Last November, while Fossey Fund gorilla staff were doing routine monitoring and protection of a mountain gorilla family led by 21-year-old silverback Noheli, the day started as usual, with the group’s females — Umuco, Ruhuka and Umwe — peacefully following the silverback. 

Everything seemed normal until the silverback revealed himself, and it wasn’t Noheli! Despite the group’s calm behavior, something significant must have occurred in the preceding days. Here is a look at the chain of events that led up to this surprise.

During the summer, we had noticed a sudden change in Noheli’s behavior. Actually, all of the gorillas in his group had seemed reserved and anxious, likely due to interactions and conflicts with neighboring groups. 

One such encounter, which was with Dushishoze’s group, clearly resulted in a violent fight, though we did not directly observe it. After this, Noheli’s females left him and Noheli traveled long distances, though he reunited with the females after a few days. By the end of September, the group actively avoided observers, with Noheli appearing distressed. We lost track of them on Oct. 10.

Fortunately, we rediscovered the group on Nov. 16. The atmosphere was calm, with the females – 34-year-old Umuco, 24-year-old Ruhuka and 23-year-old Umwe  –  seemingly relaxed. But, as the silverback revealed himself, we realized that he was not Noheli!  A replacement must have happened in the previous weeks, and a new silverback, identified as Matsiko, had taken over. The group was subsequently named after him.

Silverbacks work hard to form groups

Matsiko is an 18-year-old silverback who originates from the large and historic Susa group. He grew up in Igisha’s group after Susa’s group split in 2014 and then he became a solitary silverback in August 2019. 

Despite the challenges faced by the solitary life, about half of male mountain gorillas leave their natal group, as they aspire to form their own groups one day. It seems that Matsiko had succeeded in doing just this, while the group was out of our sight.

Silverback Matsiko took over after Noheli’s short-lived leadership.

So now Matsiko is a group leader and Noheli is again a solitary male, at age 21. Noheli’s earlier history is similar to Matsiko’s. He left his natal group at age 13 and then became solitary in August 2016. In August 2021, Noheli was spotted for the first time with the three females – Umuco, Ruhuka and Umwe  – and was able to form a group, but it was a short-lived leadership.

Fun facts:

• • We’ve observed that mountain gorilla groups formed by solitary males, in contrast to well-established multi-male groups, are more unstable and susceptible to changes. It takes many years for a group to reach stability and the Noheli-Matsiko transformation is another piece of evidence for this trend.

• • The name Noheli means Christmas –  he was born on Dec. 22, 2002. This past Christmas he spent his birthday alone but we sincerely hope to see him doing well again soon.

This article is part of a series presented by the Fossey Fund’s gorilla program Senior Advisor Veronica Vecellio, focusing on the mountain gorillas the Fossey Fund protects and studies every day in Rwanda. Veronica has worked with these gorilla families for nearly 20 years and shares her deep knowledge and insights about their lives.