Table 2. Effects of call type (scream / grunt), arousal level (LOW / MEDIUM / MAXIMUM) and their interaction on the four acoustic parameters.

Variable	effect	df	F	p
Duration (log)	call type	1, 145	99.18	< 0.001
	arousal	2, 145	0.95	0.389
	call type * arousal	2, 145	3.29	0.040
Root-mean-square amplitude	call type	1, 145	100.00	< 0.001
	arousal	2, 145	28.18	< 0.001
	call type *arousal	2, 145	8.82	< 0.001
Central frequency (log)	call type	1, 145	772.67	< 0.001
	arousal	2, 145	13.27	< 0.001
	call type *arousal	2, 145	5.29	0.006
Harmonic-to-noise ratio	call type	1, 145	13.29	< 0.001
	arousal	2, 145	2.04	0.134
	call type *arousal	2, 145	15.48	< 0.001