There are over 60 species of rat in the world, and they are all different in size. However, many of them are between 5 inches and 7 inches long. As you may know, the smaller the animal, the lower their life expectancy. That fact is mainly due to the number of beats their heart makes in a minute. For example, it is not uncommon for a rat‘s heart to beat over 300 times a minute. When you compare that to a tortoise, whose heart only needs to beat around 6-8 times a minute, it is easy to see why rats do not live that long.
Therefore, the larger species of a pet rat, the longer they are likely to live. Furthermore, captive rats will live longer than wild rats, for a few reasons. For example, they are less likely to get diseases, and they do not have to scavenge for food to eat. The average lifespan of a pet rat is 2-3 years. Although, it is not uncommon for some to live up to 7 years old. As we have already pointed out, the larger the rat, the longer they will live.