Acoustic Characteristics of White-Nosed Coati Vocalizations: A Test of Motivation-Structural Rules

Vocalizations of white-nosed coatis (Nasua narica) emitted in nonaggressive and aggressive contexts were measured and compared to determine if these calls exhibited acoustic characteristics in accordance with motivation-structural (MS) rules. “Chirp” and “squawk” calls were compared spectrographically using 11 coatis from 3 zoos. Chirps were short-duration (68.6–212.0 ms), high–maximum frequency (16.2–17.9 kHz), tonal calls with frequency modulations. Squawks were longer-duration (177.9–546.5 ms), low–maximum frequency (8.4–13.2 kHz), wide-bandwidth calls with 6 resonances and little frequency modulation. Squawks differed from chirps in duration, maximum frequency, and change in frequency (P < 0.001). Chirps were emitted during nonaggressive behaviors, whereas squawks were emitted during agonistic encounters. Squawks conformed to MS rule predictions for aggressive calls, and chirps supported MS rule predictions for nonaggressive contexts, but some exceptional characteristics were noted in chirps. Many chirps (67.7%) concluded with a short-duration, broad-bandwidth sound with high energy in low frequencies, and may represent variations of a graded call.