Psychobiology of Lizard Reproduction 
151 
social and environmental control of repro- 
duction. Of the reptiles, iguanid lizards are 
especially well suited for this type of re- 
search. Many species are small, readily avail- 
able, and easily cared for in the laboratory. 
In addition, many species retain their full 
repertoire of behavior patterns and complex 
social systems in captivity. Finally, and more 
importantly from a psychobiological point 
of view, there is already substantial infor- 
mation regarding the behavior, physiology, 
and natural history of a number of species 
of two lizard genera, Anolis and Sceloportis. 
Perhaps the best studied of these species 
has been the American chameleon, Anolis 
carolinensis. 
Anolis carolinensis is a small, temperate- 
zone lizard found throughout the south- 
eastern United States. From late September 
to late January, both males and females are 
reproductively inactive and cluster in groups 
beneath the bark of dead trees, under fallen 
logs and rocks (Fig. 2). Beginning in late 
January or early February, the males emerge 
from this period of winter dormancy and 
establish breeding territories. Approximately 
1 month later the females begin to be active, 
and by May they are laying a single-shelled 
egg every 10-14 days. Following the breed- 
ing season, both males and females enter a 
refractory phase lasting approximately 1 
month during which they are insensitive to 
the various environmental and social stimuli 
responsible for inducing gonadal recrudes- 
cence in the spring. 
There are three different series of experi- 
ments summarized in this paper. In the first, 
I illustrate how various social and environ- 
mental factors coact to control the initiation 
of seasonal ovarian activity in winter- 
dormant females. In the second, I identify 
some of the different internal and external 
stimuli to which females are exposed during 
the normal breeding season and how these 
stimuli interact to control female sexual 
receptivity. Finally, I describe experiments 
Month 
Figure 2. Schematic illustration of diiferent behavioral and physiological events in the annual reproductive 
cycle of the lizard, Anolis carolinensis (from Crews, 1975c). 
