Mice are highly social animals that use complex behaviors and vocalizations to communicate. The common observation of chasing and squeaking is not random but conveys specific information about social status, territory, or reproductive state. Understanding the context of the chase and the type of sound produced is necessary for deciphering the animal’s intent.
The Meaning Behind the Chase
The physical act of one mouse pursuing another is a dynamic behavior with several underlying motivations, each serving a function in the social structure. Chasing is often a mechanism for establishing and reinforcing the social hierarchy, where a dominant mouse will pursue a submissive one to assert its higher status. This type of chase is particularly common when mice are introduced to a new environment, as they must quickly determine their relative positions within the group.
The intent of the chase dictates its intensity and duration; for instance, chases related to territorial defense are typically aggressive and sustained. Male mice, in particular, are intensely territorial and will actively chase away competing males to expel them from their home range, often in conjunction with urine marking to signal the boundaries of their domain. In a reproductive context, a male mouse will pursue a female in estrus as part of a mating ritual, which is a specific form of sexual pursuit.
The pursuit in a mating ritual is distinct from aggressive territorial disputes. Dominant males are more likely to successfully pursue and mate with estrus females. Chasing is also a component of social play, especially in younger mice, where the intent is to build relationships and develop social skills rather than assert dominance or secure territory.
Understanding Mouse Vocalizations
The squeaking sounds humans hear are only a small fraction of the acoustic communication mice use. Audible squeaks, which fall below the human hearing limit of 20 kilohertz (kHz), are associated with high-intensity situations. These lower-frequency calls often signal distress, pain, or extreme aggression during a physical altercation.
The majority of complex social communication occurs in the ultrasonic range, above 20 kHz, often spanning from 30 to 120 kHz. These ultrasonic vocalizations (USVs) are the primary means of conveying nuanced social messages, such as those related to courtship, territorial disputes, and identifying kin. Because USVs are above the upper limit of human hearing, specialized equipment is required to perceive the bulk of a mouse’s communication.
The characteristics of USVs change depending on the context and the animal’s internal state, similar to how human speech varies in tone and pitch. For example, USVs emitted during male-female courtship are significantly longer than those produced during a mild distress situation. While males are the primary emitters of USVs during courtship, female mice also produce vocalizations that are a mix of ultrasonic calls and the more audible squeaks during these interactions.
Distinguishing Aggression from Social Play
Distinguishing between aggressive fighting and social play requires observing visual cues and auditory signals. Aggressive encounters are characterized by prolonged chasing, sustained physical contact, and body language showing intent to harm. Physical signs of aggression include piloerection (the ruffling of the fur) and a distinct sideways or lateral attack posture leading to grappling and biting.
The squeaking heard by humans is a strong indicator of aggression, signaling pain or an imminent threat. In a fight, attacks are often directed at less vulnerable areas like the back and flanks, and the dominant mouse maintains its role as the aggressor. The goal is to establish a clear victor through repeated, forceful actions that often result in visible injury.
In contrast, social play involves brief, non-contact chases that lack the intensity and sustained physical commitment of a fight. A hallmark of play is the alternation of roles, where the chaser and chased switch positions, demonstrating a mutual understanding that the interaction is not serious. Playful chases are generally quieter, with a noticeable absence of sustained audible squeaking, and they do not result in injury or the defensive postures seen in a fight.