For the Lone Ranger serials, the producers did not want the confusion of two white horses on screen. They gave Tonto a paint horse, but still called him White Feller. That alteration led the radio show producers to change Tonto's horse to Scout.
For a long time, Tonto rode White Feller on the radio. In "Four Day Ride" (August 5, 1938), the Lone Ranger and Tonto work to avoid an indian war. They are under a deadline and to make it in time, the horses have to be pushed to their limits for four straight days. At the end of this mission, White Feller has pushed himself so hard that he will likely never be the same again. Tonto is given a paint horse by his friend Chief Thundercloud, who then takes White Feller. The paint horse is later named Scout.