While not exactly the kind of pet you want to cuddle with, frogs can provide entertainment while their habitats add a peaceful element to your room. There are more than 5,400 species of frogs around the world, and the hind legs often serve different purposes depending on where a frog species lives.
When you see a frog, you likely think of its amazing ability to jump. Although not all species are good jumpers, some can jump eight times their body lengths in a single hop. Most frog species use their hind legs as jump propulsion in some way, regardless if they live on land, in the water or in trees.
Water-based frog species have special hind feet with webbing between the toes. They use their hind legs mostly to propel themselves through the water while swimming, using their front legs to steer. Swimming fast means escaping from predators and catching more prey, and those long, muscular hind legs are key to the frog's success. These frogs also jump when on land, but not usually as far as land-based species. Their jumps are more like little hops that keep them moving but without impressing your friends.
Some frog species like to burrow underground, and many have hind legs designed for just that purpose. Their toes end in tubercles, which are claw-like and help them grab and move dirt. Many of these burrowing species have short hind legs that don't allow much hopping -- they walk or crawl instead of jump to get around.
Tree frogs have an outstanding ability to climb vertical surfaces -- their toes, including their hind toes, have sticky pads that grip the surfaces of trees to keep the frogs high and safe. They use their hind legs mainly for vertical climbing power, although most of these species are also good jumpers. One type of frog, the Costa Rican flying tree frog, has large webbing between its sticky toes. This frog can leap from one tree to another, spreading out his toes so the webbing can catch the wind and act like a parachute to keep the frog aloft.