Rats are actually very good with other pets, provided they are socialised well and kept healthy. More often than not, it’s how the other pets socialise with the rats which determine whether you as the owner can let them play together.
Rats and More Rats
Having two rats is better than one. It keeps them socialised and happy. The main point of concern is introducing the two animals since they can be territorial. For this reason it is important to introduce them in neutral territory so that one does not feel it has to defend its territory against the other.
Rats and Cats
Cats can be either really good or really bad with rats. My sister has a cat that always tried to get into the rat cage and therefore had to be kept separate (and eventually gave away the rat). I have also heard other cases where the cat and the rat got on amazingly, however it is still important to always monitor the two when they are together since there is always that off chance that the cat may try to be a little too aggressive, even if it was only playing.
Rats and Dogs
Dogs are similar to cats in the threat they potentially pose. Always be careful when introducing the two since that will determine the beginning of the relationship. If the two are friendly that is great, the only concern that you may have is that if it’s a big dog it could crush the small rat by accident. So like the cat, always monitor the two together.
Rats and other small animals
Rats get along well with most small animals. It’s similar to the rat-on-rat relationship in the way that one is not huge compared to the other, like a dog or cat. I have even heard of people keeping rats and guinea pigs in the same cage (which I do not recommend personally).
Rats are social animals and the best animal companions you can give them is yourself and other rats. If they do not get along with your cat/dog you may need to keep them separate but this is of course a case by case basis. Good luck!
For more information on how to train a rat Click Here,