Rat-natomy: Hearing & Vocalization

Lend me your Ear...

   Rats can hear sounds that we cannot: they can hear ultrasonic frequencies well above the range of human perception. Rats produce ultrasound, too, and communicate with each other in squeaks, clicks, and whines that we cannot hear.

   Humans can hear sounds from about 16 to 20,000 Hz (20 kHz)*. Anything above 20 kHz is called "ultrasound," because those sounds are higher than we can hear. Anything below 20 Hz is called infrasound -- elephants communicate over miles with low, rumbling infrasound.

   Rats can hear ultrasound: the range of the rat's hearing is around 200 Hz to 80 or 90 kHz. There is a whole world of high frequency sound out there that rats can hear that we cannot, a perceptual difference that humans tend to forget.

   For example, when a human gently rubs thumb and forfinger together, we hear nothing. But this movement makes a scratchy sound in the ultrasonic range. Wire cages make a lot of ultrasonic noise in addition to audible noise when rats move around in them.

  Here are some of the frequency ranges perceptible to other species:

And I'll Sing you a Song...

    In addition to hearing sounds well above the human range of hearing, most of rats’ vocal communication is ultrasonic.

    Rats emit short, high-pitched calls during rough and tumble play, and in anticipation of feeding, as well as when they are unhappy or stressed, such as when they sight a predator, or are frightened.  Male and female rats also call to solicit attention from one another and as they approach and sniff each other. Calling may also coordinate the sequence of behaviors that leads to mating. In adults, these calls are usually in the 20,000 Hz. range.

   Infant rats also produce ultrasonic sounds, and at an even higher pitch.  They make noises from 30,000 to 50,000 hz. when rough handled, stepped on by their mothers or otherwise in distress.  These calls attract their mothers’ attentions.  And you thought human babies were loud!