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Australian Journal of Zoology Australian Journal of Zoology Society
Evolutionary, molecular and comparative zoology
RESEARCH ARTICLE

Stable isotope ecology of the koala (Phascolarctos cinereus)

L. R. G. DeSantis A B and C. Hedberg A
+ Author Affiliations
- Author Affiliations

A Department of Earth and Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235-1805, USA.

B Corresponding author. Email: larisa.desantis@vanderbilt.edu

Australian Journal of Zoology 64(5) 353-359 https://doi.org/10.1071/ZO16057
Submitted: 27 August 2016  Accepted: 8 February 2017   Published: 7 March 2017

Abstract

Australia has undergone significant climate change, both today and in the past. Koalas, due to their restricted diet of predominantly eucalyptus leaves and limited drinking behaviour may serve as model organisms for assessing past climate change via stable isotopes of tooth enamel. Here, we assess whether stable carbon and oxygen isotopes from tooth enamel record known climate variables, including proxies of relative aridity (e.g. mean annual precipitation, mean annual maximum temperature, and relative humidity). The results demonstrate significant negative relationships between oxygen isotope values and both relative humidity and mean annual precipitation, proxies for relative aridity. The best model for predicting enamel oxygen isotope values incorporates mean annual precipitation and modelled oxygen isotope values of local precipitation. These data and the absence of any relationship between modelled oxygen isotope precipitation values, independently, suggest that koalas do not track local precipitation values but instead record relative aridity. The lack of significant relationships between carbon isotopes and climate variables suggests that koalas may instead be tracking the density of forests and/or their location in the canopy. Collectively, these data suggest that koalas are model organisms for assessing relative aridity over time – much like kangaroos.

Additional keywords: aridity, climate, diet, marsupial, stable isotopes.


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