Friday 22 April 2016

When Silverbacks Kill Babies

Conflict between gorilla troops is rare, unlike chimpanzees and other monkeys, because they are not territorial. If two groups happen to meet there is a lot of chest-thumping, charging and other dramatic displays of dominance but rarely any physical contact. Avoidance is the main strategy.

During such a meeting females may try to defect to a new group, which may be prevented by the silverback leader. Defectors can be harassed by related senior females from the group they joined. The silverback leader may intervene by calming the situation down; he usually does not take sides. His interest is to limit the damage as disruption of social harmony may cause females to migrate.

Sex and dominance are only loosely linked, though competition among silverbacks can centre around females, initiated by the male who doesn’t have any. Attitudes of established leaders towards their mates vary from protective dominance when younger and complete tolerance when older.

Genetic studies have shown that the leader does not sire all the troop’s children (85%); the second-in-command, if there is one, is responsible for the balance. However once they have established a position they brook no opposition. If challenged by a younger or even by an outsider male, a silverback will scream, beat his chest, break branches, bare his teeth, and then charge forward.

If the leader is killed by disease, accident, fighting or poachers and there is no other silverback, the group will split up, as they disperse to look for a new protective male. There is a strong risk that the new male leader, if it is a new silverback, will kill the infants of the deceased. Uncertainty is created when a female has mated with more than one male, which preserves her children.

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