The Ba'ul were a species that preyed on the Kelpiens, a pre-warp species native to Kaminar. They relied on the Kelpien residents of the planet willingly submitting to their harvests.
The Ba'ul were more technologically advanced than the Kelpiens, harvesting Kelpiens who had reached the vaharai from their packs using flying ships. Pieces of technology were known to fall off these ships during the harvest, but it was forbidden for Kelpiens to keep them. (ST: "The Brightest Star")
While this was not stated outright, the Ba'ul fit the predator role said to exist in the binary predator-preyspecies map of the planet.