The Blue-Tongued Skink Scares Away Predators With Its Horrific UV Tongue

When cornered by predators, some animals use "deimatic displays" to scare their stalkers into leaving them alone. These are surprising displays — like moths that have eyespots on their wings and octopuses that squirt out jets of water — actions and details intended to momentarily startle the predator.

The blue-tongued skink has a colorful variation on this theme. When attacked, the lizard opens its mouth wide and reveals its bright blue, ultraviolet-reflective tongue. The flash of color startles predators, often giving the skink a chance to escape.

A Threatening Tongue

New research from Macquarie University in Australia finds that the very back of the tongue of the northern blue-tongued skink is much more UV-intense and luminous than the front. Typically hidden, this section is only revealed in the final stages of an imminent attack. This matters because some of the skink's enemies, like birds and snakes, are thought to be able to see UV light — meaning for them, this is a much more startling experience than what the human eye sees.

The northern blue-tongued skink (Tiliqua scincoides intermedia) lives in northern Australia and is the largest of the blue-tongued skinks. It usually has excellent camouflage due to the broad brown bands that cross its back. But snakes, birds and monitor lizards still hunt it.

Timing Is Everything

The researchers found that the skink waited until the final stages of a predator attack to show the full display of its tongue. They found that the rear of the skink's tongue was almost twice as bright as the tip. (You can see the differences in the tongue in the photo at right, which shows a skink involved in the study.)

"The timing of their tongue display is crucial," said lead author Arnaud Badiane in a statement. "If performed too early, a display may break the lizard’s camouflage and attract unwanted attention by predators and increase predation risk. If performed too late, it may not deter predators."

The study is published in the journal Behavioral Ecology and Sociobiology.

Photo of northern blue-tongued skink at right courtesy of Peter Street.