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.

KEYWORDS:

• Humpback whale
• song
• timing
• migration

Acknowledgements

From JASCO, we would like to acknowledge Briand Gaudet for his continual PAMlab support and innovation, Julien Delarue and Emily Maxner for their input and contributions during manual analysis, Bruce Martin for his ongoing support, and Karen Scanlon for her editorial guidance. Thank you, Andrew Horn and David Barclay of Dalhousie University, for your feedback on the manuscript. Sofie Van Parijs, Genevieve Davis, and Danielle Cholewiak of the NEFSC, and Christopher Tessaglia-Hymes of Cornell University, thank you for sharing the data and information for the Massachusetts Bay data set. Data collected by DFO was supported by DFO Species at Risk Implementation Funds and National Conservation Plan funds.

Ethical statement

The present study followed the ethical guidelines for scientific research of Dalhousie University.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

For access to the acoustic data used in this study please contact the corresponding author at [email protected].

Additional information

Funding

This work was supported by the Mitacs Accelerate programme through Grant number 15622 as part of Katie Kowarski’s PhD research.