The Katapiri Fauna Collapse

Australia: The Land Where Time Began

The Katapiri Fauna Collapse

According to Smith when rivers, lakes and swamps failed as the climate shifted to the drier conditions of the MIS 4 the dryland megafauna populations also collapsed along with the regional ecosystem. The last known evidence of significant megafauna populations in this region is the remains of Diprotodon from Punkrakadarinna on the Warburton River that have been dated by thermoluminescence to 64.9 ± 5 ka (Webb, 2009). Smith suggests there are a couple of factors that are likely to underlie local megafauna extinctions, such as the marked dependence of many macropods on shelter to avoid heat stress, therefore problems for larger species were created by the increasingly open vegetation. At the present medium to large species of kangaroos are not common in the heart of the Lake Eyre basin. Another problem for larger species is the need for free water, late maturity and slower reproductive rates. Therefore, most species of the megafauna would not be capable of tolerating the increasing stochasticity of the environment and fragmentation of riparian habitats (Main & Bakker, 1981; Horton, 1984).

One of the clearest examples of extinction at a regional level driven by climate change is the demise of this dryland megafauna. The critical importance of biogeographic factors is demonstrated by the collapse of the Katapiri fauna, though it has been shown by other studies that megafauna communities demonstrate resilience in the face of climatic fluctuations in the Quaternary (Prideaux, 2007). In the Cooper Creek-Lake Eyre region the interglacial palaeohydrology effectively made this area part of the desert margin. Migration corridors between the main body of megafauna in southeastern Australia (a source) and animal populations in the Lake Eyre basin (a sink) appears to have been disrupted by the switch to conditions that were drier and more variable (Webb, 2009). The dryland megafauna were not able to recover from these environmental crashes once the connection with the southeastern source was cut.

It is shown that some species survived into the period 50-45 ka, as the find of an isolated Diprotodon cranium near Lake Eyre, which was associated with an OSL date of 46.6 ± 3 ka (ANU-OD 1251) suggests that in the upper reaches of these drainage systems that were better watered these animals persisted, dispersing downstream following exceptionally heavy rain (Webb, 2009 and personal communication to Smith). Similarly the megafauna persisted into the period 66-51 ka at Lake Menindee (Cupper & Duncan, 2006). Smith suggests that the only megafauna species that is likely to have been encountered by the first people moving into the desert was Genyornis newtoni, a large flightless dromornithid bird.

Genyornis

Until 50 ± 5 ka G. newtoni was distributed widely across arid and semi-arid parts of southeastern Australia (Miller et al., 1999). This bird is believed to have been able to tolerate saline waters as it had nasal salt glands (Murray & Vickers-Rich, 2004). It appears G. newtoni may have been tethered to riparian corridors for nesting, based on the distribution of its distinctive eggshell, possibly moving up and down the channel systems and floodplains according to the seasons. In those parts of the arid interior that are interlaced with river channels, such as in western New South Wales, the Lake Eyre basin, the Murray-Darling basin and southwestern Queensland, Genyornis had a wide range. The bones of Genyornis are not known among fossil assemblages from the Nullarbor, despite several field surveys, its eggshells have not been found in the Great Victoria Desert or around Lake Gregory or Lake Mackey. According to Smith isolated Genyornis populations appear to have been present on the arid west coast at Lake McLeod and in Central Australia at Lake Lewis, the Lake Lewis population being believed to almost certainly being a limited extension of range along the corridor of the Finke River in good years. The eventual extinction of Genyornis in the Lake Eyre basin coincided with a significant decline of the rainfall of the summer monsoon (Johnson et al., 1999; Murphy, Williamson & Bowman, 2012), which is suggested to have potentially disrupted its breeding pattern in the summer and the C4 plants, which was its preferred diet. Smith suggests it may have also coincided with the first arrival of humans in these landscapes, especially as any predation on eggs or young birds would have put extra pressure on this species.