Ongoing field studies of Cuvier's, Ziphius cavirostris, and Blainville's beaked whales, Mesoplodon densirostris, around the main Hawaiian Islands address aspects of the biology and ecology of these species. These include: 1) diving behaviour, using suction-cup attached time-depth recorders (Baird et al., 2006a, b); 2) population sizes, using capture-recapture methods with photo-identification data; 3) habitat use, using GIS analyses of effort and sighting data; 4) trophic ecology, using stable isotope analyses ...