In Search of Giant Squid

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March 10, 1997 - Clyde

Dr. Adam Frankel is a research biologist at Cornell University's Bioacoustics Laboratory. He has studied sound production in whales for a number of years, particularly of humpback whales in Hawaii. Dr. Frankel and his colleagues are pioneering bioacoustic techniques of using underwater microphones (hydrophones) to record the underwater location, depth, swimming and foraging patterns and behavior of these large species of whales. The data will provide valuable information for understanding the lives of these whales underwater, where they spend over 80% of their lives.

We are using the data gathered here to help us determine where to send Odyssey and Ropecams into the inferred feeding zones of the sperm whales.

A great profile of Dr. Frankel, including wonderful photographs and some results of their tracking research, is available on the National Geographic Society's Kaikoura Web Site. Be sure to take a look at Dr. Frankel's entry in the Crew section.





Tracking the Giant Squids Predator - Dr. Adam Frankel


To obtain a window into the giant squids world, we are tracking the movement of their presumed primary predator, the sperm whale. With better knowledge of where sperm whales forage, we can direct the search for giant squid to those depths and habitats.

We can track the movements of the whales acoustically (by the sounds they make) to follow them through their dive cycles. Sperm whales produce echolocation clicks that begin just after they dive and continue throughout the entire length of the whales dive. These clicks can be recorded with an array of hydrophones (underwater microphones) hung vertically in the water. The recordings then are used to track the range and depth achieved by the whale.

Next, by plotting depth against time, we can construct a dive profile for the whale, tracking exactly where the whale went after it slipped beneath the surface of the sea. The procedure used to track a whale is called acoustic location. The four-channel recordings taken by the four hydrophones placed along the length of the array are examined back at the lab. When a click is detected, the wave form is examined very closely by computer and the precise time of the arrival of the click is measured very accurately. By measuring the difference in arrival times of a click at the different hydrophones, we can determine a directional bearing to the whale.

Imagine two hydrophones, one 10 meters above, the other 10 meters below your mouth. If you made a sound, it would arrive at both hydrophones at the same time. However, if a hydrophone was located at the same level as you, and the second was 20 meters above you, the sound would arrive at the lowest hydrophone first because it is closest. By measuring the difference in arrival times, we actually get a hyperbola of all possible positions between each pair of hydrophones. For example, with four hydrophones, there are six hyperbolae produced, and the intersection of the hyperbolae represents the depth position of the whale.

By measuring clicks all through the dive, the dive profile can be plotted, and as the data accumulate from many dives, we begin to build an understanding of the diving patterns of the whales in Kaikoura Canyon.

Preliminary results from the tracking studies here in Kaikoura waters indicate that the sperm whales are diving to, and presumably foraging at, depths of 300-500 meters in the middle of the water column.

Smithsonian Giant Squid Overview Page

gene carl feldman / gene@seawifs.gsfc.nasa.gov