(birds)

On Thin Ice

Adélie penguins are proving to be Antarctica's most sensitive indicators of climate shifts. Their falling population portends a multitude of changes that will reverberate throughout the region.

By Daniel Grossman

Braving leopard seals and frigid waters, Adélies can dive 500 feet below the icy surface to find krill and fish.

Photo by Tim Davis/Corbis

Bill Fraser's inflatable dinghy is not much bigger than a bathtub, but it plows easily through jagged ice blocks the size of basketballs on the Bellingshausen Sea. If anything, his biggest worries, besides the surging currents, are the leopard seals prowling the frigid waters—they have been known to slash a rubber boat's skin with their long teeth—and minke whales, like the one that popped up one day in 2000. "I immediately swerved to the right," recalls Fraser, a biologist and president of the Polar Oceans Research Group, a Montana-based nonprofit scientific institute. A messy collision with the whale was averted, but a National Science Foundation official traveling with Fraser was thrown overboard by the sudden lurch. She was quickly plucked from the freezing waters and thrust back into the boat.

The icy dash to Torgersen Island is only a mile-long trip from Palmer Station, a U.S. research base. But this is Antarctica, a continent so remote, forbidding, and inhospitable (at least to humans) that even a minor mishap can be life threatening. So today Fraser is outfitted in a bulky blaze-orange jacket that doubles as a life vest. He has the microphone of a walkie-talkie clipped to his lapel, so he can report his whereabouts at all times to Palmer Station.

After dodging icebergs, some as big as six-story office buildings, Fraser, 53, deftly lands the rubber Zodiac on the island's rocky shores, gunning the engine one last time to pin the boat against a rock. I leap ashore and tie up to a boulder. Still, it's hard not to be distracted by the pungent odor of guano and the boisterous, honking animals a few feet above the surf. When we step ashore, we're greeted by a colony of black-and-white Adélie penguins and their fuzzy chicks.

It is a sorry testament to the power of Madison Avenue that my first glimpse of an Adélie, with its sleek black head and pure white breast, triggers thoughts of famous penguins associated with beer (Bud Ice) and cigarettes (Kool). Full-grown Adélies are just knee-high. Their eyes have a thin white ring and big black pupils that create the impression they are staring straight at you. The diminutive, humanlike form under the feathers is so striking it's hard to resist imagining that the upright bird is a tiny person, arms at its sides, smiling smugly.

Adélies are one of only two members of the large penguin family that live and breed in Antarctica (the other is the emperor penguin). Torgersen Island, which consists of mostly barren, windswept rock piles lapped by near-freezing water, is one of the Adélies' few breeding grounds on the Antarctic Peninsula, a finger of land that points toward South America. Yet Torgy, as this island has been nicknamed by researchers, is downright cushy compared with the penguins' winter homes on ice floes, where air temperatures reach minus 40 degrees Fahrenheit. Because Adélies thrive in such brutally harsh conditions, Fraser figures they are among the "the toughest birds, if not the toughest animals," in the world.

But that was before the earth's rising temperatures set in motion a chain of climatic developments on Torgersen and other neighboring islands that are today rendering these Adélie nesting grounds inhospitable. Fraser, after decades of studying up close how Adélies live, has in recent years resolved to find out why they are disappearing before his very eyes.

Torgersen Island is located 600 miles below the tip of South America, on the western side of the Antarctic Peninsula—a region that, since the world's thermometer began rising about a hundred years ago, has warmed faster than just about anywhere else. In the past 50 years winter temperatures here have shot up an astounding 9.9 degrees Fahrenheit. Fraser says that because the increase is so extreme, the Antarctic Peninsula has become an ideal laboratory for studying the impact of climate change on wildlife. Propitiously, in the mid-1960s, Palmer Station was built close to Torgersen's Adélie colonies. So in 1974, when Fraser, then a graduate student, arrived on the island, he could easily begin documenting the Adélies' downward spiral.

