What are some physical characteristics of a bullfrog?

Bullfrogs are large amphibians with smooth, green or olive skin that may have dark spots. They have long, powerful hind legs adapted for jumping, webbed feet for swimming, and a broad, flattened body. Their eyes are prominent and positioned on top of the head, and they possess a distinctive fold of skin (the tympanum) behind each eye, which aids in hearing. Adult bullfrogs can grow to be about 3 to 8 inches long.