Yellow-spotted Tree Frog, Yellow-spotted Bell Frog
Distribution and Habitat
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 disjoint isolates separated by a distance of about 500 km (see also map in Osborne et al. 1996). The area of occurrence of the species is about 9000 km^2 (map in Mahony 1999). The northern population was known from a relatively restricted distribution centered around the town of Guyra on the New England Tableland at altitudes between 1000 and 1500 m (White and Ehmann 1997a; Mahony 1999). The species 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 1000 m) 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 800 m (Mahony 1999). The Southern Tablelands population was originally broadly sympatric with L. aurea in the north of its range and with L. raniformis in the southwest of the region (Mahony 1999). The Southern Tablelands population suffered an extensive decline (Osborne et al. 1996, Mahony 1999), but specimens were rediscovered in 2008 after having been unobserved since 1980 (see link to Sydney Herald press release from March 5, 2010, below).
Litoria castanea was formerly known from Namadgi and Kosciuszko NP (W. Osborne pers. comm.) and extensive areas of grassland used for grazing (Tyler 1997).
Life History, Abundance, Activity, and Special Behaviors
Trends and Threats
Southern Tablelands populations declined precipitously between 1978 and 1981 (Osborne et al. 1996). The cause(s) of the apparent declines observed in populations of all taxa within the L. aurea complex are unclear (Gillespie et al. 1995), although chytridiomycosis is thought to be a prime driver, based on the pattern and speed of decline in L. castanea, L. aurea, and L. raniformis (Hamer et al. 2009). Previous investigations of disappearances among the group had primarily focused on L. aurea and L. castanea and two major directions in research were pursued: the role of increased ultraviolet radiation; and the impact of the introduced fish, Gambusia (Mahony 1999).
Van de Mortel and Buttermer (1996) conducted experiments to assess the effect of increased ultraviolet radiation on the hatching success of L. aurea eggs. Hatchling success was higher under a UV-B blocking treatment than an unfiltered treatment in a repeat experiment involving one spawn, but there was no difference in the preliminary experiments involving three spawns. These results lack a coherent trend and are in several ways preliminary (Mahony 1999). Further research is needed to further examine the role of ultraviolet radiation in declines of L. aurea.
A number of studies reviewed by Mahony (1999) are consistent with the hypothesis that Gambusia contributes to the decline of frog populations. Studies have shown that Gambusia will attack and eat tadpoles including those of L. aurea (Morgan and Buttermer 1996; Webb and Joss 1997). However the importance of Gambusia as a predator relative to other factors in causing the decline of bell frogs remains unclear (Gillespie & Hero 1999; Mahony 1999). There is a great deal that remains to be understood about the impact of Gambusia. For example, at least for L. aurea and L. raniformis, there are sites where the frog has disappeared but where the fish is absent, and there are sites where the frog can be found but the fish are present (Mahony 1999; W. Osborne pers. comm.). However, very high densities of fish, along with waterbody characteristics such as high ephemerality and steep pond banks, may contribute to poor breeding at some sites (Goldingay and Lewis 1999). The dates of introduction of Gambusia to many regions are not well documented and this lack of information has hampered the ability to draw firm conclusions about its impact.
Though feared extinct after not having been sighted for over three decades, a small population of Litoria castanea was rediscovered in 2008 (read the Sydney Herald press release from March 5, 2010).
Possible reasons for amphibian decline
General habitat alteration and loss
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Cogger, H. G. (2000). Reptiles and Amphibians of Australia, 6th edition. Reed New Holland, Sydney.
Courtice, G.P. and Grigg, G.C. (1975). ''A taxonomic revision of the Litoria aurea complex (Anura: Hylidae) in southeastern Australia.'' Australian Zoologist, 18, 149-163.
Gillespie, G. and Hero, J.-M. (1999). ''Potential impact of introduced fish and fish translocations on Australian amphibians.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra, 131–144.
Gillespie, G.R., Osborne, W.S. and Mc Elhinney, N.A. (1995). The Conservation Status of Frogs in the Australian Alps: A Review. A Report to the Australian Alps Liaison Committee, Canberra.
Hamer, A. J., Lane, S. J., and Mahony, M. J. (2009). ''Using probabilistic models to investigate the disappearance of a widespread frog-species complex in high-altitude regions of south-eastern Australia.'' Animal Conservation, Online ahead of print, DOI 10.1111/j.1469-1795.2009.00335.x.
Heatwole, H., de Bavay, J., Webber, P. and Webb, G. (1995). ''Faunal survey of New England. IV. The frogs.'' Memoirs of the Queensland Museum, 38, 229-249.
Lewis, B., and Goldingay, R. (1999). ''A preliminary assessment of the status of the Green and Golden Bell Frog in north-eastern New South Wales.''
Mahony, M. (1999). ''Review of the declines and disappearances within the bell frog species group (Litoria aurea species group) in Australia.'' Declines and Disappearances of Australian Frogs. A. Campbell, eds., Environment Australia, Canberra, 81-93.
Morgan, L. A., and Buttemer, W. A. (1996). ''Predation by the non-native fish Gambusia holbrooki on small Litoria aurea and L. dentata tadpoles.'' Australian Zoologist, 30(2), 143-149.
Osborne, W. S., Littlejohn, M. J., and Thomson, S. A. (1996). ''Former distribution and apparent disappearance of the Litoria aurea complex.'' Australian Zoologist, 30(2), 190-198.
Robinson, M. (1996). A field guide to frogs of Australia from Port Augusta to Frazer Island including Tasmania. Australian Museum and Reed Books, New Holland/Sydney.
Thompson, S.A., Littlejohn, M.J., Robinson, W.A., and Osborne, W.S. (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.
Tyler, M.J. (1997). The Action Plan for Australian Frogs. Wildlife Australia, Canberra, ACT.
Van De Mortel, T. F., and Buttemer, W. A. (1996). ''Are Litoria aurea eggs more sensitive to ultraviolet-B radiation than eggs of sympatric L. peronii or L. dentata?'' Australian Zoologist, 30(2), 150-157.
Webb, C.E. and Joss, J. (1997). ''Does predation by the fish Gambusia holbrooki (Atheriniformes: Poecilidae) contribute to declining frog populations?'' Australian Zoologist, 30, 316-324.
White, A.W. and Ehmann, H. (1997). ''18. New England Bell Frog, Litoria castanea/flavipunctata.'' Threatened Frogs of New South Wales: Habitats, Status and Conservation. H. Ehmann, eds., Frog and Tadpole Study Group of NSW Inc, Sydney South, Australia, 164-169.
White, A.W. and Ehmann, H. (1997). ''19. Southern Highlands Bell Frog, Litoria sp. nov.'' Threatened Frogs of New South Wales: Habitats, Status and Conservation H. Ehmann, eds., Frog and Tadpole Study Group of NSW Inc., Sydney South, Australia, 170-175.
Written by J-M. Hero; W. Osborne; L. Shoo; M. Stoneham (m.hero AT mailbox.gu.edu.au), Griffith University
First submitted 2002-03-15
Edited by Kellie Whittaker (2010-03-24)
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