How lizards use signals

How lizards use signals

28 Apr 2011

Richard Peters of the Department of Zoology has been researching how the Jacky Lizard uses signals.

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Transcript

Hi, my name is doctor Richard Peters, I'm in the Department of Zoology at La Trobe University. My particular research interests are in animal signal evolution and in particular how animals use movement to communicate and I currently study lizards to understand movement-based signals.

My model system is the Jacky Lizard, which is a dragon lizard found on the east coast of Australia, its scientific name is Amphibolurus muricatus. It's mostly found in coastal heath, although you will find it in dry sclerophyll forest and rocky out crops on the west side of the Great Dividing Range.

The Jacky Lizard relies on motion vision for all parts of its life and that includes feeding. So it only will take live prey, so we have to feed it live insects and the motion vision system then detects the insect and he'll feed.

So Jacky Lizards like many dragon lizards are territorial and they engage in displays of aggression in order to resolve conflicts about a particular territory. When an intruder enters into the territory of a Jacky Lizard, he will start by tail flicking and then proceed through a sequence of motor patterns starting with fore leg waves, push ups and what we've termed, a body rock where he raises his body off the sub straight.

The intruder can either decide to retaliate with his own display or leave the territory and leave the resident alone. He can signal that he's not a threat to the resident by using a slow arm wave, which is basically just a slow movement of one fore leg that kind of indicates a non-aggressive stance by the lizard. Of course if territory disputes continue they will eventually escalate into fights, and the whole point about the display is that its evolved to avoid fights as much as possible because of course fights are costly and animals get injured.

So in order to understand the Jacky Lizard I've used a variety of techniques, I've started out simply by watching the animals looking at what they do when they interact with each other. I've also made use of modelling where I record and analyse sequences and try to simulate interactions. I also use playback techniques where I present replays of signals or anything else I'm interested in presenting to them by high-resolution monitors and I can manipulate what I present to them and control that. One aspect of that is using 3D animation, which allows me to re-create the signals and manipulate that signal precisely the way I want for a particular question I am asking.

So my particular focus at the moment with the Jacky Lizards is to understand the constraints on signal evolution and in terms of movement based signals one of the main constraints is plant movement, and how does an animal such as the Jackie Lizard avoid conflict from plant motion and allow the receiver to detect the signal. So I'm particularly interested in variation in plant motion noise and how that will affect signal design.

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