Ecology

Habitat. — This species is widely distributed within the river systems it occupies, from the permanent waters of the uppermost spring-fed pools to the freshwater-brackish water interface (Hamann et al. 2004). It prefers flowing waters with complex subsurface structure in the form of log tangles, undercut banks, and irregular rocky substrata. It is typically absent or rare in standing waters impounded by dams or weirs, unless associated with free-flowing streams. It does not inhabit brackish waters.

Reproductive Cycles. — The peak breeding season for males is between January and August. Females leave the water once per year between March and September to lay approximately 14 hard-shelled eggs (Hamann et al. 2004). The nest is constructed mostly on the front face and top of steep sloping banks with sand or soil substrates. Nest and hatchling predation by pigs, dogs, foxes, cats, monitor lizards, and water rats is intense. Many of these predators are exotic and their activity, coupled with habitat modification, is regarded as a major threat the persistence of the species in many parts of its range (Hamann et al. 2004).

Diet. — Elseya albagula is primarily herbivorous, feeding on fruit and buds of riparian vegetation that falls upon the water, filamentous algae, and instream macrophytes. Animal material forms a small part of the diet of adults and includes freshwater sponges and carrion. Young may be more carnivorous. In captivity, the young feed readily on snails.

DISCUSSION

Elseya albagula is distinctive not least by virtue of its large size and resides in an area of high human population. It is remarkable that it is only now being described, but it cannot be regarded as a new discovery. Elseya dentata (Gray 1863) has long been suspected to be a species complex. Both Goode (1967) and Cann (1978) recognized the distinction between populations from the Northern Territory and east coastal Queensland, and anticipated reclassification of the distinctive forms. Legler (1981) recognized five distinguishable allopatric populations of what was then regarded as E. dentata: (1) populations in the Ord, Victoria, and Daly systems, and possibly eastward to the Alligator rivers region; (2) populations in the Roper and Nicholson-Leichhardt drainages of the Gulf of Carpentaria; (3) the north Johnstone River system of east coastal Queensland; and (4) all populations south of the Atherton tableland, including the Fitzroy River and Burnett River populations. Allozyme studies, using sampling designs based on the extensive field work by Cann, confirmed the existence of a number of genetically distinctive forms, that were sufficiently divergent to be regarded as separate biological species (Georges and Adams 1992, 1996) including with some variation, those identified by the above authors. These new forms are being described progressively (Cann 1997b; Thomson et al. 1997), with this paper contributing to that progress.

We regard the species as comprising populations from the Mary, Burnett, and Fitzroy-Dawson drainage basins. Recent work using a combination of nuclear and mitochondrial markers reveal some genetic differentiation between these three drainages and within the larger Fitzroy-Dawson drainage, but there are no fixed differences established using the nuclear markers (Farley et al., forthcoming). We interpret this substructuring as the accumulation of genetic differences among populations of a single species since their isolation by distance and recent sea level rise. Thus, in our view, the populations in the three river drainages represent three contemporary evolutionary significant units (Moritz 1994) within a single morphologically well-defined biological species.

Conservation Considerations. — Elseya albagula is widespread and locally abundant in three major drainage basins of southeastern Queensland (Hamann et al. 2004), and as such may currently be regarded as secure. The predominance of adults in all populations is a concern (Hamann et al. 2004) and possibly exacerbated by heavy predation by exotic predators. In addition, the species is intrinsically vulnerable by virtue of its specialized habitat requirements, namely a reliance on flowing waters and riffle, reinforced by its dual mode of respiration (Legler and Georges 1993; FitzGibbon 1998). Flowing waters are coming under increasing threat from water resource development, and particularly the development of new impoundments or redevelopment of existing impoundments to service the needs of agriculture, industry, and urban centres. Elseya albagula would be a good candidate for monitoring as a sensitive indicator of riverine health.

ACKNOWLEDGMENTS

We thank the many people and institutions who gave access to their turtle collections: Ross Sadlier, Australian Museum; Patrick Couper, Queensland Museum; Paul Horner, Museum and Art Gallery of the Northern Territory; John Wombey, Australian National Wildlife Collection; John Legler, Utah State University; Jose´ Rosado, Museum of Comparative Zoology; Colin McCarthy, British Museum of Natural History. We also thank those who gave us access to private collections and shared their knowledge with us: John Cann, Bill McCord, Peter Pritchard, Anders Rhodin. Duncan Limpus provided invaluable field support. Uwe Fritz and Roger Bour provided comment on an earlier draft. The project was funded by the CRC for Freshwater Ecology, Canberra, and the Environmental Protection Agency, Brisbane.

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