Diet of the bilby (Macrotis lagotis) in relation to substrate, fire and rainfall characteristics in the Tanami Desert
Richard Southgate A B C and Susan M. Carthew BA Biodiversity Conservation Unit, Department of Infrastructure, Planning and Environment, PO Box 2130, Alice Springs, NT 0871, Australia.
B School of Earth and Environmental Sciences, University of Adelaide, SA 5005, Australia.
C Corresponding author. Present address: PO Box 305, Kingscote, SA 5223, Australia. Email: southgate@kin.net.au
Wildlife Research 33(6) 507-519 https://doi.org/10.1071/WR05079
Submitted: 8 September 2005 Accepted: 10 May 2006 Published: 4 October 2006
Abstract
This study uses analysis of faecal pellets to assess the diet of the bilby (Macrotis lagotis) in an area spanning over 230 000 km2 in the Tanami Desert, Northern Territory. More specifically, we examine the link between diet composition, bilby prevalence and the landscape variables of fire, rainfall and substrate. Seed promoted by fire, particularly of Yakirra australiense, was found to be one of the most important components of the diet and constituted ~36% of the relative abundance of identifiable food particles. Bulb from Cyperus bulbosus was also an important component of the diet (18.5% relative abundance). Invertebrates accounted for 39% of the identifable food particles, and termites and beetles were the most common types. Bulb and seed formed a greater component of the diet in the central part of the study area where bilbies were more prevalent. Conversely, invertebrates were more dominant in the bilby diet on the northern and southern periphery of the Tanami Desert. Substrate type and antecedent rainfall associated significantly with the amount of seed from fire-promoted plants and total plant contained in the diet. Time since fire was an additional factor associated with the abundance of dietary fire-promoted seed. This suggests that the spatial and temporal variability of these landscape variables play an important role in controlling the availability of seed and bulb resources used by the bilby, and thus affect bilby prevalence. The results support the proposition that seed and bulb plant foods are exploited opportunistically and invertebrates, especially termites, are relied upon when plant food resources are scarce. Furthermore, the findings indicate that fire management could be used as a means to increase the favourability of habitat for the bilby in parts of its current range.
Acknowledgments
We are grateful for the assistance of Rachel Paltridge, Pip Masters, Don Langford, Chris Grant and Ada Nano plus various volunteers in the field. We are also indebted for the assistance on field trips provided by Aboriginal people including Pharlap Dixon, Engineer Jack, Shorty Jangala, Darby Jampitjinpa, Irene Driver Nungarrayi, Tommy Driver Jupurrula, Jerard Driver Jampitjinpa, Lynnette Driver, Mitjili Gibson Napangangka; Cindy Gibson Nakamarra, Neville Poulson and Sarah Napangangka. Finally, the study could not have been completed without the support of the Department of Infrastructure, Planning and Environment and funding from the Natural Heritage Trust. Part of the funding for the aerial survey was provided by the Easter Bilby fund supported by Coles Myer.
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