Toward The Social And Acoustic Ecology Of Social Foraging Humpback Whales Megaptera Novaeangliae In Southeast Alaska

Relative to other baleen whale populations, the humpback whales Megaptera novaeangliae inhabiting Southeast Alaska are noteworthy in that they form large, enduring groups when foraging on schools of Pacific herring Clupea harengus pallasi. These groups use a variety of unusual feeding tactics when attacking prey, including the production of loud feeding calls, the release of bubbles, and the waving of their large pectoral flippers. Past observations of these groups have been largely anecdotal so little is known about their social behavior or the function of their feeding tactics. In particular, it is unclear if these pods are based on cooperative interactions or if they represent groups of individuals who are competing for prey that occurs in dense aggregations. In addition, little is known about the underlying social structure of these pods and whether they are composed of kin. The objective of this study was to employ field and laboratory techniques to gain insight into the function of the unusual feeding tactics, and to describe the basic social structure of these pods. In order to test the prediction that bubbles, feeding calls, and flipper movements represent prey manipulation tactics, herring schools were brought into the laboratory and subjected to various simulated humpback whale feeding behaviors. I found that these simulated behaviors produced strong avoidance responses from the herring schools, suggesting that humpback whales use these tactics to manipulate the behavior of their prey. Seven years of field observations revealed that humpbacks with enduring social bonds (i.e., high coefficients of association) specialized on herring and represented a small proportion of the entire whale population. Calves born to these "core members" were never observed to return and feed with their mothers in subsequent years, suggesting that these groups are not composed of close kin. This was verified by analysis of haplotype variation in the mitochondrial genome and microsatellite variation in the nuclear genome. Individuals within these pods appear to invest in by-product benefits, with the enduring bonds between whales in Chatham Strait (cf. krill feeders in Frederick Sound) possibly representing combinations of individuals performing compatible tasks (Le., bubble blower, herder, vocalizer).

The North Pacific humpback whale (Megaptera novaeangliae) population has been increasing at an average annual rate of ~6% since the early 1990s. In northern Southeast Alaska alone, there are now more whales than estimated for the entire North Pacific several decades ago. An understanding of how this growing population is repopulating traditional foraging grounds will benefit from detailed investigations of their prey preferences and trends in whale abundance and distribution relative to those prey. This dissertation examines these issues from late May until early September 2008 in Frederick Sound and Stephens Passage, a Southeast Alaskan feeding area historically used by humpback whales. The foundation for the study is an analysis of the life histories and abundance patterns of euphausiids, the principal prey of humpbacks in the area, during late spring and summer. Four species, Thysanoessa raschii, T. longipes, T. spinifera, and Euphausia pacifica, were identified in plankton net samples collected at random locations throughout the study site (n = 49) and in locations where a strong scattering layer was observed on a 120 kHz echosounder (n = 48). Both sample types varied in euphausiid species composition. Abundance patterns of immature euphausiids coupled with observations of females carrying spermatophores indicated differences between species in spawning schedules. Thysanoessa spp. began spawning in early April with the spring phytoplankton bloom and continued until late June, whereas E. pacifica began spawning in early June and continued until late August. This protracted recruitment of immature euphausiids was geographically widespread throughout the summer in contrast to adults, which, although present all summer, were found primarily in slope and shallow (

Humpback whales (Megaptera novaeangliae) are vocal baleen whales that exhibit complex social interactions that vary spatially and seasonally. Across their range, humpback whales produce a wide array of vocalizations including 'song', foraging vocalizations, and a range of vocalizations known as social calls -- unclassified non-song vocalizations. This study investigates the vocal repertoire and social calling behavior of Southeast Alaskan humpback whales from a sample of 299 vocalizations paired with 365 visual surveys collected over a three-month period on a foraging ground in Frederick Sound in Southeast Alaska. The results of this study describe a more varied and diverse repertoire of social vocalizations than has been previously documented, and identifies variability in vocal behavior as a function of social-spatial context. We used a three-part classification system that included aural-visual analysis, statistical cluster analyses, and discriminant function analysis to describe and classify social vocalizations. Vocalizations were classified into sixteen individual call types nested in seven vocal subclasses, within four vocal classes. The vocal repertoire of Southeast Alaskan humpbacks shows that call stereotypy ranges from discrete to continuous. This discrimination occurs at the vocal class and vocal subclass levels, and may be associated with call function. Social calls from Southeast Alaska showed anecdotal overlap with song from the 2012 North Pacific breeding season, and moderate overlap with vocalizations recorded in North Atlantic foraging grounds and along the East Australian migratory corridor. At the vocal class level aural-visual analysis had 83% agreement with cluster analysis and 90% agreement with discriminant function analysis. Results indicate that call use is not indiscriminant, and that some call types were commonly produced while others were rare. Moreover, calling rates in one vocal class, the pulsed (P) vocal class, were negatively correlated with mean nearest neighbor distance, indicating that P calling rates increased as animals clustered. This suggests the use of P calls may be spatially mediated. Results of a Poisson log linear (PLL) regression indicated that whale abundance in the survey area had no effect on vocal behavior; however, vocal behavior did vary significantly based on the spatial proximity of animals. The highest calling diversity occurred when whales were in clustered dispersion states, while the lowest calling diversity occurred when only a single whale was present. The type of calls produced during each dispersion state (clustered, random, evenly dispersed, single) varied significantly. While calls from all four vocal classes were detected during surveys containing clustered or randomly dispersed whales, calls from only two of the four classes were detected when whales were evenly distributed, and only one vocal class was detected from solitary whales. Our results indicated that vocal behavior is not correlated with abundance, that vocal behavior does vary based on social context, and that vocal behavior trends toward complexity as the potential for social interactions increases. Our evidence supports the hypothesis that social vocalizations serve a communicative purpose and may be used to maintain animal spatial proximity.

