Sully The "Male" Gorilla Surprises Zookeepers By Giving Birth To A Baby Girl

As magic tricks go, that's pretty good.


Rachael Funnell


Rachael Funnell

Digital Content Producer

Rachael is a writer and digital content producer at IFLScience with a Zoology degree from the University of Southampton, UK, and a nose for novelty animal stories.

Digital Content Producer

surprise gorilla baby

The baby (not pictured) went unnoticed as developing gorillas tuck neatly inside their mothers’ big abdomens.

Image credit: Nick Fox /

A gorilla in Ohio just pulled off a grand reveal that left zookeepers reeling when Sully the “male” gave birth to a baby girl. The birth was, understandably, not expected of the gorilla who was believed to have male reproductive organs, but marks a surprise win for a critically endangered species.

So, before we get on to that magic baby, how come nobody knew that Sully was a female?


“It’s hard to tell the sex of younger gorillas,” said the Columbus Zoo and Aquarium, which is home for Sully, in a release. “Until about age 8, males and females are about the same size, and they don’t have prominent sex organs.”

“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.”

Sully has been with the Columbus Zoo and Aquarium since arriving with her mother and fellow troop members back in 2019. She is eight years old, making her old enough to reproduce but still a little too young to be showing obvious signs of her sex.

To make matters even more confusing, gorillas don’t show outward signs of pregnancy in the same way that humans do. This is because baby gorillas are naturally much smaller than baby humans, and fit nicely into gorillas’ already large abdomens.


“The Dian Fossey International Gorilla Fund, which protects gorillas in their native lands, says its trackers are always happily surprised to see a newborn, because they have no way to tell that a baby is on the way,” said Columbus Zoo.

A pregnancy is therefore a surprise in itself, so throw in a sex-of-the-parent reveal and you’ve got yourself an eyebrow-raising twofer. It seems to have been a no-fuss arrival, with zookeepers having suspected nothing until they saw the “male” holding her new baby early on Thursday morning.

“We’re thrilled by the addition of another birth for this critically endangered species,” they said. “As the 34th gorilla born here since 1956 when the Columbus Zoo became the first zoo in the world to welcome the birth of a baby gorilla, she’s an important part of our work to conserve these magnificent animals.”

[H/T: TheMessengerNews]


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