The rat is a very popular and endearing little pet mammal. It's a very affectionate and sociable animal. Although primarily active at night, the rat adapts well to its owner's life schedule and can be a very good pet. Its life expectancy is around two years. The rat belongs to the order of rodents. Although chinchillas and degus belong to the same order, their dentition differs from that of rats. In the latter, only the incisors grow continuously, generating more problems than the molars.
Please refer to our detailed recommendation sheet to make sure you provide the right diet for your rat.
Environment
Rats are a social species, who should be kept in groups of at least 2 individuals. In the wild, rats live in colonies with well-established hierarchies.
In general, aggression can be normal in a group and becomes rarer once the colony is well established. To reduce aggression in a colony, you need to:
- Provide a large enough cage,
- Provide several hiding places with two exits (avoiding dead ends where the chased rat can’t escape),
- Neuter males, and
- Ensure that new individuals are introduced before their puberty (around 5 weeks of age).
A rat’s health is largely dependent on its environment. There are many ways to provide a suitable environment for your rat. Here are the main guidelines:
- The cage should be installed in a quiet, well-ventilated room away from predators. The cage should not be exposed to direct sunlight, or located in a humid & cool environment.
- Large cages designed for ferrets or rodents (with several levels) may be suitable. Commercial cages for guinea pigs or rabbits with a single level are not recommended.
- We recommend avoiding wooden cages (impossible to clean properly) and glass terrariums (suboptimal ventilation).
- Wire mesh cage bottoms are not recommended, as they can lead to pododermatitis and fractures. It’s preferable to install soft mats (anti-slip mats, for example), blankets or towels, and/or substrate such as paper litter.
- Paper litter is preferable to wood shavings for your pet’s respiratory health. In any case, cedar shavings are toxic and should be avoided at all costs.
- It is important to provide several hiding spots (at least as many hiding spots as there are individuals).
- Offering a portion of your pet’s meals in toys is suggested to provide enrichment and encourage exercise. Kibble can be offered in a hollow plastic ball, in paper, in an empty toilet paper roll, in a basket, or in an empty cardboard box.
- Remember that rats live in burrows in the wild. It's essential to provide toys or equipment to allow them to dig, take shelter, make a nest and then play and run, such as PVC pipes, blankets, egg cartons, cardboard rollers, balls, or exercise wheels.
- Providing both a bottle and a bowl of water is advisable in case the bottle’s mechanism becomes blocked.
Veterinary Care
- There is no vaccine currently recommended for rats in Quebec.
- A yearly veterinary examination is recommended, including a complete dental check-up.
- Regular claw trimming is recommended (frequency may vary between 4 and 12 weeks, depending on the animal).
- Preventive treatments against parasites are recommended for rats that go outside in the summer, and those that live with animals that go outdoors (dogs, cats, rabbits).
- Sterilization of young females is recommended to prevent mammary tumours.
- Sterilization of males is recommended to facilitate cohabitation between males, and to prevent pregnancy in the case of mixed cohabitation.
- It should be noted that rats can be sexually mature from 5 weeks of age.
Common Medical Issues that Warrant Consultation
If your rat presents one or more of these symptoms, consult a veterinarian as soon as possible:
- Appetite loss for more than 8 hours
- Lack of stool production for more than 8 hours
- Diarrhea
- Urinating difficulties or absence of urination
- Abundant blood in urine or stools
- Difficulty breathing
- Vocalizations associated with breathing
- Sudden decrease in activity level
- Tilted head associated with a decrease in the general condition
- Signs of fracture
- Difficulty giving birth
- Any altercation with a cat
- Open wound
Frequent Illnesses
Chromodacryorrhea
This condition includes secretion of red coloured tears that can be observed in the eyes or at the tip of the nose (the nasolacrimal duct communicates between the eyes and the nose). The red pigment, called porphyrin, is produced by the Harder's gland which is located just behind the rat's eye. It can be mistaken for blood, which is much rarer. However, overproduction of porphyrins is abnormal and is secondary to stress or disease. It is therefore advisable to consult your veterinarian if your rat displays chromodacryorrhea, in order to detect the underlying issue.
Malocclusion
The rat's incisors grow continuously. As a result of trauma, infection, tumour or congenital anomalies, incisor occlusion can be affected. In fact, the lower and upper incisors constantly wear against each other when the rat eats or gnaws on material, ensuring good wear throughout its life.
If one tooth is no longer in contact with the other, either because it has grown out of alignment or because one is missing (due to a fracture, for example), the opposite tooth is prevented from wearing down. This can quickly lead to elongation of the teeth in the mouth or towards the lips, and cause wounds or even abscesses. Affected rats may suddenly stop eating, or refuse their usual food and accept only soft foods. If not treated promptly, this condition can lead to weight loss, digestive disorders (diarrhea, constipation) and can even be fatal.
