IN THE ICEBOX
The NATURE program ANTARCTICA: THE END OF THE EARTH highlights many of the unusual strategies that the continent's animals use to survive. Penguins huddle together for warmth, balancing their precious eggs on their feet to keep them from touching the ground and freezing. Seals scour the undersides of floating ice sheets, hunting down the fish and shrimp that hide in the inky waters. But perhaps the South Polar Sea's most amazing hunters are some of its seabirds, who must soar across an endless, featureless ocean in search of food that is hidden beneath the gelid surface.
How do they do it? Simple: they follow their noses.
In remarkable experiments, researcher Gabrielle Nevitt of the University of California at Davis and her colleagues have shown that birds known as "tube noses," including some albatrosses and shearwaters, use the smell of invisible gases to home in on shrimp-like krill and other food.
It works like this: when small, shrimp-like zooplankton feed on plant-like phytoplankton, the tiny organisms produce a gas called dimethyl sufide (DMS). The gas slowly rises above the ocean's surface, gradually dispersing as winds push it away from areas thick with plankton. Like a plume of smoke, however, the cloud of odor provides those birds with the right sense of smell a way to follow the trail back to its source -- saving countless hours of fruitless searching.
Nevitt and her team showed that the birds have the ability to follow these invisible, fragrant road signs by creating vegetable oil slicks scented with the aroma of DMS and other substances. While many kinds of Antarctic birds ignored the slicks, some immediately flocked to the smell -- just the way hungry kids might pack into a kitchen filled with the aroma of fresh-baked brownies.
Other researchers trying to understand how some Antarctic creatures made a living aren't as lucky as Nevitt -- because their study animals are long dead. These paleontologists study Antarctica's remarkable fossils, which offer some insights into how Antarctica's climate, and even location, have changed over time.
Dinosaur and other fossils found on the continent show that Antarctica, Australia, New Zealand, Africa, South America and India were once part of a supercontinent called Gondwana. About 100 million years ago, it broke apart, and the land masses slowly drifted into their current positions. But before that happened, Antarctica enjoyed a warm tropical climate that supported an array of remarkable animals. In fact, about 560 million years ago, Antarctica was north of the equator!
In 1995, for instance, researchers found the remains of a Volkswagen-sized armadillo and huge seagoing squid-like creatures. And in 1998, a team of Argentinean and U.S. scientists found fossils of a duck-billed dinosaur, along with remains of Antarctica's most ancient bird and an array of giant marine reptiles. The find allowed researchers "to paint a much fuller picture of what life was like in Antarctica at the time," said Scott Borg of the National Science Foundation in Washington. "The climate was obviously very different," he notes. "There must have been a lot of vegetation to support these large plant-eaters."