Spouting off: A synthesis of humpback whale aerial blowhole sounds

For centuries, whalers listened for the “explosive” aerial spouts of their quarry. Today, whale researchers listen to and tabulate breathing rates (and rhythm) to gain insight into cetacean diving, foraging, oxygen consumption, and disturbance. However, the acoustic features (peak frequency, harmonics, emotive content) of mysticete exhalations are less well studied and consist of long-ago whaler accounts and two modern scientific notes (Watkins 1967; Thomson et al. 1986). Collectively, they described three spout types, normal, wheezed, and trumpetlike horn blast, with the latter two linked to “loudness,” “excitement,” “social significance,” “fright,” “whale meeting behavior,” and “purposeful in-air wheezing.” Utilizing a larger sample size plus new targeted aerial-sound field collections, we update measures for the three legacy sounds (normal, wheezed, and trumpet), and we also describe several new sounds (pew, pant-hoot, thrum, gargle) and map them onto the continuum (tree) of behavioral excitation. This growing aerial library is intended to inspire further conservation research into presence/absence, numerical sampling, and distance estimation, as well as behavior research of sound versus excitation, and any link between aerial expression to underwater vocalization. In addition, understanding aerial sounds from various breathing behaviors and excitation levels should help responders safely approach and engage with entangled, live-stranded, or entrapped whales.