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Ecology, management and conservation in natural and modified habitats

Indirect impacts of invasive cane toads (Bufo marinus) on nest predation in pig-nosed turtles (Carettochelys insculpta)

J. S. Doody A C , B. Green A , R. Sims B , D. Rhind A , P. West A and D. Steer A
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- Author Affiliations

A Applied Ecology Research Group, University of Canberra, ACT 2601, Australia.

B School of Botany and Zoology, Australian National University, ACT 0200, Australia.

C Corresponding author. Email:

Wildlife Research 33(5) 349-354
Submitted: 8 March 2005  Accepted: 20 June 2006   Published: 14 August 2006


The cane toad (Bufo marinus) was introduced into Australia in 1935. Because this toxic frog is novel to the Australian fauna, its introduction has impacted native fauna in a variety of ways. We anticipated a severe decline in the yellow-spotted monitor lizard (Varanus panoptes) associated with the arrival of cane toads along the Daly River, Northern Territory, and predicted a simultaneous impact on nest predation in the pig-nosed turtle (Carettochelys insculpta) because the lizard is the chief predator of C. insculpta eggs at the site. We surveyed for monitors and cane toads for five years at two sites before and after the arrival of cane toads, and surveyed for turtle nest predation for three years before, and one year after, the arrival of the toads. Collectively, our data and observations, combined with unpublished reports, indicate that: (1) cane toads arrived at our study sites during the wet seasons of 2003–04 and 2004–05; (2) the lizard V. panoptes readily succumbs to cane toad toxins; (3) . panoptes has experienced a marked decline in relative population numbers coincident with the arrival of the toads at the site; and (4) V. panoptes has been reduced to such low numbers that it is currently no longer a significant predator of pig-nosed turtle eggs.


We thank the following for assistance in surveys: R. Allen, G. Brown, C. Castellano, G. Dryden, D. Hunter, G. Kay, P. Macak and D. Steer. We thank P. O’Brien and the Douglas Daly Research Farm for accommodation and general support. We thank A. Georges for statistical advice. A portion of the project benefited from discussions with J. Hone, R. Peck, and T. Robinson. We thank T. Griffiths and an anonymous reviewer for improving an earlier draft. Monitor and toad surveys were funded in part by CSIRO Sustainable Ecosystems and the Natural Heritage Trust, Department of Environment and Heritage.


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