Non-song social call bouts of migrating humpback whales

Abstract

The use of stereotyped calls within structured bouts has been described for a number of species and may increase the information potential of call repertoires. Humpback whales produce a repertoire of social calls, although little is known about the complexity or function of these calls. In this study, digital acoustic tag recordings were used to investigate social call use within bouts, the use of bouts across different social contexts, and whether particular call type combinations were favored. Call order within bouts was investigated using call transition frequencies and information theory techniques. Call bouts were defined through analysis of inter-call intervals, as any calls within 3.9 s of each other. Bouts were produced significantly more when new whales joined a group compared to groups that did not change membership, and in groups containing multiple adults escorting a female and calf compared to adult only groups. Although social calls tended to be produced in bouts, there were few repeated bout types. However, the order in which most call types were produced within bouts was non-random and dependent on the preceding call type. These bouts appear to be at least partially governed by rules for how individual components are combined.

Common nonsong social calls of humpback whales (Megaptera novaeangliae) recorded off northern Angola, southern Africa

“…) and often produced in bouts containing the same or other call types (Rekdahl et al . ). Wops occurred commonly in the social call repertoire of the eastern Australian population (Dunlop et al .…”

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…The sounds of humpback whales have been studied extensively in Alaska [121][122][123], off the eastern USA [124], at low latitudes [125][126][127][128][129], off eastern Australia [130][131][132][133][134][135][136] and off Antarctica [137].…”

“…Source levels of all types of social sounds range from 123 to 192 dB re 1 µPa rms @ 1 m [122,130]. A 3-year study off the east coast of Australia found 34 different sound types [131], either as single sounds or in bouts [133]. However, only a small subset of these sound types remain in the repertoire over time [134], meaning that the sound catalogue is highly variable and constantly changing.…”

Diel and Spatial Dependence of Humpback Song and Non-Song Vocalizations in Fish Spawning Ground

“…Humpback non-song vocalization types have also been characterized and examined in several different ocean regions and in several different contexts. They include social sounds either vocalized or generated via surface activities, signals for coordinated movement during feeding and migration, as well as nighttime communication [1,2,[21][22][23][24][25][26][27][28][29][30].…”