The Kujukushima Zoo and Botanical Garden Mori Kirara in Sasebo City, Japan, Zookeeper, Nagasaki Prefecture, said they were surprised when a lar gibbon gave birth.
Momo had been living in her own enclosure in the zoo, without any males present.
They also recanted that Momo was protective of her offspring.
So it took two years before the zookeepers were able to collect enough stool and excrement samples from the mother and baby to perform DNA tests.
They found out that the father of the male baby was found to be a gibbon.
Itou, who is 34-year-old was never on display together with Momo.
Zookeepers explained that the apes managed to mate through one of the holes that they found.
They discovered that the partition between Momo’s exhibit and the back yard where Itou was kept while off-display had a perforated board with holes about .35 inches in diameter.
The board has now been replaced by a solid steel plate. Officials said they are now planning to attempt to introduce Itou and Momo officially so they and their child can live as a family.