Mammalian responses to Pleistocene climate change in southeastern Australia

Abstract

Resolving faunal responses to Pleistocene climate change is vital for differentiating human impacts from other drivers of ecological change. While 90% of Australia's large mammals were extinct by ca. 45 ka, their responses to glacial-interglacial cycling have remained unknown, due to a lack of rigorous biostratigraphic studies and the rarity of terrestrial climatic records that can be related directly to faunal records. We present an analysis of faunal data from the Naracoorte Caves in southeastern Australia, which are unique not only because of the species richness and time-depth of the assemblages that they contain, but also because this faunal record is directly comparable with a 500 k.y. speleothem-based record of local effective moisture. Our data reveal that, despite signifi cant population fl uctuations driven by glacialinterglacial cycling, the species composition of the mammal fauna was essentially stable for 500 k.y. before the late Pleistocene extinctions. Larger species declined during a drier interval between 270 and 220 ka, likely refl ecting range contractions away from Naracoorte, but they then recovered locally, persisting well into the late Pleistocene. Because the speleothem record and prior faunal response imply that local conditions should have been favorable for megafauna until at least 30 ka, climate change is unlikely to have been the principal cause of the extinctions.

Extinction implications of a chenopod browse diet for a giant Pleistocene kangaroo

“…At a local scale, episodic droughts undoubtedly impacted P. goliah populations given individuals' need to drink regularly, and this is consistent with its presence in a drought assemblage that accumulated 55 kyr ago at Lake Menindee in the arid southern interior of Australia (26). However, droughts have characterized the Australian interior for at least 7 million years (27) and P. goliah (and many other Pleistocene megafaunal species) survived multiple Pleistocene periods of higher aridity, including the penultimate glacial and last interglacial (5,6,28,29). Moreover, effective rainfall in southern, eastern, and inland Australia was not markedly diminished until after 40 kyr ago (30)(31)(32).…”

“…W hether climate change, humans, or a combination of factors drove 90% of Australia's large animals (''megafauna'') to extinction during the late Pleistocene has been disputed for well over a century (1)(2)(3)(4)(5)(6). Recent studies have shown that most species were gone by approximately 45,000 years (kyr) ago (2-3), leaving over-hunting (1,2), landscape burning (3,4) by humans after their arrival approximately 50 kyr ago, and/or increased aridity since the penultimate glacial maximum (6) as the 3 most strongly championed hypotheses.…”

Bayesian age-depth modelling of Late Quaternary deposits from Wet and Blanche Caves, Naracoorte, South Australia: A framework for comparative faunal analyses

“…Phreatic dissolution of this limestone and structural processes along joints contributed to cave formation (Wells et al, 1984;White, 2005). The oldest sedimentary deposits in the Naracoorte Caves have been dated to 528±41 ka using optically stimulated luminescence dating (Prideaux et al 2007), suggesting that the caves first opened to the surface during the early to middle Pleistocene. Overlying the Gambier Limestone is a series of stranded Pleistocene beach dune facies known as the Bridgewater Formation.…”

“…In south eastern South Australia, 26 caves within the Naracoorte Caves complex contain 100 known vertebrate fossil deposits ranging from early Pleistocene to Holocene age (Reed and Bourne, 2000;Prideaux et al, 2007;Fig. 1).…”

Late Quaternary Small Mammal Faunas of the Naracoorte Caves World Heritage Area

“…Research into the naracoorte Cave fossil assemblages has made significant contributions to knowledge of (i) middle to late Pleistocene faunal communities of southern Australia (e.g., Prideaux et al 2007;macken et al 2012), (ii) taxonomy and systematics of extinct and living faunas (e.g., Prideaux & Wells 1998;Williams 1999;Prideaux 2004), (iii) vertebrate taphonomy of cave deposits (e.g., Reed 2006 and (iv) environmental change over the Pleistocene (e.g., Forbes & bestland , darrénougué et al 2009. As the naracoorte Caves contain 'megafauna' species such as Thylacoleo carnifex, Zygomaturus trilobus, 'Procoptodon' gilli and Wonambi naracoortensis, research into the cave assemblages has provided insights into the diversity, distribution and extinction dynamics of this group of large body-sized faunas at the end of the Pleistocene (e.g., Pate et al 2006;Prideaux et al 2007). the naracoorte Caves also contain extensive assemblages of smaller body-sized taxa, providing a reference for the diversity, distribution and historical extinction dynamics of these often understudied faunas through the late Quaternary (e.g., macken et al 2012).…”