Across the otherwise pristine blanket of desolate white, a living, pulsating entity appears on the Antarctic plain. It’s an emperor penguin huddle, composed of more than 4,000 individuals—all of them male—weathering out bleak winter nights that can drop to -58?F with winds over 110 miles per hour.
The huddle “looks like one large life form that’s constantly moving,” says physicist Daniel Zitterbart from the University of Erlangen-Nuremberg in Germany. “It’s so incredibly homogenous, so dense, that if you are far away you will not spot single animals anymore, and you won’t see any movement at all.” For around 115 days the fasting males endure egg-incubating duties, often to the brink of starvation, while their partners are away.
Huddling is key to the penguins’ survival in such harsh conditions; it keeps them warm and helps them conserve energy. But scientists have long wondered how animals on the outside of the tightly packed group ever manage to finagle their way into the interior. “If you press one thousand people that densely together, they never could move,” Zitterbart says. Turns out, penguins altruistically overcome this problem by taking a series of coordinated, small movements that eventually allow each bird to take his turn in the center.
Zitterbart and his team endured the harsh Antarctic winter along with the penguins, taking high-resolution time lapse images of the colony every 1.3 seconds over four hour increments to study the birds’ movements. They used the penguins’ white and yellow facial patches as markers to track hundreds of individual animals, then mapped each bird’s trajectory in the huddle to form an overarching picture of the group’s flux. It was only possible to see the huddle’s movements when they sped up the footage by about 25 times, Zitterbart says. They found that movement waves occur every 30 to 60 seconds at the speed of about five inches per second. These small movements add up, Zitterbart and co-authors describe in their PLoS One article, leading over time to large movements. During the few seconds the penguins are on the move, Zitterbart says, it’s as if the dense, solid huddle has liquefied, only to return to its packed state as the penguins resettle.
With global warming looming and emperor penguin populations already on the decline, it’s more important than ever to understand as much as possible about the animals. Zitterbart plans to continue his research by building a permanent observatory near the colony that will continuously record the penguins’ activities. He hopes to answer lingering questions, such as what triggers the huddle’s movement. “What we know is that the huddle stays mobile,” he says, “but we have no idea if it’s just one penguin who screams or steps on someone’s foot or just presses into the huddle and tries to move it all.”
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