When a blue whale dives below the waves, their heart rate plummets to conserve oxygen. She led a study, recently published in PNAS, to understand how flexible whales' heart rates might be, given that they are also exerting large amounts of energy underwater. The researchers tracked and tagged five blue whales and four humpback whales in Monterey Bay and the Channel Islands in California, and in the Western Antarctic Peninsula. "The heart rate data during this time is likely the closest anyone has come to a measurement of resting heart rate in a free-ranging whale!" Its resting heart rate was 18.5 bmp: much slower than the human average, which is about 60 to 100 bpm.