Cane Toads Killing Crocs

Photo credit: Mike Letnic/ University of Sydney

New Scientist reported June 27, 2008, on a wave of deaths of freshwater crocodiles in Australia.

Dead freshwater crocodiles in Australia's Northern Territory were once a rare sight. But since 2005, locals have witnessed mass die-offs in some semi-arid regions of the territory. Researchers now say the toxic and invasive cane toad (Bufo marinus) is to blame.

Two surveys, in 2005 and 2007, suggested that the mass croc deaths have progressively moved inland from the mouth of Victoria River, at a pace that matches that of the cane toad invasion. The toads secrete a milky-white toxin which is lethal to many predators from glands behind their eyes and on their backs.

Mike Letnic of the University of Sydney and his team say a massive 77% of some populations of freshwater crocodiles – or "freshies" – have died since 2005.

The numbers are particularly worrying, says Letnic, because removing top predators like freshwater crocodiles (Crocodylus johnstoni) can boost the number of their prey and trigger a cascade of ecosystem changes that are difficult to predict.

Scientists haven't positively identified the cane toads as the cause of the crocodile deaths, because crocs digest amphibians quickly. But the circumstantial evidence is pretty clear.

Cane toads were introduced to Queensland in 1935 in the hope that the toads would eat cane beetles that were harming the sugar cane crops. I don't know if they were successful in helping the cane crops, but the toads thrived in their new home and began to spread.

What the crocodiles need is for someone to find a profitable use for cane toads. Maybe some cane toad cowboy boots and purses, or cane toad venom as a botox substitute. If there's enough money in it, the trappers will descend on the amphibian pests and snatch them away from the jaws of double-death.