This guy was studying rat and mice behavior, and he built what he called a mice utopia— a mouse city where the mice wouldn't need to fight for anything. First generation thrived, but subsequent ones got all sorts of fucked up.

It got overpopulated, some animals refused to leave their houses, they got depressed— there's a lot of conclusions to be drawn for it. But if this is a zoo then these missions and this supposed goal to save our universes is how they keep us from going insane, probably.