The gorilla, Sully, has lived at the Ohio facility with her mother since 2019.
Staff at a US zoo received a surprise when a gorilla they believed for four years to be a male gave birth to a female baby gorilla. In a Facebook post, Columbus Zoo and Aquarium in Ohio announced that the gorilla, Sully, has lived at the facility with her mother since 2019 and was thought to be male until the gorilla care team discovered her holding the unexpected baby gorilla early Thursday.
"We have an adorable surprise to share with all of you today! Our gorilla family just got a little bigger with the unexpected birth of a female baby gorilla! But here's the other incredible part: our dedicated keepers recently discovered that the proud mom, who was initially believed to be a male, is actually a female gorilla. Talk about a surprise twist!" the zoo announced on Facebook.
As per the zoo's official blog, such a situation occurs because it can be difficult to tell the sex of a gorilla when they are young. "Until about age 8, males and females are about the same size, and they don't have prominent sex organs," the blog stated.
"As gorillas age, they become sexually dimorphic, meaning males and females look very different. However, males don't develop their characteristic large size, silver backs, and large head bumps (called sagittal crests) until age 12 or later," the zoo explained.
Sully was not born at Columbus Zoo, and her original carers maintained a "hands-off approach in their care," which may explain why her previous home thought the new mom was a male, the Columbus Zoo noted. When Sully arrived in Columbus, she was a "young and healthy animal" and didn't require any medical procedures that would have led to the discovery sooner, the zoo said.
The pregnancy was also missed because "gorillas rarely show outward signs" they are carrying because "newborns are smaller than human babies and gorillas naturally have large abdomens," the blog noted.
The zoo said that the infant appears to be a healthy female. "The veterinary and animal care teams have not yet approached the infant, giving them time to bond with one another and with the rest of the troop, but will conduct a wellness exam soon," the facility said.
Further, a DNA test will be performed later to determine the newborn's father. The new mother and baby will be on display for guests at the zoo's gorilla habitat starting Friday, according to the release.