Producers: Hazel Stark & Joe Horn Host: Hazel Stark For such a small, elusive frog, their call is anything but elusive. The call of the gray tree frog is one of the loudest calls of all North American frogs. They breed later than most other local frogs, so we start hearing them after the clacking of the wood frogs has ended and once the chorus of peepers in the evening is no longer a novelty. Photos, a full transcript, references, contact information, and more available at thenatureofphenology.wordpress.com.