Q & A

From the March/April 1998 Rat & Mouse Gazette


I have owned a series of pet mice, and each one has had the habit of filling its water bowl with shavings from the bottom of its cage. Why they do that? Is it a modification of some behavior in the wild?

I've tried books and (other) sources. They all say it's typical behavior for caged mice, but none can tell me "why" they do it. Can you help?


First, in nature, mice would not have their water source located in their den, so I would not consider this a "wild" behavior. However, it may stand to reason that because they do not have their water source in their home naturally, they would try to cover it up or dry it out to maintain a clean/dry environment. I'm not sure our domesticated mice would react on the same level, though.

My observation is that mice like to run, jump, and play about and during the course of these activities bedding is kicked up and lands in the bowl. The bedding then soaks up the water, as it should, and then makes a mess. This is common of any pet housed in a small cage with bedding material, not just mice.

My recommendation is that you invest in a hanging water bottle. This eliminates the threat of bacteria or insect contamination of the water, and keeps the bedding clean and dry. If you intend to continue using the bowl method, you should place the bowl on top of something so that it is not ground level with the bedding, but this may make it difficult for the mice to reach it.

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I have had pet mice for the past three years. I have had about 5 out of 20 mice die from tumors. Is this a high number? What causes tumors in mice? Perhaps a better question - are there factors that can be controlled...such as diet, inbreeding or something else? I love my mice and do not want to see them suffer. How much suffering is involved in a death by tumor? Would it be more humane to have a mouse with a tumor euthanized? Also, I am now, I hope, in a financial position that I could afford to pay for surgery. Can you give me some rough guidelines as to how much a surgery to remove a tumor on a mouse should cost? I live in Monterey, Califorrnia, if that is helpful in regards to the pricing question.


Yes, I do think five of 20 mice is a fairly high number. I, myself have had about 10 in 200 pass on due to tumors. I have observed that the mice that have developed tumors were either from a pet store and did not have a lineage available, or were pedigreed mice that demonstrated inbreeding in their background. I further recognized in my own mice that the children of mice that develop tumors appear to have a higher incidence of tumor occurrence also. This information suggests that it may be hereditary.

There are a few things you can do to minimize the occurrence of tumors. You can record your breedings to be sure there is not any inbreeding, as inbreeding can weaken the immune system of the offspring and make them susceptible to other ailments. You can then discontinue breeding from any individual that develops tumors and track down and avoid breeding from their offspring. Another deterrent is to obtain mice from a reputable breeder who can provide you with a pedigree and tumor history of the line when you purchase your pet, and be available for questions when you have them.

Diet can also play a role in causing tumors in both mice and rats. A high fat diet can cause fatty tumors, so it is recommended to feed a low fat diet consisting of good healthy foods.

Pain and suffering caused by tumors depends entirely on where and what type of tumor it is. For the most part, if your pet does not appear to be in any pain it probably isnít, but it is still recommended to have the tumor removed as early as possible. You need to be sure to find a capable veterinarian as many are not trained in performing surgery on such small animals. Once you find a good vet, expect to pay anywhere from $50 to $150 for tumor removal surgery on a mouse or rat.

If the tumor is inoperable, be sure to feed your pet very well as the tumor will sap the energy from your pet. Thereís no need to consider euthanasia until your pet either seems to be in pain, or is no longer eating, drinking, and enjoying his life.

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My ratís head is tilted to one side and sheís having a hard time walking. She falls over sometimes and canít get her balance back. What could be wrong with her?


Her condition, commonly referred to as "wry neck" could be caused by a number of things, but the most likely cause is an inner ear infection. She will need to be seen by your vet to determine whether or not her eardrum is still intact and to decide upon the proper course of treatment. If the cause is an infection, she definitely will need to be treated with antibiotics from your vet, but he may also prescribe an ear drop which contains both a topical antibiotic and an anti-inflammatory drug.

In most cases with this treatment, it only takes a few days for a rat to get its balance back, but the treatment must be continued for at least one to two weeks.

Another possible cause of head tilt can be a pituitary tumor, which is more common in older female rats, but can be seen in younger rats and even in male rats. There is no treatment for this condition that will cure it, however, anti-inflammatory drugs, such as Prednisone or Dexamethasone, may reduce the swelling slightly and prolong the life of the rat for a short time. Spaying female rats is said to reduce the risk of pituitary tumors, but it is still no guarantee.

A stroke is another possibility. Again, it would be more common in older rats, but itís not impossible for a younger rat to have a stroke. Anti- inflammatory drugs may help in this situation, too, but for the most part, only time will tell if the damage is permanent or not. In many cases, a full recovery from a stroke can be made in a short period of time (a few days to a week).

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