|The Virtual Whale Project
3D Animation and sound environment for the visualization of the feeding behaviours of Pacific Humpback Whales
|What goes on below the waves?
The humpback is the renegade among the mysticete whales. Whether wooing mates with song, or engaging in combative sexual displays, this whale breaks all the rules. Perhaps nowhere is their enigmatic behaviour more evident than on the feeding grounds in Southeast Alaska. After traveling thousands of miles to these northern summering areas, Hawaiian humpbacks engage in bizarre feeding behaviours, many of which we are only beginning to understand.
Schools of Pacific herring are one of their favourite targets. But capturing these fast agile fish requires an arsenal of feeding tactics. One of their most effective ploys is to band together in large groups, which may number nearly two dozen whales. The whales will then deploy bubbles, broadcast of loud, trumpet-like sounds, and the flash of their flippers at the schools. These tactics apparently herd the prey up towards the surface, where they then become trapped within the confines of a huge bubble net. Rocketing up through this tunnel of bubbles, the whales engulf the entire fish school in their cavernous mouths.
Despite this grand finale, most of the complex behaviours that lead up to the surface lunge take place underwater. Here at Simon Fraser University, we are using a variety of research tools including sonar, dive tags, and hydrophones to understand what happens when these whales slip below the waves. The Virtual Whale Project was developed help us interpret our data with the use of 3D Graphics and sound. Perhaps one of our most important goals, however, is to use the Virtual Whale Project as an education and conservation tool to celebrate the lives of humpback whales.
One of the interesting things about Pacific Humpback Whales is the way they feed. They eat herring and krill mostly, but they don't just chase the prey wildly. Herring and krill have evolved behaviours to avoid predators: they
spread out and dive for the bottom of the ocean. By spreading out, they make it so that whale can only get a few of them, at a time. Diving offers the protection of the dark ocean bottom where they can hide.
The whales in turn have evolved some very interesting techniques for catching prey with the above avoidance behaviours. They work in groups, and use noise, fin motions, and bubbles to scare the prey twords the surface of the water, and corral them so that they cannot spread out. When the prey are trapped by walls of bubbles, and near the surface of the water, that is when the whales lunge up with their mouths open to engulf the schools of herring or krill.
|The release of bubbles during foraging activity has been
noted in a number of marine predators. Compared to 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
|The purpose of our visualization is twofold:
it is a tool for the researcher to experiment with timing and three dimensional motion to
give a feel for the motions of the whales, prey, bubbles and sound in the underwater
world. It is also a teaching tool to be used to explain complex 3D relationships and
motions to those who want to know more.
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The Virtual Whale Project at Virtual-Whales@sfu.ca