Where, when, and why do western North Atlantic humpback whales begin to sing?

Abstract

At the onset of the winter breeding season, male humpback whales begin a prominent breeding behaviour, singing. Early songs are produced on summer feeding grounds prior to migration, but little is known about the proximate cues for the initiation of this behaviour, nor where or when it begins. We document the phenology of humpback whale singing along the western North Atlantic coast ranging from Newfoundland and Labrador, Canada to Massachusetts, USA through the fall-winter of 2015-16 (seven stations) and 2016-17 (three stations). Acoustic data from static recorders were categorised as containing humpback whale non-song calls, song fragments, or full songs. First heard in September, singing occurred throughout the fall-winter, but was not regular until October. Latitude, temperature, photoperiod, sea surface pressure, and wind speed were considered as potential explanatory variables for four definitions of song onset using forward stepwise regression. Final models included the environmental variables with photoperiod negatively correlated to singing (coefficient = −657; p-value = 0.04). Reliable environmental cues, such as photoperiod, may produce a heritable physiological response, resulting in whales acquiring the capacity and motivation to sing, with the subsequent timing and nature of song production influenced by other factors.

Cetacean acoustic occurrence on theUSAtlantic Outer Continental Shelf from 2017 to 2020

“…Similar to blue and fin whales, male humpback whales are prolific singers through the winter breeding season with songs in the North Atlantic heard from September through May, though some songs have been reported in summer (Kowarski, Cerchio, et al, 2021; Stanistreet et al, 2013). In addition to songs, humpback whale nonsong vocalizations, of which many types have been described (Rekdahl et al, 2015), can be heard throughout the year and are produced by both males and females.…”

Acoustic occurrence of baleen whales, particularly blue, fin, and humpback whales, off eastern Canada, 2015-2017

“…Humpback whales generally migrate from northern summer feeding grounds to lower-latitude winter breeding grounds. However, passive acoustic moni-toring (PAM) studies have revealed that a portion of the population remains in high-latitude waters in winter, or migrates late in the season, such that the species is present in Canadian waters for most of the year (Kowarski et al 2018, 2021a, Davis et al 2020.…”

Seasonal and diel patterns in singing activity of humpback whales migrating through Bermuda

“…Although historically believed to exclusively occur on breeding grounds (Winn and Winn, 1978), humpback whale song has been increasingly recorded on their feeding grounds during the breeding season, which suggests that some males may not migrate at all but instead remain year-round in their feeding grounds (Mattila et al, 1987;Vu et al, 2012;Baumgartner et al, 2019;Magnuśdottir and Lim, 2019;Kowarski et al, 2021;Tyarks et al, 2021). In the North Atlantic, humpback whales start singing in early autumn (around September) and continue singing through winter, stopping in late spring (around June) (Mattila et al, 1987;Vu et al, 2012;Kowarski et al, 2019;Kowarski et al, 2021). Transitions between song and "non-song" periods at the start and end of summer are dominated by "song fragments", i.e., only a short part of the complete song is sung (Mattila et al, 1987;Vu et al, 2012;Kowarski et al, 2019;Kowarski et al, 2021).…”

“…In the North Atlantic, humpback whales start singing in early autumn (around September) and continue singing through winter, stopping in late spring (around June) (Mattila et al, 1987;Vu et al, 2012;Kowarski et al, 2019;Kowarski et al, 2021). Transitions between song and "non-song" periods at the start and end of summer are dominated by "song fragments", i.e., only a short part of the complete song is sung (Mattila et al, 1987;Vu et al, 2012;Kowarski et al, 2019;Kowarski et al, 2021). The seasonal singing behaviour displayed by males is thought to underlie a hormonally triggered physiological mechanism (Wright and Walsh, 2010;Vu et al, 2012), as the males' testosterone levels are the lowest during the summer months and highest during the winter months, i.e., during the breeding season (Cates et al, 2019).…”