Stress Assessment, Reduction, and Science | 545 rodents’ light/dark cycle is reversed, this means that most observations will be made when the animals are asleep, and so any behavioral indicators of stress will not be manifested What Makes Laboratory Animals Stressed? Although laboratory animals not lack essential physical needs such as food and water, there are many major and minor environmental perturbations encountered in animal facilities that can significantly contribute to a stress response in the animals For example, when an animal is moved to a new cage, increases in blood pressure, heart rate and locomotor behavior occur, which are indicative of a stress response With regard to the environment in the rooms inhabited by laboratory animals, the lighting, temperature and humidity are usually well controlled However, there are many uncontrolled sources of noise in animal facilities, most of which derive from human activities These include high-pressure hoses, cage cleaners, and air-conditioners or heaters, squeaking doors, carts, and movable chairs, and jangling keys Rodents, in particular, are sensitive to these noises, and studies show that this sensitivity does not diminish with time, as is commonly assumed These noises can alter rodents’ behavior and even adversely affect their health Yet, surprisingly, many scientists are unaware that loud noises in their animal facilities can affect research outcomes and compromise their data The noise and vibration of building construction have caused major problems with rat behavioral studies and experiments requiring unstressed control rats One study in rats (Shepherd et al., 2004) even showed that building- induced stress rapidly inhibited glucose absorption by the intestinal transporter, GLUT2 Several studies have shown that noise in animal care facilities can reach as high as 90 –100 dB Such levels of noise can induce physiological and behavioral responses in laboratory rodents such as increased plasma corticosterone levels, reduction in body weight, decrease in gastric secretion, changes in immune response and tumor resistance, and a decrease in reproductive function Much of the noise in institutional animal facilities is caused by personnel activity, because measurements have shown that environmental noise levels decrease dramatically at night and during the weekends Apart from noise problems, research animals are often housed in small cages with no source of enrichment, such as wheels, shelves, or tubes Such devices enable animals to exert some control over their environment, such as escaping an attack from a cage-mate by moving to another level in the cage or hiding Often, researchers are unwilling to include such items in their animals’ cages because other researchers not However, rigorous standardization of the environment, particularly if it leads to barren surroundings, increases the risk of obtaining results that, because they are specific to a narrow set of conditions, cannot be compared with other researchers’ results The word boredom is used to describe the experience of animals who spend their lives in highly monotonous environments Sometimes the animals fill the time with abnormal behaviors including excessive grooming of self and cage-mate(s), and repetitive patterns of movement known as stereotypies The excessive grooming can cause regions of inflammation, especially on the neck area These behaviors disappear when the animals are provided