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Somehow, a zoo in Japan had no idea that a hippo they thought a male was actually female.
Japan's Osaka Tennoji Zoo took in a hippo named Gen-chan seven years ago and the paperwork said it was male.
They never checked until now.
The zoo says Gen-chan failed to make courtship calls to females and caretakers were never able to find boy parts.
They finally did a DNA test and discovered the truth. Officials say they won’t make this mistake again.