Skip NavigationSkip to Primary Content

Rats & Mice Information Package

Welcome

We are extremely proud of our clinic and of our team of caring and experienced staff. We are committed to excellence in care for our patients and their families. We also are very involved in our community through our popular Junior Vet Program, our Be a Tree program, and our pro bono treatment of injured wildlife.

Please join us on Instagram, Facebook, or Twitter to share information on veterinary medicine, and stories about the amazing human animal bond.

Please feel free to call in any time to our knowledgeable staff with any questions or concerns you may have.

We look forward to being your "other family doctor"!

Sincerely,

Bowmanville Veterinary Clinic

Rodent General Information

Rats

Life Span: 2-3 years

Environmental Temp. Range: 65-80 F

Relative Humidity Range: 40-70%

Sexual Maturity: 5 weeks

Gestational Period: 3 weeks

Litter Size: 6-12

Weaning Age: 3 weeks

Mice

Life Span: 1.5-2 years

Environmental Temp. Range: 65-80 F

Relative Humidity Range: 40-70%

Sexual Maturity: 50 days

Gestational Period: 3 weeks

Litter Size: 10-12

Weaning Age: 3 weeks

Rodent Diet

As with any pet, good quality food and clean, fresh water must be provided at all times. In the wild, these animals feed on leaves, seeds, roots, fruits and insects. Pellet rodent rations are recommended for feeding in captivity (Oxbow), which is processed as dry blocks or pellets. Typical maintenance diets contain about 14% protein and 4 to 5% fat, while diets for growth and reproduction contain 17 to 19% protein and 7 to 11% fat. Seed diets are also formulated for mice and rats, but these diets should only supplement the basic rodent pellet as a treat item. Rodents prefer sunflower-based diets to pellets, but these seeds are low in calcium and high in fat and cholesterol. When fed exclusively, seed diets can lead to obesity and nutritional deficiencies.

The pet’s appetite should be monitored closely. Many factors affect the rodent’s food intake, including the ambient temperature, humidity, food quality, breeding status as well as the pet’s health status. On average, an adult mouse will consume about 15grams of feed and 15ml of water per 100grams of body weight daily. Rats and mice typically eat at night.

Water should be provided in water bottles equipped with sipper tubes. The sipper tube keeps the water free from contamination. The tubes must be positioned low enough to allow the pet easy access. Inadequate water consumption leads to dehydration, lower body weight, infertility and death. These rodents drink only a fraction of the total bottle volume, but the bottle should be emptied, cleaned and refilled with fresh water daily.

Handling and Housing Rodents

Handling

Pet rodents become tame and rarely bite when properly restrained and accustomed to handling. Some rats can be very territorial of their cage, and these should be coaxed out of the cage before being handled. Mice housed individually may be more aggressive and apprehensive than those housed in groups. Most pet mice and rats enjoy being handled when away from their cage. Mice can also be lifted by grasping the base of the tail. Rats can be picked up this way, but be careful not to injure them due to their larger size. For any rodent, never pull on the tip of the tail because the skin can easily tear and become stripped from the tail

Housing

Several types of cages are available which are suitable for housing small rodents. Many of these units come equipped with cage “furniture” such as exercise wheels, tunnels and nest boxes. These accessories contribute to the pet’s psychological well-being.

Cages should be constructed with rounded corners to discourage chewing. Rodents readily chew through wood and thin plastic. Recommended caging materials are wire, stainless steel, durable plastic and glass. Glass and plastic enclosures restrict ventilation and may lead to temperatures and humidity problems. These materials are acceptable when at least one side of the enclosure is open for air circulation.

These pets thrive in solid bottom cages with deep bedding and ample nesting material. Bedding must be clean, nontoxic, absorbent and relatively dust free. Shredded paper, pine shavings and processed corncob are acceptable beddings. Wood shavings and ground corncob must be free of mold, mildew or other contamination. Cedar chips or chlorophyll scented shavings should be avoided because of association with respiratory and liver disease. With all bedding be sure your pet is not consuming it. At least one inch of bedding should be provided to allow for normal burrowing behavior. Cotton and shredded tissue paper make excellent nesting materials.

Rats can be litter trained. They will still urinate in small amounts in different areas of their living space to mark territory, however, a large volume of their urine and all or most of their fecal material will be isolated to the litter box once trained.

Adult mice require a minimum floor area of 15 square inches and a cage height of 5 inches. Rats need at least 40 square inches of floor space and a minimum of 7 inches height. Optimal temperature range for these pets is between 65 to 80 degrees F, with a relative humidity of 40 to 70%. Twelve hour light cycles are preferred, with most rodents being more active during the night. Pet rats and mice can be housed singly or in groups, however, we recommend housing them with at least one other of their species as they are very social animals. If they are housed alone they will need a high level of human interaction. These rodents are colony oriented by nature. Occasionally an overly aggressive mouse or rat may have to be caged individually. Territorial disputes also develop when the cages are overcrowded or when they lack food or water.

As a rule of thumb, the cage and accessories should be thoroughly cleaned at least once weekly. An exception to this schedule is when newborn babies are present, then wait until they are at least 10 days old. Other factors that may require increased frequency of cleaning are the number of animals in the cage, the type of bedding material provided and the cage design and size. Cages should be sanitized with hot water and nontoxic disinfectant or detergent then thoroughly rinsed. Water bottles and food dishes should be cleaned and disinfected daily.

