inches for the tail, a large chuckwalla would be 17 to 18 inches long. Chuckwallas of this size are very old.

Reproduction
Adult females lay from 6 to 14 eggs from late May to early July. Females do not lay a clutch every year; they probably lay eggs only when there is an abundance of annual wildflowers for food.
We know little about where females lay their eggs. There has been only one field observation of a female excavating a nest in a crevice, depositing her eggs, and covering them with dirt. One of my captive females laid a clutch of eggs in an outdoor lizard pen in my backyard in July. They did not hatch for 160 days, in late November. When the hatchlings emerge from the eggs in fall, the little lizards probably enter hibernation immediately.

Home Ranges
Each chuckwalla has an area it frequents during the season. This is called the home range. During the spring, a chuckwalla is likely to traverse its entire home range in a day. In summer, it may remain for weeks in a single rockpile and travel only occasionally.
Compared with other desert lizards, the chuckwalla has a large home range. Adult males had home ranges averaging
The Study Area
4.7 acres (maximum 8.3 acres), whereas those of females are much smaller and average about 2 acres.
The home ranges of males and females overlap extensively. The larger areas of males reflect the increased movement, aggressiveness and higher activity levels of the male.

Seasonal Activities and Hibernation
This species is generally above ground only four to five months of the year. Chuckwallas emerge from hibernation in early March and are active, weather permitting, on a daily basis until early June. At that time, activity diminishes and the lizards may be seen only occasionally. Some can be found basking on rocks into July and early August. However, by mid-August, most remain underground or in deep crevices until the following spring.
The seasonal activities are closely tied to food supply. Chuckwallas are active when food is available during the spring. The chuckwalla is a plant-eating lizard, or herbivore, and relies on leaves, stems, flowers and seeds of both annual wildflowers and shrubs. Chuckwallas eat a wide variety of plants and can be seen climbing in creosote bushes and eating the flowers and fruits. They have also been observed climbing the thorny ocotillo branches to reach the red flowers at the tips. Annual wildflowers are also eaten and form a substantial part of the diet in early spring. A chuckwalla can eat the heads of 15 desert dandelions or Fremont pincushions in less then 3 minutes.

Communication Between Lizards
Chuckwallas communicate with one another by head bob displays, by posturing their bodies, and by depositing chemical signals. The head bob displays are especially important for communication and are used in aggression, statements of territory, and courtship. Chuckwallas have excellent vision and can see and respond to one another at distances of 50 to 100 yards.
The chuckwalla does a head bob display by moving the 'head, neck and shoulder regions up and down vertically as the arms are flexed and extended. The bobbing can simultaneously involve extension of the gular fold (the loose skin underneath the chin), partial inflation of the body, and raising the body off the rock or ground so that the lizard is standing on all four feet.
There are several kinds of displays. Some are called assertion, threat, challenge, courtship, and rejection. Most displays are performed by large, adult male lizards; females do very few.

(Next month: The Social Structure: Tyrants and Territories.)

NOTE: There Is a limited supply of Dr. Berry's paper, at $4 per copy, at the University of California Press, 223 Fulton St., Berkeley, Ca., 94720. The title: "The Ecology and Social Behavior of The Chuckwalla
 
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