An animal that is alarmed by environmental stimuli will display freezingFreezing An autonomic reaction that causes the animal to stiffen briefly when faced with sudden danger or when frightened. behaviour, alternating with scanningScanning 1) Probing using some form of imaging; e.g., encephalography (recording the activity and structure of the brain). 2) As a behavioral concept: alert posture in a fight/flight situation. Slow sideways swaying of the head and anterior part of the body.. Both behaviours will disappear when the animal is at ease again.

A deviant response to a stimulus can be determined in several ways. Most tests are geared towards demonstrating a weakening of a reflexReflex An involuntary reaction to a certain stimulus., such as the closure of the eyelid when an object approaches the eye (eyelid reflex), the narrowing of the pupil in response to light (light reflexLight reflex Reflex narrowing of the pupil when light shines into the eye.), the response to noise (such as clapping hands above the cage, see movie 1), the toe pinch reflex and the tail pinch or flick reflex (see pictures and movies 2 and 3).

Reponse to handlingHandling Manipulating the animal, picking it up, holding it, and restraining it.

Handling an animal has a function in detecting 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./distressDistress It indicates a disadvantageous environment in which the animal is no longer able to adapt in a biologically successful manner to the stressors to which it is exposed. One speaks of distress when the level or the duration of stress are such that significant changes in biological function are required to survive. since the investigator/animal care worker can focus on abnormal signs that may not be specific items on the score sheetScore sheet Form for recording clinical signs to determine animal well-being and if appropriate the application of a humane or scientific endpoint. (e.g. weight loss, hypothermiaHypothermia A decreased in body temperature (mouse <36.5 °C/97.7 °F; rat <37.5 °C/99.5 °F). The extremities (ears and paws) may be white and are cold to the touch., the presence of tumorsTumor Neoplasm, new growth. Is predicated upon autonomous growth of cells or tissues into benign or malignant tumors.). Responses which may be observed on handling include: vocalisationVocalisation Sounds produced by animals that may or may not (ultrasound, infrasound) be audible to humans. The rat associates 20 kHz sounds with fear or pain and 50 kHz sounds with pleasant situations., aggression, lethargyLethargy 1. somnolence; 2. state of disinterest and inactivity., or weakness (see movies 4 and 5).

Righting reflex

When an animal is placed on its back, it will immediately attempt to return the body to an upright position. This righting reflex may be abnormal or even absent (see movie 6). This is often indicative of serious health problems, sometimes of a neurological nature, but more usually, exhaustion. The inability of an animal to get to its feet can be a clear indication for euthanasiaEuthanasia Killing by applying methods that rapidly lead to unconsciousness and death without pain or discomfort to the animal. Methods for euthanasia can be divided into mechanical and physical..

Response to noise

Rodents are sensitive to sudden noises particularly in the high-frequency range, such as 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.. This sensitivitySensitivity Awareness of sensations. This includes the response to touch, pressure, varying temperature (heat, cold), light, and awareness of muscle tension (proprioception). Excessive stimulation of the nociceptors causes a sensation of pain. Chemicals can also cause sensory effects. can be reduced by providing continuous background noise (for example, radio music). The animal’s reaction to sound can be tested by making a sudden noise e.g. hand clapping above the cage (see movie 1). A healthy animal will respond with a startle reflex: it jumps up, then freezes, and hunches. A response to noise that differs from the reactions above needs to be investigated.

Response to light fluctuations

A light intensity of more than 25 lux will awaken an animal from its sleep, after which it will leave its resting place to find a darker location to go back to sleep. The red light response test consists of switching off all normal lighting and observing the animal in a dark environment (with infrared lighting, if needed). A healthy nocturnal animal will become active within five minutes; it will start groomingGrooming The behavior animals engage in to keep clean. Grooming removes dirt from fur and body openings. Absence of this behavior indicates reduced well-being., stretching, exploring, climbing, or playing.

Albino specimens do not tolerate light well. The absence of a (protective) pigment in the eye makes it susceptible to damage from prolonged exposure to > 60 lux, which can cause degenerationDegeneration Pathological changes in cells or tissues that reduce their viability. of the retinaRetina The inner membrane of the eye that contains the nerve cells (light-sensitive)..

Interaction with conspecifics

By nature, rats and mice are social animals that need interactions with their own kind (both during rest and activity) in order to function optimally. Their social behaviourSocial behaviour The gamut of behaviours displayed by an animal in the presence of other animals that are either not displayed when solitary, or are not displayed in the same manner. covers a wide range of activities. Aggression intended to determine the social hierarchy in the group may be an aspect of this behaviour. Aberrant behaviour directed at cage mates is a reason for increased vigilance.

SolitarySolitary Alone, separated. In the context of mice and rats, the term pertains to housing the animal in a cage by itself. Social isolation is often an adverse welfare situation. housing in rodents can cause aberrant behaviours such as stereotypic behaviourStereotypic behaviour A phenomenon that appears as a response to chronic stress. It is manifested as a set repeated pattern of seemingly purposeless activity.. With the exception of adult male mice, solitary housing should be avoided. Should this be unavoidable, then it is important to organize the housing in such a way that exchange of scents and sounds with conspecifics can take place and that cage enrichment is provided (see movie 7).

Interaction with the environment

As soon as an animal is placed in an unfamiliar environment, it will start to engage in exploratory behaviour (see movie 7). This helps the animal to get to know its surroundings, which then become controllable and predictable. Controllable means that the animal can exert an influence on its environment such as make a burrow. This way, the animal can adapt its environment to its needs. Predictability means that an animal can predict what will happen in its environment.

Controllability and predictability contribute significantly to laboratory animal welfareWelfare A complex and dynamic internal state that includes: successful biologic functioning, positive experiences, and absence of negative conditions. The animal adapts effectively to internal needs and external stimuli and maintains a good mental state..