One of the things I love most about rats is that they are such happy, enthusiastic creatures. They seem to cherish every second spent playing with their humans or rat companions, exploring or causing trouble. One of the easiest ways to give a rat more opportunities to enjoy life is to make sure it has another rat to live with. It saddens me a great deal that many rats live alone simply because their owners do not know that they are far happier with company.
Rats are highly social animals which gain a great deal of enjoyment and stimulation from each other's company. It just isn't natural for them to live alone. Rats play, groom each other, and cuddle up to sleep together, keeping each other warm. They also communicate by touch and smell, and by sound at frequencies we can't hear. No amount of human attention can entirely replace the company of another rat. Even though rats love their humans, having your own human plus a rat friend is always preferable to just having your own human!
Rats with company live more full and active lives than those kept alone. There are many experiences open to them which the single rat simply cannot have. And no matter how much attention a person gives a single rat, she will not be available 24 hours a day and willing to play in the middle of the night when rats are at their most active. Rats are just too intelligent and easily bored to be left alone when they want to play. Although some rat books say that it is "acceptable" to keep a rat alone, most pet owners want the best lifestyle they can give their rat, not one that is merely acceptable.
Occasionally a rat will be too aggressive to live with another. Males who are often used for stud or who weren't introduced to a companion when young, may fall into this category. In some cases there is little alternative to keeping them alone. But in many cases, all that's required is a more gradual introduction process or neutering. Most rats are not so vicious that they need to be kept in solitary confinement! Why on earth would anyone settle for just one rat when they could have two?! Two rats are no more work than onein fact, they can be less demanding because they keep each other amused. You don't need to feel guilty if one day you can't let your rats out to play. A single rat lives for his daily freedom, but a pair of rats can entertain themselves for the odd day.
Some people think that only a single rat will truly bond to humans, but anyone with a group of rats who plays with them regularly knows this is nonsense. As long as each rat gets some individual attention, they will bond strongly to their human. Others think that you can introduce rats only as babies. But as long as you use care, adult rats can be successfully introduced to new babies or adults.
So please remember two is better then one