Researchers have found young alligators along Lake Okeechobee's northern shore have very low levels of hormones controlling reproduction, growth and resistance to disease.
"Our results raise a very large red flag," said Louis F. Guillette Jr. of the University of Florida."Something is clearly causing dramatic changes in the environment for these alligators," he said. "But are pesticides or some other contaminants doing the damage? Or have there been changes in the alligators' food supply or some other environmental conditions?"
The answers may shed light on whether there's a health hazard for people, too. Like humans, alligators have a long life span and are at the top of their food chain.
"We just don't know enough yet," said federal biologist Franklin Percival.
Researchers saw similar problems in alligators in Lake Apopka after a 1980 spill of difocol, a pesticide containing significant amounts of DDT and related compounds. The lake's alligator populations plunged as the percentage of successful hatchings fell from 54 percent in 1983 to less than 4 percent in 1988.
Guillette and his fellow researchers chose Lake Okeechobee this time because it had had no known major chemical spills and alligator hatch rates there are generally 40 percent to 50 percent. They also studied hormone levels in alligators at Woodruff National Wildlife Refuge near DeLand, where 80 percent to 90 percent of gator eggs hatch successfully.
Their research, to be published in the March issue of the journal Environmental Toxicology and Chemistry, indicated that hormone levels in the reptiles correspond with fertility rates.
"What worries me is that we're still looking at the impacts caused by old chemicals like DDT," Guillette said. "And while we're studying them individually, there's no good information about what happens when all these old and new chemicals are combined.