Banded mongooses live together in big troops. Unlike most troops of animals, the young don’t venture off into the world to find or found troops of their own. There are consequences to families staying together, and the mongoose avoids them in a way we still don’t understand.
Plenty of social animals have ways to police each other's behavior — so that if an animal enters the wrong territory or reproduces when it's not supposed to, it's punished. But researchers have found that banded mongooses have a more repressive system, which forces all females to give birth at the same time. Or else.