When he first came to Torgersen, he was greeted by a "sea" of Adélies—about 17,000 adults, Fraser says. Other nearby islands were similarly striking. "You could not go anywhere [on the islands] without seeing hundreds to thousands of Adélies," Fraser recalls. Since then, however, the Torgersen population has plummeted 60 percent, to fewer than 6,500 adults. "Now you can walk on some of these islands and they are completely silent," he says with a grimace. Adélie populations elsewhere in Antarctica are holding steady, and the species is even thriving in some areas, like the Ross Sea, where warming is less pronounced. Still, Fraser insists that "Adélies are proving to be the most sensitive indicators of climate change" and that the declining Torgersen population is a harbinger of a variety of changes that will be felt throughout Antarctica.

Despite the gradual slide in its penguin population, Torgersen Island has become a tourist destination for the growing Antarctic cruise industry. About 13,600 tourists set foot in Antarctica last season, nearly double the 8,000 who visited a decade earlier. In the past few years Fraser and his team of penguin researchers have grown accustomed to sharing Torgersen each year with up to 1,400 birdwatchers and their tripods and salami-size telephoto lenses. Blondie, a strange, beige Adélie who looks like she had her feathers bleached, is a favorite attraction and quite possibly the most photographed Adélie in the wild.

When I visited Torgersen with Fraser last January, the weather was a bit warmer than usual, at one point rising to within several degrees of the area's record high of 51 degrees Fahrenheit. Soon after we arrived, one concerned tourist, who had stripped down from his own cold-weather gear, approached Fraser and asked how the down-covered chicks survived the heat. Another visitor offered to feed a prostrate chick a handful of snow.

In fact, the chicks do fine in the heat, Fraser says, and they will ride out this warm spell. Rather, it is the subtle long-term changes—resulting from warmer regional temperatures and from the Adélies' hardwired biology—that Fraser has only recently pinpointed as the cause of their population decline here.

Evolutionarily adapted to withstand bitter cold, Adélie penguins have been known to plunge 500 feet below the sea ice in search of Antarctic silverfish and krill—a tiny shrimplike crustacean—the two major staples of their diet. During the breeding season Adélies will sometimes travel more than 60 miles on foraging trips, swimming through waters colder than 32 degrees Fahrenheit, all the while risking attack by leopard seals, their most serious predator. Fraser once saw an Adélie penguin with a laceration so deep from a leopard seal attack that he could see the bird's internal organs, and even peer right into its stomach cavity. Amazingly, the penguin not only returned to feed its chicks, it eventually healed and, along with its mate, successfully raised its brood. That is an "extreme case of how tough they are," Fraser says admiringly.

Adélies are as stubborn as they are hardy, which may well be contributing to their undoing. Although they spend 90 percent of their 15- to 20-year lifetimes at sea or huddled on drifting ice packs, they require dry ground for nesting. Hence the annual summer stopover at Torgersen and other neighboring islands, a pilgrimage they have been making for at least 600 years, according to a recent scientific analysis of materials found under current nesting grounds. Fraser says the Adélies' long-running mastery over their harsh environment is due in large part to their success at finding a niche and sticking with it—such as their spartan nesting sites on Torgersen's rocky slopes.

But the same rigid behavioral traits that have long worked to the Adélies' advantage—when the climate was fairly constant—have left them vulnerable and unprepared for the environmental changes occurring today. "Even when conditions change slightly," says Fraser of his birds, "they show the impact." For example, sea ice during winter months is the habitat for algae and diatoms, the food for krill. But warming temperatures over the past half-century have reduced the amount of sea ice along Antarctica's coastlines. This, in turn, has led to reduced algae and diatom populations and, consequently, diminished schools of that Adélie mainstay, krill.

