DIEL DIVE DEPTH IN PENGUINS IN RELATION TO DIEL VERTICAL MIGRATION OFPREY - WHOSE DINNER BY CANDLELIGHT

Diel vertical migration by zooplankton is thought to allow marine anim als to exploit the more abundant food resources in the upper water str ata at night while minimizing predation from optically orientating pre dators. Contrary to this, consistantly shallower dives at night made b y marine reptiles, mammals, and birds have been attributed to enhanced feeding conditions as predators exploit prey that have become accessi ble near the surface. We found foraging success in penguins reduced at night and dive depth limited exclusively by ambient light levels. Con sideration of foraging strategies adopted by air-breathing predators m ay explain typical vertical migration patterns of prey, as well as dep artures from them.