Project Title: Humpback Whale Social Foraging and Its Implications on Community Structure
Primary Investigator: Dr. Fred Sharpe

Compared with other baleen whales, the humpback whales that inhabit the Pacific Coast of North America are unique. This population is characterized by a variety of remarkable feeding behaviors that include the production of loud, trumpet-like feeding calls that are apparently used to herd schooling fishes such as the Pacific herring. These whales also demonstrate a type of tool use by deploying large bubble nets around fish schools or krill swarms. The prey is then devoured in a spectacular communal lunge as the whales come rocketing up through the center of the bubble net. Up to two dozen whales may take part in these lunging events, which turn the surface of the water into a boiling cauldron of bubbles, baleen, and bait fishes. In the image to the right, you can see whales surfacing together with the bubble net also coming to the surface around them. A detailed description of bubble net feeding can be found in our education section.
     When AWF was formed in 1995, this project was its centerpiece and raison d'etre. Fred Sharpe explains how he came to study this fantastic behavior:

"I remember my first bubble net. It was 1987 and my first time researching whales in Alaska. Sitting quietly on the waters of Chatham Strait, a circle of bubble began to form at the surface. Over the hydrophone [underwater microphone] came a wild cacophony of trumpet blast. As the whales burst through the surface, I leapt up and cheered. That was the moment I became captivated with the Alaskan humpbacks. We were following these groups, and the research was like being assigned to a gang squad. It was my duty to get the mug shots and find out who was in charge
     In 1992, I formalized my studies by joining Larry Dill at Simon Fraser University in British Columbia, Canada. The goal was to use the lens of behavioral ecology to investigate these remarkable pods. This involved field studies utilizing sonar, hydrophones, and the collection of tissue samples. This research also involved the novel approach of simulating whale predation in a laboratory environment. This was done by constructtion of an “artificial whale” at the Bamfield Marine Station. This permitted the testing of predictions concerning the effect of bubble nets, flipper movements and feeding calls on live herring schools."

Social Foraging humpback whale pods possess a social complexity that is rarely observed in baleen whales. For example, individuals within these groups may develop long-term associations that may last for many years. There also appears to be a division of labor, with particular whales constantly leading the group, deploying the bubble nets, and producing the feeding calls. Furthermore, on each lunge, each whale in the group maintains the same position, indicating that this is an intricately choreographed feeding maneuver. In order to better understand these unusual feeding behaviors, AWF is using a variety of innovative techniques, including sonar imaging, genetic analysis, acoustics, tagging, laboratory experiments, and computer simulations.

SONAR STUDIES:
The release of bubbles during foraging activity has been noted in a number of marine predators. Compared with other predators, however, the humpback whale is unusual in that it deploys bubbles in a much more elaborate manner, and uses them on several different prey types. There has been considerable speculation on how bubbles assist in capturing prey organisms. Most observers generally agree that predators use bubbles to frighten or herd prey, although it is not known specifically if it is the acoustic, visual, or mechanical component of the bubbles, or a combination of these attributes, that frightens the fish. Our approach has been to use sonar to conduct a systematic investigation into the role of the bubbles deployed by humpback whales feeding on Pacific herring.
     Sonar is used to document bubble structures including their depth, geometry, and relationship to prey aggregations, bottom topography, and subsurface whale activity. To the left, you can see a sonar image of components of bubble net foraging as they would appear on a sonar readout. The image is not a "snapshot" of where features are at any single time. To correctly interpret the image, one should be aware that the horizontal axis of the image proceeds forward in time as one moves from left to right. What is shown on the sonar screen for any single point in time is what is in the water below the boat. In this image, the boat has passed over the bubble net after the whales have surfaced. The approach curtain is the "tail" of the bubble net that leads up to the actual enclosed column of bubbles. The dive plume is the group of bubbles generated when the whales dive. The boat passed over the point where the whales dove after they "fluked-up" and went to the bottom. Whales don't always show up clearly on sonar, but in this case circumstances allowed us to be certain that the three shadowy images were whales. The black cloud that is labeled prey is a school of fish, probably herring,

