A zoo in southern Japan has been baffled for two years trying to solve a mystery: how could Momo, a gibbon kept alone in a cage, become pregnant?
The 12-year-old gibbon has lived in solitude with no companions. While it was evident that her neighbors included a few male gibbons, their enclosures were separated by sturdy bars and barbed wire fences, making it implausible for Momo and any male gibbon to quickly mate by overcoming two layers of protection, a scenario dismissed by zoo management. In 2021, Momo gave birth to a male gibbon (yet to be named), featuring black hair and a white coat neatly surrounding its face.
Momo with her baby
Finally, the mystery was unraveled with the help of DNA testing. The caretakers at the Nagasaki zoo identified the father of the baby gibbon and discovered how the parents met.
After enlisting a researcher to analyze DNA from fecal and hair samples collected last year from six gibbons: Momo and her baby, along with four potential male contenders in the race to be the “father of the child”, the Kujukushima Botanical Garden and Zoo announced the identity of the baby’s father on Tuesday: Itoh, a nimble 34-year-old gibbon.
“It took us two years to decode this mystery, simply because we couldn’t easily approach to collect DNA samples – Momo was very protective of her baby,” said zoo director Jun Yamano.
While the identity of the father has been established, another pressing question remains: if Momo never had direct contact with Itoh, how did she become pregnant in the first place?
The zoo lacked clear evidence such as surveillance footage, but Yamano speculated that the gibbons’ point of contact was likely a hole in the wall measuring just 9mm in diameter.
At the zoo, Momo and Itoh took turns showing off for visitors during morning and afternoon sessions in the same exhibition area right in front of Momo’s cage; these two spaces were separated only by a partition – a perforated board – intended to prevent the gibbons from getting too close to each other.
However, if there’s a will, there’s a way.
“We believe that it’s possible that on a day when Itoh was confined in the exhibition area, he and Momo engaged in mating through one of the holes in the partition,” Yamano said.
And Itoh, the father of the baby
Such mating habits have never been documented before, Yamano noted. Typically, zoos arrange pairings for gibbons after a series of trials and errors to help the gibbons become familiar and truly bond with each other.
In the wild, gibbons choose mates based on criteria such as appearance, social behavior, and vocalizations, often through complex songs they perform. The zoo did not disclose any further information about how Itoh may have “wooed” Momo (if at all).
Since the mystery has been solved, Yamano stated that the zoo hopes to move Itoh to live with Momo and their child.
“All three will need to get acquainted first, but we hope they will live together as a family,” the zoo director said.
To prevent a similar story from happening again, the zoo has replaced the aforementioned perforated board with a barrier that has no openings at all, Yamano added.
