Ventilatory frequency as a measure of the response of tammar wallabies (Macropus eugenii) to the odour of potential predators
Valentina S. A. Mella A , Christine E. Cooper A B and Stephen J. J. F. Davies AA Centre for Ecosystem Diversity and Dynamics, Department of Environment and Agriculture, Curtin University of Technology, Perth, PO Box U1987, Perth, WA 6845, Australia.
B Corresponding author. Email: C.Cooper@curtin.edu.au
Australian Journal of Zoology 58(1) 16-23 https://doi.org/10.1071/ZO09083
Submitted: 10 October 2009 Accepted: 12 January 2010 Published: 7 April 2010
Abstract
This study uses changes in ventilatory frequency to quantify the physiological response of an Australian terrestrial herbivore, the tammar wallaby (Macropus eugenii), to olfactory cues suggesting the presence of potential predators. Ventilatory frequency proved to be a quantifiable measure to assess the response of this macropod marsupial to olfactory cues. Ventilatory frequency increased from mean resting levels of 45 ± 5.1 breaths min–1 to 137 ± 11.2 breaths min–1 during the first minute of exposure to all odours. These physiological responses diminished over time, with ventilatory frequency in the first minute after introduction of the scents greater than that during the subsequent four, suggesting that the initial reaction was due to disturbance and was investigative in nature. However, the ratio of ventilatory frequency in the remaining 4 min after introduction of the odours compared with before was greater for fox (3.58 ± 0.918) and cat (2.44 ± 0.272) odours than for snake (2.27 ± 0.370), distilled water (1.81 ± 0.463) and quoll (1.71 ± 0.245) odours, suggesting that fox and cat odour provoked a greater response. However, the wallabies’ response to the odour of these introduced predators and to horse odour (2.40 ± 0.492) did not differ. Our study indicates that a long period of co-history with particular predators is not a prerequisite for detection of potentially threatening species. We do not find any support for the hypothesis that an inability to interpret olfactory cues to detect and respond to potential predation by introduced predators is responsible for the decline of these macropod marsupials.
Acknowledgements
We thank the Western Australian Department of Environment and Conservation (DEC) for providing the wallabies. We are grateful to Professor Philip Withers (University of Western Australia; UWA) for allowing us to conduct the experiment in his laboratory and for providing advice and equipment. Thanks to Sylvie Schmidt (UWA) for sharing equipment and research animals. Stefanie Hilmer (DEC) and Alan Neaves provided feral cat and horse urine respectively, and Dr Graham Thompson donated the python skin. This study was approved by both the University of Western Australia (RA/3/100/528) and Curtin University (N79-07) Animal Ethics Committees, and animals were held under licence from DEC. Funding was provided by an Australian Research Council Linkage Grant (LP0776652; CEC) and by Curtin University in the form of a Curtin International Research Tuition Scholarship and student stipend (VSAM). This paper is contribution CEDD61-2009 for the Centre for Ecosystem Diversity and Dynamics, Curtin University.
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