Welcome to brain Stuff, a production of I Heart Radio, Hey brain Stuff Lauren bog Obam. Here. Rabbits, grasshoppers and frogs share a special spring in their steps, but Australia's native kangaroo out hops them all. Aresa cotton tail rabbit against a red kangaroo, and the rue would leap ahead up to thirty five miles per hour or about fifty kilometers per hour, more than twice the top speed of the rabbit. In fact, these marsupials are the only large
mammals to use this pogo stick styled locomotion. The tall, furry, red and gray kangaroos that we know best are part of the family macro pott Today. These macro Pottids are so named for their large hind feet. They're marsupials, like possums and koalas, which all carry their offspring and pouches. Today, more than sixty species of the macro potted family exist, including the large redd and gray kangaroos down to the
palm saised musky rat kangaroo. Fossil evidence dating back million years has revealed that kangaroo ancestors did not hop At that time. Rainforests covered most of Australia, and these predecessors most likely fed from fruits and leaves and could climb trees. One existing species, the tree kangaroo, still inhabits parts of
the rainforests in Papua New Guinea. As the continents climate heated up, though, the rainforests gave way to dry, grassy plains, guiding the ruse to their current terrestrial existence, and what better way to cruise the plains than by leaps and bounds. If you were to take a close look at a kangaroo's hind foot very carefully out assume you'd noticed that its toes aren't like ours. Kangaroos have an enlarged fourth toe on each foot, starting from the inside of the foot.
The kangaroo's first toe is tiny and may not even be present. The second and third toes are small and appeared to be fused together, although there are separate nails. The fourth toe is at the center of the hopping action. The kangaroos leg bone aligns with this oversized digit, allowing it to propel the foot off the ground. According to fossils, this adaptation of the enlarged fourth toe preceded the kangaroos hop The fifth toe provides additional support and thrust for
the hop as well. Traveling up the foot to the hind leg, we hit the powerhouse of the kangaroos hop. The strong elastic tendons and its legs store energy for jumping. Think about sitting on top of a spring. If you press your weight down to compress the spring as much as possible, you'll get a decent bounce when you relax. In the same way, whenever a kangaroo's feet hit the ground, its tendons compressed to gather elastic energy for the kangaroo
to rebound. To stabilize that motion, the kangaroos sizeable tail acts as a counterbalance to its hind feet. If you watch a kangaroo hop in slow motion, you'll see that the tail moves down to almost meet the feet in mid air. As the marsupial lands, the tail rises again by transitioning from that horizontal position when the feet are on the ground to being quasi vertical during the hop,
The tails downward thrust helps propel the kangaroo up. This counterbalance effect is similar to what happens when you ride a see saw. Put all of this together and what do you have the red kangaroo motors along at an average speed of fifteen to twenty miles per hour. That's about thirty two kilometers per hour. A single hop can propel it twenty five ft forward and six ft high. That's seven and a half meters forward and almost two meters high. Your backyard trampoline might be the closest way
that you'll ever get to experience kangaroo travel. So what's the point of all of these ausee aerobatics. It's all about conservation. To figure out exactly why kangaroos hop, researcher Terence Dawson put rus on treadmills and measured their speeds and energy outputs. The result at higher speeds, kangaroo hopping ranks among the most energy efficient means of land travel in the animal kingdom. You see, when kangaroos speed up, they don't increase the frequency of their hops, but rather
the range. The greater the range, the more energy they harness, and their muscles and tendons after they touched down With a heart twice as big as comparably sized mammals, a kangaroo has a naturally strong physical endurance, even their respiratory systems operate more effectively during this exercise. The motion of landing and jumping causes their stomach muscles to contract and expand, forcing air in and out of their lungs without expending extra energy to do so. At lower speeds, however, the
efficiency drops off. When a kangaroo needs to graze or move slowly. It uses its tail as a fifth leg, balancing back on it, shifting forward with its smaller front legs. Referred to as pentapedal walking. The kangaroos don't walk on all fours because, except when swimming, they have trouble moving their hind legs independently of each other. But why walk when you can hop anyway? Today's episode was written by
Christen Conger and produced by Tyler Clang. For more on this lots of other topics, you can hop around to visit how stuff works dot com. Brain Stuff is a production of I Heart Radio or more podcasts my heart Radio visit the iHeart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.