Displays / hour 
Psychobiology of Lizard Reproduction 157 
o o Male - Male Aggression 
Figure 6. Transition of predominant male behavior patterns when winter-dormant males are exposed 
to a stimulatory environmental regime (from Crews, 1975c). 
sion (Fig. 7). A fourth group of females 
exposed to 6 weeks of predominantly male 
courtship was not run since the previous two 
experiments had already demonstrated the 
effect of 4-to-5 weeks of predominantly male 
courtship; that is, facilitation of environ- 
mentally induced OR (see Fig. 4). 
Results from this experiment indicated 
that the hypothesis that male courtship facili- 
tated, while male-male aggression inhibited, 
environmentally induced OR was correct: 
Females exposed to male-male aggression 
for 6 weeks exhibited a low, unchanging 
level of ovarian activity. Females exposed 
initially to 3 weeks of male-male aggression 
exhibited a comparable level of ovarian 
activity, but, when the social stimulus was 
changed to male courtship, ovarian activity 
was dramatically stimulated (Fig. 8). 
Finally, females exposed first to male court- 
ship followed by male-male aggression ex- 
hibited the facilitated rate of environmentally 
induced OR as in the previous experiments, 
but when the predominant male behavior 
pattern was changed to male-male aggres- 
sion, ovarian activity declined. 
There are several reasons for the low level 
of ovarian activity to be regarded as an 
active inhibition by male-male aggression 
rather than an instance of nonactivation. 
First, the ovarian follicles in an increasing 
percentage of females exposed to male-male 
aggression after 3 weeks exposure to male 
courtship became atretic, and no new follic- 
ular cycles were initiated. Secondly, female 
A. caroUnensis exhibit an endogenous cir- 
cannual ovarian cycle (Crews, 1973a; Licht, 
1973). This finding, combined with the ob- 
servation that females exposed to high levels 
of male-male aggression at a time when 
females in the field (Field Control) were 
undergoing OR, would further argue for an 
active inhibition of environmentally induced 
ovarian activity by male-male aggression. 
