View Research: Reptiles that eat frogs

Reptiles that eat frogs

A number of reptiles are predators of frogs. Which of these are likely to be at risk from Cane Toads moving into their location and how serious is the risk.
Keelback Snakes and some species are reported to survive eating toads.
Anecdotal reports from Moroke station indicate a decline in general snake numbers and Freshwater Crocodile numbers after the toads arrived. Snake numbers appear to have reduced greatly, no one is sure about the crocodiles.
We also have reports of Freshwater crocodiles dying in the Katherine Gorge and other wayterways across ArnhemLand as a result of the Toads.
We also have anecdotal reports of the local extinction?? of Water monitors in the Mount Isa area.
Some research on monitors is being done by the Key Centre at NTU and Wildlife management International are monitoring some crocodile populations. What other Information do we have in this area?

Author: Graeme Sawyer 02-Nov-2001
Last Updated: 11-Mar-2002
Category: Animals at Risk from Cane Toads » Reptiles


  • There is concern asbout a number of snake species as indicated by the following extract from Australian Reptile Park director, John Weigel, "Frog-eating snakes such as the death adder, the red bellied black snake and the king brown snake have disappeared in some parts of Queensland where they once thrived. "They don't have to swallow them, just get a mouthful," he said. "Ten years ago people wouldn't have cared that snakes are disappearing. Nowadays they realise what a terrible thing it is."
    Submitted by Graeme Sawyer on 30-Jan-2002
  • Freshwater Crocodiles are another species about which we have received regular reports of deaths , probably due to predation of Cane Toads by the crocodiles. Reports from Moroke Station, Katherine Gorge, Aboriginal Communities in ArnhemLand and other locations are further supported by this autopsy report from Kakadu National Park. The report is from Sam Sweet about a Freshwater Crocodile found in Kombolgi creek. "No external injuries, fresh or otherwise, save for a small well-healed contusion on one side of the lower jaw about 2/5 of the way back from the chin. Limbs and tail without evident injury. 2-3 teeth recently missing at middle of upper jaw on right side (quite possibly postmortem). Overall, the animal appeared to have been robust and healthy shortly before death. Internally, no signs of physical trauma; coelomic fluid clear, peritoneal lining without hemorrhages or lesions. Lungs of normal appearance, the right filled with water (presumably postmortem, as there was no hemorrhaging of alveolar blood vessels), no residual blood in the pulmonary veins. Liver dark red, normal in size and consistency, no lesions. Kidneys and renal arteries plus renal portal veins full of residual blood, the kidneys without gross lesions externally. Stomach with diffuse capillary hemorrhages all across the external surface; empty, save for 10-12 small angular pebbles; stomach lining covered with thin mucus, but no capillary hemorrhages evident. Lower GI tract virtually empty, no hemorrhages on surface, not bloated; considerable residual blood in the mesenteric vessels. Heart not examined, but both the aortic and pulmonary vessels were empty when cut. Mouth, throat and esophagus clear, no hemorrhaging evident. No nematodes or other parasites in stomach, lungs, peritoneal lining or mesenteries. General appearance of viscera quite normal, the only thing noticeably not right being the gastric hemorrhages, but these are relatively slight. The overall impression is of a healthy animal that died very suddenly (as indicated by the residual blood in the renal and intestinal circuits, vs. none in the lungs, and apparently little/none in the heart). So, we don't know why it died. However, the signs are consistent with rapid death by poisoning, for example by ingestion of a cane toad that could have been regurgitated before death. The gastric hemorrhages are consistent with violent stomach contractions. The animal had no chronic disease, macroscopic parasites, or external/internal physical trauma, and in fact looked to have been in excellent nick, just dead. Under the conditions at the creek, I would say it had been dead for 12-18 hours, probably more like 12. We found it at about 1130 hrs. I am not sure that there would be a postmortem test for bufotoxin, as I don't think it is very stable in tissues. Since its primary action is on nerve transmission leading to cardiac arrest and CNS dysfunction, it is unlikely that organs such as liver or kidney would show much if any effect even at the histological level. Often an animal that dies of rapid poisoning will have little residual blood in the pulmonary circuit but quite a bit in the vessels of the posterior part of the coelom, simply because the heart rapidly becomes incompetent.
    Submitted by Graeme Sawyer on 27-Feb-2002
  • Anecdotal reports from the katherine indicate that Frilled Lizard numbers may have declined as a result of Cane Toads arriving. Aboriginal people are reporting less of the lizards making it harder to find Bush tucker.
    Submitted by Graeme Sawyer on 11-Mar-2002
  • Evidence that the Death Adders are being killed by Toads.
    This image was taken by Anne Ferguson in Kakadu National Park.
    It show a dead Death Adder with the Toad, also dead, still in its mouth.
    Submitted by Graeme Sawyer on 01-Dec-2002