Figure 2.

With the development of electronic biologging devices and suction cup attachment techniques, investigations of diving heart rate from among the smallest to the largest of oceanic cetaceans have been accomplished under a variety of research protocols. Examples include a spontaneous dive in a tank by a harbour porpoise, a trained dive at sea to 100 m by a bottlenose dolphin, a 250 m deep dive of a narwhal at sea after capture/release and a 176 m dive of a blue whale after unrestrained recorder deployment at sea. Heart rate profiles are 20 s averages for the narwhal; all other profiles are beat-to-beat heart rates. Gaps in the blue whale heart rate profile are secondary to artefact on the electrocardiogram record. Adapted from [49,53,101,102].