Gorillas are animals that live in a troop. Which is to say that a single male assures protection and reproduction for a group of females, obliging their male offspring to leave the troop, when they reach sexual maturity, perhaps from 10 to 13 years old.
When these young leave the troop, they cannot live alone, so they then form a troop of males. When the situation so permits, one of them leaves it to usurp an older male and start his own family. In Zoological gardens, this changeover is allowed to happen. Entities such as the Amnéville Zoo welcome males coming from breeding at other zoos and when one troop of females becomes vacant in Europe, one of our males goes there to take up his role.
Gorillas have shown us on many occasions, whether in Zoos or in the wild, their ability to choose and employ tools to achieve their ends. All the large primates do not know how to swim, but gorillas of the western plains have been filmed while using sticks of their same size and testing the bottom of watering holes, while standing on hind legs, thus to determine their depth and wade in without drowning.