The behavior of lizards pushing themselves up and down on their forelegs is a communication device, usually used to indicate aggression or make territorial claims; it can also be used as a mating display. Essentially, the lizard is attempting to draw attention to itself in a show signifying that it is large, powerful, and in control of the situation; whether to make other lizards behave docilely,attract a mate, or scare off a predator. In many lizard species, this behavior is complimented by the lizard expanding his throat sack to appear larger or darker in color.