Zookeepers solved mystery of female monkey who got pregnant while alone in her cage

Japanese zookeepers were left baffled when they realised a female monkey was suddenly pregnant - despite apparently being left alone in her cage.

Back in 2021, a 12-year-old female white-handed gibbon called Momo was found to be with child.

This conception was initially perceived as miraculous by zookeepers of Nagasaki’s Kujukushima Zoo & Botanical Garden, because there had never been a male monkey in Momo’s enclosure… or so animal experts thought.

Momo's pregnancy was initially a mystery (Kujukushima Zoo and Botanical Garden)

It wasn’t until the endangered gibbon gave birth to her sweet offspring that staff began to poke around the situation, trying to come up with answers.

On social media, workers admitted that they weren’t sure who the father of Momo’s child was, while also confessing that testing the newborn had been impossible because of the mother’s protectiveness of Momo.

Taking to Instagram, the zoo explained: “Just so everyone wants to know ‘who's the dad’ hasn't been found out yet because we haven't done DNA testing, but we found out the gender is male.”

A miracle conception of the animal world? Not quite, because two years later, the zookeepers revealed just how Momo got herself in this situation.

Explaining why it took so long to solve the mystery, Jun Yamano, the superintendent of the zoo, said: "It took us two years to figure it out because we couldn't get close enough to collect samples - she was very protective of her child.”

Japanese animal experts were scratching their heads over the conception (Kujukushima Zoo and Botanical Garden)

Firstly, they carried out a DNA test on the baby, and discovered that its dad was Itoh, a male gibbon who was held in a separate enclosure.

But love knows no bounds, and a simple thing such as being housed in a separate unit was not enough to keep Momo and Itoh apart.

Yamano told Vice that staff believe the pair were able to mate due to an area next to Momo’s enclosure that both she and Itoh took turns using, while on display to the public.

The investigation found a tiny hole, measuring nine millimetres in diameter, in the board that separated that unit from Momo’s enclosure.

Although the zoo didn’t manage to capture any footage of the copulation, it’s thought the two gibbons were able to get it on while Itoh was inside the display area and Momo was next door on the other side of the hole.

Yamano went on to say that the mating and subsequent pregnancy was unprecedented at the zoo, as the gibbons are usually paired together intentionally after being introduced to each other.

They now plan to allow Itoh into the same enclosure as Momo and their baby, and have also fixed the pesky hole in the wall.