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Subfossils suggest worse-than-realised losses of small-bodied mammals in northern Australia

Vikram Neelesh Vakil , Jonathan Cramb, Gilbert Price, Julien Louys, John Stanisic, Gregory Webb

Abstract

Abstract Context: Examining Australia’s late Quaternary subfossil record can be valuable in assessing whether the current diversity of small-bodied mammals seen across some parts of northern Australia is ‘normal’. Such records are important for establishing baselines for measuring historic changes in communities today and into the future. These datasets are becoming increasingly important given trajectories in current global climate change, and predicted habitat losses and other potential anthropogenic impacts. Aims: The main aim of this study is to utilise the local subfossil record from northeastern Australia to establish a natural baseline for assessing changes in small mammal communities post-European colonisation. Methods: Subfossils of vertebrates and other taxa were recovered from surface deposits adjacent to cave entrances at Broken River, near Greenvale in northeast Queensland and were subjected to taxonomic, taphonomic and statistical analyses. These were then compared with local faunal records from modern surveys to compare differences in faunal communities between past and present. Key results: Radiocarbon dating shows that these subfossils are geologically young, dating to around the time of European colonisation. We provide evidence for the former presence of extinct species of hopping mice (Notomys spp.) and rabbit rats (Conilurus spp.) in the region. Additional locally extirpated taxa such as Cape York bandicoot (Isoodon peninsulae) and Shark Bay mouse (Pseudomys gouldii) demonstrate considerable range contractions since the deposits accumulated, compared with their current distribution. Independent evidence from subfossil land snails recovered from these deposits are, with two exceptions, all modern-day vine thicket, karst-dwelling species indicating a long-term maintenance of vine thicket habitat. Thus, the loss of several mammal species is unlikely the result of habitat loss. Conclusions: Analysis of the surface deposits shows that local historic small-mammal communities were much more diverse compared to the region’s extant faunas recorded by modern surveys. Many extinctions and extirpations evidently occurred prior to such faunas being recorded as local inhabitants of the region. Implications: Our data suggests that post-European colonisation small mammal losses are likely substantially worse than previously realised.

WR24149  Accepted 24 December 2024

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