a position floating on the surface. The tiny northern cricket frog (Acris crepitans) can "skitter" across the surface of a pond with a series of short rapid jumps. Slow-motion photography shows that the muscles have passive flexibility. They are first stretched while the frog is still in the crouched position, then they are contracted before being stretched again to launch the frog into the air. The fore legs are folded against the chest and the hind legs remain in the extended, streamlined position for the duration of the jump. In some extremely capable jumpers, such as the Cuban tree frog (Osteopilus septentrionalis) and the northern leopard frog (Rana pipiens), the peak power exerted during a jump can exceed that which the muscle is theoretically capable of producing. When the muscles contract, the energy is first transferred into the stretched tendon which is wrapped around the ankle bone. Then the muscles stretch again at the same time as the tendon releases its energy like a catapult to produce a powerful acceleration beyond the limits of muscle-powered acceleration. A similar mechanism has been documented in locusts and grasshoppers. Early hatching of froglets can have negative effects on frog jumping performance and overall locomotion. The hindlimbs are unable to completely form, which results in them being shorter and much weaker relative to a normal hatching froglet. Early hatching froglets may tend to depend on other forms of locomotion more often, such as swimming and walking. Walking and running Frogs in the families Bufonidae, Rhinophrynidae, and Microhylidae have short back legs and tend to walk rather than jump. When they try to move rapidly, they speed up the rate of movement of their limbs or resort to an ungainly hopping gait. The Great Plains narrow-mouthed toad (Gastrophryne olivacea) has been described as having a gait that is "a combination of running and short hops that are usually only an inch or two in length". In an experiment, Fowler's toad (Bufo fowleri) was placed on a treadmill which was turned at varying speeds. By measuring the toad's uptake of oxygen it was found that hopping was an inefficient use of resources during sustained locomotion but was a useful strategy during short bursts of high-intensity activity. The red-legged running frog (Kassina maculata) has short, slim hind limbs unsuited to jumping. It can move fast by using a running gait in which the two hind legs are