In the book, Tab is a male cat (but he is female in the movie) who taunts his prey. He also has a sort of goal to kill Hazel, and has somewhat of a rivalry towards him. When Hazel and Pipkin were trying to steal a couple of hutch rabbits, Clover, Boxwood, Haystack, and Laurel from the farm, Tab and his farm cat companions scouted them out. Pipkin was the first rabbit to see him, do to his keen sense of vision. However, Hazel taunted Tab, leading them to escape.
Later during the Battle of Watership Down, after Hazel released the guard dog, Bob, Tab went after Hazel, seriously injuring him. However, the cat's owner, Lucy, found and saved Hazel's life. This made Tab's hatred towards the rabbit grow. In the book, Tab is allied with the Nuthanger Farm's guard dog, Bob. There is also a female cat in the book, from Nuthanger Farm, who's name is unknown. This unnamed cat got into a fight with Bigwig and lost, with minor injuries. This cat is often mistaken for Tab.
In the animated series, Tab is characterized as a female cat, known as Tabitha.