Usually through battles of strength. A potential leader would challenge the head of the troop, and they would fight until either one of them was defeated. But i do not know if proboscis monkey does. (not confirm yet)
They choose their leaders according to their bodies size.
Elections.
Yes, they do. Democracy countries has their citizens vote their leaders.
Enlightenment thinkers believed people should choose their own leaders.
Monkeys make good lookouts for any predator trying to stalk the antelopes.
By adult franchise.
Yes, they do. Democracy countries has their citizens vote their leaders.
because bad leaders would lead badly
They don't, it's royal blood.
No, these houses (Legislative Branch) choose their own leaders.
there is no why. animals do not choose their habits. They adapt to where they are.
democrocay