Subscribe | UPI Odd Newsletter Subscribe SAPPORO , Japan, Oct. 2 (UPI) -- The Maruyama Zoo in Japan said zookeepers discovered repeated attempts to breed their two spotted hyenas were doomed from the start -- both animals are males. The zoo in Sapporo said the hyenas, Kamutori and Kami, were born to different sets of parents at the Daejeon Zoo in South Korea in 2008 and 2009 and they were given to Maruyama in 2010 as a gift celebrating the sister city relationship between Sapporo and Daejeon. Advertisement Kamutori was labeled as a male and Kami a female when they arrived at the Maruyama Zoo and zookeepers were initially encouraged by the pair's behavior, often cuddling and frolicking together. However, relations between the two animals became frosty in 2012 and they eventually had be separated in 2014 due to constant fighting. Officials said they performed some tests on the hyenas after they were separated and it was determined Sept. 26 that both animals are actually male. Experts said the sex of hyenas can be difficult to determine because females can grow "psuedo-penises," clitorises that are nearly the same size as a male's penis.