To help determine what was drawing the turtles onto the runway, Ms. Francoeur hired Jeff Kolodzinski, a senior wildlife biologist. Working together starting last fall and on through this spring, the pair helped lay miles of black plastic tubing, the kind used to prevent soil erosion, along the airport’s razor-wire border. The barrier stopped many turtles from climbing up from the nearby shore.

Whenever a turtle does shimmy past the plastic barrier, members of Ms. Francoeur’s team are dispatched to fetch it. The terrapins are often spotted by pilots, for whom even a small creature on the tarmac is a potential hazard on par with a stray chunk of pavement, dropped bolt or shred of tire. (The most terrapins struck by planes in a single year was six, Ms. Francoeur said.)

Once they have the turtle in hand, the biologists probe under its shell with their fingers to feel whether it is full of its marble-size, peach-colored eggs. If so, they release it over a fence onto a sandy beach where it can nest. If not, the turtle gets a ride to airport headquarters and temporary shelter in a Coleman cooler.

Then, working in an air-conditioned conference room overlooking a section of runway, Ms. Francoeur and her team lay the turtles on a mahogany meeting table surrounded by swivel chairs. In plastic bowls, the biologists mix water with powdered alginate, the substance dentists use to make molds of human mouths. The paste is purple, and smells and tastes like cherry candy. It is globbed onto the backs of the turtles until it hardens into a cast. Then the cast is removed and the turtle is returned to the wild.

“You get to know the personalities of different turtles,” Melissa Zostant, a graduate student of Dr. Burke’s and a summer intern with the wildlife biologist team, said as she spooned paste onto the back of a squirming terrapin one recent afternoon.