Riolu are sensitive to a special type of energy called Aura. Riolu's evolved form, Lucario(OMFG CAN'T WAIT!), can use these waves to attack, or study these waves to predict the movements of their opponents, and use them to track anyone. However, Riolu does not have the ability to fully use these powers, although it can still emanate these waves to communicate and sense them - albeit only in "ripples" as opposed to the "waves" of energy its evolution can sense and guide. Most notably, it cannot learn Aura Sphere or Detect naturally, two moves that Lucario learns that are often attributed to its aura powers.