What Is a Silverback Gorilla? The Leader of the Group

Why are they called silverbacks?

As a male gorilla reaches adulthood, the short hair on his back turns silver-gray, forming a pale saddle that stands out against his dark coat. This change usually begins at around 12 years of age and marks the end of adolescence. The name “silverback” simply describes this feature.

The extent of the silver varies. In eastern lowland (Grauer’s) gorillas it is mostly limited to a saddle on the back, in mountain gorillas it often reaches the hips, and in western lowland gorillas it can spread onto the rump and thighs. At the same time, the male develops a tall bony crest on top of the skull, long canine teeth and massive shoulders and arms. A full-grown silverback weighs about 136–227 kg (300–500 lb), roughly twice as much as an adult female; see How much does a gorilla weigh?

What is a blackback?

Younger males that are physically mature but have not yet developed the silver saddle are called blackbacks. They are usually between about 8 and 12 years old. Blackbacks are bigger and stronger than females but lack the full size and status of a silverback.

Within a group, blackbacks often act as lookouts and backup protectors, staying at the edges of the group and joining in displays against threats. Many eventually leave the group they were born in to become independent males.

What does a silverback do?

The silverback is the center of the group’s attention. His roles include:

• Leading the group: he decides when the group wakes, where it travels and which feeding sites it visits, and the others follow his lead.
• Settling conflicts: when females or young quarrel, a silverback often steps in to stop the squabble, sometimes with a short grunt or a look.
• Protecting the group: he places himself between his family and danger, whether a leopard, people or another gorilla group. Silverbacks have been seen defending their groups even at great risk to themselves.
• Fathering offspring: he is usually the father of most of the infants in the group.
• Caring for the young: silverbacks are tolerant of infants, let them play nearby and protect them from rough treatment by other group members. Young mountain gorillas whose mothers died or left have been looked after by the silverback, even sharing his nest.

Females choose to join a male, so a silverback must be able to attract and keep them. Females that stay close to a strong male are better protected, especially from outside males that might kill their infants.

How do silverbacks show their strength?

A silverback usually avoids real fights by showing off instead. A full display can include hooting that gets faster and faster, standing up on two legs, throwing plants, beating the chest with cupped hands, a sideways run on all fours, tearing at vegetation and slapping the ground. Most charges stop short or swerve away.

Research on mountain gorillas suggests that bigger males produce deeper chest-beat sounds, so the noise may tell rivals and females how large a male is. Serious fights happen mainly when two groups meet or when a new male tries to take over, and can cause deep wounds from the canine teeth. For more about gorilla power, see How strong is a gorilla?

One silverback or several?

Gorilla group structure varies between species and populations.

• Western gorillas: most groups contain a single silverback, several adult females and their young. Young males usually leave home, then live alone or in all-male groups for several years before attracting females.
• Mountain gorillas: many groups contain more than one adult male. In the Virunga Mountains, roughly a third of groups have two or more silverbacks, usually a dominant male and a younger son, brother or other relative who is subordinate to him. The subordinate male may father some infants and can take over when the leader dies.
• Grauer’s gorillas: groups are usually led by one silverback, similar to western gorillas.

Multi-male groups can be an advantage: when the leader dies or grows old, another male can take over, so the group stays together and the infants remain protected.

What happens when a silverback dies or is replaced?

When the only silverback in a group dies, the group usually falls apart. The females and their young then join other groups or a lone male, and infants are at risk if an unrelated male takes over, because a new male may kill infants fathered by another. If another adult male is already in the group, he may take over as leader, and the group can carry on.

Silverbacks also grow old. An aging leader may gradually lose his position to a younger male, often one who grew up in the same group. On average, a mountain gorilla silverback in the Virungas holds the top position for only a few years, though some lead their groups for much longer.

Silverbacks in both gorilla species

Silverbacks lead groups in both gorilla species, the western gorilla of Central Africa’s lowland forests and the eastern gorilla of the eastern Congo, Rwanda and Uganda. Nearly all gorillas in zoos are western lowland gorillas, so a zoo silverback is usually of this kind, often with brownish hair and silver extending down onto the thighs.