Speaker 1: Welcome to brain Stuff, a production of I Heart Radio,
Speaker 1: Hey brain Stuff Lauren bog Obam. Here. Rabbits, grasshoppers and
Speaker 1: frogs share a special spring in their steps, but Australia's
Speaker 1: native kangaroo out hops them all. Aresa cotton tail rabbit
Speaker 1: against a red kangaroo, and the rue would leap ahead
Speaker 1: up to thirty five miles per hour or about fifty
Speaker 1: kilometers per hour, more than twice the top speed of
Speaker 1: the rabbit. In fact, these marsupials are the only large
Speaker 1: mammals to use this pogo stick styled locomotion. The tall, furry,
Speaker 1: red and gray kangaroos that we know best are part
Speaker 1: of the family macro pott Today. These macro Pottids are
Speaker 1: so named for their large hind feet. They're marsupials, like
Speaker 1: possums and koalas, which all carry their offspring and pouches. Today,
Speaker 1: more than sixty species of the macro potted family exist,
Speaker 1: including the large redd and gray kangaroos down to the
Speaker 1: palm saised musky rat kangaroo. Fossil evidence dating back million
Speaker 1: years has revealed that kangaroo ancestors did not hop At
Speaker 1: that time. Rainforests covered most of Australia, and these predecessors
Speaker 1: most likely fed from fruits and leaves and could climb trees.
Speaker 1: One existing species, the tree kangaroo, still inhabits parts of
Speaker 1: the rainforests in Papua New Guinea. As the continents climate
Speaker 1: heated up, though, the rainforests gave way to dry, grassy plains,
Speaker 1: guiding the ruse to their current terrestrial existence, and what
Speaker 1: better way to cruise the plains than by leaps and bounds.
Speaker 1: If you were to take a close look at a
Speaker 1: kangaroo's hind foot very carefully out assume you'd noticed that
Speaker 1: its toes aren't like ours. Kangaroos have an enlarged fourth
Speaker 1: toe on each foot, starting from the inside of the foot.
Speaker 1: The kangaroo's first toe is tiny and may not even
Speaker 1: be present. The second and third toes are small and
Speaker 1: appeared to be fused together, although there are separate nails.
Speaker 1: The fourth toe is at the center of the hopping action.
Speaker 1: The kangaroos leg bone aligns with this oversized digit, allowing
Speaker 1: it to propel the foot off the ground. According to fossils,
Speaker 1: this adaptation of the enlarged fourth toe preceded the kangaroos
Speaker 1: hop The fifth toe provides additional support and thrust for
Speaker 1: the hop as well. Traveling up the foot to the
Speaker 1: hind leg, we hit the powerhouse of the kangaroos hop.
Speaker 1: The strong elastic tendons and its legs store energy for jumping.
Speaker 1: Think about sitting on top of a spring. If you
Speaker 1: press your weight down to compress the spring as much
Speaker 1: as possible, you'll get a decent bounce when you relax.
Speaker 1: In the same way, whenever a kangaroo's feet hit the ground,
Speaker 1: its tendons compressed to gather elastic energy for the kangaroo
Speaker 1: to rebound. To stabilize that motion, the kangaroos sizeable tail
Speaker 1: acts as a counterbalance to its hind feet. If you
Speaker 1: watch a kangaroo hop in slow motion, you'll see that
Speaker 1: the tail moves down to almost meet the feet in
Speaker 1: mid air. As the marsupial lands, the tail rises again
Speaker 1: by transitioning from that horizontal position when the feet are
Speaker 1: on the ground to being quasi vertical during the hop,
Speaker 1: The tails downward thrust helps propel the kangaroo up. This
Speaker 1: counterbalance effect is similar to what happens when you ride
Speaker 1: a see saw. Put all of this together and what
Speaker 1: do you have the red kangaroo motors along at an
Speaker 1: average speed of fifteen to twenty miles per hour. That's
Speaker 1: about thirty two kilometers per hour. A single hop can
Speaker 1: propel it twenty five ft forward and six ft high.
Speaker 1: That's seven and a half meters forward and almost two
Speaker 1: meters high. Your backyard trampoline might be the closest way
Speaker 1: that you'll ever get to experience kangaroo travel. So what's
Speaker 1: the point of all of these ausee aerobatics. It's all
Speaker 1: about conservation. To figure out exactly why kangaroos hop, researcher
Speaker 1: Terence Dawson put rus on treadmills and measured their speeds
Speaker 1: and energy outputs. The result at higher speeds, kangaroo hopping
Speaker 1: ranks among the most energy efficient means of land travel
Speaker 1: in the animal kingdom. You see, when kangaroos speed up,
Speaker 1: they don't increase the frequency of their hops, but rather
Speaker 1: the range. The greater the range, the more energy they harness,
Speaker 1: and their muscles and tendons after they touched down With
Speaker 1: a heart twice as big as comparably sized mammals, a
Speaker 1: kangaroo has a naturally strong physical endurance, even their respiratory
Speaker 1: systems operate more effectively during this exercise. The motion of
Speaker 1: landing and jumping causes their stomach muscles to contract and expand,
Speaker 1: forcing air in and out of their lungs without expending
Speaker 1: extra energy to do so. At lower speeds, however, the
Speaker 1: efficiency drops off. When a kangaroo needs to graze or
Speaker 1: move slowly. It uses its tail as a fifth leg,
Speaker 1: balancing back on it, shifting forward with its smaller front legs.
Speaker 1: Referred to as pentapedal walking. The kangaroos don't walk on
Speaker 1: all fours because, except when swimming, they have trouble moving
Speaker 1: their hind legs independently of each other. But why walk
Speaker 1: when you can hop anyway? Today's episode was written by
Speaker 1: Christen Conger and produced by Tyler Clang. For more on
Speaker 1: this lots of other topics, you can hop around to
Speaker 1: visit how stuff works dot com. Brain Stuff is a
Speaker 1: production of I Heart Radio or more podcasts my heart
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