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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