Emperor penguins are known to huddle for warmth, but their regal relatives prefer personal space.
Aerial photos of two king penguin breeding colonies show that individuals and couples keep their distance from neighbors but still stay together as a group. That arrangement resembles a simulated 2-D liquid in which molecules on a flat plane simultaneously attract and repel one another, researchers report April 4 in the Journal of Physics D: Applied Physics.
“Simple physics models are elegant and can explain a lot,” says study coauthor Dan Zitterbart, a physicist at Woods Hole Oceanographic Institution in Massachusetts.
King penguins are forced together by lack of space on the small South Atlantic islands that the birds primarily inhabit, while also being pushed apart by their territorial tendency to peck one another. This push and pull creates a consistent but dynamic distance, like that between molecules of a liquid.
Unlike some penguin species, king penguins (Aptenodytes patagonicus) don’t make a nest — they cradle their eggs on top of their feet. So the birds can move as a whole, similar to a fluid, to avoid disruptions such as a barreling elephant seal before settling back into place.
Understanding this dynamic could allow researchers to extrapolate how many birds are in a colony from just one photo. The technique may help scientists better track population numbers of these penguins, which are threatened by warmer sea temperatures.