AMONG THE ALLIGATORS OF GEORGETOWN COUNTY -- Dr. Louis Guillette has just ticked off a nine-foot gator.

Plucked from the swamp by a three-pronged hook, the hissing critter has tired after a 10-minute tug-of-war where it tried to spin out of a wire-harness clamped firmly around its neck.

When the fight ebbed, extra-strength rubber bands were placed around its snout, while a wet towel covered its eyes.

"It's a female," one of the wranglers says. That makes Guillette, a reproductive biologist at the Medical University of South Carolina, smile.

The alligators of South Carolina are the latest "canary in a coal mine" species. They are animal-sentinels that will help tell whether and how far along the flood of pollutants, toxins and agricultural runoff in state waters are on their way toward adversely affecting humans.

Female gators are the best test creatures because weaknesses in the reproductive system are among the best harbingers of bad things to come.

It's not that far a stretch to use alligators as a comparison to how poisons affect humans, Guillette says. "There are as many commonalities as there are differences."

For example, both man and alligator are top of the food chain. Both are long-life species stretching into the decades, and both have a reproductive life cycle spanning about 30 to 40 years. Plus, "at the gene level and at the cell level, an ovary is an ovary, a testes is a testes," he said, no matter the animal.

That distinction is important because the PCBs, heavy metals and other chemicals threatening the planet now, usually go after the reproductive cycle hardest.

Guillette's workplace is the Tom Yawkey Wildlife Center Heritage Preserve, 20,000 pristine marshy acres spread across three islands near the mouth of Winyah Bay. Its former owner was one of the original Boston Red Sox families who later gave the property to South Carolina.

Though the site is owned by the state, access is limited, which can be a good thing considering that the mosquito swarms there on Friday rivaled Messerschmitts in their ferocity.

Guillette who spent the last 25 years studying alligators in Florida, recently arrived at MUSC to study the gators here. He has a lengthy title that includes an endowed chair of marine genomics at the school, and professorial work in obstetrics and gynecology.

While South Carolina is new to this kind of gator study, Florida has been doing it for some time. "We had animals that watched John Glenn go up the first time," he said.

The Florida study also uncovered some unsettling results. Some of the female alligators were found to be exposed to agricultural chemicals and showed signs of ovarian failure and infertility, essentially giving what would be a human woman in her 20s or 30s the body of a 50-year-old.

Over the next few years Guillette and his team hopes to lasso as many of the Georgetown gators as possible, take blood and urine samples plus other measurements needed to track the health of the population. What they uncover could later affect what pregnant humans are taught, including what foods to eat and chemicals to avoid, or if a pollutant is registering dangerously high.

Catching gators for the study remains the tricky part. A three-pronged treble hook, minus the sharp barbs, is tied to the end of a rope that is tossed at a gator as it swims by. It is not as easy as it sounds to set the hook and drag one of the beasts to shore since alligators will dive at the slightest disturbance.

Also, when you see an alligator head moving on top of the water, it can be deceptive as to where their bodies are below the waterline. The animals often will hang perpendicular fashion, "sea-horse style," making the "hook" hard to set.

Once an animal is dragged to shore the sampling goes fast, because stress levels can affect blood samples. The gator gets tagged to show its habitat and record where it goes if it is caught again. None of the alligators in Guillette's study are "volunteers," he likes to joke. Collecting and monitoring gator eggs is also part of the study.

The nine-foot female, or "sow" to the male "bull," examined Friday probably weighed more than 200 pounds. Age wasn't easily discernible but she was probably 24 or older.

After the samples were taken, she slowly made her way back into the murky water.

Philip Wilkinson, a retired S.C. Department of Natural Resources biologist, and the widely identified father of alligator studies in the state, accompanied Friday's mission, saying there's still much to be learned, and that can be learned, about the alligator's role on the planet.

"Most people don't give 'em too much credit," he said. "But they have more sense than you think they do."

Reach Schuyler Kropf at 937-5551.