WEST ORANGE, N.J. — Forget the giraffes, gibbons and leopards. About a dozen visitors at the Turtle Back Zoo gathered one recent morning around the most unusual sight of all. It was a small, light-brown tortoise getting a veterinary checkup. Over the next half-hour, spectators watched through a plate-glass window as the young sulcata tortoise — an endangered species also known as the African spurred tortoise — underwent measurements, X-rays, a blood draw, microchipping and more. Inside the