Perhaps more important, though, is that this cascading ecological shift has combined with what Fraser calls a "landscape effect" on and around Torgersen Island that has degraded the penguins' habitat. To demonstrate what he means, Fraser, an energetic man with thinning dirty-blond hair, leads me past a stone ridge that roughly bisects Torgersen along an east-west axis. The first thing I notice as we reach the island's south side is the absence of the cacophonous trumpets and wheezes we heard when we landed on the north side. Although this half of the island appears to have as much prime nesting space as the other side, there are just 150 Adélie breeding pairs here, a small fraction of the 2,800 pairs on the island's northern half. In 1974, when Fraser began counting Adélies, the ratio was much less skewed. But in subsequent trips he began noticing that the penguins were disappearing faster from the south side than the north.

It wasn't until 1997 that Fraser started to figure out what was going on. That year snow fell heavily and stayed late; normally most of it would have melted by early December, with the approach of the Southern Hemisphere's summer. But instead the region was covered with snow in January, long after the ground is usually bare. To Fraser's surprise, the Adélies, which had always waited for dry ground before nesting, began laying eggs in the snowbanks. "They were desperate," he recalls. "They had to lay eggs." If the breeding birds had waited any longer, Fraser says, the hatching chicks would have missed the peak of the krill population. But as the natural summer warmth melted the late snow, the nests became flooded with water, addling the eggs.

Fraser has since noticed that this pattern seems to repeat itself every few years. It turns out, strangely enough, that the warming climate is unleashing more snowfall on Torgersen, making life increasingly untenable for the island's Adélie penguins. The cause and effect works like this: Rising temperatures on the Antarctic Peninsula have increased snowfall by reducing sea ice, the frozen sheet that covers vast swaths of Antarctic waters in winter. The ice acts like an impermeable cap, preventing evaporation and reducing the atmospheric moisture that fuels precipitation. Reduced sea ice means more moisture and, in this part of the world, more snow.

Fraser has discovered that this extra precipitation has increased the depth of spring snowbanks, especially on southerly slopes on and around Torgersen Island, which receive the least sunlight and are thus the last to melt out when winter ends. Adélies are so loyal to their respective colonies that they return to the same breeding spots year after year, refusing to seek out more suitable nesting areas on the island. The added snow is no danger to adults, but it is making it impossible to raise chicks. So these colonies have stopped reproducing and have begun to waste away as older birds are eaten by predators or die of old age. Fraser says that when he began his research, there were so many Adélies "you just did your work without thinking that their numbers would ever reach the low levels that we are at today."

During the past three decades, Fraser has journeyed to Antarctica almost every year, enduring nature's harshest elements. Steering his tiny rubber boat back and forth to Torgersen and neighboring islands, he has braved sea squalls with 15-foot waves and 70 mile-per-hour winds. Once, lost in a dense fog, he followed a swimming flock of Adélies to safety. "Most people would be skeptical about putting your life in the hands of a bunch of traveling Adélie penguins," he says. In this case, as he had hoped, the penguins were swimming to Torgersen Island.

Sadly, Fraser predicts that the Adélie populations on Torgy and its neighboring islands will be gone within a decade. It is some consolation to him that Adélie colonies still flourish elsewhere in Antarctica, particularly in the Ross Sea, site of the continent's largest research base, McMurdo Station. "The species is not going extinct," he admits.

Nonetheless, Fraser believes his life's work on Torgersen will help alert people to the impact of global warming on wildlife. "The Adélies are an honest barometer of global changes," he says soberly. "Antarctica is not behaving independently of the rest of the planet."

Daniel Grossman is a freelance science journalist and radio producer based in Boston.

 

© 2003  NASI

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bird's-eye view

Name: Adelie penguin (Pygoscelis adeliae)

Size: Length averages 27.5 inches; weight averages 8–11 pounds

Plumage: Black with a white belly and a white ring around the eyes. The sexes are almost indistinguishable.

Range: Antarctica and surrounding islands

Song: Loud, monosyllabic krohk

Nest: On rocky ground near the shoreline

Food: Krill, small fish, and cephalopods