by Kagari Aoki (Atmosphere and Ocean Research Institute, University of Tokyo)

During feeding seasons, it is essential for humpback whales to accumulate a sufficient amount of energy for migration, growth and/or reproduction. However, fatter whales having positive buoyancy may not be efficient in terms of locomotion because neutral buoyancy is the most efficient. Using animal borne recorders, we investigated body tissue density of humpback whales in relation to the time spent in feeding in two different feeding grounds (Norway and Canada).