Rats are nocturnal animals and they have rather poor visionVision The sense of sight. In rodents this sense is moderately well developed.. They avoid areas with a light intensity of > 25 lux. Their senses of smell, touch, and hearing are well developed. The animals perceive and are sensitive to 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. (> 20 kHz). Rats communicate with each other by means of pheromonesPheromones Scented substances that have a signaling function for the animal species that secretes them. and (ultrasonic) vocalizationsVocalisation 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.. Of the sounds they produce, a frequency of ~20 kHz is associated with 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. or discomfortDiscomfort A state of pain and distress in laboratory animals. (see movie 1), and a frequency of ~50 kHz with increased well-beingWell-being 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. (see movie 2). Specific ultrasonic calls are produced in aggressive and sexual situations as well as mother-pup interactions.

Pheromones

Pheromones play an important role in rat communication. Pheromones are emitted to warn conspecifics of danger, to scent-mark territories, to interact with the opposite sex etc. In rats, as in mice, the olfactory organ is the most important sense organ.

Whiskers

Rats also have well-developed whiskers. Deflection of a whisker, whether through direct contact or air movement, triggers a nerve impulse that is processed in the cerebral cortex.