Here's why:
* Reproduction: Mice are prolific breeders, and females can have multiple litters per year.
* Protection: Living in groups provides safety from predators and allows for better access to resources.
* Social Hierarchy: Within a colony, there's often a hierarchy with a dominant male, who mates with the females.
So, while mice might sometimes be seen together, it's not necessarily a "pair" as we might think of a romantic couple. They are simply part of a larger social unit.