Pittsburgh Zoo swaps gorillas with Boston, acquires infamous silverback Little Joe

The Pittsburgh Zoo & Aquarium is getting a new silverback — one with a storied past.

The zoo announced Thursday it is sending 7-year-old male western lowland gorilla Frankie to Boston’s Franklin Park Zoo and welcoming 33-year-old silverback Little Joe in return. The exchange is part of the American Association of Zoos and Aquariums’ Gorilla Species Survival Plan, which actively monitors gorillas living in human care and makes recommendations for social groupings based on genetics, age and housing availability.

Little Joe is no stranger to headlines. In 2003, he made national news when he escaped the zoo grounds and wandered through nearby streets in Boston’s Dorchester neighborhood, injuring a 2-year-old girl. The zoo made safety upgrades in the years that followed. The escape touched off a two-hour pursuit, drew large crowds of curious spectators and even included a rest stop at a bus stop on Seaver Street. In the two decades since, the gorilla has stayed put and built a very different reputation. His keepers now describe him as “curious, intelligent and gentle,” noting he gets along well with other gorillas and young offspring and is especially skilled at solving puzzle feeders to retrieve food.

Franklin Park Zoo announced in April that Little Joe would be leaving for a breeding program at an unnamed zoo, and Pittsburgh confirmed Thursday it is the destination.

Little Joe will become the silverback of the Pittsburgh Zoo’s gorilla family group, which includes females Moka, 29, and Ibo, 35, along with youngsters Charlotte, 3, and Bo, 2. A typical gorilla troop consists of one mature male, several females and their offspring. The move fills a void left by back-to-back losses: Ivan died in October 2024, and Harry died the following March, both from cardiac events.

Frankie, meanwhile, is headed to a situation better suited to his age. As young male gorillas mature, they reach a point where they’re too old to be juveniles but too young to be silverbacks, so they typically band together with other “blackbacks.” Keepers praised Frankie for his “good vibes” — described as playful and easygoing — before sending him off to a newly formed bachelor group at Franklin Park Zoo alongside two other male gorillas close to his age and size.

Visitors to the Pittsburgh Zoo shouldn’t expect to see Little Joe right away. Assistant mammal curator Karen Vacco said in a press release that keepers will work at the gorillas’ pace and comfort level when determining the right time for introductions.

“The best-case scenario is four to seven weeks,” she said, adding that keepers will focus first on building trust with Little Joe before moving to physical introductions with the troop. He will have visual access to the group throughout that period.

Once Little Joe becomes acclimated to his new family, zoo visitors will be able to see the full troop together in the Tropical Forest Complex.