Rats possess a highly developed sense of hearing, important for their survival and interaction with their environment. Their auditory capabilities extend far beyond what humans can perceive. This acute sense allows them to navigate, detect dangers, and communicate.
The Science of Rat Hearing
The auditory range of rats is considerably broader than that of humans, spanning from approximately 200 Hz up to 80 or 90 kHz. In contrast, human hearing typically ranges from about 20 Hz to 20 kHz. This extended range means rats can perceive sounds in the ultrasonic spectrum. Their most acute hearing sensitivity lies between 8 and 38 kHz, with some research indicating peak sensitivity around 40 kHz.
Rats demonstrate high sensitivity to even faint noises, capable of detecting sounds as subtle as a thumb and forefinger rubbing together. While humans generally exhibit better hearing at lower frequencies (e.g., 1000 Hz at 2 decibels), rats require a louder sound (e.g., 24 decibels) to perceive the same frequency. However, their ability to hear higher frequencies compensates for this difference. Although rats possess two ears, their smaller head size results in less precise sound localization compared to larger animals.
How Rats Use Their Hearing
Rats rely on their hearing for survival, often compensating for their relatively poor eyesight. Their hearing helps detect potential predators, such as owls and rattlesnakes, which rats can perceive before a strike. It also plays a role in navigating their surroundings, particularly in dark environments where visual cues are limited.
Communication is a primary function of rat hearing, primarily through ultrasonic vocalizations (USVs). These high-frequency sounds, inaudible to humans, facilitate complex social interactions. Rats emit different types of USVs depending on their emotional state; 22 kHz calls signal distress, while 50 kHz calls are linked to positive states like play or mating. Infant rats also produce specific ultrasonic “isolation calls” when separated from their littermates.
Rats and Sound: Implications for Humans
Understanding rat hearing has practical implications, particularly in pest control and the care of pet rats. Ultrasonic pest repellents, designed to emit high-frequency sounds that are supposedly intolerable to rodents, are marketed to deter rats. However, numerous studies have shown these devices to be largely ineffective, as rats adapt quickly to the sounds. The Federal Trade Commission has even issued warnings against unsubstantiated claims made by manufacturers.
For pet rats, their sensitive hearing means they are highly sensitive to loud noises. Exposure to excessive sound can lead to stress, anxiety, and fear. It is advisable to house them in quiet areas, away from loud music, televisions, or other electronics. In urban environments, rats have adapted to human-generated sounds because their social communication occurs in the ultrasonic range, above the din of human noise. Despite this adaptation, prolonged exposure to high noise levels can still negatively impact rat populations.