Medical Conditions

Chronic Murine Pneumonia (Murine Mycoplasmosis)

Mycoplasma pulmonis is a very elusive bacteria that causes one of the most common and serious infections of rats and mice. The organism is difficult to isolate by standard laboratory culture procedures. As a result, a presumptive diagnosis is typically made based on the patient’s signs and symptoms.

Signs of mycoplasmosis include sniffling, sneezing, labored breathing, squinting, red-brown tearing and a rough hair coat. If the inner ear becomes infected, a head tilt and neurologic signs develop. In addition to respiratory signs, a genital infection may occur. Manifestations of the genital form include infertility, embryonic resorption and small litter size. Compromise to the respiratory tract by other bacterial or viral infections or exposure to inhalant irritants can increase the severity of mycoplasmosis. The disease runs a chronic course, which may result in death if not treated early.

Antibiotic therapy should be initiated at the first suspicion of infection. Severely affected individuals may need injectable medications and extensive supportive care. In addition, secondary infections with other organisms are common, sometimes requiring the use of multiple medications. The goal of therapy is to reduce the severity of symptoms, but complete elimination of the infective bacteria is practically impossible.

The disease is highly contagious. The bacteria are spread by direct contact with affected individuals or from an affected mother to her unborn young while still in the womb. Transmission usually occurs through respiratory aerosol and sexual activity. Rabbits, guinea pigs and other rodents can serve as carriers of the disease without exhibiting clinical signs. Other mice and rats can also serve as carriers. It is extremely important to restrict contact between mice and rats of unknown health status until a quarantine period has elapsed. A quarantine period of four to six weeks is recommended. Any animal exhibiting even the slightest signs of respiratory illness should remain isolated.

Tyzzer’s Disease

A common infectious disease of rodents is Tyzzer’s disease, caused by a bacteria (Bacillus piliformis) that infects living cells. The disease causes a high death rate in young, stressed rodents, particularly mice and gerbils. Clinical signs are nonspecific, but primarily appear as ruffled fur, lethargy, hunched posture and poor appetite. Diarrhea may also be present. The disease causes changes in the heart, liver, lymph nodes and digestive tract, which can be observed at post mortem.

Sendai virus

The Sendai virus causes one of the most significant and severe respiratory infections of laboratory rodents. Suckling and weaning mice are most commonly affected, posing a serious problem to mouse colonies. Other affected species include rats, hamsters, guinea pigs and swine. It is unlikely for a pet mouse to become infected unless it was acquired from an affected colony.

Signs of infection are usually expressed in nursing mice, while affected adult mice rarely show symptoms. Signs include labored breathing, chattering, rough hair coat, weight loss and death. Secondary bacterial infections often worsen the disease, resulting in a higher death rate. Sendai virus infections are usually sub-clinical in other susceptible rodents, but these species may be a source for infection in young mice.

There is no specific treatment for this disease. Supportive care and treatment of secondary bacterial infections may lessen the severity of signs. A vaccine is available, but it is only practical for use with large colonies of affected mice. Prevention involves selecting pet mice from a Sendai virus-free source and keeping them isolated from mice of unknown backgrounds and other susceptible rodents, which may carry the disease.

Sialoacryodenitis

Rats are the natural host for this highly contagious viral disease. The disease is usually self-limiting in young rats. Recently weaned mice may also be affected. The disease is spread from affected individuals through respiratory aerosol or direct contact with respiratory secretions. Infected rodents carry and secrete the virus for about seven days.

Signs are variable depending on the age and immune status of the affected rat or mouse. The most serious signs are seen in 2 to 4 week old rats with no maternal antibody protection. Initial symptoms include squinting, blinking and rubbing of the eyes. Sneezing and swelling in the neck area develop later. Finally, swellings below or around the eyes, bulging of the eyes, production of red-brown tears and self-trauma to the eyes are noted. Respiratory signs may be present, especially if complicated by Sendai virus or murine mycoplasmosis. The affected rat usually remains active and eating during the course of this disease.

Tumors

Rats and mice are very susceptible to the development of tumors. It is reported that rats over two years of age have an 87% chance of developing tumors. The most common type of cancer in the rat is mammary fibroadenoma (breast cancer). Numerous other forms of cancer occur, but to a lesser degree. Mice develop tumors in a wide variety of tissues, both internal and external. Leukemia, cancer of white blood cells, is also common in the mouse.

The most common type of cancer in these pets is the mammary tumor of rats. This form of breast cancer can occur in both female and male rats. Since rats have widely distributed mammary tissue beneath the skin, it is not unusual to find these tumor lumps behind the front legs, along the sides, in the flanks, as well as along the underside of the body. These tumors can be removed surgically, but often recur. If not treated and surgically removed, these masses continue to enlarge, ulcerate and become infected. Early surgical removal allows for the best outcome with the least chance of complications or recurrence.

Red-Brown Tears of Rats

Rats secrete red tears from a gland behind their eyes. This is a normal secretion of porphyrin pigments produced by the harderian gland. These tears are often mistaken for blood. They usually appear during stressful situations and disease. The eyelids, nares and forepaws may be smeared with pigment. When present, the underlying cause of stress should be sought and relieved.

Ring Tail

Low humidity and high temperatures may result in ring tail of young rats. Ring tail presents as constrictive bands along the tail. Other factors that have been implicated in this condition include the vascular structure of the tail, the presence of endotoxins and high dietary lipids. Treatment involves correcting the environmental conditions.