Figure 2. Sonograph of different call types produced by pups in the isolation paradigm.

The frequency is shown in kHz on the Y axis and time scale is expressed in sec on the X axis. The CF and MF refers to constant and modulated frequency respectively. In single syllable MF category, numeral i, ii, iii and iv denotes Upward, Downward, U-shaped and Inverted U-shaped calls.