Psychobiology of Lizard Reproduction 
169 
Dose of FSH (/ig) 
Figure 13. Effect of mammalian gonadotropin (bovine NIH-FSH-S9) on ovarian and oviduct growth in re- 
factory Anolis carolinensis following removal of the atretic (CA-X) or normal (Foll-X) ovarian follicle 
(from Crews and Licht, 1974). 
onset of sexual refractoriness in female A. 
caroliensis occurs spontaneously, independ- 
ent of external factors; hence A. carolinensis 
may be regarded as an obligatory seasonal 
breeder. 
It is generally assumed that the ultimate 
factors underlying the evolution of seasonal 
breeding in temperate species act (a) to 
insure that the young will not appear at a 
time when food resources are declining or 
are nonexistent, and (b) to prevent the fe- 
male from investing energy into reproduc- 
tion rather than the fat deposition necessary 
for overwintering. The correlation between 
the occurrence of CA and the initiation of the 
refactory period following the normal breed- 
ing season and the close temporal relation- 
ship between the disappearance of the CA 
and the onset of sexual responsiveness to 
environmental stimuli suggest that the CA 
dramatically increases ovarian responsive- 
ness to exogenous gonadotropin further sup- 
ports this hypothesis. 
CONCLUSION 
A number of ecological factors, including 
climatic (e.g., photoperiod, rainfall, humid- 
ity, temperature), structural (e.g., vegeta- 
tional changes, food availability), and social 
(e.g., behavioral interaction, experience) 
stimuli, have been implicated in the control 
of annual sexual cycles of vertebrates. These 
factors, whch are believed to modify the 
timing of partly endogenously determined 
reproductive cycles and serve to coordinate 
breeding between individuals, interact to 
“fine-tune” reproductive processes. Finally, 
there is good evidence to suggest that, in 
many species, the male cycle is under strict 
environmental control while the female cycle 
