The American bullfrog is the largest of the "true frogs" family. Bullfrogs can reach a length of . Females are larger than males. Bullfrogs can weigh up to . Bullfrogs are either brown or green. They also have darker spots on their back. Bullfrogs have webbed feet for swimming. They can leap up to . Male bullfrogs can be heard roaring when mating with a female. Males also have bigger tympanic membranes which cover their ears. Bullfrogs have brown or gold eyes. They also have broad flat heads and bodies. The mouth of a bullfrog are small and have tiny teeth inside.