Grazing kangaroos act as local recyclers of energy on semiarid floodplains
Jordan Iles A C , Jeff Kelleway A , Tsuyoshi Kobayashi A , Debashish Mazumder B , Lisa Knowles A , David Priddel A and Neil Saintilan AA NSW Department of Environment, Climate Change and Water, PO Box A290, Sydney South, NSW 1232, Australia.
B Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia.
C Corresponding author. Email: jordan.iles@environment.nsw.gov.au
Australian Journal of Zoology 58(3) 145-149 https://doi.org/10.1071/ZO10020
Submitted: 5 March 2010 Accepted: 24 June 2010 Published: 25 August 2010
Abstract
On Australian semiarid floodplains, large herbivores such as kangaroos have a role in the cycling of energy (carbon) through the mechanism of feeding and defaecation of vegetative material. The degree to which kangaroos are vectors of energy within this system is not fully understood. This study describes the stable carbon isotope signature of floodplain plants and kangaroo scats at two close study sites. Kangaroos were found to deposit scats that mirrored the forage composition at each particular feeding site. Scats were 3.94‰ higher in δ13C values at the site where C4 grasses were available, indicating that this grass contributed ~25–30% of the diet of these kangaroos. The difference in diet due to the relative availability of C3 and C4 forage, detectable in the carbon stable isotope signature of scats, is used to demonstrate that kangaroos are recycling and redistributing energy locally, rather than transporting it more broadly across the floodplain.
Acknowledgements
We thank Narelle Jones, Paul McInnis, Russell Hampton, James Maguire, Paul Childs, Jeff Hillan, Derek Rutherford, Tim Pritchard, Louise Goggin, Gillian Dunkerley and Beth Alexander for logistic support and advice; Steve Jacobs and Li Wen for fieldwork; Barbara Triggs for scat identifications; and Val Sadler (ANSTO) for stable isotope sample processing. Daryl Codron, Brett Murphy and two anonymous reviewers provided constructive feedback on an early version of this manuscript. This project was funded by the Rivers Environmental Restoration Program (RERP). The RERP is jointly funded by the NSW Government and the Australian Government’s Water for the Future Program. The views and conclusions expressed in this paper are those of the authors and do not necessarily represent the official policies, either expressed or implied, of the respective organisations.
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