Like most rodents, mice are prey animals with a range of predators such as urban owls and cats. As a prey species, mice will attempt to hide any signs of distress or pain. In the wild, this is can be a beneficial behaviour because many predators will choose prey which appear weaker or slower than the rest. However, it can also make it difficult to determine the health of your mouse.
A happy and healthy mouse has a sleek coat that is well groomed and tidy. His eyes are bright and alert and his skin is flush slightly pink. When pinched at the scruff, the skin should be elastic and smooth. His body should be filled out and usually slightly plump. When placed in the cup of your hand, the mouse should be curious and attempt to investigate his new surroundings. A mouse that has been well cared for and well acclimatized to humans should not attempt to bite.
An unhappy or distressed mouse many show many or few symptoms. General signs of stress may present itself as a ruffled, ungroomed appearance. The eyes may be dull. This is when you should start taking a closer look at your mouse.
- She may show other grooming-related symptoms such as an oily coat (eg. diarrhea) or patchy fur (eg. over grooming, ulcerative dermatitis).
- She may have signs of skin irritation, in the form of reddened areas and inflammed skin (eg. ulcerative dermititis)
- She may be isolating herself from cagemates. As mice like to hide their discomfort, when it is obvious that a mouse is acting “differently” from the other mice, it is a definite sign that some thing is wrong. When isolation is accompanied by a lethargic appearance and lack of activity, this often indicates that the mouse is in extreme pain or discomfort and should be taken very, very seriously.
If these signs are not noticed immediately, an unhappy mouse may progress to more serious symptoms. For example, the spine may begin to show itself as the mouse loses weight. When pinched at the scruff, the skin might show a “tented” appearance rather than being elasticky – this is a sign of dehydration.
Keep in mind that mice are very little animals and when things go downhill, they can get bad very quickly. Do your mice a favour and keep an eye on them! Things like dehyration or over-grooming should be treated immediately. Stress and over-grooming can often be prevented through gentle handling and adequate environmental enrichment. Give your mice something to chew on other than each other! And finally, if it looks like a mouse might be in pain, realize that he’s probably been in pain for longer than you realized and euthanize the poor little guy.
(And then go revisit your protocol and ask yourself what you can do to prevent this from happening again!)