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Antarctica is the coldest, windiest, driest, emptiest place on Earth. Its size is disorienting; immensity revealed in the smallness of things. Mountains a hundred miles away are clearly visible in air uncluttered with humidity. Looking off toward the pole, an ice sheet seven hundred miles long ends abruptly at the horizon, just beyond arm’s reach. Sledgers from early expeditions used to report toiling for hours toward a distant outcrop, only to discover it was a discarded tin.

So you might be forgiven for misjudging the two-foot-tall Adélie penguin: an animal it’s impossible not to anthropomorphize, a toddler in a tuxedo. In fact, it’s the largest land animal in Antarctica (emperors are larger, but nest on sea ice and rarely touch land). About five million Adélies breed along Antarctica’s coastline, and if you encounter an animal any farther inland you’ll need a micro­scope to look at it. Adélies are vertebrates living at the edge of what’s possible.

If they survive their first year (80 percent don’t), they spend the next few years at sea just learning how to feed themselves, giving no thought to breed­ing. Those that breed along the Ross Sea migrate more than two thousand miles round trip each year, chasing to keep up with sunlight and the sea ice they use for rest stops and hunting grounds. After learning how to stay alive, they return to their natal colony, often to within a hundred meters of where they hatched, and spend the next several years learning how to build a nest, find a mate, and work as a pair. Adélie penguins live about twenty years, and they don’t even have the luxury of being at the top of their food chain. Skuas eat their eggs and chicks, and leopard seals take the adults.

Adélies shrug off hardships that are beyond the experience of other penguin species. Popular ideas of penguins aside, Adélies are one of only two species that breed only in Antarctica (the emperor is the other). Relatives like the gentoo and chinstrap live on islands farther north. They breed on largely icefree coasts and forage in open water. Adélies spend 10 percent of their lives on land, and 90 percent either standing on floating sea ice in the Southern Ocean, or hunt­ing beneath it. They can hold their breath for three minutes while swimming, and this exceptional ability gives them more range under the ice than either gentoos or chinstraps.

While gentoos and chinstraps are penguins of land, and emperors are pen­guins of the sea ice, Adélies have to live in both worlds. They come ashore to nest on dry, rocky hillsides, grudgingly walking over several miles of ice to reach land. After laying two eggs each, females return to sea to refuel. The males stay behind to incubate, and they fast for the week their mates are gone—another feat of endurance that separates them from other species. Time pressures them, too: parents have about two months of summer in which to fatten their chicks to forty times their birth weight. It’s this staggering capacity for survival that brings biologists like David Ainley to Antarctica.

Ainley first came to Antarctica in the late 1960s, as a graduate student at Johns Hopkins. Early on, he studied Adélie behavior, hoping to learn how they survive in the face of such exacting conditions. Now a senior biologist at H. T. Harvey and Associates in California, he is the architect of a wide-ranging pen­guin study in the Ross Sea, with colleagues including Katie Dugger of Oregon State University, Grant Ballard of the Point Reyes Bird Observatory, Phil Lyver of Landcare Research Ltd. in New Zealand, and Stanford graduate student Viola Toniolo. While much of what the team does finds its way into the scientific literature, Pennycook takes their studies directly to classrooms by tending the group’s popular website, . She posts photographs and time-lapse videos, answers questions, and helps teachers and pupils follow the fates of individual nests from day to day.

Begun in 1996, the project follows penguins at their nests, out at sea, and from season to season at four colonies: Cape Royds, Cape Bird, Beaufort Island, and Cape Crozier. It began as an attempt to understand what caused the four colonies to grow or shrink over the years. But as the study progressed, Ainley realized what he was seeing was the Adélies’ relationship, resilient but tenuous, with climate.

To study an Adélie penguin is to study sea ice, for example, and sea ice obeys the wind. On land, Adélies need bare rock slopes and thimble-sized pebbles. Summer snowfall can mean catastrophe even though winter snow is nothing to a penguin. Ice, wind, rock, snow—the Adélie occupies the knife-edge between too much and too little of each. So in this one respect, everyone’s first reaction to Adélies—that they look like little humans—is worth exploring. They’ve been living at the edge of what’s possible for about three million years, through cycle after cycle, epoch after epoch, of warm and cold. They must have something to teach us about climate change.

Reprinted with permission from , by Chris Linder, published by The University of Chicago Press. © 2011 The University of Chicago. All rights reserved.