Caring for your new rat or mouse


Biological facts

Average lifespan (rats): 2.5-3.5 years
Average lifespan (mice): 1.5-2.5 years
Weight (rats): 225-500g
Weight (mice): 20-63g
Sexual maturity (rats): 6-8 weeks
Sexual maturity (mice): 6-7 weeks
Gestational period (rats): 20-22 days
Gestational period (mice): 19-21 days.
Respiratory rate (rats): 70-150/min
Respiratory rate (mice): 100-250/min
Heart rate (rats): 260-450/min
Heart rate (mice): 500-600/min
Body temperature (rats): 38C
Body temperature (mice): 37.5C

Most rats and mice will live together with others of the same species quite happily, although males housed together will often fight. They are social animals and are often more relaxed if given company. It is important to introduce animals simultaneously into their environment. Fights may occur if integration is staggered.

General Care

Being a “prey” species, it is important that rats and mice be kept in an environment that is physically protected from predators. Good ventilation is important, as is ease of cleaning. Fish tanks are not recommended. Wire floored enclosures can lead to foot and leg damage. The wire flooring can be covered with newspaper or towelling for additional safety. Hiding places in the form of boxes, shredded paper or PCV pipes should be provided. These animals are escape artists so the cage should be carefully checked for small defects that may allow an enterprising rodent freedom. Rats are site-attached meaning they are likely to return to the same area. Mice are less likely to be recaught after escaping.
Soiled bedding should be removed daily and the enclosure should be thoroughly cleaned once or twice a week. Appropriate substrates include newspaper, towels, grass and artificial turf.
Toys for chewing are greatly appreciated. Toilet rolls, branches and paper are favourites. Rats and mice often like to work out in an exercise wheel. Make sure there are no sharp areas that could catch a leg or a tail.
Rats and mice handled frequently when young usually grow into well socialised adults. When picking up a rodent, it is important to support the entire body. This particularly applies to children as an animal that does not feel securely held will struggle.


Like all animals, rats and mice need access to fresh water. This can be provided as a sipper or bowl. Take care with new pets as they may not recognise the water placed in a different type of container and may dehydrate.
Rats and mice are omnivorous, which means they eat anything that they can! They are usually fed on a basic diet of rodent pellets supplemented with fresh foods. Fresh foods can include vegetables, some fruits and low fat table scraps. Obesity is a common problem so treats must be carefully controlled.


The young usually wean around 3 weeks of age in both species. Mice can begin to breed at 6 weeks of age and rats at 4 weeks of age. It is NOT recommended to breed them prior to 9 weeks of age. If mixed pairs or groups are kept together then castration of the males is advisable.

Common problems

Rats and mice seem quite prone to mammary tumours. These can become very large. In rats 90% of the tumours are benign but in mice 90% are likely to be malignant. Surgical removal is advisable although tumours are likely to recur in other areas of the body.
Respiratory problems can be severe in rodents. Good ventilation, quarantine of new animals and good hygiene will help reduce the incidence of respiratory problems. Reducing the dustiness of the enclosure is important.
Pododermatitis or foot problems can also occur. This can be reduced by close attention to flooring and hygiene. Nails are usually kept trim by exercise.

Health checks

We recommend a post-purchase check of your new rodent to ensure early detection of any problems. It will also ensure that husbandry is optimal. Additionally, regular health checks are advisable, to monitor general health and address any problems sooner rather than later.