Megafauna Mobility: Assessing the Foraging Range of an Extinct Macropodid, from Central Eastern Queensland, Australia

Abstract

For extant megafaunal herbivores, it has been demonstrated that large body size provides the potential for greater geographic range. Although this trend is prominent in extant placental mammals, it has not been readily examined in Australia’s extinct megafaunal marsupials. Here we use strontium isotopes (87Sr/86Sr) in fossil enamel of specimens from Mt Etna Caves, central-eastern Queensland, to estimate home range in the extinct giant wallaby, Protemnodon. Fossil ages are also determined using in-situ uranium-thorium and single-grain TT-OSL dating. TT-OSL and U-Th ages are in agreement with previous site chronologies narrowing the range for fossil deposition between 210 – 330 ka. Generally, 87Sr/86Sr ratios in Protemnodon enamel have values similar to the Sr isotope composition of the Mount Etna Beds limestone (the formation that hosts Mt Etna Caves) suggesting individuals foraged close to where remains were deposited. Restricted foraging is somewhat unexpected, considering Protemnodon species occur across many different palaeoenvironments, however, we suggest they are due to a combination of resource availability, dietary preferences, and biomechanics limiting terrestrial dispersal. We propose that the local extinction of Protemnodon during the Middle Pleistocene at Mt Etna was driven by less vagile taxa rainforest taxa being unable to adapt to intensifying aridity.

Keywords: marsupials, strontium isotopes, palaeobiology, home range, U-Th dating, TT-OSL dating