Basic acoustic measurements of the stem of the six different loud calls produced by adult male Campbell's monkeys.

Duration of call stem: duration of the first section of krak-oo, wak-oo or hok-oo calls (excluding the affix) or the entire call for boom, krak or hok calls that carry no affixation. Transitions were calculated by subtracting the frequency at the beginning from the frequency at the end of the call or call stem. Results of Tukey post hoc tests for dyadic call comparisons: same letter = no significant difference; different letters = significant difference (p<0.001).