Rats are highly social animals that communicate through various vocalizations. These small rodents use a complex system of sounds to interact, conveying different messages. This helps them navigate their environment and maintain social bonds.
Beyond Human Hearing: The Ultrasonic World of Rat Calls
Rats produce a range of sounds, but much of their communication occurs in the ultrasonic range, beyond human hearing (above 20 kilohertz, or kHz). These high-frequency sounds, known as ultrasonic vocalizations (USVs), range from 20 to 100 kHz. Specialized equipment, such as “bat detectors,” is necessary to convert USVs into an audible range for human study.
While USVs form the majority of their vocal communication, rats also produce some audible sounds. These include squeaks, chirps, and hisses, often heard during intense interactions. However, most social behavior communication primarily takes place in the ultrasonic realm.
What Rat Calls Mean
Rat vocalizations, both ultrasonic and audible, carry specific meanings depending on their frequency and context. Researchers categorize USVs into two main types, signaling distinct emotional states:
22 kHz Calls
Adult rats emit these calls in aversive or threatening situations, serving as alarm signals that warn other rats of danger or stress. These calls are long in duration and have a relatively constant frequency.
50 kHz Calls
These USVs associate with positive emotional states and appetitive situations. These shorter calls are emitted during social interactions, play, mating, or in anticipation of rewards like food. The presence of 50 kHz calls can indicate pleasure, social bonding, and even a form of “rat laughter.”
Beyond these, rat pups emit distinct 40 kHz USVs when isolated from their mother and litter, signaling distress and prompting maternal retrieval behavior.
Audible sounds also convey meaning. High-pitched, loud squeaks indicate fear, pain, or distress. Softer, more playful squeaks are heard during social interactions and playtime. Rats may also produce chirps or clicks, which are often interpreted as expressions of happiness or excitement.
How Rats Make Their Sounds
Rats produce their vocalizations using their larynx, similar to how other mammals generate sounds. The larynx contains specialized structures, including vocal folds, which vibrate to create audible sounds. For ultrasonic vocalizations, the mechanism is thought to involve a unique “whistle” system.
In this whistle mechanism, an airstream from the lungs is directed against a sharp edge within the larynx. This action sets an adjoining air column into rapid pulsations, producing high-frequency sounds. The ventral pouch, an air sac-like cavity in the larynx, may also act as a resonator, amplifying these ultrasonic signals. The rapid contractions of intrinsic laryngeal muscles precisely control the vocal folds and glottis to shape these diverse sounds.
Why Understanding Rat Calls Matters
Studying rat vocalizations provides valuable insights across various fields, from scientific research to animal welfare. In scientific research, analyzing rat calls helps scientists understand complex behaviors, neurobiological processes, and communication across species. For instance, the two main USV types (22 kHz and 50 kHz) are reliable indicators of a rat’s emotional state, making them useful in studies of affect, motivation, and social behavior.
Understanding these calls is also important for pet owners, enabling them to better interpret their rats’ well-being and social cues. Recognizing signs of distress or contentment through vocalizations can help owners provide better care and improve their pets’ quality of life. Furthermore, this knowledge contributes to enhancing animal welfare, especially in laboratory settings, by providing objective measures of stress or positive states. The ability to decode rat communication allows for a deeper appreciation of these animals’ complex social lives and their responses to their environment.