Already invasive, rampaging and poisonous, cane toads have another crime added to the charge sheet this week: croc killers.

Saltwater crocodiles seem unaffected by the toads but new evidence has emerged that this is not the case with freshwater crocs. Mike Letnic, of the University of Sydney, says there has been a 75% reduction in their numbers in an area in Australia’s Northern Territory where the toads recently arrived, and the bodies are pilling up (press release).

“When we first went in we counted about 700 crocodiles [in the area] and found no dead ones at all,” Letnic says (Cosmos, and a similar quote from AAP). “But then we went back … after the cane toads had started moving through. This time we found less than 400 crocodiles … and, in the space of a week, we found over 30 dead.”

And it is definitely the toads causing the problem.

“When we cut them open they were all just rotten inside,” he told Perth Now. “We found two or three with toads in their guts. Cane toads had arrived in that river system – and all of a sudden we’ve got this.”

In February it was reported that the toads were also wiping out rare pygmy crocodiles. Whacking day can’t come soon enough.

Northern Territories news is one of the Australian papers highlighting that there is some hope for the region’s crocs. Their relatives in North Queensland have managed to survive, by a simple expedient.

“It may be that the animals learnt not to eat the toads,” explains Letnic. However, conservation strategies based on animals learning the error of their ways seem a touch faith based.

Letnic’s work will be presented to the 14th Australasian Vertebrate Pest Conference in Darwin next week.