Ernest Thompson Seton 
The Pacing mustang [EPUB ebook] 

Tales of animals are not accidentally so loved in many countries by adults and children. The heroes of the stories written by the famous Canadian writer Ernest Thompson Seton, and among them stands out for its originality the 'The Pacing Mustang’, are animals and birds. However, often their life and behavior are more exalted and noble than that of people.
A beautiful black mustang was a pacer, that is, when running, he moved first both right legs, then both left. The Mustang took home mares with him and they eventually got used to the wild life.