When the sizes of penises were compared between lakes, alligators in Lake Apopka had on average 24% smaller penises than alligators in Lake Woodruff. When the time came for these juveniles to reproduce, this significant reduction in penis size made it difficult to mate and certainly didn’t impress the lady alligators.

This study showed that male alligators in Lake Apopka, which is contaminated with endocrine disruptors, were significantly different than alligators from a lake that had relatively little pollution. In order to help determine the physiological drivers, in other words the chemical pathways in the body that shape these physical differences, behind this reduction in penis size, Dr. Guillette also looked at plasma testosterone concentrations. Plasma testosterone is responsible for the formation and development of male external genitalia. He discovered that juvenile alligators in Lake Apopka had 70% lower concentrations of plasma testosterone than those at Lake Woodruff. Abnormal hormone levels like these are associated with decreased sperm counts and reduced fertility. This can be disastrous for maintaining healthy wildlife populations. The results of this study inspired Dr. Guillette to continue to look at the physiological effects of endocrine disruptors on reproductive systems.