When the National Geographic Society's hunt for living giant squid sends sperm whales with video cameras to the ocean depths this month off New Zealand's South Island, the whales will be tracked by the Cornell University Bioacoustics Research program.

Distinctive click sounds produced by diving sperm whales will reveal their whereabouts to an array of hydrophones (underwater microphones) hanging vertically in the water, using Cornell equipment that pinpoints sound sources.

"Fortunately, New Zealand sperm whales usually return to the surface at the same place where their dives began," said marine biologist Kurt Fristrup, assistant director of the Cornell Bioacoustics Research Program. "We hope to learn where they go and what they're eating when they dive," he said, noting that sperm whales can otherwise cover a lot of territory, traveling at 3-4 knots during their 15-minute dives.

That's where the "crittercams" will come in handy, as the digital video cameras, attached by temporary cords, attempt to record high noon in the high seas: the epic battles between sperm whales and one of their favorite meals, the giant squid (Architeuthis dux). Cameras have never before pictured a living giant squid in its deep-water habitat. But squid-inflicted scars and stomach-content analyses suggest that sperm whales know where to find giant squid, and they may be the best collaborators a marine biologist could hope for.

The Cornell sound survey actually begins about two weeks before the first crittercams are attached to the sperm whales' blubber layer by tethers that dissolve in about two hours and allow the football-sized camera to float to the surface.

"The first week or two of sound recording will give us baseline data about the whales, whether they will be affected by the crittercams, and even whether they will be disturbed by close approaches from boats," Fristrup said. Monitoring of the sperm whale click sounds by Cornell bioacoustician Adam Frankel will continue as the whales dive for giant squid and as Odyssey, a camera-equipped robotic vehicle developed at MIT's AUV Laboratory, conducts surveys of the deep habitats. Clyde F.E. Roper of the Smithsonian Institution is the scientific leader of the expedition, and James Bellingham of MIT leads the Odyssey team.

"There is good evidence that sperm whale clicks are used for echolocation and for depth-sounding, but they may not work for locating squid," Fristrup said. "Squid are poor reflectors of sound." The clicks, which occur in a variety of patterns called click trains, may be better understood by biologists after the crittercam sessions, he added, noting that rapid series of clicks are sometimes heard when sperm whales are "socializing" and rubbing against one another. Having on-the-scene pictures to go with the sounds may reveal what all the racket is about.

Bioacousticians don't expect to hear much from the giant squid, Fristrup said. Squid apparently have no hearing organ and perhaps no strategic reason for producing sound. Precisely where they lurk -- on the ocean bottom or at lesser depths -- is not even known. "It's like looking for an eagle's nest in a series of forests stacked hundreds of layer thick," he said of the mesopelagic zone, which in tropical waters is about 400 to 1,000 meters down.

"But even if we don't find giant squid," Fristrup said, "we will have gathered a tremendous amount of information about life in the mesopelagic zone, about community organization and how predator-prey relationships are sorted out. It's a part of the ocean that is tremendously rich in biodiversity and biomass. There's a lot going on down there."