How Is A Traffic Jam Like A Penguin?

Courtesy Flickr/Christopher Michel

It’s been cold in New England recently.  With all the talk of polar vortex and arctic chills, I’ve been wishing to be a slightly smaller, slightly more fur-lined animal as I traverse the streets of Cambridge.  And if only I were a penguin!  To be an animal that can casually smush itself up against others of its own kind for warmth!

But what I have long believed to be a sort of magical, cutesy, loving action, has been revealed by the cold heart of science to have more in common with another atrocity of the great state of Massachusetts: traffic.

Scientists set up a camera to watch the movements of two colonies of Emperor Penguins, one in Germany and one in France.  While the German colony was tracked at the individual penguin level, every 1.3 seconds for four hours, the French colony was tracked for overall movement of the colony.

What they found, was that the shuffling of tuxedoed birds wasn’t so different from the average traffic jam (or flock of birds, or school of fish).  While they knew small density waves, small jams of sorts, happened every 35-55 seconds as the huddles of penguins shifted, they didn’t know how the waves were triggered.  It turns out, it takes just one penguin from any given direction.  (Or one gawking car, one Sunday driver…)

Any penguin within the huddle occasionally performs a step. This locally disturbs the triangular configuration of the huddle and triggers each of the neighboring penguins to also perform—after a small time-delay—a single step.

Figure 2b. from Gerum, RC, et al. (2013).

Figure 2b. from Gerum, RC, et al. (2013).

A penguin step forward of about 2cm is enough to trigger movement from the rest of the pack.  However, unlike traffic, the penguin huddle could create stop-and-go movement (frustrating for humans, adorable for penguins) from any direction, not just an arbitrary front.

After the wave has traveled through the whole huddle, the conformation of the huddle is the same as before the wave, but the whole huddle has now moved one step forward.

Huddles could also merge and break apart at will, following the same wave patterns that caused the penguins to move in the first place.

You can watch the abstract here (skip to 0:24 to see the penguins):

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