Table 1. List of acoustic variables used in the cluster analysis.
| Duration | Call duration (s) | |
| MaxF0 | Maximum fundamental frequency (Hz) | |
| MeanF0 | Mean fundamental frequency (Hz) | |
| MinF0 | Minimum fundamental frequency(Hz) | |
| RangeF0 | Difference between maximum and minimum frequencies (Hz) | |
| PosBout | Position within bout: First-Intermediate-Last-Single | |
| DC/No DC | Occurrence of deterministic chaos | |
| F1, F2,..., F8 | Centre frequency of the first 8 formants (Hz) | |
| ΔF | Formant dispersion (Hz) | |
| eVTL | Estimated vocal tract length (cm) | |
| dB | Relative intensity of the call (dB) | |
| DurTot | Duration of the bout (s) | |
| Calls/Bout | Number of units into the bout | |