National Geographic : 2012 May
DOMESTIC CAT Cat hands grow narrow, curved claws. Most of the time ligaments running over the top of a cat's hands keep the claws retracted inside sheaths. To catch prey, a cat pushes off its hind legs and stretches out its arms. Muscles along the top and bottom of its hands contract, which draws the claws out like switchblades. The claws sink into the prey, the cat shifts its weight to its hind legs, and the hands draw the prey to the cat's mouth. FROG Frogs have evolved into thousands of species with hands that have changed to accommodate different activities. Some of the species that live in water grow webbed hands so that they can swim. Tree frogs use long fingers with expanded finger- tips for climbing; they have even evolved tiny adhesive disks on their fingers that help them stick to smooth surfaces such as leaves.