Impact of invasive cane toads on native species
The cane toad (Bufo marinus) is one of the most successful invasive species on earth, having colonised over 50 countries this century. In Australia it was introduced to control a beetle pest of sugar cane around Cairns in 1935, and has since spread southward and especially westward. Numerous native predators die while trying to consume the toxic toads, and some suffer serious declines such as quolls, goannas, and crocodiles. Invasive species theory insists that any control measures need to be informed by assessment of the damage.
Most examples of impacts of cane toads on native animals are at the level of the individual. However, some predators show marked population-level declines, such as goannas. Some of these declines are so severe that cascading effects are seen. The generality of impacts has not been established; for example, some crocodile populations experience significant declines while other populations do not. Thus, damage assessment of cane toads on native predators is incomplete.
In order to better understand the generality of impacts of invasive toads on native predators and their cascading effects when impacts are severe, we have initiated a long-term study of selected predators and their prey in the Kimberley region, where toads are beginning to invade.
Our research can be divided into direct and indirect impacts. Our research on direct impacts focuses on goannas, quolls, crocodiles, and turtles. We conduct surveys using 9 different methods to assess the relative abundance of these animals before, during, and after toad arrival. Specifically, we investigate impacts on the Yellow-spotted Monitor (Varanus panoptes), Merten's Water Monitor (V. mertensi), Mitchell's Water Monitor (V. mitchelli), the Northern Quoll (Dasyurus hallucatus), and the freshwater crocodile (Crocodylus johnstoni). These studies began in the Top End of the Northern Territory, Australia and are now conducted in the Kimberley region of Western Australia.
Also in the Kimberley region, our research on indirect impacts focuses on measuring abundance and reproductive output in small lizards, frogs, and birds. Specifically, we are interested in gilbert's dragons (Amphibolorus gilberti), four species of frogs (Litoria spp., Uperolia spp.), crimson finches (Neochmia phaeton), and the purple-crowned fairy wren (Malurus coronatus).
We collaborate with, Dr. Mike Letnic, Univ. of Western Sydney, Dr. Brian Green, Univ. of Canberra, Dr. Christina Castellano, Healesville Sanctuary (http://www.zoo.org.au/Conservation), Dr. Adam Britton (http://crocodilian.com/big-gecko/), Micko Bass, El Questro Wildlife Park (http://www.elquestro.com.au), Kim Hands, Stop the Toad Foundation, and Graeme Sawyer, Frogwatch.
Articles stemming from our research and funding sources
- Shine, R. and Doody, J. S. 2010. Invasive species control: conflicts between researchers and the general community. Frontiers in Ecology and Environment (In press).
- Shanmuganathan, T., Pallister, J., Doody, J. S., McCallum, H., Robinson, T., Sheppard, A., Hardy, C., Halliday, D., Venables, D., Voysey, R., Strive, T., Hinds, L., Hyatt, A. 2010. Biological control of the cane toad in Australia: a review. Animal Conservation (In press).
- Doody, J. S., Milenkaya, O., Rhind, D. Penrose, K., and Eastley, T. 2010. Varanus Mitchelli (Mitchell's Water Monitor): Diet and foraging behavior. Herpetological Review 41:233-234.
- Doody, J. S., Castellano, C., Green, B., Rhind, D., and Sims, R. 2009. Impact of invasive cane toads on predatory lizards. Animal Conservation 12:46-53.
- Doody, J. S., Green, B., Sims, R., and Rhind, D. 2007. A preliminary assessment of the impacts of invasive Cane Toads (Bufo marinus) on three species of varanid lizards in Australia. Mertensiella 16:218-227.
- Doody, J. S., Green, B., Sims, R., Rhind, D., West, P., and Steer, D. 2006. Indirect impacts of invasive Cane Toads (Bufo marinus) on nest survival in Pig-nosed Turtles (Carettochelys insculpta). Wildlife Research 33:349-354.
- Doody, J. S., B. Green, D. Rhind, and R. Sims. 2006. Initial impacts of invasive cane toads (Bufo marinus) on predatory lizards and crocodiles. Pp. 33-41 In: Molloy, K.L. and Henderson, W.R. (Eds). Science of Cane Toad Invasion and Control. Proceedings of the Invasive Animals CRC/CSIRO/Qld NRM&W Cane Toad Workshop, June 2006, Brisbane. Invasive Animals Cooperative Research Centre, Canberra.
- 2003-2008 Natural Heritage Trust (DEWHA)/CSIRO $41,000
- 2009 Caring for our Country Scheme (DEWHA) $143,000
- 2010 Australian Geographic $10,000