54 SONORAN HERPETOLOGIST 21 (5) 2008 Howard O. Clark, Jr. H. T. Harvey & Associates, Fresno, California, USA. hclark@harveyecology.com T he Common Chuckwalla (Sauromalus ater) is a large, diurnal, heliothermic, iguanid lizard occurring in the desert regions of southeastern California, western Arizona, and in portions of Nevada, Utah, and Mexico (Johnson, 1965; Werman, 1982). The species is re- stricted to rocky areas and volcanic outcrops within its range (Smith, 1946; Nagy, 1973). Chuckwallas escape from predators in a unique manner. Their habitat consists of numerous cracks and crevices that they use as refuge. Smith (1946) not- ed that chuckwallas he observed were very wary and slipped easily into concealment while he was several hundred feet away. Likewise, Johnson (1965) reported that chuckwallas moved without hesitation headirst into these cracks when approached. When found in rock crevices, the lizards swell their bodies by inlat- ing their lungs which wedges them tightly between the rock surfaces, making removal practically impossible. Here I describe the behavior of a chuckwalla using a rock crevice as a retreat. On 17 June 2006 I was hiking along a trail on an unnamed hill near Ridgecrest, Kern County, California (913 m; N 35° 34.466 W 117° 39.557, NAD83/WGS84). As I approached the chuckwalla, it ran into a boulder that was cracked in half. The boulder was situated such that I could widen the crack with my hands until the chuckwalla was further exposed. As the crevice widened, it puffed its body up and extended its four limbs outward, to a point where its body was suspended and outstretched between the rock surfaces using only its four limbs. At that time I was able to reach in and capture it. Upon inspection, it appeared to be an immature male in good health. I released the lizard, and it immediately returned directly to the same crack I originally found it. I wanted to place the boulder back the way I found it so as to not disturb the microhabitat (Goode et al., 2004), but I did not want to injure the chuckwalla. I captured the lizard again and released it a meter or so further away. Again, it returned to the same crack. For a third time, I captured the lizard and released it a meter or so away in another area. It returned to the same crack again. I did not want to stress the chuckwalla any more than I had to so I carefully placed the boulder back the way I found it with the chuckwalla safely hidden within. No obvious injury was inlicted to the lizard, and it appeared in good condition after its removal and handling. The peculiar behavior of the chuckwalla is worth noting. Even after being stressed on three successive occasions, it insisted on returning to the same crevice. There were other crevices nearby, but apparently this particular crevice had an important characteristic that I was unable to determine. Perhaps because the chuckwalla appeared to be an immature, it may not have learned avoidance behavior by using several cracks as refuge, especially after a particular crack exposed it as vulnerable to potential harm. Literature Cited Goode, M.J., D.E. Swann, and C.R. Schwalbe. 2004. Effects of destructive collecting practices on reptiles: a ield experiment. Journal of Wildlife Management 68:429-434. Johnson, S.R. 1965. An ecological study of the Chuckwalla, Sauromalus obesis Baird, in the western Mojave Desert. American Midland Naturalist 73:1- 19. Nagy, K.A. 1973. Behavior, diet and reproduction in a desert lizard, Sauromalus obesis. Copeia 1973:93-102. Smith, H.M. 1946. Handbook of Lizards: Lizards of the United State and Canada. Comstock Publishing Co., Ithaca, New York. 557pp. Werman, S.D. 1982. Notes on the ecology of the Chuckwalla, Sauromalus obesis Near Baker, California. Journal of Herpetology 16:417-418. Editor’s Note: As a friendly reminder, prying and moving cover can be detrimental to habitat. The THS tries to discourage these collecting techniques. Note also that destructive sampling is frowned upon, and habitat should be returned to its original condition when searching for reptiles and ampibians, as indicated by the author. Note also that it is illegal to use manual or powered jacking or prying devices to take reptiles or amphibians in Arizona (Arizona Game and Fish Commission Rule R12-4-303.C). NATURAL HISTORY NOTE Common Chuckwalla (Sauromalus ater): Behavior Figure 1. Common Chuckwalla (Sauromalus ater) near rock bolders. Photo by K.W. Hughes, near Ridgecrest, CA. When found in rock crevices, the lizards swell their bodies by inlating their lungs which wedges them tightly between the rock surfaces.