What We are Learning About Whale Songs

A humpback whale acoustic study used underwater sound recordings from the Bartlett Cove hydrophone in 2007-2008 and compared them with other recordings from elsewhere in Southeast Alaska in 1976-2012. Based on their comparison, researchers determined that much of the call repertoire of humpback whales persists across generations of whales. The stability of whale calls on the Alaska feeding grounds stands in strong contrast to the breeding-season songs of males, which change continually over time.

Some things never change: multi-decadal stability in humpback whale calling repertoire on Southeast Alaskan foraging grounds

Abstract

Investigating long term trends in acoustic communication is essential for understanding the role of sound in social species. Humpback whales are an acoustically plastic species known for producing rapidly-evolving song and a suite of non-song vocalizations (“calls”) containing some call types that exhibit short-term stability. By comparing the earliest known acoustic recordings of humpback whales in Southeast Alaska (from the 1970s) with recordings collected in the 1990s, 2000s, and 2010s, we investigated the long-term repertoire stability of calls on Southeast Alaskan foraging grounds. Of the sixteen previously described humpback whale call types produced in Southeast Alaska, twelve were detected in both 1976 and 2012, indicating stability over a 36-year time period; eight call types were present in all four decades and every call type was present in at least three decades. We conclude that the conservation of call types at this temporal scale is indicative of multi-generational persistence and confirms that acoustic communication in humpback whales is comprised of some highly stable call elements in strong contrast to ever-changing song.

Fournet, M. E. H., C. M. Gabriele, D. C. Culp, F. Sharpe, D. K. Mellinger, and H. Klinck. 2018. Some things never change: multi-decadal stability in humpback whale calling repertoire on Southeast Alaskan foraging grounds. Scientific Reports 8: 13186.

More of the same: allopatric humpback whale populations share acoustic repertoire

Abstract

Humpback whales (Megaptera novaeangliae) are a widespread, vocal baleen whale best known for producing song, a complex, repetitive, geographically distinct acoustic signal sung by males, predominantly in a breeding context. Humpback whales worldwide also produce non-song vocalizations (“calls”) throughout their migratory range, some of which are stable across generations. We looked for evidence that temporally stable call types are shared by two allopatric humpback whale populations while on their northern hemisphere foraging grounds in order to test the hypothesis that some calls, in strong contrast to song, are innate within the humpback whale acoustic repertoire. Despite being geographically and genetically distinct populations, humpback whales in Southeast Alaska (North Pacific Ocean) share at least five call types with conspecifics in Massachusetts Bay (North Atlantic Ocean). This study is the first to identify call types shared by allopatric populations, and provides evidence that some call types may be innate.

Fournet, M. E., L. Jacobsen, C. M. Gabriele, D. K. Mellinger, and H. Klinck. 2018. More of the same: allopatric humpback whale populations share acoustic repertoire. PeerJ 6:e5365

Humpback whales cooperatively bubble-net feeding on herring in Alaska.

NPS/Jim Pfeiffenberger

Researchers have known for many years that Southeast Alaska humpback whales use a specialized trumpeting call when group-feeding on herring. The “core group” of whales that used to spend summers sub-surface feeding on herring in Icy Strait used this call routinely (listen to the call), and so do lunge-feeding groups in Chatham Strait and Frederick Sound who use bubble-nets to capture herring.

The loud, intense feeding call is thought to function in group coordination, (“Ready, set, GO!”) or in startling the herring into a tighter school, potentially increasing the amount of herring the whales can capture per gulp. The call may also serve the purpose of recruiting new whales to join a feeding group. If lone whales produce feeding calls, it suggests that the call functions primarily in manipulating the herring. Hakai Magazine interviewed the study’s lead author Michelle Fournet for this story.

Feeding calls produced by solitary humpback whales

Abstract

Humpback whales (Megaptera novaeangliae) are acoustically oriented baleen whales that are well known for complex vocal behaviors that are seasonally and geographically stratified. Their acoustic repertoire includes highly stereotyped songs that have been associated with breeding behaviors and a series of lesser-studied nonsong vocalizations, also known as “social sounds” that are produced throughout their migratory range and across behavioral contexts. Nonsong vocalizations, which are defined as any phonation produced independently of song, are diverse and vary widely in their acoustic structure and use. On migratory corridors, the use of nonsong vocalizations appears to be context-driven and may serve to facilitate intragroup or intergroup communication, while on breeding grounds nonsong vocalizations have been documented in groups of aggressively competing males and in cow-calf pairs. Efforts to classify nonsong vocalizations have been made on North Atlantic and North Pacific foraging grounds; however, only one call has been placed into a definitive behavioral context.

Fournet, M. E. H., C. M., Gabriele, F. Sharpe, J. M. Straley, and A. Szabo. 2018. Feeding calls produced by solitary humpback whales. Marine Mammal Science.

Source levels of foraging humpback whale calls

Abstract

Humpback whales produce a wide range of low- to mid-frequency vocalizations throughout their migratory range. Non-song “calls” dominate this species' vocal repertoire while on high-latitude foraging grounds. The source levels of 426 humpback whale calls in four vocal classes were estimated using a four-element planar array deployed in Glacier Bay National Park and Preserve, Southeast Alaska. There was no significant difference in source levels between humpback whale vocal classes. The mean call source level was 137 dB_RMS re 1 μPa @ 1 m in the bandwidth of the call (range 113–157 dB_RMS re 1 μPa @ 1 m), where bandwidth is defined as the frequency range from the lowest to the highest frequency component of the call. These values represent a robust estimate of humpback whale source levels on foraging grounds and should append earlier estimates.

Fournet, M. E., L. P. Matthews, C. M. Gabriele, D. K. Mellinger, and H. Klinck. 2018. Source levels of foraging humpback whale calls. The Journal of the Acoustical Society of America 143(2), pp.EL105-EL111.

For more ocean science stories, check out the Glacier Bay National Park and Preserve blog, Currents.