Gorillas live in groups called troops. Troops tend to be made of one adult male or silverback, multiple
adult females and their offspring. However, multiple-male troops also exist. A silverback is typically
more than 12 years of age, and is named for the distinctive patch of silver hair on its back, which
comes with maturity. Silverbacks also have large canine teeth which also come with maturity. Both
males and females tend to emigrate from their natal groups. For mountain gorillas, females disperse
from their natal troops more than males. Mountain gorillas and western lowland gorillas also
commonly transfer to second new groups. Mature males tend to also leave their groups and establish
their own troops by attracting emigrating females. However, male mountain gorillas sometimes stay in
their natal troops and become subordinate to the silverback. If the silverback dies, these males may
be able to become dominant or mate with the females. This behavior has not been observed in
eastern lowland gorillas. In a single male group, when the silverback dies, the females and their
offspring disperse and find a new troop. Without a silverback to protect them, the infants will likely fall
victim to infanticide. Joining a new group is likely to be a tactic against this. However, while gorilla
troops usually disband after the silverback dies, female eastern lowlands gorillas and their offspring
have been recorded staying together until a new silverback transfers into the group. This likely serves
as protection from leopards. All-male troops have also been recorded.
The silverback is the center of the troop’s attention, making all the decisions, mediating conflicts,
determining the movements of the group, leading the others to feeding sites and taking responsibility
for the safety and well-being of the troop. Younger males subordinate to the silverback, known as
blackbacks, may serve as backup protection. Blackbacks are aged between 8 and 12 years of age
and lack the silver back hair. The bond a silverback has with his females forms the core of gorilla
social life. Bonds between them are maintained by grooming and staying close together. Females
form strong relationships with males to gain mating opportunities and protection from predators and
infanticidal outside males. However, aggressive behaviors between males and females do occur, but
rarely lead to serious injury. Relationships between females may vary. Maternally related females in a
troop tend to be friendly towards each other and associate closely. Otherwise, females have few
friendly encounters and commonly act aggressively towards each other. Females may fight for social
access to males and a male may intervene. Male gorillas have weak social bonds, particularly in
multiple-male groups with apparent dominance hierarchies and strong competition for mates. Males in
all-male groups, though, tend to have friendly interactions and socialize through play, grooming and
staying together, and occasionally they even engage in homosexual interactions