Woola is the pet calot of John Carter and his family. A great beast, Woola once served as a guard-dog for the Tharks at Korad, and it was in this capacity that he first met Carter, when the green woman Sola assigned him to guard the virginian so that he would not escape. Korus, after all, was plagued by the white apes, and Sola feared for Carter's safety. Carter, however, mistook Sola's intentions and broke out, attempting to run away from the city, only to discover that Woola was almost as fast as he was. He leapt up onto a second-story window and was grabbed by a white ape. Before he knew what was happening, the ape had pinned him, while a cohort was preparing to smash his brains in with a great stone cudgel. But then Woola pounced upon the ape with the cudgel, tearing at its breast even as it attempted to choke the life out of the brute. Carter returned Woola's favor by smashing the monster's head in. He then defeated the other ape, whereupon he and Woola were discovered by the Tharks.
Later on, Carter, in a little experiment, wrapped an arm around Woola's neck and began to stroke his head as one would stroke the head of a dog. Woola, who'd never before experienced kindness, felt an immediate love for the Earthman, and thereafter became his loyal hound.
Woola would go on to become Carthoris's pet after John Carter is forced to leave Mars and then that of his younger sister Tara.