Albatross-borne loggers show feeding on deep-sea squids: implications for the study of squid distributions

How surface-feeding albatrosses feed on deep-sea squids has long been a mystery. We investigated foraging behavior during daylight hours of 20 Laysan albatrosses Phoebastria immutabilis breeding in Hawaii using GPS- and camera-loggers. The birds traveled to the North Pacific Transition Zone up to 600 km north of their breeding site. The camera images showed that Laysan albatrosses fed on large (～ 1 m body length), intact floating dead squids (6 events) and floating fragmented squids (10 events) over deep oceanic water (>2000 m) while they flew in a straight path without sinuous searching. Feeding events on squids were not observed during trips when fishing vessels were photographed and seemed to be distributed randomly and sparsely. Thus, this study suggests that Laysan albatrosses found large, presumably post-spawning, squids opportunistically while they were traveling during daylight hours. Although we did not find cetaceans in our surface pictures, we could not rule out the possibility that birds fed on squids, especially fragmented specimens, in the regurgitates of cetaceans at depth. This study demonstrates the usefulness of combining animal-borne GPS- and camera-loggers on wide-ranging top predators for studying the distribution of little known deep-sea squids and their importance in the diet of marine top predators.