Listen: Martin Whiting in conversation with Stephen O’Doherty.
We all know Australian animals are a bit weird and different and sometimes the reason why is fascinating.
Blue tongue lizards have developed a kind of super power related to their blue tongues which has proved to be a very effective (and unexpectedly technical) defence against predators.
Why a blue tongue?
A new study by researchers at Macquarie University has shed light on why blue tongue lizards have such an outrageously coloured tongue, given that the vast majority of lizards have a regular pink tongue. The study, just published in the journal Behavioral Ecology and Sociobiology, found that the colour is not accidental, and likely evolved as a protection against predators.
One of the study authors, Associate Professor Martin Whiting, from the Department of Biological Sciences, spoke recently on Open House.
Just add UV to be really fierce
“Not only are their tongues blue, but they also have a very pure UV component, and the purest or most obvious UV was also at the rear of the tongue. UV is not visible to most mammals (and therefore humans), but is visible to lizards, birds and snakes.”
“Given that both male and female blue tongues have UV tongues, we tested the hypothesis that the tongue colour probably evolved in response to predation pressure,” he says.
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Give your predator sensory overload
According to Associate Professor Whiting, some animals use a highly conspicuous display in an attempt to overwhelm the sensory system of a potential predator. This acts as a form of sensory overload that causes a predator to pause or even abandon its attack.
“Blue tongue lizards have a highly conspicuous tongue, but unlike many other kinds of lizards, it’s a big tongue—the surface area is large. When blue tongues do a ‘full tongue’ display, the mouth is opened widely and the tongue is flattened and expanded. At the same time, they may hiss and puff-up their body for maximum effect.”
“This behaviour, in combination with a highly conspicuous tongue, can be quite intimidating for anyone that has got too close to a wild bluey,” says Associate Professor Whiting.
It seems like our own backyard ‘bluey’ has it all over dinosaurs too. Often portrayed in movies as sticking out their tongues, apparently the ferocious T.Rex imagined by Hollywood probably couldn’t stick out their tongue.
Testing with fake predators
The researchers, Associate Professor Whiting, Pau Carazo, a postdoctoral researcher at Macquarie (now at the University of Valencia) and Sam Price-Rees, placed blue tongues in a large-outdoor enclosure, where they held them briefly in order to test their behavioural responses to model, or fake, predators.
The lizards were presented with a model snake, bird, fox, goanna, and a control element (a piece of wood) in order to establish if they use their full-tongue display as a means to intimidate or overwhelm the sensory system of a predator.
A piece of wood isn’t a threat
“Blueys did not respond much to the piece of wood (control) while they showed a strong response to the model predators that would normally represent the greatest threat. By delaying their display until the predator was very close, and exposing the rear of the tongue, which has the most UV and which is the brightest, blueys maximise their chance of intimidating a predator and surviving another day,” concluded Arnaud Badiane, a PhD student on the research team.
Robotic blueys are next
Future research will involve building a robotic bluey with interchangeable tongues of different colours and then to present it to predators to confirm the anti-predator hypothesis. Associate Professor Whiting’s lab has done exactly that, and is in the process of testing the response of predators to UV-tongues and pink tongues.
To listen to the Open House podcast of this story, click the red play button at the top of the page, or you can subscribe to Open House podcasts in iTunes and they will appear in your feed.
Blue Tongue Lizard Photo Credit: Shane Black