Physical factors

Pups, sick animals and those who have undergone surgery, have a strong preference for slightly elevated ambient temperatures and they like a place to hide. 

Humidity and ventilation

The animals are also sensitive to large fluctuations in humidity and frequency of ventilation; i.e. respiratory problems and ringtail (see picture) are associated with high and low relative humidity, respectively. Extremes of high- and low ambient air humidity, and rapid changes thereof, are to be avoided. 

Ultrasound sensitivity

In addition, rats are very sensitive to high frequency sound (ultrasound). This type of noise has to be avoided, especially while the animals are resting. Electronic equipment in animal rooms can generate this type of disturbance. Albino rats are particularly sensitive to light. Light intensity should be limited to a maximum of 60 lux around these animals.