The question of whether a rat “screams” when it dies or is severely injured is a common perception, often depicting a high-pitched shriek audible to humans. While rats are capable of loud vocalizations under threat, their primary alarm signal is far more complex than a simple scream. Understanding the rat’s communication system reveals a sophisticated language that operates just beyond the limits of human perception.
The Direct Answer: Do Rats Really Scream?
Rats emit intense vocalizations when they are in pain, under attack, or facing imminent danger, contexts that often precede death. However, the sound most commonly associated with these moments is not the human-audible shriek often portrayed in media. This is because the majority of the rat’s communication occurs in the ultrasonic range, frequencies too high for the average adult human ear to detect.
Some rats may produce a high-pitched squeak or screech within the human hearing range (below 20 kilohertz, or kHz), especially when physically restrained or severely injured. This audible noise is typically a short, sharp vocalization that can be startling. Yet, the foundational biological response to fear, pain, or a predator is the emission of powerful, sustained ultrasonic calls that are functionally inaudible to us.
The Science of Rat Vocalizations
The rat’s vocal repertoire is divided into two major categories based on frequency, each signaling a distinct emotional state. Vocalizations around 50 kHz are generally associated with positive emotional states, such as during play, mating, or in anticipation of a reward. These calls are often short and frequency-modulated, sometimes referred to as ‘chirps’ or ‘trills’ among researchers.
In contrast, the distress signal is a long, low-frequency-modulated call centered around 22 kHz. An adult human’s hearing typically cuts off around 16 to 20 kHz, meaning this 22-kHz alarm call falls just outside our range of perception. This difference explains why people rarely hear the alarm signal, even when standing nearby. Special equipment, such as a bat detector, is required to convert these ultrasonic calls into a frequency that human ears can process.
The evolutionary benefit of using these high frequencies is likely linked to avoiding detection by certain predators, while still communicating clearly with conspecifics. A sound at 22 kHz travels less effectively over long distances than lower frequencies, which helps keep the distress signal somewhat localized. The 22-kHz call is long in duration, often lasting several hundred milliseconds up to over a second, and lacks the rapid frequency shifts of the happier 50-kHz calls.
What Distress Calls Communicate
The 22-kHz vocalization is a clear alarm call, communicating a negative affective state to nearby rats. These long, aversive calls are produced in stressful situations, including the presence of a predator, fear conditioning, or defeat in a social encounter. The call is not solely a signal of imminent death, but rather an indicator of severe discomfort, anxiety, or acute danger.
When a rat emits a 22-kHz call, it serves as a social alarm, prompting specific defensive behaviors in other rats within earshot. Conspecifics exposed to the playback of these distress calls often exhibit freezing behavior, a typical fear response in rodents. This reaction suggests the call functions to alert the community to danger, allowing them time to hide or prepare a defense.
The duration of the 22-kHz call can also communicate the level of distress experienced by the animal. Shorter calls may indicate frustration or uncertainty, while longer calls signal a more profound state of alarm or anxiety. The distress call serves a clear purpose in group survival by maximizing the chances that nearby relatives will avoid the source of the threat.