Do mice cry in the same way humans do, shedding tears and making distressed vocal sounds? While mice do not produce watery tears like humans, their responses to pain and distress are observable through specific physiological and behavioral changes. Understanding these unique expressions provides insight into their well-being.
Visible “Tears” in Mice
Mice do not shed watery tears in response to emotional states. Instead, they produce a distinctive reddish-brown secretion known as porphyrin, or “red tears.” This substance originates from the Harderian glands, located behind their eyes. The scientific term for this phenomenon is chromodacryorrhea, which literally means “excessive production of colored tears.”
The appearance of these porphyrin-pigmented tears is a physiological indicator. Increased porphyrin secretion often signals that a mouse is experiencing stress, illness, or irritation. For example, factors like poor nutrition, dehydration, pain, systemic infections, or environmental stressors such as overcrowding can lead to chromodacryorrhea. This reddish staining around the eyes and nostrils, sometimes transferred to the paws from grooming, serves as a visible cue that an animal may be unwell.
Understanding Mouse Vocalizations
Mice communicate through a range of vocalizations, many of which are beyond the limits of human hearing. These high-frequency sounds, known as ultrasonic vocalizations (USVs), typically occur above 20 kilohertz. Mice use them in various social contexts, including distress, pain, and discomfort.
Mice also produce audible squeaks and chirps, particularly when experiencing stress or pain. Young mouse pups, for instance, emit USVs when separated from their mothers or when they are cold, signaling their distress. Recent research suggests that pain-stimulated USVs from one mouse can induce heightened pain sensitivity, or hyperalgesia, in other mice exposed to these sounds. This indicates a form of emotional transmission through auditory cues, highlighting the significance of these vocal expressions in their social environment.
Behavioral Signs of Distress
Mice exhibit various behavioral changes that indicate pain, distress, or discomfort. Observing these behaviors is important for assessing a mouse’s welfare. Common signs include a reduction in overall activity levels and a disheveled appearance, such as ruffled fur or a lack of grooming.
Mice in distress may also adopt an abnormal posture, like a hunched back, or show a decreased interest in food and water. Behavioral shifts such as increased aggression when handled, or conversely, withdrawal and separation from cage mates, can also signal that a mouse is not well. Other indicators include squinty eyes or teeth grinding. Scientists have also identified that mice display changes in facial expressions that correlate with different emotional states, similar to humans.