Like tiny air raid shelters, protective cages sheltering the terrapin nests along Great Bay Boulevard in Little Egg Harbor keep them safe from predators, among them crows and gulls from the air and foxes and raccoons on the ground. The Great Bay Boulevard Terrapin Habitat Project site, commonly called the terrapin garden by its founder, Ben Wurst, habitat project manager for the Conservation Foundation of New Jersey, already has at least 50 nests on its sandy beach next to the salt marsh.

Many of the Northern diamondback terrapins find it by themselves, but most are shifted from the roadside to the…