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Rats and ultrasound

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 (Fay 1988, Kelly and Masterson 1977, Warfield 1973). 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 (Milligan et al. 1993, Sales et al. 1998).

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 that are perceptible to other species:

Dogs: up to 40,000 Hz
Cats: 100 to 60,000 Hz
Bats: 1,000 to 100,000 Hz
Dolphins: up to 150,000 Hz

20 kHz range: Rats emit long 20 kHz vocalizations when they are unhappy or stressed. These calls are emitted when an adult or juvenile is defeated socially (Thomas 1983), sees a predator (Blanchard 1991), experiences pain (Cuomo 1988, Tonue 1986) or anticipation of pain (Antoniadis 1999), or when an untame rat is handled (Brudzynski and Ociepa 1992).

30 to 50 kHz range: Infant rats produce very high pitched distress calls. These cries elicit maternal care such as retrieving the infants to the nest (Allin and Banks 1971; Carden and Hofer 1992).

Infants may also call when their mother steps on them. Infants who can't call are stepped on more roughly by their mothers, so the calls of infants in this case may reduce rough handling by their mothers (Allin & Banks 1972, Hofer & Shair 1978, Noirot 1972, White 1992).

Rats also emit short, high-pitched calls under positive contexts. Adults and juveniles emit them during rough and tumble play (Knutson 1998, Burgdorf and Panksepp 2001, Panksepp and Burgdorf 1998), and in anticipation of feeding (Burgdorf 2000).

Male and female rats also call in a sexual context (Barfield 1979). Before copulation, males and females emit such calls as they approach and sniff each other. When males emit these calls, females solicit them more (McIntosh et al. 1978). Female calling also solicits male sexual behavior. Calling may also coordinate the sequence of behaviors that leads to intromission (White 1998).

SOURCE: http://www.ratbehavior.org/rathearing.htm#Perception