Cane toads killing crocs

Charles Darwin University’s Research Institute for the Environment and Livelihoods senior research associate Dr Adam Britton and senior research fellow Clive McMahon, with Big Gecko's Erin Britton, investigated the impact of cane toads on the smallest crocodile species found in northern Australia’s upstream escarpments.

Dr Britton said cane toads provided the dwarf freshwater crocodiles, whose growth is stunted by a lack of food, with a plentiful, albeit deadly, dinner.

“The dwarf species found in upstream escarpments are unique because they are so small – less than half the size of your typical freshwater crocodile,” Dr Britton said.

“We already know that cane toads kill freshwater crocodiles, but we were concerned that cane toads might have a major impact on dwarf populations because of their small size and lack of alternative food sources.”

Dr Britton said that like many other native species, dwarf crocodiles were poisoned when they ingested bufotoxins in cane toads, presenting a significant conservation issue not only for the dwarf crocodiles but also potentially for the entire upstream escarpment ecosystem.

“We still have a long way to go in our understanding of how native populations deal with invasive species, however, this study gives insight into why toads wipe out some populations but leave other ones largely unaffected,” Dr Britton said.

Despite a substantial decline in numbers, the CDU research team found possible evidence that dwarf crocodiles could adapt their behaviour in the future by only eating the back legs of toads to avoid being poisoned.

The team is conducting further research into the genetics of dwarf freshwater crocodiles to better understand the long-term impacts of cane toads on their populations.

The paper, entitled “Impact of a toxic invasive species on freshwater crocodile (Crocodylus johnstoni) populations in upstream escarpments” is available for download at www.publish.csiro.au/paper/WR12215.htm