Introduction 
Rats make excellent pets! They are clean, extremely smart, and very social toward humans, making them one of the best pocket pets out there. Of course, they are often greatly misunderstood -- many people continue to associate them with the kind of rats you'd find in a city sewer. However, domesticated rats are as different from wild rats as labrador retrievers are from wolves! Jack Hanna says that rats are the nearest thing to a dog you'll find in a small mammal! Times are changing, and rats are becoming very popular as household pets. 
Rats Need Company 
Rats should always be kept as pets in same-sex groups of two or more, for many reasons. In the wild, rats live in immense colonies, and naturally need and enjoy the company of other rats. They groom each other, sleep together and play together. No amount of human attention can replace the company of another rat. Therefore, pet rats are better off with at least one other for companionship. 
It is also believed that pet rats fare better emotionally when kept in groups, which not only keeps them happy, but healthy, too! Single rats often seem to be more easily stressed and can be more prone to disease -- some rats can even develop behavioral problems or neurotic tendencies when kept alone. Since caring for two rats is no more difficult than caring for one, and the extra cost is nominal compared to the benefits of having two together, there really is no reason not to get two or more. As long as you give them attention individually, they will each bond with you -- in fact, many people believe that keeping two rats actually helps them bond to you more easily.  Though it is very possible to introduce a new rat as a companion for a single rat, it is much easier to get both at the same time, preferably from the same litter, as they have grown up together and already know each other. 
Human Socialization 
Rats are very social animals, and are most easily socialized with humans when they are young. Therefore, it is important in their social development to have contact with humans from almost the moment they are born. Not only should breeders and pet store employees handle or interact with the rats at least once a day, they should also allow you to have direct contact when visiting. In many cases, the best way to choose a pet rat is to allow the rat to pick you! The most social rats make the best pets of all. Just be sure that your hands are clean -- the rats may detect food scents and try to bite (thinking it is a morsel, not to be mean), or may smell another animal and become very frightened. 
Most human illnesses are not transmitted to rats (strep throat is one exception), but itÕs better to be safe than sorry. If you are ill, avoid the pet store or breeder until you are feeling better. 
HOW TO PICK UP A RAT 
When picking a rat up, you should never grab him or her by the tail. This is very uncomfortable to them, makes them feel unsafe, and does not help in their socialization. Tails have also been known to break off or lose skin with improper handling. Skin that has come off the tail cannot be reattached, nor will the tail grow back. Amputation of the tail tip is often required. You should always pick up a rat around its middle, and then support their feet with your other hand or your body. This makes them feel very secure, and reduces the chance of someone dropping them if they squirm. Rats that are regularly lifted by their tails tend to harbor a distrust of humans, and may not make the best pets.
CAGES 
A hamster cage or Habitrail is NOT an acceptable home for a rat. Such habitats are far too small and offer poor ventilation. Glass aquariums are acceptable, but do not offer the same ventilation as a wire cage, so must be cleaned more often to avoid harmful ammonia buildup. A cage should offer a bare minimum of 2 cubic feet for one to two rats -- about the equivalent of a 20-gallon long aquarium, but more room is always better.  Wire cages (such as rabbit and ferret cages) are by far preferred. They offer superior ventilation, plenty of climbing opportunities, and better flexibility for modification and "decorating." Space between wires should be between 1/2" x 1/2" (for babies) and 1" x 2" for adults.
BEDDING 
It has been found that both cedar and pine shavings are NOT acceptable as bedding for rats, mice and other pocket pets. Studies have shown that exposure to the phenols in cedar and pine (the chemical that makes them smell nice) can cause respiratory difficulty, as well as liver and kidney damage. With so many better, safer products on the market, there is no longer any reason to use these soft wood shavings as bedding.  
Keep in mind, also, that clumping and clay-based kitty litters are not advised. Clay-based litters are very dusty, and can cause problems with the rat's delicate respiratory system. Clumping litters can cause problems if ingested. It's important to remember that cats only visit their litter box to do their business. Rats live in their litter. 
CLEANING 
Cages should be cleaned at least once a week in a home setting. Depending on the size of the cage, ventilation, and number of rats, cages may need to be cleaned more or less frequently. A rat cage should never smell, as they are very clean animals. If the cage smells, it is because it is long overdue for a cleaning. Rat urine creates ammonia fumes, so a dirty cage leads to an unhealthy build up of ammonia. 
Though cages can be cleaned with a commercial pet cage cleaner, sometimes the fumes from these types of products can cause respiratory problems. It is recommended to clean the cage with warm water and a mild soap, rinsing thoroughly. A very diluted bleach solution is also acceptable. Household cleaners, such as Windex, Fantastik, etc., should never be used due to harmful fumes. 
ACCESSORIES AND TOYS 
Rats need to be stimulated mentally, as they are very intelligent creatures. Toys can range from bird toys to something as simple as cardboard tubes. Some rats enjoy PVC tubes, purchased at a hardware/ home improvement store for about $3.00 each. Ferret litter pans and terra cotta or plastic flower pots can make great sleeping spots. 
Some rats enjoy exercise wheels, but usually only the females, and only if they have been exposed to a wheel at a young age.  Of course, since a rat is bigger than a mouse, hamster or gerbil, they need a bigger wheel. 
