a migration
The mass movement of a group of people out of a country is an exodus.
If the movement is more or less en masse (all the animals move the same way at the same time), it's a migration. These can be either recurring or permanent. If some animals sort of wander off to establish new territories while others stay on the home ground, it's called radiation.
The group of animals called a hand are raccoon's. They are only called a hand when there are at least three of them in a group.
What group of animals are in a kindle? What group of animals are in a nide?
A group of Spiders is called a cluster or clutter. Spiders belong to the group of animals called arachnids.
A bale of animals is a group of turtles.
A group of Gerbils is called a clan.
A group of hares is called a down.
Animals in large groups have really interesting names. For example, a group of crows is called a murder, and a group of rhinos is called a crash. Kangaroos are commonly known as a mob, but some people call them a riot.
A group of whales.
A group of ravens.
I'm fairly certain that a group of newly hatched/born animals, of any kind, is called a brood.