In this book, an international team of leading marine mammal scientists, with a remarkably diverse set of backgrounds and areas of expertise, lead you through a synthesis of current knowledge on baleen whales. Baleen whales are the largest animals ever to have lived on this planet. They also have the lowest and most intense voices on Earth, most likely evolved to take advantage of ocean acoustic transmission conditions so as to be detectable across ocean basins. Some baleen whales can live to be 150-200 years old. They migrate many thousands of kilometers between feeding and breeding areas. They produce songs and calls that serve as behavioral foundations for establishing, maintaining and expanding their cultural identities. To conclude that we know the behavioral limits of these large brained, long-lived animals would be naïve. As baleen whale scientists, we are still beginning to comprehend the enormous complexities and natural histories of these remarkable animals. Today, the fact that whales sing is known throughout much of the world. This awareness started 50 years ago with the publication and popularization of a collection of humpback song recordings that motivated research into baleen whale behavioral ethology. In this book’s chapters, a reader’s experiences will stretch from learning about baleen whale laryngeal anatomy associated with their different voices to learning about the vast ocean areas over which their voices can be heard and the emerging complexities of their culturally defined societies. These are accompanied by chapters on the fundamental ethological contexts of socializing, migrating, and foraging. Two common themes permeate the book. One theme highlights the phenomenal increase in scientific knowledge achieved through technological advancements. The other theme recognizes the impacts of human-made activities on ocean acoustic environments and the resultant influences on the health and survival of individual whales and their populations. Although the book is intentionally ambitious in its scope, as scientists, we fully recognize that baleen whale science is still in its infancy. Many profound revelations await discovery by cohorts of young, multi-talented explorers, some of whom are stretching their wings in this volume and some of whom are reading these scientific stories for the first time.

This book provides a general introduction to the biology of marine mammals, and an overview of the adaptations that have permitted mammals to succeed in the marine environment. Each chapter, written by experts in their field, will provide an up-to-date review and present the major discoveries and innovations in the field. Important technical advances such as satellite telemetry and time-depth-recorders will be described in boxes.

Increases in the humpback whale (Megaptera novaeangliae) population have generated considerable interest in understanding the foraging habits of these large marine predators in the Gulf of Alaska. Globally, humpback whales are classified as generalist predators but are known to exhibit localized differences in diet. Intensified predation pressure is of particular concern to resource managers, who have observed whales feeding at juvenile hatchery salmon release sites in Southeast Alaska. We assessed the diets and behavioral tactics of humpback whales foraging near Hidden Falls Hatchery release sites (in Chatham Strait, 2016 to 2018) to better understand their predatory effects on juvenile hatchery-reared salmon. We used skin biopsies, prey sampling, and stable isotope analysis to estimate whales’ diet composition. Aerial footage and photographic sequences were used to assess the foraging tactics used on this prey source. We observed three individual whales repeatedly feeding on juvenile hatchery-reared salmon, and we were able to sample them multiple times over a period spanning shifts in diet. Overall, the diets of these whales were higher trophically than other humpback whales foraging in the area, even before feeding on juvenile hatchery salmon started. These hatchery-feeding whales may be generally more piscivorous than other whales, which focused on planktivorous prey. Our repeat sampling, in conjunction with scheduled introductions of a novel prey source, provided a semi-controlled feeding experiment that allowed for incorporation and turnover rate estimates from humpback whale tissue in a way that was not previously possible for large, free-ranging cetaceans. Finally, during the course of this study we discovered an undescribed feeding tactic employed by hatchery-associated whales. We observed the use of solo bubble-nets to initially corral prey, followed by calculated movements to establish a secondary boundary with the pectoral fins that further condensed prey and increased foraging efficiency. Our study provided the first empirical evidence for what we describe as “pectoral herding”. This work deepens our knowledge about humpback whale foraging ecology, how this innovative species is able to exploit newly available prey, and to what extent they feed on commercially valuable hatchery salmon.