Diel dive depth in penguins in relation to diel Vertical migration of prey: whose dinner by candlelight?

Abstract

Diel vertical migration by zooplankton is thought to allow manne animals to exploit the more abundant food resources in the upper water strata at night while minimizing predation from optically orientating predators. Contrary to this, consistantly shallower dives at night made by marine reptiles, mammals, and birds have been attributed to enhanced feeding conditions as predators exploit prey that have become accessible near the surface. We found foraging success in penguins reduced at night and dive depth limited exclusively by ambient light levels. Consideration of foraging strategies adopted by air-breathing predators may explain typical vertical migration patterns of prey, as well a s departures from them.