Ecological impacts of invasive cane toads

Ecological impacts of invasive cane toads

Hot Topics in Ecology

Ecological impacts of invasive cane toads

Rick Shine
Large predators like this freshwater crocodile (Crocodylus johnstoni) can be in big trouble when cane toads invade, but most smaller species are less affected by toad invasion. Indeed, the collapse of apex predator populations is good news for the species previously consumed by those predators. Photograph by G. P. Brown.

 

Cane toads (Rhinella marina) were brought to Australia in 1935, and released in northeastern Queensland. They have since spread westwards (through Queensland, the Northern Territory, and into Western Australia) and southwards (into NSW). Concern about the toads’ impacts on wildlife spawned predictions that most native species encountering toads would be severely affected, and thus decline in abundance. Recent research is revealing a more complex picture. Toads do indeed cause precipitous population declines (of >80%) in some large-bodied predator species, due to lethal poisoning when predators attempt to eat toads. However, populations of smaller predator species are unaffected; some individuals are fatally poisoned, but most survive (because small toads contain far less toxin than large adult toads) and learn to avoid toads thereafter. Most Australian birds and rodents have inherited a tolerance of toad poison from Asian ancestors, and thus are not affected. Even for heavily impacted predators, populations might eventually recover. Simplistic predictions on the ecological impact of cane toads in Australia have not been supported by field studies - indirect impacts of toads often outweigh direct effects. For example, the abundance of native frogs appears to be unaffected by cane toads, because negative impacts (e.g. frogs being eaten by toads, poisoned by toads, competing with toads) are balanced by positive impacts (e.g. toads reducing abundance of frog-predators). Some native snake species predicted to be vulnerable to toads, have become more common since toad invasion – presumably because of the disappearance of predatory goannas. In summary, the impacts of invaders may be complex, and difficult to predict. Any disruption to one native species is likely to have indirect effects on others. Some native species are winners not losers as the toad invasion rolls across the landscape.

Hot Topic Lead Author: 
Name: Prof Rick Shine
Email: rick.shine@sydney.edu.au
Phone: 02-9351-3772

Date approved: 
Saturday, October 21, 2017 - 00:42
ID Title Location Type
6943 Beckmann C. & Shine R. (2009) Are Australia's birds at risk due to the invasive cane toad? Conserv. Biol. 23, 1544–9. Australia-wide Review paper
6944 Brown G. P., Phillips B. L. & Shine R. (2011a) The ecological impact of invasive cane toads on tropical snakes: field data do not support predictions from laboratory studies. Ecology 92, 422–31. Darwin area Field study
6945 Caller G. & Brown C. (2013) Evolutionary responses to invasion: cane toad sympatric fish show enhanced avoidance learning. PLoS ONE 8, e54909. northern NSW Behavioural study
6946 Doody J. S., Green B., Sims R., Rhind D., West P. & Steer D. (2006) Indirect impacts of invasive cane toads (Bufo marinus) on nest predation in pig-nosed turtles (Carettochelys insculpta). Wildl. Res. 33, 349–54. Northern Territory Field study
6947 Letnic M., Webb J. K. & Shine R. (2008) Invasive cane toads (Bufo marinus) cause mass mortality of freshwater crocodiles (Crocodylus johnstoni) in tropical Australia. Biol. Conserv. 141, 1773–82. Northern Territory Field study
6948 Lettoof D. C., Greenlees M. J., Stockwell M. & Shine R. (2013) Do invasive cane toads affect the parasite burdens of native Australian frogs? Int. J. Parasitol.: Parasite. Wildl. 2, 155–65. northern NSW Field study
6949 O'Donnell S., Webb J. K. & Shine R. (2010) Conditioned taste aversion enhances the survival of an endangered predator imperiled by a toxic invader. J. Appl. Ecol. 47, 558–65. Northern Territory Field study
6950 Phillips B. L. & Shine R. (2006) An invasive species induces rapid adaptive change in a native predator: cane toads and black snakes in Australia. Proc. R. Soc. B 273, 1545–50. east coast of Australia Field and laboratory study
6951 Pizzatto L. & Shine R. (2011) Ecological impacts of invading species: do parasites of the cane toad imperil Australian frogs? Austral Ecol. 36, 954–63. tropical Australia Field and laboratory study
6952 Shine R. (2010) The ecological impact of invasive cane toads (Bufo marinus) in Australia. Q. Rev. Biol. 85, 253–91. Australia-wide Review paper
6953 Shine R. (2014) A review of ecological interactions between native frogs and invasive cane toads in Australia. Austral Ecol. 39:1-16. Australia-wide Review paper
6954 Shine R. & Doody J. S. (2011) Invasive-species control: understanding conflicts between researchers and the general community. Frontiers Ecol. Environ. 9, 400–6. Australia-wide Opinion article
6955 Ward-Fear G., Brown G. P., Greenlees M. & Shine R. (2009) Maladaptive traits in invasive species: in Australia, cane toads are more vulnerable to predatory ants than are native frogs. Funct. Ecol. 23, 559–68. Northern Territory Field study