Synchronous Underwater Foraging Behavior in Penguins

Abstract

We used electronic time-depth recorders to examine the synchronous foraging behavior of penguins both at the surface and underwater. During a daily foraging trip in the chick guarding stage, two females of the Northern Rockhopper Penguin Eudyptes chrysocome moseleyi dove in synchrony over seven consecutive hours during which they performed together 286 dives between 3 and 60 m, and fed on the same prey, the swarming euphausiid Thysanoessa gregaria. Most of the synchronous dives began (71%) and ended (59%) with a time interval of ≤ 4 see between birds. Differences in the duration and maximum depth of dives were slight: ≤ 2 see for 44% and ≤1 m for 62% of the dives. Indirect evidence suggests that the two birds were part of a larger flock of foraging penguins. One bird initiated and ended 70% of the dives first and consistently dove deeper (95% of the dives) during the deep dives. The close similarity of the two time-depth profiles indicates that the penguins were visually in contact during the dives and suggests a coordinated underwater behavior to search and catch prey.