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About the Authors:
Ellen C. Garland
* E-mail: [email protected]
Affiliation: National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
Jason Gedamke
Affiliation: Ocean Acoustics Program, Office of Science and Technology, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Silver Spring, Maryland, United States of America
Melinda L. Rekdahl
Affiliation: Cetacean Ecology and Acoustics Lab, School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia
Michael J. Noad
Affiliation: Cetacean Ecology and Acoustics Lab, School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia
Claire Garrigue
Affiliation: Opération Cétacés, Noumea, New Caledonia
Nick Gales
Affiliation: Australian Marine Mammal Centre, Australian Antarctic Division, Kingston, Tasmania, Australia
Introduction
Male humpback whales produce a long, stereotyped and constantly evolving vocal breeding display, termed ‘song’ [1], [2]. Within a population, males conform to the current arrangement and content of the song [3]–[5]. The conformity to a single song type within a population is thought to occur via vocal learning from surrounding males and, when song transmission is examined at the ocean basin scale, is considered one of the best examples of horizontal cultural transmission in a non-human animal [6]. Song similarity has also been documented between populations, although the degree to which this occurs is dependent upon the geographical distance between such populations [6]–[13]. Thus, song similarity among populations indicates that acoustic contact is likely to have occurred, although there is currently little known about the mechanism(s) through which song transmission is mediated. Therefore, identifying all potential mechanisms of transfer is essential to understanding the dynamics of song transmission within and across regions.
Within an ocean basin, populations in closer proximity to each other typically display a higher degree of song similarity [6]–[12]. In the North Pacific, for example, studies of song sharing have shown that the geographically close populations of Hawaii and Mexico shared a higher number of themes, compared to Japan [8]–[9], [11]. Similarly, in the Southern Hemisphere, songs recorded across the South Atlantic were similar across the ocean basin within a year [12]. In more geographically isolated populations, such as in the Indian Ocean (Madagascar and western Australia), little song sharing was found to occur across the ocean basin (shown through a...