Unlike their fire-breathing counterparts, Jacky dragons are rather gentle lizards. These dragons spend most of their lives perched in trees waiting to trap a passing morsel. But they don't take kindly to intruders. If a Jacky dragon invades another's personal space, the diminutive lizard begins an elaborate dance routine, warning the trespasser that it's time to move on. So how does the dragon catch an intruder's eye before getting the message over?Richard Peters explains that most animals either call or flash a patch of brightly coloured skin to attract attention, but the Jacky dragon has neither of these options. Peters and his supervisor Christopher Evans suspected that the lizard relies on its enormously long flicking tail to catch an intruder's eye, so they decided to test the reptile's reactions to a variety of tail flick techniques (p. 4293).

But could Peters convince a Jacky dragon to vary its tail flicks so that he could discover the flicks' eye-catching formula? Unfortunately not, so he turned to a technique more familiar to moviegoers. Peter's learned to animate. Next he needed to be sure that the lizards were taken in by his home animations. Choosing a 6.5 s tail flick sequence, Peters painstakingly fitted the tail animation to each frame of the real tail's movement's. After carefully simulating the lizard's skin tones and lighting conditions, the results looked convincing. And the dragons were taken in too, turning quickly to watch the cinematography. Knowing that most dragons have to react to a tail set against a shifting foliage background, Peters also superimposed the tail movie over footage of rustling trees, and again the dragons jerked to attention. Peters was ready to manipulate his movie to see what made a tail flick attractive.

Speeding up and slowing down the animation, Peters monitored the lizard's reactions. Surprisingly, the Jacky dragons were more attentive to a long slow flick than an abrupt movement, even though most other lizards seem more responsive to fast movements.

But what else would attract the lizard's attention? Peter's played the lizards tail flicks with a variety of amplitudes, from a narrow flick to a wide waggle. The lizards reacted no matter how wide the amplitude of the movement, so Peters switched his attention to the speed and duration of a train of flicks. Playing the lizards a sequence of animations that ranged from a short series of slow flicks to a long series of fast flicks, Peters realised that long duration flicks were the best at catching a Jacky dragon's eye.

So why does the Jacky dragon introduce its brief territorial display so languidly? Peters explains that it's much harder to attract attention with a visual signal than a loud cry. He suspects that a lengthy series of flicks is probably the most effective way to catch an intruder's eye to make sure they get the rest of the message.

References

Peters, R. A. and Evans, C. S. (
2003
). Introductory tail-flick of the Jacky dragon visual display: signal efficacy depends upon duration.
J. Exp. Biol.
206
,
4293
-4307.