How a gorilla swap between St. Louis and Chicago may ensure the species’ survival

By Emily Woodbury

Published February 10, 2023 at 5:24 PM CST

Western lowland gorilla Zachary is 7 years old. He recently was moved from Brookfield Zoo in Chicago to St. Louis Zoo.

Western lowland gorilla Jontu is 26 years old. He recently moved from St. Louis Zoo to Brookfield Zoo in Chicago.

Two western lowland gorillas — Jontu of St. Louis Zoo and Zachary of Brookfield Zoo in Chicago — recently swapped homes. The move marks a major milestone for Jontu, who, at 26 years old, will now be the leader, or “silverback,” of the gorilla group at Brookfield.

“They were looking for a silverback dominant male to lead their family group [at Brookfield],” said Helen Boostrom, zoological manager of primates at St. Louis Zoo. “Zachary is related to all the females there, and also, he's just too young to lead a family group.”

For 7-year-old Zachary, the St. Louis Zoo offers a chance to grow up and develop social connections with other gorillas in a bachelor group. “And that's very similar to what would happen to gorilla males in the wild,” Boostrom added.

Zachary arrived in St. Louis last week, and Boostrom said he’s still settling in.

“It’s a very slow integration process,” she said, adding that they are taking cues from Zachary to determine when he will be fully integrated into the group.

Boostrom joined Friday’s St. Louis on the Air to talk about how the recent gorilla swap plays into the goal of creating genetically healthy populations of the critically endangered species.

Listen: Why St. Louis Zoo and Brookfield Zoo exchanged gorillas

The Species Survival Plan for the western lowland gorillas, led by the Association of Zoos and Aquariums, involves keeping track of the family histories and relatedness of zoo gorillas in the United States.

“We hold workshops, and we communicate amongst each other all about the different personalities … looking at both the genetics and at those individuals and what groups they may fit in best … and they make recommendations based on that,” Boostrom said.

For Jontu and Zachary, “it just kind of worked perfectly,” she added.

“St. Louis on the Air” brings you the stories of St. Louis and the people who live, work and create in our region. The show is produced by Miya Norfleet, Emily Woodbury, Danny Wicentowski, Elaine Cha and Alex Heuer. Avery Rogers is our production assistant. The audio engineer is Aaron Doerr. Send questions and comments about this story to talk@stlpr.org.