By Jessica Hershman, Media Relations Staff
Even as Port Authority Wildlife Biologist Laura Francoeur and members of her team mark and then release to safety hundreds of Diamondback Terrapins that invade the runways at JFK Airport annually, nobody is sure exactly why they come. The answer defies easy explanation.
Biologists such as Francoeur and her assistant, Melissa Zostant, a Hofstra University Master’s candidate writing her thesis on why the turtles prefer JFK, believe the likely reason the turtles come ashore from Jamaica Bay is because of the sandy soil, which is above the high tide line.
“The original airport planners never could have imagined that all the sandy fill they put down would one day become the perfect nesting habitat for terrapins,” Francoeur said.
“I think the terrapins also are attracted to Joco Marsh and the area surrounding the airport for the food and habitat provided. They then nest at JFK since that’s the closest land that appears to have good nesting habitat – sandy, loose soil,” she said.
“The marsh around JFK is healthier than other marshes in the area too, which provides an ideal source of food,” said Zostant. “The turtles may prefer JFK because the fencing around the airfield keeps out raccoons, who prey on hatchlings and eggs.” Once ashore, females use their powerful back legs to dig a hole, dropping their huddle of eggs into the hole, and then covering it up. The nests are then tagged and an enclosure is constructed to protect the eggs, leaving a small opening through which the hatchlings can escape.
In 2012, JFK personnel constructed a barrier from plastic piping to keep out the terrapins along much of Runway 4L, because the dozens of turtles crossing the runway were causing flight delays. The number of turtles on the airfield has gone down dramatically since fencing was installed.
If turtles get past the barrier, the Port Authority wildlife team capture the animals manually and place them in the beds of JFK trucks before inserting microchips beneath their skin. Through this method, a turtle is assigned a number that is recorded each time the turtle is captured. The microchip does not have GPS capability, however, and cannot track the movement of the terrapins.
The animal is marked with a single, triangle-shaped notch. Each year the notch is placed in a different location, but the terrapin only receives one notch over its lifetime, the first year it is captured. The marking provides scientists with information about the year the terrapin was first collected, and it also provides a visual aid to know whether a terrapin has been collected previously.
According to the Port Authority, 501 terrapins have been processed in 2016 to date. Since the terrapin program began in 2011, a total of 2,266 new terrapins have been processed.
Terrapins have green and yellow rings on their shells, which are encircled by actual ridges that are counted to estimate the age of the animal similar to the rings encircling a tree trunk. To assist in the counting of a turtle’s rings, a concoction of acids, salts and brown seaweed is applied to the turtle’s shell, creating a casting of the shell in much the same way a dentist creates a dental impression of his patient’s mouth. The turtle is then returned to the wild.
Many of the terrapins at JFK are between seven and nine years old, which makes them younger than at other locations on Jamaica Bay, but a significant number of the terrapins are much older.
“It’s unclear whether the terrapins recognize the aircraft and vehicles as predators, but if they have previously nested successfully at the airport, that predator interaction is one from which they were able to return alive so they repeat it and it doesn’t pose a deterrent to them,” said Francoeur.