A DNA test was carried out on 12-year-old Gen-chan after zookeepers noticed that the wallowing giant did not display typical male hippo behavior of splattering faeces around while defecating with a propeller-like tail motion in order to mark territory nor was it making courtship calls to female hippos.

A zoo in Japan confirmed Tuesday that a hippopotamus thought for seven years to be a he is, in fact, a she.

A DNA test was carried out on 12-year-old Gen-chan after officials at Osaka Tennoji Zoo noticed that the wallowing giant did not display typical male hippo behavior of splattering faeces around while defecating – with a propeller-like tail motion – in order to mark territory.

Gen-chan came to Osaka in 2017 from the Africam Safari animal park in Mexico. Officials at the time attested on customs documents that the then five-year-old was male.

The Osaka Tennoji Zoo confirmed the news about Gen-chan’s actual sex in a post published on their website.

The post said Gen-chan was declared as a male when she first arrived at their zoo from Mexico. The statement added that because the hippo was still a calf at the time, they did not question the documents.

But zookeepers got suspicious as Gen-chan got older and they could not visually identify male reproductive organs, a dangerous task in such a large and potentially aggressive beast.

A spokeswoman for the Osaka Tennoji Zoo told the AFP news agency on Tuesday that typical male hippo behaviour that Gen-chan was not displaying included making courtship calls to female hippos, or scattering faeces around while defecating with a propeller-like tail motion in order to mark territory.

According to the Mainichi newspaper, the zoo’s vice director Kiyoshi Yasufuku said: “We recognise the importance of confirming the sex, and we want to ensure that such mistakes will not happen again.”

“We will keep doing our best to provide comfortable environment to Gen-chan, so everyone, please come and see,” the zoo added, while confirming that the animal will not be getting a name change.