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One of three weeks old lion twins walks around in a cage at the Fuji Safari Park in Susono, at the foot of Mt. Fuji, southwest of Tokyo, Monday, July 13, 2015. Three days into the debut, the twin toddlers snarl, yawn, and sleep delighting the visitors. (AP Photo/Koji Ueda)

One of three weeks old lion twins walks around in a cage at the Fuji Safari Park in Susono, at the foot of Mt. Fuji, southwest of Tokyo, Monday, July 13, 2015. Three days into the debut, the twin toddlers snarl, yawn, and sleep delighting the visitors. (AP Photo/Koji Ueda)