RELATEDNESS OF COOPERATIVE GROUPS:
In a collaborative project with Scott Baker of Hatfield Marine Science Center (formerly of the Molecular Ecology Lab at the University of Aukland, New Zealand), our objective is to examine the relatedness of humpbacks in social foraging groups through genetic analysis. When whales breach or interact aggressively, they can slough off the outer layer of skin. We collect sloughed skin from the surface of the water or take biopsy samples with a crossbow or "air rifle," a well-established technique in which a tiny plug of tissue is taken from the whales back near the dorsal fin. This sampling technique appears to cause minimal disturbance to the whale. Our research permit allows us to collect data in this manner.
     Specifically, we are interested in the relatedness of individual whales within and between cooperative pods, in addition to the local genetic sub-structuring of the population. This information will be useful for understanding local genetic variability in the population as well as providing information about the movement and dispersal patterns of juvenile humpbacks. Our preliminary results indicate that individuals in bubble netting groups are not related, an intriguing finding given that tightly bonded mammalian groups often consist of relatives. Currently accepted behavioral theory expects that animals that work together and may bestow a benefit on others in the group through their actions are usually related. This is because the actions of the helping individual are bringing a benefit to genetically related individuals that may gain a fitness benefit that could translate into those genes being passed on in resultant offspring.

OPTIMAL GROUP SIZE:
Scientists have long puzzled about why animals live in groups. A number of ideas have been put forth including defense against predators, increasing capture success, deterrence of scavengers, information exchange, defense against infanticidal males, and territorial defense. Humpbacks feeding on schooling fishes along the Pacific Coast have been found in groups that vary widely in size. Presumably, individual whales join these feeding groups to increase their individual rate of prey intake or to access schooling prey that is unavailable to solitary foragers. However, many basic questions about the nature of these pods have not been answered or even addressed. These include: what sets the upper limit on group size?, does each position in the group provide the same rate of food intake?, and do late arrivals take rear or peripheral positions in a feeding group? We are attempting to answer these questions by conducting long term research on these groups. This involves taking photographs of the natural pigmentation patterns on the undersides of the humpbacks' flukes, allowing us to identify individuals. We can also determine if certain individuals tend to interact with favored traveling or feeding companions.

COMMUNITY SOCIAL NETWORK:
An aspect of this research in which Sean Hanser has taken the lead is the analysis of the social network of humpback whales in our study area. This study is possible only because of Fred Sharpe's years of diligent data collection. Using an area of math known as social network analysis, Sean is beginning to gain a broader understanding of how humpback whales in Chatham Strait and Frederick Sound associate with each other each year and over the years. We will be able to construct social networks like the one illustrated to the right, which was created from some data taken in 1994. We hope to be able to address questions like:

• How many communities of humpback whales are there in the Chatham Strait and Frederick Sound area?
• Do these communities interact?
• Who are the key members of these communities?
• What environmental and behavioral factors influence the formation and structure of these communities?
• How does humpback social structure compare with that of other animals described in the scientific literature?

To the right, a group of herring observed on the video monitor can be seen schooling in the tank at the Marine Station.

The image to the right shows a still image from actual video footage of a whale deploying bubbles. The whale's eye can be seen at the bottom edge of the picture.

The beautiful long pectoral flippers of the humpback whale can be seen on the photo to the right. Photo by Deborah Ferrari.

THE VIRTUAL WHALE 3-D ANIMATION
In order to gain insight into the unusual feeding behavior of humpback whales, we collaborated with the Graphics and Multimedia Research Lab at Simon Fraser University to produce 3D graphic simulations of underwater feeding activity. Using the data that that we collected from the wild and in the laboratory, we were able to recreate underwater feeding events that would otherwise be difficult or impossible to observe. By modifying various features of these computer simulations, we are attempting to test ideas about the interactions among the whales, bubble nets, feeding calls, and flipper movements. These simulations also serve as a useful communication and educational tool for conveying ideas about whales to other scientists and the general public. In 1995, this work was given the Society for Marine Mammology Award for Excellence in Scientific Communication.
     Since 3-D animation has come a long way since this initial animation was created, AWF and its UC Davis collaborators are updating the animation to incorporate new information and improve the visualization of this behavior. We hope to make this available for public viewing in the next few years.

Fred completed his Ph.D. in 2001. That document and other formal publications that have resulted from Fred's research are listed below.

Publications
D'Vincent C.G., R.M. Nilson, and F.A. Sharpe. 1988. Observations of humpback whale mother-calf pairs in Southeast Alaska. Cetus 8:25-26.

D'Vincent, C.G., D. Haley, and F.A. Sharpe. 1989. Voyaging with the whales. Oakwell/Bolton Books. Toronto, Ottawa. 135 pp

Sharpe, F.A. and L.M. Dill. 1997. The behavior of Pacific herring schools in response to artificial humpback whale bubbles. Can. J. Zool. 75:725-730.

Sharpe, F.A. 2001. Social foraging of the Southeast Alaskan humpback whale. Ph.D. dissertation, Simon Fraser University. Burnaby B.C. 129 pp. (PDF format - 6.13 MB).