Here's why:
* Competition for resources: Both rats and mice are highly competitive for food, water, and shelter. If they are in close proximity, they will likely fight over these resources.
* Territoriality: Both species are highly territorial, and males, in particular, will fiercely defend their territory against intruders, including those of the same species.
* Predator-prey relationship: While not always the case, rats are larger and more aggressive than mice. In some cases, rats may view mice as prey and attack them.
* Different social structures: Rats and mice have different social hierarchies. Rats live in large, complex social groups, while mice tend to live in smaller, more loosely structured groups. This difference can make it difficult for them to coexist peacefully.
However, there are some exceptions:
* Young animals: Young rats and mice may be more tolerant of each other than adults.
* Captive environments: In controlled environments like zoos or laboratories, rats and mice may be able to coexist if they are introduced carefully and have sufficient space and resources.
Overall, while rats and mice may occasionally share space, it's unlikely that they will be true friends. Their natural instincts and competition for resources make it more likely that they will conflict than cooperate.