Company for Rats
Rats are sociable animals, and should be kept in the same sex (female) pairs or groups. It is recommended that you buy your rats at the same time as it is easier to introduce them to each other. A Rat which is kept alone will need lots of attention from you.
Male rats tend to fight with each other, so should not be kept together.
Lifespan
The average lifespan for a Rat is between two and four years.