We generally differentiate between acute painPain The negative sensory or emotional experience that indicates awareness in the animal of injury or the threat of injury to the body. This negative experience induces changes in an animal’s behavior and physiology, intended to limit the effect of, or avoid the injury, to reduce the chances of repeated injury and to promote recovery. and chronic pain. Acute pain (post-surgery or disease-related) is often characterized by a number of behavioural changes, such as aggression, isolation in the group, restlessness and self-mutilationSelf-mutilation Self-destructive behavior (self-mutilation). It may be an aspect of stereotypic behavior and the result of boredom. Self-injury may also be caused by chronic pain/itching or by a central nervous system disorder. Synonyms: autotomy, automutilation, self-injury., as well as by autonomic reactions such as dilated pupils and rapid breathing.

Chronic pain

With chronic pain, such as seen with tumorsTumor Neoplasm, new growth. Is predicated upon autonomous growth of cells or tissues into benign or malignant tumors., notable effects may be poor overall condition, piloerectionPiloerection Erection (standing up) of hair (fur) — (also known as a starey or harsh coat) often caused by poor health. Frequently one of the first signs of pain, distress and discomfort in animals., social isolation and a hunched posture (see picture). The animals will lose weight and are less active. Diseased mice tend to take in little water, which will lead to rapid dehydrationDehydration “Drying out” because of reduced fluid intake or excessive fluid loss. The degree of dehydration can be determined by gently pinching and twisting the skin and releasing it, allowing the skin to fold and flatten (the turgor test)..

Pica behaviourPica behaviour A pathological tendency to eat or drink unusual substance(s) e.g., bedding material.

When mice are in either acute or chronic pain, they may start to engage in pica behaviour, which is defined as eating bedding materialBedding material The material (also called “substrate”) used to cover the floor of a cage. This material needs to be absorbent, non-toxic, non-dusting and comfortable to the animals. or other strange, non-food objects (see movies).