Acoustic features measured in Gru1, Gru2, Short-growl and Long-growl sounds.

Values are means ± SEM and range is given in parentheses below. For Pf, Lf and Uf the median value is given in parentheses on the right. SD = sound duration; PN = number of pulses; PD = pulse duration; PP = pulse period; PI = pulse interval; PRR = pulse repetition rate; Pf = peak frequency; Lf = lower frequency; Uf = upper frequency 3dBBW = 3 dB bandwidth; Q = damping coefficient. * = significant difference between means within each of the two different types of grunts and growls using t-tests at (P < 0.05) with sequential Holm-Bonferroni correction for Type I error inflation.