Nutrition 
STAPLE DIET 
Hamster and gerbil mixes, rabbit food and cat food are NOT acceptable as rat food. Hamster mixes do not contain complete nutrition, and often feature fatty seeds and nuts. Rabbit feed is made from alfalfa, which rats cannot digest. Cat food contains far too much protein, which will cause coat problems, especially for males.  The best nutrition for rats is in the form of a Lab Block. It has all of the daily requirements a rat needs. Be sure to choose a block that does not have corn as its first ingredient; soy- or wheat-based blocks are preferred.  Some dog kibble is fine for babies and nursing mothers, as it helps the babies grow, and helps mom retain her strength while nursing. Seed mixes formulated for rats and parrots are fine as a supplement to the staple diet, but should not be the sole diet. These mixes often contain items that go to waste, such as alfalfa pellets and tiny seeds. They also do not provide complete nutrition, and contain a lot of seeds and nuts that are high in fat, which can cause obesity and protein problems (where the rat will become itchy, and scabs will develop).
WATER 
Rats should have access to fresh water at all times, supplied in a water bottle. A bowl can be tipped and soiled by urine, feces and bedding, so a hanging, on-demand water bottle works best. The water should be refreshed every few days, and the bottle should be cleaned well each time the cage is cleaned. 
In the summer, two or more bottles should be maintained, if possible. Store unused, full bottles in the refrigerator, and switch them throughout the day. Rats can only release excess body heat through their tails, so they can become overheated fairly quickly.
TREATS 
Of course, eating lab blocks and grains all the time can be incredibly boring. Rats relish their treats! As omnivores, they will eat almost anything, but it is always best to give them healthy treats such as fresh fruits (blueberries, grapes) and vegetables (carrots, broccoli), raw or cooked pasta with no sauce (they love it!), instant oatmeal, dry cereal and other healthy goodies. Commercial treats are fine in small quantities, but fresh foods are generally better for them. Small items -- such as Rice Krispies, Cheerios and rolled oats -- make excellent training aids. Rats love them, and they are small enough to eat quickly. In addition, the animal will not get full too quickly, so training sessions can last longer. One product that offers acceptable commercial treats is Vitakraft. Two products of theirs that are very popular with rats are the yogurt drops (any flavor) and the Cheese Wedges.
Health Concerns 
There are two major concerns that one should watch for -- respiratory problems and parasites. Always consult a veterinarian in all medical matters when it comes to your pets. 
RESPIRATORY PROBLEMS 
The most common health problems in rats are often respiratory in nature. All pet rats have the bacteria mycoplasma pulmonis in their system, though it can remain dormant and show no symptoms. Active myco can be triggered by environment (cedar or pine bedding, drafts, air fresheners, cigarette smoke, etc.) and secondary bacterial or viral infections (SDA). If left untreated, these secondary infections can lead to pneumonia and, ultimately, death. The most obvious symptoms of most respiratory illnesses (whether viral or bacterial) include: 
• Wheezing or noises while breathing 
• Excessive sneezing 
• Porphyrin staining (red discharge) around nose and eyes 
Advanced symptoms may include: 
• Labored breathing or gasping 
• Lethargy 
• Drop in body temperature 
• Disinterest in food or water 
• Loss of coordination 
• Noticeable weight loss 
If your rat exhibits any of these symptoms, it should be treated with antibiotics from a vet. Observe the other animals in the cage for similar symptoms -- secondary infections are often contagious. It is often advisable to treat all of your rats at the same time. 
EXTERNAL PARASITES 
Though not as common as respiratory ailments, external parasites, such as lice and mites, can occur in rats. Rat parasites are species-specific, so humans and other household pets cannot get them from an infested rat. Scratching and hair loss can also be caused by too much protein in the diet or a bacterial infection, so check these possibilities first before treating for parasites. Some symptoms may include: 
• Excessive itching 
• Scabs and/or hair loss from scratching 
• Visible nits on hair shafts - lice 
• Moving, brownish-red specks - mites 
The best treatment for parasites is a visit to the vet.  Flea powders should never be used, as they are far too dusty, and can irritate a rat's delicate respiratory system. Shampoos will only kill the adults, and does not stay in the system long enough to affect the eggs as they hatch. 
Breeding 
Female rats should not be bred from until they are at least three months old. There should be a space of at least two months between litters (starting after the last litter is weaned), to allow the mother to regain her strength after bearing and nursing a litter. Lastly, each female should not be bred more than two or three times in her lifetime. A female comes to the end of her breeding cycle at about 18 months of age, so it is not a good idea to breed her after that time. Litter sizes will decrease as her fertility wanes, and there could be complications. 
Breeding, however, is not something to be taken lightly, by any means. Breeding any animal responsibly means making an effort to improve the species as a whole, not just to make more animals. This particularly applies to rats. If you are considering breeding, it is important to know rat genetics, have a breeding goal that involves improving the species, mentoring with a reputable breeder, and starting with good breeding stock from a reputable breeder. Pet store rats are NOT breeding material. You need to know the health and temperament history of your rat's line, going back several generations, including extended family, before you think about breeding him or her. Breeding is a monumental responsibility, and requires a lot of dedication and hard thinking before you begin.