Komodo Dragon’s Lethal Saliva is a Myth, Says New Study

According to biologists led by Dr Bryan Fry from the University of Queensland, the oral flora of Komodo dragons does not differ from any other carnivore.

A Komodo dragon Varanus komodoensis at the Cincinnati Zoo (Mark Dumont / CC BY 2.0)

A Komodo dragon Varanus komodoensis at the Cincinnati Zoo (Mark Dumont / CC BY 2.0)

It has long been believed that Komodo dragon bites were fatal because of toxic bacteria in the reptiles’ mouths. But the new study has found that the mouths of Komodo dragons (Varanus komodoensis) are surprisingly ordinary.

“Komodo dragons are actually very clean animals. After they are done feeding, they will spend 10 to 15 minutes lip-licking and rubbing their head in the leaves to clean their mouth,” said Dr Fry, who with colleagues has reported the results in the Journal of Zoo and Wildlife Medicine.

The scientists have studied the aerobic and anaerobic oral bacteriology of 16 captive Komodo dragons aged 2 to 17 years for adults and 7–10 days for hatchlings. Saliva and gingival samples were cultured for aerobes and anaerobes.

The oral flora of Komodo dragons consisted of 39 aerobic and 21 anaerobic species. “Adult dragons grew 128 isolates, including 37 aerobic gram-negative rods, especially Enterobacteriaceae; 50 aerobic gram-positive bacteria, especially Staphylococcus sciuri and Enterococcus faecalis, present in eight of 10 and nine of 10 dragons, respectively; and 41 anaerobes, especially clostridia. All hatchlings grew aerobes but none grew anaerobes. No virulent species were isolated.”

Pathogenic bacteria found in komodo mouths were simply the remnants from when the dragons drank from sewage filled watering holes.

“The inside of their mouth is also kept extremely clean by the tongue. Unlike people have been led to believe, they do not have chunks of rotting flesh from their meals on their teeth, cultivating bacteria,” Dr Fry said.

“The dragons do not have enough bacteria in their mouths to infect an injured animal.”

Dr Fry said that the next step for the team is to conduct tests on the watering holes to prove that they are the true source of any infection to animals injured by a komodo dragon.

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Bibliographic information: Ellie J. C. Goldstein et al. 2013. Anaerobic and aerobic bacteriology of the saliva and gingiva from 16 captive komodo dragons (Varanus komodoensis): new implications for the “bacteria as venom” model. Journal of Zoo and Wildlife Medicine, vol. 44, no. 2, pp. 262-272; doi: 10.1638/2012-0022R.1