One of the mountain gorilla groups monitored every day by Fossey Fund staff and which has been stable for many years, is starting to exhibit interesting changes. The group – named after the late silverback Ntambara – has been thriving under the leadership of silverback Twibuke since 2015.
At top: Dominant silverback Twibuke. Above left, brother/second-ranking silverback Inkumbuza and lower-ranking Umuganda.
But now, his younger brother Inkumbuza is showing a greater interest in gaining power. He turned 19 in July and his impressive size is attractive to females and youngsters, as it suggests he can provide protection from outsiders and potential dangers. Inkumbuza has already been helping Twibuke keep the group safe and strong.
The group also has a third silverback – Umuganda – who has been quietly observing the dynamics of the older males and playing a role in keeping the group cohesive and entertaining the youngsters. We know from our studies of growth and development that he is unusually small for his age (15), which likely is the reason for his lower level of power.
Females play a role in male power
On the female side, high-ranking female Tegereza and younger females Kurinda, Nsanganira and Urahirwa remain loyal to Twibuke but are developing their relationships with Inkumbuza, often engaging in physical contact with him, which is a significant bonding action.
This growing attention from the females has likely made Inkumbuza more ambitious. Currently, Twibuke is winning all disputes, but Inkumbuza doesn’t give up easily, as indicated by the superficial wounds all over his body. These suggest frequent physical fights, although Twibuke’s responses seem more like warnings than real threats so far.
Silverback Inkumbuza and female Urahirwa enjoy some grooming time, while the almost 2-year-old Turikumwe cannot sit still!
The rising dominance of Inkumbuza is noted by the females, who sometimes seem confused about whom to follow. When Inkumbuza initiates group movements, most females and youngsters follow him. Twibuke doesn’t seem disturbed by this and seems to accept spending more time alone. However, when Inkumbuza’s actions become too bold, Twibuke intervenes to stop him.
A strong but evolving relationship
Inkumbuza and Twibuke have always lived together and have a strong relationship. They were both born in the former Shinda’s group, which split after the death of dominant Shinda, their father. Twibuke, now 26, has been in charge of this group for about nine years and has done a great job ensuring the group’s stability in terms of composition and range.
In fact, the group still uses the area that was historically used by Shinda’s group, on the slopes of Mount Bisoke, which is not often visited by other groups. That means interactions with other groups are infrequent, though they do occur sometimes. For example, there was a recent interaction with Segasira’s group, and both Twibuke and Inkumbuza seemed intimidated by silverback Segasira. After a few hours of loud screaming, displays and physical fights, Twibuke decided to move away but Inkumbuza was determined to keep facing the opponent.
To protect the group, Twibuke had to forcibly drag Inkumbuza away, which involved biting him. This incident showed Twibuke’s mature leadership in minimizing risks, while Inkumbuza wanted to continue to challenge the opponent despite the consequences. It was interesting to see Twibuke teaching his younger brother a hard lesson.
It is normal in gorilla families to observe conflicts among males. While most are just occasional, some may lead to dominance challenges or to one male leaving the group. Ntambara’s group provides another opportunity to learn how hierarchy is maintained, which often results in better protection for the entire group.
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 20 years and shares her deep knowledge and insights about their lives.
Join our newsletter and
receive exciting updates
from the field, exclusive offers,
and gorilla photos!
