Udyr uses the stance mechanic. His abilities all have a persistent effect which remain until he activates another ability. Each ability also has a temporary activation effect that occurs upon being cast; the temporary effect of each stance persists for its full duration even if Udyr changes stance again. Switching stances sets off a 2 second global cooldown.
All of Udyr's abilities have 5 ranks, but as Udyr can only gain a maximum of 18 skill points at level 18, he cannot ever max out all of his abilities. He may max three abilities (with the fourth only reaching its 3rd rank) or he may max two abilities (with the other two reaching their 4th rank).