Two young male western lowland gorillas have moved into the Saint Louis Zoo. Gus, 10, and Bukavu, 8, arrived from the Fort Worth Zoo in early July 2026 on a transfer recommendation from the Association of Zoos and Aquariums Western Lowland Gorilla Species Survival Plan, and they will join the zoo’s bachelor troop at Jungle of the Apes.
The pair spent their first weeks behind the scenes. Waiting for them are 10-year-old Zachary and 10-year-old Kayin, the two males who already make up the troop.
Why a zoo keeps a troop of males together
A bachelor troop is not a holding arrangement. It is a copy of something gorillas do on their own.
Young males leave their birth group at roughly the age Gus and Bukavu are now. In the forests of central Africa they do not strike out alone: they fall in with other males and travel together, sometimes for years, until one of them is mature enough to attract females and start a family group. Those traveling parties include full silverbacks, the older males named for the saddle of pale hair that comes in across the back at about twelve.
So a zoo bachelor troop is where a male gorilla learns to be a gorilla among gorillas. It is also, in practical terms, how the North American population works. Every family group needs one adult male, which leaves a surplus of young males with nowhere obvious to go, and a well-run bachelor troop keeps those animals in good social company and ready to lead a family later.
What the Species Survival Plan is deciding
A Species Survival Plan is a breeding and transfer program run across AZA-accredited institutions for a single species. Its working document is a studbook, an animal-by-animal pedigree covering every individual in the managed population, and the recommendations that come out of it are about genetics first: which animals should breed, which should not, and who should move where.
Gus and Bukavu’s move is the second kind of recommendation. Nothing about it is a breeding decision yet. It places two juveniles in the right social setting at the right age, in a troop the Saint Louis Zoo has the space and the staff to run.
How endangered are western lowland gorillas?
Seriously endangered. The IUCN Red List assesses the western gorilla as Critically Endangered under criteria A4bcde, in an assessment published in 2018 as an amendment to a 2016 review, with the population trend listed as decreasing. Western lowland gorillas are the subspecies most people have seen, and they are the most numerous of the gorillas, which is a statement about the other gorillas rather than a reassuring one about these.
Commercial hunting for meat and the spread of Ebola have driven most of the decline, and both act fastest in the places that are easiest to reach. The zoo supports the species through the SSP and through its own WildCare Institute Center for the Conservation of Congo Apes.
Other institutions are working the same problem from the birth side. Zoo Antwerpen reported a western lowland gorilla born to its family group earlier this year.
When can you see them?
The zoo said the two would make their public debuts at Jungle of the Apes later in the summer, after settling in behind the scenes. Gus and Bukavu will be easy enough to pick out once all four are together: at eight and ten, every male in this troop is still a blackback, and the silver will not arrive for a few years yet.
Quick answers
- Why does the Saint Louis Zoo have a bachelor troop of gorillas?
Young male gorillas leave their birth group in the wild and travel with other males until they are mature enough to lead a family. A bachelor troop copies that, and it gives the surplus of young males in the managed population good social company.
- How old are Gus and Bukavu?
Gus is 10 and Bukavu is 8. They join 10-year-old Zachary and 10-year-old Kayin in the troop at Jungle of the Apes.
- Where did the gorillas come from?
The Fort Worth Zoo, on a transfer recommendation from the AZA Western Lowland Gorilla Species Survival Plan.
- Are western lowland gorillas endangered?
The IUCN Red List assesses the western gorilla as Critically Endangered, with a decreasing population trend, in an assessment published in 2018 amending a 2016 review.
