Rukus is good friends with Runk.
Rukus was with Rogon and Runk in the episode Warrior Within, when they were forced to detuor by Gorzan. Rukus and his friends were not too happy.
Rukus was also seen in episode 4 Joy Ride, while play-fighting with his buddy Runk. He and Runk had to explain to Lagravis how Rhinos like to fight for fun as friends.
In Legends of Chima Online, he is a boss in the Dismal Bog dungeon, along with Runk. They were hired by the Crocs to guard Reegull.
Rukus has the traditional Rhino blue kilt and black belt, just like Rhigor and Rogon. His horn has darker scratches on the tip, suggesting he has had some tough battles, or mabye just smashed a hard rock.