Mice, like most species have a circadian rhythm. Investigators should be aware that this may affect biological data and should standardize the time of day that samples/measurements are taken to avoid this affect. The standard light dark cycle is 12/12. This light cycle can be modified upon the request of the investigator in special circumstances. The adult mouse weighs approximately 40 grams and this small size and resulting large surface areabody weight ratio makes them susceptible to changes in environmental conditions. The core body temperature is easily affected by small changes in temperature which may modify the physiologic responses of the animal The acute hearing of mice makes them highly sensitive to ultrasounds and high pitched noises inducing a stress response that has been empirically related to cannibalism of pups by their dams. The well developed sense of smell is used to detect pheromones used in social interactions. The poor vision of mice makes them unable to detect color and red light is often used to observe animals during the dark cycle