"The Most Advanced Quadruped Robot on Earth -- BigDog is the alpha male of the Boston Dynamics family of robots. It is a quadruped robot that walks, runs, and climbs on rough terrain and carries heavy loads. BigDog is powered by a gasoline engine that drives a hydraulic actuation system. BigDog's legs are articulated like an animal’s, and have compliant elements that absorb shock and recycle energy from one step to the next."Check it out and watch the BostonDynamics video. Pretty cool and surprising. Your tax dollars at work!
p.s. But a gasoline engine?