Tooth trimming, usually under sedation, is necessary. It must be carried out by a veterinarian using an appropriate instrument (never pliers!) to ensure that they fit the animal's normal anatomy, don't interfere with its ability to hold and chew food, and don't cause bleeding or pain. In many cases, the occlusion is permanently affected, and tooth trimming will need to be repeated every 3 to 5 weeks over the long term.
Rats can develop cavities as they age. Sweet foods (cookies, fruit, chocolate and yogurt) should be avoided. Apples in particular can cause cavities. In some cooperative rats, it may be helpful to gently brush the molars (the small white teeth in the back of the mouth that are not easily visible) with a small toothbrush moistened with chlorhexidine. It is not necessary to brush the incisors (the visible orange teeth). To maintain incisors, we recommend offering toys that can be chewed (wooden toys, apple tree branches, etc.).
Parasites
The haematophagous (bloodsucking) flea is by far the most common parasite found in rats. The animal scratches a lot during infestation and can lead to a skin infection secondary to excessive scratching lesions. Heavily infected rats will also show signs of despondency due to anaemia secondary to the loss of blood ingested by too many lice. Diagnosis is made by visualization of the fleas in the coat and microscopic observation. Topical application of an antiparasitic to all rats in the house is recommended, and is usually very effective as treatment. Lastly, the environment must be disinfected to prevent recurrence.
Chronic Respiratory Syndrome
Chronic respiratory disease is primarily caused by the bacterium Mycoplasma pulmonis, but can be complicated by other minor bacterial and viral respiratory pathogens. Clinical signs are variable and depend on the main site of infection, i.e., the lungs, throat, nose, eyes and ears. The rat's age and genetics, the presence of other health issues, and environmental conditions (sanitation, diet, overcrowding, etc.) all play a role in the clinical presentation of this disease. In the early stages, infection is often asymptomatic. Respiratory signs such as sneezing, coughing, eye discharge and head tilt may occur before or with breathing difficulties. More general clinical signs such as despondency, stooped posture and loss of appetite occur as the disease progresses.
The other important clinical form is bacterial pneumonia. This form mostly affects young rats, and is mainly caused by a bacterium called Streptococcus pneumoniae. As with chronic respiratory disease, the infection is often complicated by other respiratory pathogens, including Mycoplasma pulmonis. Clinical signs resemble those of chronic respiratory disease, but typically progress very rapidly.
All domestic rats purchased from pet shops or breeders are contaminated with these pathogens at birth through their mothers. Young rats in particular are prone to developing clinical signs following stressful events such as adoption or relocation. It is therefore pointless to isolate a rat with respiratory signs from another rat from the same source, as the latter is an asymptomatic carrier of the same pathogens. On the other hand, your veterinarian may recommend that you separate your sick rat from other healthy rats, to avoid aggression between them and to monitor its appetite and stool production more closely.
The management of a respiratory infection, regardless of its clinical form, involves a multi-level approach. Chest X-rays may be recommended by the veterinarian to confirm the diagnosis and rule out other hypotheses, such as heart disease or cancer. When the infection is at an early stage, antibiotics alone can control it. Critically ill rats also require supportive care (thermal support, fluid support, oxygen supplementation, nutritional support, nebulization). Unfortunately, it is impossible to eliminate all pathogens, and some patients show little or no response to treatment. In those who recover from respiratory infection, recurrence is frequent. To reduce the risk of recurrence, it's important to reduce stress in your pet's environment. It's therefore advisable to pay close attention to air quality and cage hygiene: clean the cage daily, prevent urine build-up, and avoid dusty products such as shavings or shavings. Substrates made from recycled newspaper are preferable. A healthy diet is also important, as obesity is an aggravating factor in the condition. Please refer to our detailed recommendation sheet to ensure you provide the right diet for your rat.
Mammary Tumours
Mammary tumours are common in rats, but are mostly benign (fibroadenoma), unlike mice in which mammary tumours are rare but often malignant.
In about 10% of cases, it is a malignant tumour -this is then called adenocarcinoma. These tumours are influenced by hormonal stimulation, so early sterilization (less than a year and preferably even less than 3 months) considerably reduces the risk of developing breast mass.
The mammary tissue in rats extends from the belly to the back, so it is not uncommon for a mammary tumour to develop on a rat's flank or back. Breast tumours are treated surgically. Identification of the type of breast cancer requires analysis of the mass, as benign and malignant masses are similar.
When a benign tumour is removed, the prognosis is good, but the appearance of new tumours along the mammary chain is very frequent.
When the tumour is malignant, the prognosis is worse, as lung metastases are frequent. Palliative treatment may be administered until the patient's quality of life is no longer optimal.
Hélène Rembeaux DMV, IPSAV (zoologic medicine)