake George – Canberra and around Bombala – Delegate. The two areas are separated by about 500 km (NSW NPWS 2001). Unconfirmed historical records of a frog resembling Litoria castanea also exist from the Central Tablelands, centred around Orange and Bathurst, a region between the northern and southern occurrences (White & Pyke 1999). These unconfirmed records date from the late 1960s to mid 1970s.
4. There is some uncertainty surrounding the taxonomic status of the northern and southern populations of the Yellow-spotted Tree Frog. Courtice & Grigg (1975) described the Guyra population as a separate species, Litoria flavipunctata. However, Thomson et al. (1996) suggest that the Guyra and southern tableland populations represent one species consisting of two disjunct isolates that show some divergence in colour pattern and head morphology. The inclusion of both groups of populations within L. castanea is currently the most widely accepted taxonomic hypothesis and is applied in this Determination.
5. The Yellow-spotted Tree Frog has been found in permanent ponds, swamps, lagoons, farm dams and the still backwaters of slow flowing streams usually with emergent vegetation such as tall reeds or with overhanging grassy banks (Courtice & Grigg 1975; White & Ehmann 1997a, b).
6. Despite searches of the historic localities and other streams with similar habitat within the known distribution of the Yellow-spotted Tree Frog, the species has not been seen in the wild since 1980 (Osborne et al. 1996; NSW NPWS 2001) indicating that the entire population of the species has undergone a very large reduction and may be extinct. There is a possibility that some individuals of Litoria castanea persist and remain undetected, as some further areas of potentially suitable habitat have yet to be searched.
7. There have been declines in populations of all taxa within the Litoria aurea complex (Osborne et al. 1996), but the causes are unknown. On the southern tablelands, the declines occurred precipitously between 1978 and 1981 (Osborne et al. 1996). Possible causes include: disease, particularly chytrid fungus; loss or modification of wetlands, swamps and slow-flowing creeks and the adjacent vegetation; changes to natural water flows and water quality; application of herbicides and other pesticides in or adjacent to habitat; removal of fallen timber, rocks or other debris used as shelter; predation of eggs and tadpoles by introduced fish, particularly Gambusia holbrooki; increased ultraviolet radiation; predation of frogs by foxes and cats (NSW NPWS 2001; Mahony 1999). ‘Infection of frogs by amphibian chytrid causing the disease chytridiomycosis’, ‘Alteration to the natural flow regimes of rivers, streams, floodplains & wetlands’, ‘Removal of dead wood and dead trees’ and ‘Predation by the Plague Minnow ( Gambusia holbrooki)’ are listed as Key Threatening Processes under the Threatened Species Conservation Act 1995 .
8. The Yellow-spotted Tree Frog Litoria castanea (Steindachner, 1867) is eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, it is facing an extremely high risk of extinction in New South Wales in the immediate future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:
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:
(a) a very large reduction in population size
based on either:
(d) an index of abundance appropriate to the taxon
(e) geographic distribution, habitat quality or diversity, or genetic diversity.
The estimated total number of mature individuals of the species is:
(a) very low
and:
(d) a projected or continuing decline is observed, estimated or inferred in either:
(i) an index of abundance appropriate to the taxon
(ii) geographic distribution, habitat quality or diversity, or genetic diversity.
The total number of mature individuals of the species is observed, estimated or inferred to be:
(a) extremely low.
Dr Richard Major
Chairperson
Scientific Committee
Proposed Gazettal date: 04/12/09
Exhibition period: 04/12/09 – 29/01/10
References:
Cogger HG (2000) ‘Reptiles and Amphibians of Australia.’ 6th edition. (Reed New Holland: Sydney).
Courtice GP, Grigg GC (1975) A taxonomic revision of the Litoria aurea complex (Anura: Hylidae) in southeastern Australia. Australian Zoologist 18, 149-163.
Mahony M (1999) Review of the declines and disappearances within the bell frog species group (Litoria aurea species group) in Australia. In: ‘Declines and Disappearances of Australian Frogs’ (Ed. A Campbell) pp. 81-93. (Environment Australia: Canberra)
NSW National Parks and Wildlife Service (2001) ‘Yellow-spotted Bell Frog (Litoria castanea) and Peppered Tree Frog ( Litoria piperata) recovery plan’. NPWS, Sydney.
Osborne WS, Littlejohn MJ, Thomson SA (1996) Former distribution and apparent disappearance of the Litoria aurea complex from the Southern Tablelands of New South Wales and the Australian Capital Territory. Australian Zoologist 30, 190-198.
Robinson M (1996) ‘A field guide to frogs of Australia from Port Augusta to Fraser Island including Tasmania.’ (Australian Museum and Reed Books/New Holland: Sydney)
Steindachner (1867) Amphibien. In Reise der Osterreichieschen Freggate Novara um die Erde in den Jaren 1857-1859. Vienna Zoologische Thiel 1, 1-70.
Thompson SA, Littlejohn MJ, Robinson WA, Osborne WS (1996) Taxonomy of the Litoria aurea complex: a re-evaluation of the Southern Tablelands populations of the Australian Capital Territory and New South Wales. Australian Zoologist 30, 158-169.
White AW, Ehmann H (1997a) New England Bell Frog, Litoria castanea/flavipunctata. In: ‘Threatened Frogs of New South Wales: Habitats, Status and Conservation’. (Ed. H Ehmann) pp. 164-169. (Frog and Tadpole Study Group of New South Wales, Sydney South: Australia)
White AW, Ehmann H (1997b). Southern Highlands Bell Frog, Litoria sp. nov. In: ‘Threatened Frogs of New South Wales: Habitats, Status and Conservation’. (Ed. H Ehmann) pp. 170-175. (Frog and Tadpole Study Group of New South Wales, Sydney South: Australia)
White AW, Pyke GH (1999) Past distribution of Litoria aurea and Litoria castanea in the Bathurst-Orange Area of New South Wales. Herpetofauna 29, 2-9.