S'Latch explains to Rick that from time to time, a Sleestak is born with the traits of their ancestors, such as he had been, who were usually cast out by the Sleestak tribe, considered a "freak" by the others. The "Sleestak Leader", introduced at the end of Season Two and featured prominently in the show's final season, must've been born in that manner also, but seems to possess only a limited portion of S'Latch's inherited traits, possibly explaining why the Sleestak accept him as their Leader.
Rick learns from S'Latch that the Sleestak call Big Alice, the Allosaurus: Salima, meaning "Protector," because she protects their unhatched eggs from other predators.