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.
Enlightenment thinkers believed people should choose their own leaders.
Yes, they do. Democracy countries has their citizens vote their leaders.
Monkeys make good lookouts for any predator trying to stalk the antelopes.
Yes, they do. Democracy countries has their citizens vote their leaders.
By adult franchise.
because bad leaders would lead badly
No, these houses (Legislative Branch) choose their own leaders.
They don't, it's royal blood.
there is no why. animals do not choose their habits. They adapt to where they are.
a meeting of members or leaders or a political party tomake plans,choose candidates,or decide how to vote a meeting of members or leaders or a political party tomake plans,choose candidates,or decide how to vote