Scattered remnants in the shallow depressions, newly dug, bore all the hallmarks of a crocodilian crime scene.
The first hatch of the summer nesting season was not expected for weeks. Yet staff members at the Crocodile Lake National Wildlife Refuge last week discovered two nests of the protected American crocodile had been torn asunder, the hatchlings’ tough but pliable egg sacks scattered and empty.
A raid by predators in the hardwood hammocks of North Key Largo seemed highly possible. Refuge manager Jeremy Dixon grimaced, then walked through a cloud of mosquitoes to peer into the edge of a mangrove-lined waterway a few yards away.
“Over here,” Dixon said quietly, breaking a smile. “Baby crocs.”
A half-dozen or more hatchlings, eight inches long and well-camouflaged amid the fallen mangrove leaves and twigs, floated on water surface. Only 3 days old, they submerged or darted for cover when they realized someone was watching.
Crocodile nests usually hatch “toward the middle or end of July, even into August,” Dixon said later. “So these are at least a couple weeks early.”
In the dark of Wednesday night, U.S. Fish and Wildlife Service staff and interns returned for a baby crocodile roundup that counted, weighed, measured and marked 49 new hatchlings from the two nests. “It’s very important for us to be able to see if an adult crocodile is one that we’ve been following,” Dixon said.
Another five suspected nest sites in the 6,700-acre refuge created in 1980 are being watched by wildlife cameras triggered by a motion sensor.
“Sometimes the crocodiles play tricks on us by creating a mound — a false nest,” Dixon said. “It may be they’re testing the soil, but we really don’t know why. So we won’t know until the end of the season how many nests we actually have.”
Refuge interns Dan Erickson and Savannah Sutherland often are tasked with kayaking out to change memory cards and batteries in remote areas of the refuge.
A review of images taken by the wildlife camera trained on one of the newly hatched nests shows the mother digging into the burrow Saturday, about three months after she laid from about 20 to 40 eggs in the nest she carved out of the sandy soil, on higher ground unlikely to flood. Dredged soil deposited along canals dug for development that never occurred has become important habitat for crocodile survival.
A mother crocodile returns to the nest several times toward the end of incubation, then digs the hatchlings free when the moment is right. She may carry the baby reptiles to nearby water or nudge them along, but her maternal duties generally end there.
Then the juveniles are on their own, potential prey for birds, raccoons, sharks and tarpon. “Roughly about 10 percent survive to become adults,” Dixon said.
Unlike crocodiles found in Africa, Australia and South America, the American crocodile native to South Florida is a shy sort that generally will avoid humans — unless there is a food source handy. No human deaths have ever been attributed to an American crocodile in the U.S., with only one confirmed injury bite that likely was defensive in nature.
Still, any toothy reptile that can reach 15 to 20 feet long should give people reason for caution.
The American crocodile appeared on the verge of extinction in the 1970s with only 200 to 300 animals in the United States, most of them in the Keys and Everglades National Park. Once listed as critically endangered, the American crocodile population has increased to an estimated 1,500 to 2,000 adults. In 2007, its status was changed to threatened but the crocodile remains fully protected from harvest or harm.
“The population appears to have become generally stable over the last 30 years, but there are still issues that give us some cause for concern,” Dixon said. “Crocodiles are being hit by cars, there are human interactions and some concerns about invasive exotic species.”
Prime among those is the tegu, a South American lizard that can grow to 4 feet in length. Colonies are known to exist on the mainland, not far from the Keys. “Tegus are omniverous, and known for digging up reptile eggs,” Dixon said. “To date we have not seen any in the refuge; it’s a big reason we have the wildlife cameras out there.”
Kevin Wadlow: 305-440-3206