Jontu eating lettuce | Courtesy of ST. Louis Zoo

Brookfield Zoo welcomed a new adult male silverback gorilla on Feb. 4 from the St. Louis Zoo, sending one of its adolescent male gorillas in exchange, the Chicago Zoological Society announced on Feb. 6.

Jontu, a 26-year-old western lowland gorilla, will spend the next several weeks off display in order to get familiar with his new home, his new animal care team and Brookfield Zoo’s five remaining gorillas, all female.

The group’s new silverback comes to Brookfield Zoo six months after the sudden death caused by cardiac arrest during a medical procedure of 42-year-old JoJo, who arrived at Brookfield Zoo in 2012 and sired three offspring, including Zachary, now 7 years old.

According to a press release announcing the gorilla swap, adolescent male gorillas like Zachary, known as “blackbacks” leave their “natal group.” Some set off on their own and seek out females to form their own family groups, while other blackbacks form what are known as “bachelor groups,” who travel together until individual males find their own breeding groups.

Brookfield Zoo’s new silverback, Jontu | Courtesy of ST. Louis Zoo

Zachary is destined to be placed with a bachelor group at St. Louis Zoo, which has two gorillas, including Joe, 25, and Bakari, 18. The move will result in a family reunion of sorts as Zachary is Bakari’s grandnephew.

“Since Zachary is unable to mate with any females at Brookfield, now is the right time to make this transition,” said Tim Snyder, vice president of animal care at Brookfield Zoo, in a press release.  “[Zachary] has a great opportunity to interact and learn important skills that are needed to become a successful leader from the silverbacks.”

According to the press release, the gorilla transfers were based on a recommendation from the Association of Zoos and Aquariums Gorilla Species Survival Plan. Western lowland gorillas are considered critically endangered species due to hunting, diseases, illegal pet trade and habitat destruction.

Experts estimate that there are about 300,000 western lowland gorillas living in west equatorial Africa. About 320 live in accredited North American zoos like Brookfield and St. Louis.

According to the press release, Brookfield Zoo’s female gorillas will still have access to their Tropic World: Africa habitat while Jontu settles in, although there may be times the habitat is closed to the public during that time.

The females will also have access to their night quarters, where they can choose to also spend time with Jontu.