Some uncertainty surrounds the taxonomic status of the northern (L. flavipunctata of Courtice and Grigg 1975) and southern populations of Litoria castanea. Thomson et al. (1996) suggest that the northern and southern populations represent one species consisting of two disjunctive isolates separated by a distance of about 500km (see also map in Osborne, Littlejohn and Thomson 1996). The northern population was known from a relatively restricted distribution centred around the town of Guyra on the New England Tableland at altitudes between 1,000 and 1,500m asl (White and Ehmann 1997a; Mahony 1999). It occupied the headwaters of the west flowing Booroolong Creek and to a lesser extent those of the east flowing Anne River and Sarah River (Heatwole et al. 1995). Near Armidale, the species has been recorded from Commissioners Waters, a tributary of the east flowing Gara River (Heatwole et al. 1995). There are 13 known sites in the region (most above 1,000m asl) all of which have been verified by examination of museum specimens or photographs (Mahony 1999). The southern population has a restricted distribution between Canberra and Bombala on the Southern Tablelands at altitudes between 700 and 800m asl (Mahony 1999). The southern population was broadly sympatric with L. aurea in the north of its range and with L. raniformis in the south-west of the region (Mahony 1999).
Habitat and Ecology
Litoria castanea occupies similar habitat to L. aurea and L. raniformis which includes permanent ponds, swamps, lagoons, farm dams and the still backwaters of rivers usually with tall reeds present (Courtice and Grigg 1975; White and Ehmann 1997a, b). The species was also found in ponds or slow moving streams with overhanging grassy banks in the absence of reed beds (Courtice and Grigg 1975). Litoria castanea was found to over-winter in the hollow centres of rotting logs and in the earth surrounding the roots of uprooted trees (Courtice and Grigg 1975), and in the base of sedge tussocks (Humphries 1979). Little is known about the biology of this species; however, it is likely to be similar to that of L. aurea and L. raniformis (Gillespie, Osborne and McElhinney 1995). Individuals reach sexual maturity at three years and live for six years.
There are no verified records of the northern population after 1975 (White and Ehmann 1997a) and the last specimen to be placed in the museum was collected in 1973 (Australian Museum Register in Mahony 1999). The southern tablelands population suffered an extensive decline, with no confirmed records since 1980 (Osborne, Littlejohn and Thomson 1996; Mahony 1999). It is not yet considered extinct because of the lack of surveys of potential habitat, especially in areas between the northern and southern populations.
The cause(s) of the apparent declines observed in populations of all taxa within the L. aurea complex are unclear (Gillespie, Osborne and McElhinney 1995), although chytridiomycosis must be strongly suspected. Investigations of disappearances among the group have primarily focused on L. aurea and L. castanea and two major directions in research have been pursued: the role of increased ultraviolet radiation; and the impact of the introduced fish, Gambusia, which is native to southern and eastern USA (Mahony 1999). However, it is likely that disease, such as chytrid fungus or a viral infection, contributed to the decline of this species (W. Osborne pers. comm.).
Further survey work is required to determine whether or not this species still survives, particularly in the southern tablelands, and in areas of suitable habitat between the northern and southern populations. Research into possible causes of this species' disappearance and the decline of similar species (L. aurea and L. raniformis) is urgently needed.
Jean-Marc Hero, Harry Hines, Frank Lemckert, Peter Robertson 2004. Litoria castanea. In: IUCN 2014