What follows are signs that you should be aware to help you judge if an animal is in pain.
Signs of Pain
An animal in pain, regardless of species, usually displays one or more of the following signs:
- Attraction to the area of pain
- Increased skeletal muscle tone
- Altered electroencephalogram response
- Increased blood pressure and heart rate
- Pupillary dilation
- Change in the respiratory pattern
Signs of Acute Pain
- Protection of the painful part
- Vocalization (especially on movement or palpation of the painful part)
- Scratching or shaking of affected area
- Increased rate of respiration
Signs of Chronic Pain
- Licking of area affected
- Licking of other areas if the painful part cannot be reached
- Reluctance to move
- Loss of appetite
- Change in personality
- Changes in eye brightness
Species-Specific Signs of Pain
In compiling general guidelines it has become clear that there are species-specific signs of pain, which should be taken into account when making a practical assessment. Such signs are often associated with what is believed to be a painful condition, although no sign can by itself be regarded as diagnostic of pain and may also occur in conditions in which pain is unlikely to be a feature.
Although a comprehensive description of species-specific signs has not been produced, the following notes and comments might be helpful.
Rabbits in pain may be apprehensive, dull, inactive and assume a ‘hunched’ appearance. They sometimes, however, show aggressive behavior, and activity may be increased with excessive scratching and licking. Reactions to handling are exaggerated, and acute pain may result in vocalization. Respiratory rate may be increased, and there may be a change in feeding activity.
Ferrets in pain often become lethargic and stop bodily grooming resulting in a disheveled look. They usually show a loss of appetite and may also stop drinking.
Pain in rodents usually results in decreased activity, piloerection and an un-groomed appearance, or there may be excessive licking and scratching. They may adopt an abnormal stance with ataxia, but rats and mice may become unusually aggressive when handled. Acute pain may cause vocalization. Inappetence or a change in feeding activity may be noted and, if housed with others, a change in the normal group behavior may be apparent.
Birds in pain may show escape reactions with vocalization and excessive movement. There may be an increase in heart and respiratory rates. Prolonged pain will result in inappetence and inactivity with a drooping, miserable appearance. When handled, the escape reaction may be replaced by a state of tonic immobility.
It is difficult to determine the nature of the response to pain in fish. Responses to harmful stress include an increased ventilatory pattern with excessive movement of fins.
Additional Resources and Information
Recognizing Post-Operative Pain in Animals: Assessing the Health and Welfare of Laboratory Animals (AHWLA)
American Association for Laboratory Animal Science (AALAS) Learning Library