It’s warm now, but remember last winter? When cold feet were endemic? When you tried to warm up by cuddling close to someone else? – or perhaps to a non-human companion, since American households are now more likely to contain a dog than a child.
Mammals aren’t the only ones to help each other get warm. A recent New York Times article exploring research on emperor penguins, who – nestling their eggs – huddle tightly together for warmth in the face of almost incredible Antarctic night temperatures (down to below minus 45 degrees Centigrade), reports that the penguins make sure each of them gets a chance to be in the warm mid-huddle. They call no names or plays. Instead, they do The Wave.
Yes, just like football fans. Only it’s their feet traveling in tiny increments.
From the research: “The jammed state of the huddle is interrupted every 30–60 s by small 5–10 cm steps of the penguins, reminiscent of a temporary fluidization. These steps are also spatially coordinated and travel as a directed wave with a speed of ~12 cm/s through the entire huddle. After the wave has reached the end of it, the huddle re-enters the jammed state.”
Translated, the huddle of penguins takes a wave-like series of steps (5-10 centimeters total) every 30 to 60 seconds. The steps are coordinated, and the wave travels through the entire huddle. When the wave is finished, the penguins are again in tight huddle – only the birds who were outside now have the inside track.
Penguins gather in tiny huddles when the weather is merely cold. As the thermometer plummets, small groups join together to make larger and larger huddles. The biggest huddles form when cold is at its most bitter.
Does a shivering penguin simply waddle up and ask if the seat is saved? Of course not. There’s a protocol: “The penguins in a huddle mostly face in the same direction, which defines a rear end and a front end of the huddle. When a penguin joins the huddle, it does so by aligning itself first in the direction in which the other penguins are facing, and then moving closer to the huddle. As a result, penguins tend to join a huddle at its rear (trailing) end and leave it at the front (leading) end.”
The researchers (who, let’s remember, also brave ridiculously frigid weather) go on to discuss analogies to density and liquids. Penguins couldn’t care less. They’ve got a method for ensuring everyone’s survival in brutal cold.
So if loved ones’ cold feet annoy you this coming winter, keep in mind they’re just doing their version of the penguin Wave – as should you.
NYTimes article: http://www.nytimes.com/2011/06/07/science/07obpenguin.html?hpw
Original article in the journal Plos One: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0020260