Understanding Your Lizards' Social Behavior

Most desert lizards are territorial which means they will protect some part of their home range from others of the same species. Research in the Mojave Desert of California has documented that large male chuckawallas will actively defend large rocky outcrops from other male chuckawallas, but will allow several females and even juvenile males to inhabit their area. Although this is commonly thought to be a male behavior, females can also be territorial.

Desert lizards exhibit a variety of behaviors to discour­age other males from trespassing. Head bobbing, accompa­nied by flattening the body to give the illusion of larger size, is observed in many species. If the visiting male does not leave the area, as most will do, then a fight will ensue. The resident male is usually the winner and the trespasser quickly leaves.

In captivity, lizards are forced to live in a confined area that is usually much smaller than the territory they occupy in the wild. If more than one male is present, the animals will often fight until one individual establishes dominance and then aggressive behavior will decline. In effect, an un­easy truce is declared because the submissive animal can not flee the area as it would do in the wild.

Although this truce may appear as a harmonious rela­tionship to us, it can be extremely stressful to the submis­sive lizard. A hierarchical relationship is not natural to most lizards, since they will most often separate them­selves in the wild with each defending its own territory. The submissive animal will often suffer stress that is exhib­ited by an increase in the size of the adrenal glands, a de­cline in the efficiency of the immune system, decreased growth, and increased mortality. Researchers at the San Diego Zoo found that young male iguanas exhibit de­creased growth rates if they are even in the same room with a large male iguana. They detect the other males by sight and smell.