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1996 McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 109<br />

rea tridentata), and other major components of the<br />

vegetation included saltbush (Atriplex), Haplopap-<br />

pus, Lycium andersonii, and Dalea. McCoy (1967)<br />

discussed the ecology of this species in the Colorado<br />

River valley, Mesa County, Colorado, where it was<br />

found in association with greasewood (Sarcobatus<br />

vermiculatus) and big sage (Artemisia tridentata). In<br />

southeastern Arizona, the species was found on sand<br />

dunes with sand sap (Artemisiafilifolia) and indigo<br />

bush (Dalea sp.) and on bajadas characterized by<br />

cat-claw acacia (Acacia constricts), jimmyweed<br />

(Haplopappus taenuisecta), Opuntia, and Agave<br />

(Mitchell, 1984). Near the northeastern limits of its<br />

range (1 1.5 mi S Monahans, Ward County, Texas),<br />

Tinkle (1959) found them on sandy flatlands in as-<br />

sociation with mesquite (Prosopis), creosote bush<br />

(Larrea tridentata), Acacia, and dwarf shin oak<br />

(Quercus havardii). Montanucci (1970) found G.<br />

wislizeniirestricted to the high elevation (above 3600<br />

ft) pinyon-juniper woodland habitats of the Cuyama<br />

and Lockwood valleys, southern California, near the<br />

hybrid zone between this species and G. siltts. How-<br />

ever, the pinyon-juniper zone is thought to be sub-<br />

optimal habitat for G. wislizenii and they are often<br />

absent from such areas (Tanner and Jorgenson, 1963;<br />

McCoy, 1967). Gambelia wislizenii appears to be<br />

most common on sparsely vegetated flatlands with<br />

large numbers of rodent burrows (Tanner and Banta,<br />

1963; McCoy, 1967; Nussbaum et al., 1983).<br />

Unlike Crotaphytus and Gambelia silus, G. wis-<br />

lizenii lacks temtoriality (McCoy, 1967; Montan-<br />

ucci, 1970; Tollestrup, 1979, 1982, 1983) and there<br />

is ofien much overlap in home ranges (Tollestrup,<br />

1979, 1983). Females may even nest communally<br />

(Parker and Pianka, 1976). Females attain much<br />

larger size than males and appear to consume a high-<br />

er proportion of vertebrate prey (Parker and Pianka,<br />

1976; Tollestrup, 1979, 1982, 1983). Southern pop-<br />

ulations reach larger adult sizes than more northern<br />

populations which Parker and Pianka (1976) again<br />

linked to an increased emphasis on vertebrate prey.<br />

Gambelia tvislizenii are ambush predators, often<br />

resting in the shadows at the base of a bush before<br />

dashing out to capture passing prey items (Tolles-<br />

trup, 1979, 1983). They are able to move with great<br />

speed and have been observed to leap as high as 0.6<br />

m to capture flying insects (Franklin, 19 14). Known<br />

prey items include arthropods, especially onhop-<br />

terans, as well as coleopterans, lepidopterans, hy-<br />

menopterans, hemipterans, homopterans, dipter-<br />

ans, isopterans, neuropterans, and arachnids<br />

(Knowlton and Thomas, 1936; McCoy. 1967; Snyder,<br />

1972; Tanner and Krogh, 1974a, 1974b; Essghaier<br />

and Johnson, 1975; Parker and Pianka, 1976;<br />

Tollestrup, 1979; Mitchell, 1984). Vertebrate prey<br />

include the lizards Callisaurus draconoides, Cnemidophorus<br />

tessellatus. C. tigris, Lfta stansburiana,<br />

Phrynosoma platyrhinos, Sceloporus graciosus, S.<br />

undulatus, smaller G. ~vislizenii, and small snakes,<br />

as well as the pocket mouse Perognathtis longimembris<br />

(Taylor, 19 12; Richardson, 1 9 15; Camp, 19 16;<br />

Van Denburgh, 1922; Knowlton and Thomas, 1936;<br />

Banta, 1967; McCoy, 1967; Snyder, 1972; Tanner<br />

and Krogh, 1974a, 19746; Parker and Pianka, 1976;<br />

Tollestrup, 1979, 1983; Pietruszka et al., 1981;<br />

Crowley and Pietruszka, 1983). As has been reported<br />

for several Crotaphytus species (i.e., C. bicinctores,<br />

C. vestigium), Lycium berries are often<br />

consumed and may even represent a preferred food<br />

item during pans of June and July (Tanner and<br />

Krogh, 1974a). Turner et al. (1969) observed individuals<br />

climbing into Lycium bushes to eat the<br />

bemes, indicating that this plant material is not<br />

consumed inadvertently. Jorgensen and Orton<br />

(1962) collected two G. ~vislizenii in traps baited<br />

with oatmeal and found oatmeal in the stomach<br />

contents of both.<br />

Garnbelia wislizenii shares a number of behavioral<br />

similarities with G. copeiand G. silus. All three<br />

are often observed basking on small roadside rocks<br />

and the berms along the edges of graded dirt roads.<br />

"Freeze" behavior (Brooking, 1 934; McCoy, 1 967)<br />

wherein threatened individuals run to the base of a<br />

nearby bush, flatten themselves to the ground, and<br />

remain motionless (presumably as a means of<br />

avoiding detection) is also a shared behavior. A behavior<br />

present in G. ~vislizenii but not yet noted in<br />

other Gambelia is vocalization (Taylor, 19 12; Jorgensen<br />

et al., 1963; Wever et al., 1966; Crowley and<br />

Pietruszka, 1983). Wever et al. (1 966) described the<br />

sound emitted as "vocal cries of a wailing or moaning<br />

character." The ability to vocalize, although extremely<br />

unusual within iguanians, has also been noted<br />

in C. bicinctores (Smith, 1974) suggesting that all<br />

crotaphytids may possess this ability.<br />

Accounts of predation on Gambelia bvislizenii are<br />

rare in the literature. Tollestrup (1 979) observed a<br />

failed predation attempt on an adult female by a<br />

Prairie Falcon (Falco mexicanus). Tollestrup (1 979)<br />

considered the following species to be potential<br />

predators at the California City study site: the coachwhip<br />

snake (Masticophis flagellum), sidewinder

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