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 stressStress An animal’s biologic response in trying to deal with a threat to its internal equilibrium (homeostasis) by internal and external stressors. A failure to do so may lead to ‘distress’ resulting in an inability to cope, leading to poor welfare. are often associated with jumping, freezingFreezing An autonomic reaction that causes the animal to stiffen briefly when faced with sudden danger or when frightened., squeaking, biting, escape behaviour, and sunken sides (in case of abdominal pain).

Rats rarely vomit. However, they can passively bring up food (regurgitateRegurgitate The result of antiperistaltic activity of the esophagus, or violent contractions of the stomach, that result in the return of swallowed food/drink.). When a rat is ‘nauseated’, it may repeatedly lift its head in a motion resembling gagging. They can also display pica behaviourPica behaviour A pathological tendency to eat or drink unusual substance(s) e.g., bedding material., 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.

When rats experience pain, they communicate by squeaking, whistling and screeching, and by producing ultrasoundUltrasound Sound with a wavelength outside the audible range of the human ear. A ~20 kHz frequency is associated with possible discomfort, a 50 kHz frequency is considered environmentally acceptable. Ultrasound is associated with a state of animal welfare in that animals may emit more when they are stressed..