House mice are highly communicative animals, constantly relaying information about their environment, social status, and reproductive readiness. The great majority of their “conversations” take place in a frequency range inaccessible to the human ear. Understanding mouse vocalizations requires looking beyond the occasional, faint squeak to the sophisticated world of sound we rarely perceive.
The Audible Range: Squeaks vs. Ultrasonic Calls
Human hearing typically spans a range from 20 Hertz (Hz) up to 20,000 Hz, commonly referred to as 20 kilohertz (kHz). However, the upper limit for most adults is often closer to 15-17 kHz, as the ability to hear high frequencies naturally diminishes with age.
The high-pitched sounds a person might hear, such as squeaks, peeps, or chatters, are generally limited to moments of high stress. These are audible distress signals, warning calls, or sounds made during aggressive encounters, peaking near the upper boundaries of human hearing, just under 20 kHz. Such sounds are often loud enough or low enough in frequency to cross the threshold into our perception, but they represent only a small fraction of the mouse’s total acoustic repertoire. Most mouse communication occurs in the ultrasonic range, starting at frequencies above 20 kHz, making it inaudible to human ears.
The Science of Ultrasonic Communication
The true language of mice is found in their ultrasonic vocalizations (USVs), which primarily range from 30 kHz to 120 kHz. These high-frequency sounds are used for almost all social interactions. One of the most studied USVs is the isolation call, produced by mouse pups when they are separated from their mother or feel cold. These distress calls, often ranging from 40 to 80 kHz, prompt the mother to search and retrieve her young.
Adult male mice also use USVs as complex courtship “songs” when they encounter a female. These vocalizations are not simple, single-note squeaks but are highly structured, frequency-modulated calls that resemble the complexity of birdsong. The USVs play a significant role in mate selection, as the female mouse can discriminate between the individual signatures within the male’s song. Mice evolved to use these high-frequency calls because ultrasonic sound waves attenuate, or fade, more quickly than low-frequency sounds, which helps prevent detection by predators with better low-frequency hearing.
Non-Auditory Signs of Mouse Presence
Since most mouse communication is silent to us, detecting their presence relies on looking for physical evidence rather than listening for squeaks. The most definitive indicator is the presence of droppings, which are small, dark, and pellet-shaped, about the size of a grain of rice. These are often found scattered along established pathways, near food sources, or inside cabinets.
Mice have continuously growing incisor teeth, requiring constant gnawing on various materials for trimming. Evidence of this behavior appears as fine, shredded gnaw marks on food packaging, wood, plastic, or electrical wiring. As mice repeatedly travel the same routes along walls and baseboards, the oil and dirt from their fur leave behind dark, greasy streaks known as rub marks. These physical indicators, along with a distinct, musky, ammonia-like odor from accumulated urine, are far more reliable signs of a mouse presence than the rare, audible squeak.