Infantile Vocalizations in Rats

Abstract Rat pups are reared in a nest with a pile of littermates. When a preweaning pup is placed in isolation for a brief period of time, it displays an increase in activity that includes vocalization with frequencies in the ultrasonic range (~ 40 kHz). The vocalization response to isolation is used to investigate early life communicatory, social, and affective behaviors. The rate of vocalization is influenced by multiple sensory stimuli including thermal, tactile, and olfactory. Measured at room temperature, the rate of isolation-induced ultrasonic vocalizations conforms to an inverted-U shaped pattern, peaking between postnatal days 7–11 when the thermoregulatory and locomotor capabilities of the pup remain poor. Other acoustic variables such as duration, amplitude, frequency range, frequency at maximum amplitude, and waveform are also reported in the literature and described in this chapter. Vocal parameters are often correlated but there is no fixed relationship among them.