Stable nitrogen isotope values in arid-land kangaroos correlated with mean annual rainfall: Potential as a palaeoclimatic indicator

Abstract

Bone collagen stable nitrogen isotope values are reported for modern kangaroos (Macropus spp.) from eight field sites along a 1160 km south-north transect from temperate coastal to arid interior South Australia, in order to investigate δ15N tissue variability in relation to rainfall and relative humidity. Mean annual rainfall along the transect ranges from 775mm at Mount Gambier in the southeastern coast to 176 mm at Innamincka in the arid northern interior, while 3pm relative humidity ranges from 73% at coastal Flinders Chase to 36% at Innamincka. In arid habitats (176-238 mm rainfall), the δ15N values of kangaroo bone collagen become more positive in relation to decreasing mean annual rainfall (r2=0.98), while there is only a weak correlation with relative humidity (r2=0.67). In contrast, in temperate and semi-arid coastal habitats (350-775 mm), there is no correlation between kangaroo bone collagen δ15N values and rainfall (r2=0.0011) or between δ15N values and relative humidity (r2=0.0035). Thus, in South Australia, kangaroo bone collagen δ15N values do not show a simple linear correlation with either rainfall or relative humidity across all habitats. These results suggest that stable nitrogen isotope analyses of herbivore bones obtained from archaeological and palaeontological sites may provide a reliable proxy for past rainfall values in arid-land ecosystems. Copyright © 2007 John Wiley & Sons, Ltd.