Key Points About Rats

Here is a brief summary of the information we have found to be most helpful for Animal Care Professionals. More complete information on health issues, including drug dosages, can be found in the booklet Rat Health Care by Debbie "The Rat Lady" Ducommun. More complete information on rat care and behavior can be found in the book Rats, and The Complete Guide to Rat Training, also by Debbie Ducommun. For more description of these publications go to


These additional pages can be accessed from the sublinks above:

-A Rat Care Sheet
-Live Rodents as Pets, Frozen Rodents as Food
-Standards for Selling Rats and Mice in Pet Shops
-Maximizing Sales of Pet Rats
-Forms and Policies for Shelters

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Rat Facts

Average life span - 2 to 3 years
Maximum life span - 7 years 1 month (Guiness Book of Records)
Estrus cycle - Every 4-5 days, and immediately after giving birth
Gestation period - 21 to 23 days, 28 days for a post partum pregnancy
Average litter size - 12
Eyes open - 2 weeks
Weaning age - 4-5 weeks
Age at puberty - 5-6 weeks
Physical maturity - 8 months

Rat Behavior

Domestic rats are true domesticated animals and are born tame, but they still need to be socialized to bond to humans. Baby rats need to handled as much as possible beginning at birth and especially between 2 and 4 weeks of age to make sure they will be friendly and calm. It is a myth that handling the babies will cause the mother to kill them.

Rats who were not properly socialized as babies will often exhibit fear toward humans. But even many of these rats can be rehabilitated using a method called Trust Training. This technique uses soft food on a spoon as both a lure and reward for desired behavior. For more info on this technique go to

There are a few rat behaviors that are sometimes mistaken for health problems. One of these is when a rat stares into space, swaying or weaving his head back and forth. This behavior is most common in pink-eyed rats and means the rat has poor eyesight. Moving their head back and forth helps their depth perception through a phenomenon called parallax. As they sway back and forth, closer objects seem to move more than objects farther away.

A female rat in heat can become jumpy, especially when touched on the back. When touched, she may also arch her back and vibrate her ears! Female rats in heat can be quite determined and inventive in reaching a male rat, for instance, leaping huge distances or squirming through cage bars, and must be securely confined.

About 5% of male rats show abnormal aggression. The only solution to this behavior problem is to have the male neutered. It can take up to 8 weeks (probably because the brain must reorganize), but neutering will eventually be 100% effective in eliminating the aggressive behavior toward humans and 90% effective for aggression toward other rats. Neutering will also reduce urine-marking behavior, as well as the normal secondary sexual characteristics such as rougher coat and heavy oil production from the skin on the back, although it does not have any significant health benefits for male rats.


Rats are highly social animals and do best with a cagemate. A single rat can become insecure and nervous. Studies have also shown that single rats tend to get sick more than rats in groups. We recommend that rats be kept in same-sex or altered pairs or groups. As long as the rats are properly socialized, they will still enjoy interacting with their owner. A single rat must have several hours of human interaction every day. It's best if rats can come out of their cages to play for at least 30-60 minutes every day.

Rats need a cage large enough to provide room for toys and exercise. Minimum should be 14" X 12" X 24" but bigger is better. Rats also need a place to hide and sleep such as a box or a hammock. Toys are not optional, they are required for the rats' health and well-being. They enjoy climbing toys such as ladders, branches, concrete blocks, and ropes as well as tubes and boxes. A large plastic exercise wheel is highly recommended as most rats really enjoy running on a wheel. We recommend Wodent Wheels at

Pine and cedar shavings should not be used in rat cages because they contain acids that damage the respiratory tract. This is especially dangerous since the most common health problems in rats are respiratory infections. Pine and cedar shavings also contain toxic phenols that are absorbed into the blood. Studies show that long term exposure can cause an enlarged liver, altered immune response and decreased fertility and litter size. (If you would like a copy of these studies please let us know.) You will find a list of safe alternative beddings at

The best commercial food for rats are rat blocks or nuggets. These food pellets supply a complete and balanced diet. A fortified grain mix can also be used, but many rats will pick out and eat only their favorite bits leading to an imbalanced diet and wasted food. Their diet should also include a variety of fresh fruits and vegetables.

Baby rats should be weaned no earlier than 4 weeks, and waiting until 5 weeks is better. At 5 weeks the males and females must be separated because some rats become sexually mature at this age and pregnancies can result.

It is a myth that rats need hard things to chew on to keep their teeth from over-growing. Their incisors are designed to rub against each other to keep them the proper length and sharpness. Only when disease affects the teeth, or they are out of alignment, will they overgrow.

