How Old? Rats go through different stages in their life just like people do. Here are some of the things you can expect in each stage... Youngsters (4-8 weeks old)... (Note: Baby rats should not be weaned from there mother until at least 4 weeks of age, preferably 5 weeks. Do not adopt a baby rat that is younger than this as they should still be with there mother.) This is equal to 8-13 years of age in a human life span. During this period of time, between 5 and 6 weeks of age, a rat reaches their puberty and will now become sexually active. This means once they turn 5 weeks of age, it becomes very important to keep the males and females separate from each other, or you will end up with pregnant females and lots of babies. A rat's appearance at this age is beyond adorable. They are very small in size, and their ears, eyes, and feet look quite oversized for their little, rounded bodies, leaving them with a cute gangly appearance. Youngsters are active, playful, mischievous, and full of high amounts of energy. The males slightly more than the females. Many people refer to youngsters as popcorn, because they will literally bounce all over the place while they play. It is at this age that an unsocialized rat has the highest chance of being easily socialized. Rats are most excepting of new roommates at this age. WARNING! Rats this young will not have the strength to grip your shoulder and can fall and get hurt. So wait until at least eight weeks of age before giving your rats any shoulder rides. Teenagers (8 weeks - 6 months old)... This is equal to 14-18 years of age in a human life span. Males, starting at the age from 3-6 months and lasting up to the age of 12 months, will go through a possible spurt of increased aggression as their hormones dramatically increase. This can cause them to become overly aggressive with their cage mates, or sometimes, rarely, even with you. If you have a male that has become too aggressive to live with, you can solve this problem by having him neutered. (See "Should I Spay/Neuter my Rat?" located in this Guidebook to learn more about this subject.) Female temperaments will usually not be affected much in this stage of growth. Between 5-6 months of age, rats reach their social maturity. Throughout these months your rats will grow into their adult sized bodies, males becoming almost twice as big as the females. Females and most males remain playful in this stage of growth. This is the best time to introduce rats to games! Adults (6 - 20 months old)... This is equal to 19-50 years of age in a human life span. By 12 months of age, your rats should be fully grown with strong, sleek, healthy bodies. It is during the adult stage of their life that a rat has the highest chance of becoming an alpha rat, due to the fact that they have reached their physical peak. Males who were still playful as teenagers will probably finally begin to slow down and mellow out, becoming sluggish and lazy. Females, though, will still remain playful and energetic. Rats are least accepting of new roommates at this age. However, it can be done. Respiratory infections are not uncommon during the adult stage of life. Many females will develop tumors during this stage of life if they haven't been spayed (See "Should I Spay/Neuter my Rat?" located in this Guidebook to learn more about this subject.) The Elderly Rat (20 months on up)... An elderly rat will start to have a much more haggard appearance than a rat who is in their prime. Their fur will loose it's shine, become coarser, start to thin, and will not lay down as smoothly anymore. Their eyes will seem duller, and their movements will be slower, and more cautious. A host of health issues can arise during this stage of a rat's life. You may see a more frequent occurrence of respiratory problems, possible heart problems, possible pituitary problems, possible occurrence of spinal nerve degeneration. It is important that a rat guardian, at this stage, keep a watchful eye on their rats, and that they seek immediate veterinary care if any illness is suspected. Elderly rats can be very set in their routines and don't like to see that change. Elderly rats will sleep more. At this age rats sometimes become much more affectionate to you, their human parent, needing to spend more time with you. Elderly rats need special care. (See "Special Care for the Elderly" within this Guidebook for more information.) WARNING! Do not give elderly rats shoulder rides. They no longer have the strength to grip your shoulder and could easily fall. So What Age Rat Should You Adopt as a First Time Parent? What age rats you should adopt depends on what kind of time commitment you want to make. If your not sure rats are the right companion animal for you, you might want to consider adopting a couple of older adult rats from the shelter. That way if you discover that rats aren't the right kind of companion animal for you, you are committed to only a short time of care before they pass on. An older, well handled pair of teenage or adult rats from the shelter might be a good choice for kids. This way the rats are already full grown and more laid back, making them easier to handle and bond with. Youngsters are squirmy and full of energy which might be daunting to young children. We have found some of our sweetest rats at the shelter. On the other hand, if you want the longest time possible with your rats, you should look for youngsters or young teenagers. Youngsters are easier to introduce to one another, and unsocialized youngsters are easier to socialize than unsocialized adults. Not to mention that youngsters are cute as can be, and loads of fun to play with.