KUALA LUMPUR, April 25 -- A zoo in Osaka, Japan has after seven years found that its male hippopotamus is actually a female.

According to the Osaka Tennoji Zoo's website, the zoo conducted a DNA test after zookeepers noticed that the hippo called Gen-chan did not show typical male hippo behaviour.

The 12-year-old arrived in Osaka from Mexico in 2017 when she was five and customs documents at that time declared she was a male.

The statement said Gen-chan first arrived at their zoo from the African Safari Animal Park in Mexico when she was five and her reproductive organ could not be visually confirmed.

"The zookeepers, however, got suspicious as the hippo got older and could not visually identify male reproductive organs.

"We will kee...