Synchronous underwater foraging behavior in penguins

We used electronic time-depth recorders to examine the synchronous foraging behavior of penguins both at the surface and underwater. During a daily fo raging trip in the chick guarding stage, two females of the Northern Rockho pper Penguin Eudyptes chrysocome moseleyi dove in synchrony over seven cons ecutive hours during which they performed together 286 dives between 3 and 60 m, and fed on the same prey, the swarming euphausiid Thysanoessa gregari a. Most of the synchronous dives began (71%) and ended (59%) with a time in terval of less than or equal to 4 sec between birds. Differences in the dur ation and maximum depth of dives were slight: less than or equal to 2 sec f or 44% and less than or equal to 1 m for 62% of the dives. Indirect evidenc e suggests that the two birds were part of a larger flock of foraging pengu ins. One bird initiated and ended 70% of the dives first and consistently d ove deeper (95% of the dives) during the deep dives. The close similarity o f 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.