TABLE A-6 Common clinical signs associated with pain in small mammals

Production of fewer, smaller, or no fecal pellets

Reluctance to curl when sleeping (ferrets)

Tucked into abdomen


Strained facial expression, bulging eyes

Half-closed, unfocused eyes

Increased frequency and depth of respiration or shallow breathing


Pushing abdomen on the floor


Stiff movements

Polyuria/polydipsia (especially with GI pain)


Head extended and elevated

Overgrooming/lack of grooming


Vocalization (squeal usually fear in rabbits)

Porphyrin secretion

Stretching with back arched


Stinting on palpation

Squinting (especially ferrets)

Hunched posture

Absence of normal behavior

Teeth grinding (bruxism)


Reprinted with permission from Macmillan Publishers Ltd: [Lab Animal] (Mayer 2007), copyright (2007). Mayer J. Use of behavioral analysis to recognize pain in small mammals. Lab Anim 36(6):43-48.

On the following page is a score sheet that may be used for behavioral phenotyping in mutant mice. As stated in the report, genetically modified mice may exhibit abnormal behaviors, but those behaviors may be characteristic of the background strain or environmental factors rather than a result of genetic modification. Background strain effects are particularly important where new genetic lines are not completely inbred. In those cases, variation should be expected as a result of different proportions of the progenitor background strains in each animal. Careful review of the characteristics of the background strains is necessary to avoid erroneously attributing differences in test results to the genetic modification. The score sheet was developed by Julie Watson, MA, VetMB, DACLAM, Johns Hopkins University Department of Molecular and Comparative Biology, adapted from Crawley and Paylor (1997).

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