Frogs have smooth (soft) skin, while toads have rough (hard) skin. Frogs need their skin to be wet in order for them to get oxygen. Frogs and toads have broad heads and plump bodies. They have short fore limbs and long webbed hind feet. This helps them to move and swim in water. They can also use their legs to crawl, hop and leap. Frogs are good jumpers, and some can leap up to six feet in the air. Tree frogs can climb on any surfaces, they use their sticky hands to do this. The tympanum membrane can only be seen on frogs. The tympanum membrane can be found between the frog's ears and eyes. Frogs have tiny teeth inside their mouths. They are found on the lower jaw. The African bullfrog is the only species where the males are longer than the females. Males can reach up to 9½-10 inches in length, while the female only grows up to 4½ inches. Frogs belonging to the suborder Neobatrachia, such as the poison dart frogs and Mantellinae frogs, can kill humans. Like most poisonous animals, they get their toxin from their food.