184 
Regal 
Pygopodidae (Underwood, 1971) may en- 
gage in “ambush” predation (Cogger, 1967). 
Many herbivorous lizards live where plant 
food is abundant and extensive searching is 
not necessary, e.g., Sauromalus ohesus 
(Nagy, 1973) and Iguana iguana (Moberly, 
1968a). Some Anolis will change position 
frequently and are, to that extent, “intensive 
foragers.” 
Intensive foraging is well developed in the 
autarchoglossan Varanidae (C. Cans, E. 
Pianka, personal communication ; Auffen- 
berg, this volume) and (macro) Teiidae 
(Hardy, 1962; Hirth, 1963; personal obser- 
vations), and in certain species of Lacertidae 
(C. Cans, E. Pianka, R. Huey, D. Karns, per- 
sonal communication), and Scincidae (Fitch, 
1954). 
I suspect (see below) that the primitive 
lizard was a cruising forager and that there 
was an evolutionary trend toward specializa- 
tion as (1) visually oriented sit-and-wait 
predators among the Ascalabota and (2) 
“olfactory” as well as visual searchers and 
active foragers among the Autarchoglossa. 
It is interesting that Klauberina (Xantusi- 
idae), which may be the most “primitive” 
lizard extant (Regal, 1968; Underwood, 
1971), is intermediate in spontaneous locomo- 
tion between a sit-and-wait strategist and an 
intensive forager (Fig. 1). The presence of 
intermediate foraging strategies in both of 
the major groups is, then, best viewed as the 
retention of an ancestral pattern. 
I made quantitative field observations on 
the foraging activity of an iguanid (Leio- 
cephalus schreibersi) and a teiid {Ameiva 
chrysolaema) at Barahona, Dominican Re- 
public. LeiocephaliLS basked in the sun from 
sunrise to sunset, and movements consisted 
of short rapid dashes of never more than 2 
seconds in duration to catch insects or chase 
conspecifics. The frequency of such dashes 
was only 9.6/hour. Although the animals 
sat immobile for more than 99 percent of the 
day, they were usually alert and obviously 
capable of quick movement. 
The Ameiva were active for only 4 to 5 
hours during the middle of the day, but were 
moving for probably more than 70 percent 
of this time (except for one windy day when 
they were largely immobile and basking). 
The constant movement in and out of low 
thorny vegetation complicated precise esti- 
mations, but my estimation is that Ameiva 
move their length every 2 to 5 seconds while 
foraging and constantly probing with their 
snouts. 
Leicephalus, Ameiva, and the xantusid 
Klauberina were captured and maintained in 
the laboratory on a 12:12 light-dark cycle 
in thermal gradients and fed on meal worms 
and ground beef. After 1 year their spon- 
taneous activity was measured in a 1 x 1 m 
white open-field apparatus marked into 25 
squares, with a 250 watt red-glassed heat 
lamp in one corner to permit thermoregula- 
tion. To avoid disturbance, observations were 
made by closed-circuit television. All lizards 
were fed. 
The differences between the three lizard 
species in the rates at which lines were 
crossed were all statistically significant (Fig. 
1). The rate for Ameiva was comparable to 
a laboratory mammal under the same condi- 
tions. The behavior of Leiocephalus and 
Ameiva appeared to reflect their activity in 
nature. Klauberina is a secretive species and 
its behavior in nature is unknown. 
Thus, the usual image of a lizard as primi- 
tively sluggish is incorrect and misleading. 
Activity or its lack largely reflects foraging 
strategies and there is a spectrum of these 
among lizards. 
Teiids and varanids possibly serve as a 
much better model for the organization of 
“mammalian behaviors” at a reptilian level 
of organization than do the more commonly 
studied iguanids or other less active reptiles. 
Detailed studies of reptilian ecology, neur- 
ology, and behavior provide useful insight 
into the selective factors that shaped the 
mammalian brain, as will be made clear in 
the latter sections of this paper. 
INDICES OF AROUSAL 
Behavior 
A lizard’s behavior is not a reliable indi- 
cator of its level of arousal. Immobile lizards 
