It's hatchling season for American crocodiles and while the species is imperiled overall, mother and baby crocs are thriving in the swamp surrounding a South Florida nuclear power plant.

During the rainy season that comes at this time of year, young crocodiles hatch, leave their nests and try not to become prey to other crocs before they become full-grown predators. It's also the time when biologist Mario Aldecoa goes out to catch the hatchlings, mark them for a lifetime of scientific tracking and then release them back into the waters that surround the Turkey Point Nuclear Power Plant.

Aldecoa is part of a group hired by the state's largest public utility, Florida Power and Light, to monitor the hundreds of crocodiles that roam the swamps surrounding the plant. Its cooling canals are prime croc habitat and have been credited with helping the crocodiles' recovery in Florida over the last few decades.

"That's where we get the main data," Aldecoa said of the tracking program. "Because one day or two or three years down the road, we may capture that same individual and we can see how much it's grown, how far it's traveled. That helps us get a better picture of survival rates, growth rates and distribution of these animals."

There are between 1,500 and 2,000 crocodiles in Florida — 40 years ago there were 300. They are listed as an endangered species by the state, but were downgraded a few years ago to "threatened" on the federal list. They can often be confused with their plentiful cousin the alligator, which are black, have broad, rounded snouts and are found throughout the deep South. Crocodiles are grayish, have narrow tapered snouts and are so sensitive to cold that their only U.S. habitat is South Florida.

In March, the female crocs begin building nests on elevated and drained sites to prevent hatchlings from drowning. The females lay about 40 eggs in a clutch by late April or early May. The eggs, about the size of a chicken's, have a leathery texture with a tough outer shell and a flexible membrane inside.

The incubation period lasts between 80 and 90 days. In late July or early August, females return to their nest, open it and help their hatchlings reach the water.

"Without her they will actually die within the nest," Aldecoa said during a recent airboat ride. "So there is some cue that informs the female that 'Hey, it's time for the babies to pop out.' One of those cues is the hatchlings will actually start grunting from within the eggs, which is pretty neat."

After the hatchlings leave the nest, Aldecoa and his team search the murky waters for the crocs' red eyes in order to capture the youngest in designated areas.

He had searched weeks earlier for hatchlings at a spot where he was sure he would find a nest but came up empty. Once he started pounding on the dirt, the grunting from underground began. He dug up 34 crocodiles, "the highlight of the year so far," he said.

In the mid-1970s, only about 10 to 20 nests were laid each year. Today there about 100 nests.

Since the croc monitoring program began at the plant in 1978, some 5,000 hatchlings have been captured and marked. Aldecoa said that indicates that some female crocodiles are returning year after year to the habitat surrounding Turkey Point to lay their eggs.

After capturing by hand a dozen baby crocs one recent night, Aldecoa bagged them and took them to the onsite lab where they were measured, weighed and tagged with a microchip to track them. Their scutes — bony plates or scales on crocodiles — were clipped to serve as a sort of thumb print or identification number. Then they were released back into the swamp.

Surviving the wild, though, is the toughest part for these animals. From a clutch of 30 or 40 crocodile eggs, only three or four will survive due to predation. Aldecoa captured an older croc and scanned its belly for any chips, but it looked like the croc didn't eat any previously tagged crocs, making it difficult to know if or how many baby crocs it may have eaten.

"But that's kind of how it's been designed through nature," he said, pointing out that many older crocs here were at one point a little hatchling that survived the odds and "grew up to be such a big dinosaur." He still worries, though, for the small ones he released the next afternoon.

"Releasing them is bittersweet. I often really do think 'Are they going to be OK at night? Are they going to get eaten? But at this point we just let nature take its course and we let them go."