This retro shot shows the seal's hind flippers in action. In the foreground you see the battery pack and video recorder. That's ice on top. Download quicktime movie 616K.
A scientific first: The Weddell seal is the only animal known to use bubbles to scare fish from their hiding places under the ice. (That's the seal's snout in the foreground.) Download quicktime movie 1.7MB.
The first fish escapes, but we wouldn't want to bet on the second. Download quicktime movie 2.3MB.
Movies courtesy of Randall Davis, department of marine biology, Texas A&M University at Galveston.
Seal of approval
What's going on beneath the sea? Nobody knows. The sea is murky and dark, its depths mysterious. How does a penguin make a living? How does a seal find its prey? How does a turtle hear?
Welcome to the black hole of biology. Want to watch a lion hunting? Then use a spotting scope. Want to watch a fungus growing? Then drag out your microscope. Want to watch a Weddell seal hunting? Then slither into your triple-thick wet suit, dive through a hole in the Antarctic ice, and try to follow this large, graceful and speedy mammal as it dives hundreds of meters below the ice.
You not only won't want to do it. You won't be able to. That profound limitation -- applicable to penguins, dolphins and whales as well as seals -- makes "the marine environment quite opaque to us," according to Randall Davis, professor of marine biology at Texas A&M University at Galveston. "We know practically nothing about seal behavior in the water."
You guessed it. This is not a story about limitation. It's a story about high-tech solutions.
Smile. We're taking home videos
Weddell seals were chosen because of accidents of geography and animal behavior. As air breathing animals, they must surface every so often (although they've been known to last 80 minutes between breaths). In the thick ice of McMurdo Sound, just off the Antarctic coast, they must return to the same breathing hole so long as no other hole is within about 5 kilometers.
Those accidents are enough to make scientists drool. "Weddells were chosen because of their ability to work on sea ice over deep water, through an isolated ice hole," says Davis. "We can study an animal that's free to come and go. I don't know of another place in the world to study diving behavior as we can at McMurdo Sound."
No deposit, no return
Weddells are also an easy animal to work with, if your definition of "easy" includes manipulating 450-kilogram carnivores on the windblown Antarctic ice pack. Amazingly, Weddells are docile and don't mind being caught in a net and hauled to a "scientific station." Inside the station (which looks suspiciously like a fishing shack), the seals are sedated and a camera mounting is glued to the fur behind their heads (when the animal molts its fur, the mounting will fall off).
After the seal recovers from the sedative, it is hauled back and set down beside the breathing hole. Davis's crew typically follows a seal through four days of diving before removing the camera and saying so long to the seal.
The $30,000 black-and-white video camera takes 30 frames per second, using light from near infra-red light-emitting diodes. Since this light is invisible to seals and their prey, Davis says it should not affect the results. One roll of videotape can record six hours of action. But beyond seal home videos, the instrument also records depth, ambient sound, heart rate and other data of interest. After another two years of field work, the information will be blended into a picture of the animal's underwater hunting tactics.
Prepare to dive!
It would seem that Weddell seals look up to see fish that are backlit against the ice. Then the seals exhale, forming a stream of bubbles that flush the fish from their hiding places under the ice. Finally, with a quick lunge and a gobble, it's fishwich time. Weddell seals eat up to 200 fish a day.
As Davis's group shines a light on seal behavior, similar instruments are being used on elephant seals and harbor seals, and on bottle-nose dolphins. They aren't alive, but The Why Files did cover undersea robots.
The seal instrument package is already just 13" long by 5" in diameter. But Davis expects further miniaturization, and hopes eventually to attach even smaller packages to such animals as penguins. The result, he says, will be an entirely new view of the deep -- seen as its denizens see it.
How did first Americans reach North America? Hint: they probably didn't get their feet wet.