CVMA | Documents | Keeping Your Mouse in Good Health for Life

Keeping Your Mouse in Good Health for Life

October 24, 2012

Not everyone wants to keep their house mouse-free! Mice are popular pets and proper care will help to ensure that they live happy, healthy lives.

The mouse is a member of the Order Rodentia, Family Muridae and sub-family Murinae. The scientific name for the common pet and research species of mouse is Mus musculus. Originally from Europe and the Far East, the mouse is quite happy with its pet status since historically mice were considered vermin and were promptly exterminated.

 When selecting a mouse for a pet, make sure that the source stock is healthy and that the mouse appears healthy, with normal activity levels, bright eyes and shiny coat.

Basic Biology

  • The average size of the common adult mouse is 33 g for females and about 30 g for males.
  • With proper care, a mouse lives an average lifespan of 18-36 months.
  • Mice have a very fast heart rate, with 400-750 beats per minute being average! They also breathe very fast, often approaching 100-150 breaths per minute!
  • A mouse’s front teeth, or incisors grow continually over their lifespan.
  • Though mice do not hibernate, they have a special kind of body fat called brown fat, located mostly in a deposit between the shoulder blades. Bears and other hibernating animals possess brown fat; neonatal humans also possess a small brown fat pad, though only a few patches of these special fat cells remain in us as adults! In mice, the brown fat helps them cope with changes in the environmental. Instead of shivering, they increase their metabolic rate and draw upon the fat pad for energy.
  • Though it is not understood, a mouse has a much more developed right lung (4 lobes) than left lung (1 lobe).


It is best to feed your pet mouse a commercial pelleted mouse feed. This feed will contain all of the nutrients essential to your mouse’s diet. Buying small bags of feed at a time will ensure that key nutrients do not break down due to long storage times. Fresh water should be available at all times.


By about 2 months of age, mice are old enough for breeding. The females cycle every 5 days, and when they accept the male the heat period lasts only one night. If breeding is to occur, the male and female mouse should be housed together. Pregnancy lasts about 20 days and there are approximately 11 pups in a littler. Pups are weaned from their mother at approximately 21 days old when they weigh about 11g.


When it comes to housing your mouse, bedding with ground corncob is inexpensive and safe. Aspen shavings and newsprint ink-free paper products are fine but pine and cedar shavings should be avoided. It is important to use a cage designed for mice, as they can wiggle between the bars of cages intended for large rodents and rabbits. Aquariums are a popular housing option.

 You should clean your mouse’s cage every 2-4 days. Provide lots of bedding material and a cubby in which to nest. Water should be provided in a bottle. Avoid placing your mouse cage in drafty areas, in direct sunlight, or exposing your mice to extremes of temperature.

Toys are much appreciated; toilet paper rolls and Kleenex boxes are a fun diversion!

Handling and Behaviour

When mice are surprised, they can give a firm nip with their incisor teeth. Approach them slowly and let them know you are there before picking them up. Lift your mice by gently grasping the tail base. Holding the tail further down can lead to serious injury. When tame, a one handed lift is preferred. Avoid squeezing a mouse’s body and be careful not to drop a mouse during transport.  Many people carry their pet mice in their pockets to keep them secure. Tame mice will enjoy sitting in your lap or hand and being petted.

Health Considerations

An interesting feature of mice is the distribution of the mammary glands or milk producing tissue. Rather than being near the nipples as with most mammals, a mouse’s mammary glands extend all the way up to the neck and sides of the body wall. This spread out pattern means that if mammary gland cancer develops, mastectomy or surgical removal of mammary glands is not a good option as it is with most mammals.

If social stress is present, wounds may be a problem. Some mice also “stress barber” their fur if dominance issues exist in a group.

Your veterinarian will provide information on the common bacterial, fungal, parasitic and viral diseases in mice. When introducing new mice to the home, make sure that they are isolated from other mice until you are sure no diseases (ex. ringworm) are being carried into the environment.