Florida Game and Fresh Water Fish Commission

SCIENTISTS PROBE ALLIGATOR DEATHS ON LAKE GRIFFIN

June 1, 1998

CONTACTS: (GFC) Tim O'Meara (850) 488-3831
(UF) Perran Ross (352) 846-2566

Wildlife scientists from a variety of state agencies are trying to figure out what is killing alligators on 9,000-acre Lake Griffin. At last count, at least 40 gators have died of unknown causes. Meanwhile, adult gators are producing few viable eggs.

The Game and Fresh Water Fish Commission has contracted with Dr. Perran Ross of the University of Florida's Museum of Natural History to unravel the mystery. Ross summoned scientists and other officials to Gainesville May 19 to firm up a plan to find out why the gators are dying. Major players in the task force include the Game and Fresh Water Fish Commission, St. Johns River Water Management District and the University of Florida.

"Since the spring of 1997, we've had low hatch rates and high mortality of adult alligators in Lake Griffin," Ross said. "Eggs are dying during incubation or within 5 - 10 days of laying."

Only 4 percent of the lake's alligator eggs are hatching, and the die-off of adult alligators began in April.

Researchers decided to focus their efforts on four possible causes of the alligators' problems: Cylindrospermopsis (a type of blue-green algae), disease, chemical contamination and nutrition.

Cylindrospermopsis, although never scientifically linked to alligator deaths before, can result in conditions that can kill fish and other animals. It is not toxic to humans in natural concentrations, however.

Habitat degradation, usually the result of human population increases, is a massive statewide problem that affects all wildlife, and can cause a variety of diseases.

Chemical contamination, which already has caused a great decline in the alligator population in nearby Lake Apopka, is another potential cause.

"Lake Griffin has been getting agricultural and urban runoff for the past 30-40 years," Ross said.

Nutrition is another possible culprit. In recent research involving sea turtles, scientists found that turtles that ate a diet artifically high in protein were inclined to produce more eggs -- but with an extremely low fertility rate among the eggs.

"Lake Griffin's problems could be the result of any one of these factors or any combination of them," Ross said. "Or it may be something else that we aren't aware of."

Aside from the alligator mortality, the lake's black crappie (speckled perch) population also is in decline and is at its lowest level on record.

Scientists are preparing research proposals to submit to funding agencies.

HPC/OIS