This is Cali and Summer, two California Sea Lions (Zalophus californianus) at the National Zoo in Washington, D.C. Both rescued from wild populations (Summer was abandoned by her mother and Cali's mother died soon after Cali was botn), the two were raised by human keepers and so require a lot of care. They still play with each other nearly constantly, however, this shot taken during a sort of "King of the Rock" game.