I jump when I walk and sit when I stand. What am I?

The animal in question is a kangaroo, a creature uniquely adapted to its environment. When a kangaroo moves, especially at higher speeds, it doesn't walk in the traditional sense like most four-legged animals. Instead, it propels itself forward by rhythmically leaping or hopping on its powerful hind legs. This distinctive form of locomotion is incredibly energy-efficient for covering vast distances across the Australian landscape. Even when moving slowly, a kangaroo employs a "pentapedal" gait, using its forelimbs and its strong tail to form a tripod, pushing off the ground to bring its large hind legs forward in a coordinated, almost jumping motion.

This remarkable marsupial also "sits" when it stands by utilizing its robust, muscular tail. When a kangaroo is upright, whether resting, observing its surroundings, or even engaging in a boxing-like confrontation, its tail acts as a crucial third leg, forming a stable tripod with its two hind feet. This allows the animal to maintain balance and support its substantial body weight, effectively leaning back and "sitting" on its tail without needing to lie down.

Kangaroos are the only large mammals that primarily use hopping for movement, a strategy that enables them to reach impressive speeds of up to 70 kilometers per hour (43 miles per hour) and cover significant ground with each bound. Their tails are not merely for balance; they are so strong that they can provide as much propulsive force as their front and hind limbs combined during slow movement. These fascinating adaptations highlight the kangaroo's specialized evolution, making it perfectly suited to its unique niche.