A gorilla at Gladys Porter Zoo gave birth to a baby late last month, surprising staff, zookeepers, and veterinarians who thought Penny was unable to conceive.
Penny the gorilla has a tumor over her pituitary gland which interacted with her ability to conceive. Doctors diagnosed Penny with the adenoma — which produces excessive prolactin — nearly a decade ago.
“Prolactin is the hormone that encourages lactation for the breasts to produce milk. In some way it’s part of the feedback mechanism as to why some women don’t get pregnant when they’re nursing, but not always,” said the zoo’s senior veterinarian Dr. Thomas DeMaar.
Penny’s baby, who has yet to be named, was born on Aug. 20. The zoo’s nightkeepers discovered the gorilla with her newborn and reported that Penny was holding the baby in the correct position, DeMaar said.
The zoo plans to hold an online auction to be announced in the near future where donors can bid to select the baby gorilla’s name.
The newborn isn’t Penny’s first child, though zoo staff fully expected that she would not give birth again. Ten years ago when the zoo treated Penny for her pituitary condition, the gorilla gave birth to a daughter, Samantha, after one dose.
“Samantha grew up and weaned. We tried to treat Penny again and she did not get pregnant. And then we treated her again at an augmented dose and she still didn’t get pregnant. Then we said well, that’s what we can do. That’s about as far as you can take that.”
The condition also exists in humans. As DeMaar explained, a woman could keep trying with the drug to conceive. Zoo staff decided to simply leave Penny be.
“That’s where it was left. What we learned is that sometimes these pituitary gland tumors will do what’s known as wax and wane. The level of hormone can vary. And so it must have been that her hormone dropped due to forces we had nothing to do with,” said the vet.
Penny was living with a male and as staff believed her to be infertile, she wasn’t on birth control. The rest is history.
According to zoo staff, the baby is healthy and Penny is doing well caring for her newborn.
“We know that Penny already raised a baby by herself earlier. She knows what to do. In addition, she is in a family group, so she has seen several young offspring. Two females both have babies who are now several months old,” said DeMaar.
“There’s innate behavior but there’s also learned behavior. She appears to be a very good mother.”