Common Health Problems

The most common health problem in rats is bacterial respiratory infections, which in older rats are often accompanied by congestive heart failure. Also common are tumors, abscesses, spinal nerve root degeneration causing paraplegia in older rats, and lice or mites. Rats have a brownish-red pigment in their tears called porphyrin and when a lot of this gets caked around their eyes or nose or on their ears or fur it is a common non-specific sign that can be caused by respiratory disease, stress, or eye irritation.

See below for more details on the most common problems. More info is available at and in the booklet Rat Health Care, which is described at

Respiratory Disease

The underlying cause of respiratory disease in rats is infection with the bacteria Mycoplasma pulmonis. This disease is extremely contagious and is transmitted from mother to offspring shortly after birth. Pretty much all pet rats have it, whether or not they have symptoms, and it is incurable, although aggressive antibiotic treatment can keep it under control. Mycoplasmosis makes the rats more susceptible to frequent secondary bacterial infections as well.

Respiratory symptoms in young rats are almost always caused by secondary infections, which are best treated with amoxicillin. Secondary infections can quickly become acute and deadly so should be treated promptly.

When treating rats, if there is no improvement within the first 2-3 days another antibiotic should be tried. When a treatment is effective, antibiotics for a secondary infection should be continued for 2-3 weeks, to prevent relapse. When enrofloxacin or doxycycline is used to treat mycoplasma, treatment should continue for at least 6 weeks and these antibiotics can be used long-term without any danger. (One of my vet’s patients was a rat who lived 4 years, and was on Baytril the last 2 years of her life.)

Congestive heart failure is common in older rats, but fortunately, can usually be successfully controlled with drugs.


Rats usually heal quickly due to their fast metabolism, and often veterinary treatment is not needed for injuries. Lacerations - even if all the way through the skinl - up to 1 ½" long do not need suturing. Even broken legs usually heal well on their own. Degloving of the tail is a natural response and the damaged tail normally does not need to be amputated. The exposed tissue will dry up and fall off on its own in a few weeks. Treatment is needed only if infection or self-mutilation occurs.

Severe swelling of a foot due to injury does need treatment as it will tend to get worse due to compression of the veins. Ibuprofen can also be given at 60 mg/lb twice a day.


About half of all unspayed female rats will develop benign mammary tumors, and it is common for a rat to get multiple tumors. Although these tumors are easily removed by minor surgery, it is expensive, so it is best to get female rats spayed when young. Spaying significantly reduces the chance of both mammary and pituitary tumors. If a rat does get mammary cancer, surgery won’t help, but treatment with tamoxifen can be highly successful. Mammary tumors are uncommon in male rats, but male rats often get benign fibroma tumors on their side. The only treatment for these is surgery.

Pituitary tumors, which grow under the brain, occur in about 16% of unspayed female rats and in about 4% of male rats. The main symptom is poor coordination and eventually the rat will have trouble eating. Treatment with cabergoline can be highly effective for up to 8 months.


Abscesses are a common occurrence in rats and most abscesses on the body will open, drain and heal up on their own. Males are particularly prone to abscesses in the groin. Abscesses on the face can be much more serious. An abscess on the face or under the ear that does not quickly heal after being drained is most likely caused by a cancer.

External Parasites

The two most common external parasites in rats are lice (Polyplax spinulosa) and fur mites (Radfordia ensifera). The species specific lice are visible and often do not cause symptoms. They can be treated with oral ivermectin at 100-200 mcg/lb once a week for 3-6 weeks or by one dose of selamectin at 6 mg/lb or one dose of moxidectin at 1 mg/lb.

Fur mites are also species specific, are microscopic and live in the hair follicles. Skin scrapings can often be negative even when mites are present. Rats can harbor these mites without symptoms, but when symptoms occur they are scabs on the shoulders, neck, throat or chin. In the United States ivermectin used to be effective for fur mites but they are now immune to it. The only effective treatment for rat fur mites now is selemectin or moxidectin at the same dose for lice.

Nursing Care

The best nutritional supplement for sick rats is powdered soy baby formula, which can be mixed as thick or thin as needed. Rats will also often take foul-tasting medications in it. It is best to try to get rats to take their medications willingly by mixing them into a tasty liquid or food. However, medications can be forced by putting only 0.1 ml in the back of the mouth at a time.

The best place to give injections to a rat is in the loose belly skin in front of the hind leg. The skin at the nape is ten times thicker. All injections can be given subcutaneously.

Rat Health Insurance

The Veterinary Pet Insurance company offers major medical policies for almost any type of animal. This policy can make more extensive health care, such as mammary tumor removals and diagnosis and treatment of heart failure, affordable. For more info go to or call 800-USA-PETS

For More Information

For more information see or Debbie's booklet, Rat Health Care described at

All site content © 2003-2018 by Debbie Ducommun and the Rat Assistance & Teaching Society, unless otherwise noted.
All information contained herein may be reprinted if both author and the Rat Assistance & Teaching Society are credited.
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