A Physio-Logging Journey: Heart Rates of the Emperor Penguin and Blue Whale

Abstract

Physio-logging has the potential to explore the processes that underlie the dive behavior and ecology of marine mammals and seabirds, as well as evaluate their adaptability to environmental change and other stressors. Regulation of heart rate lies at the core of the physiological processes that determine dive capacity and performance. The bio-logging of heart rate in unrestrained animals diving at sea was infeasible, even unimaginable in the mid-1970s. To provide a historical perspective, I review my 40-year experience in the development of heart rate physio-loggers and the evolution of a digital electrocardiogram (ECG) recorder that is still in use today. I highlight documentation of the ECG and the interpretation of heart rate profiles in the largest of avian and mammalian divers, the emperor penguin and blue whale.

Keywords: bio-logging; blue whale; cetacean; dive response; electrocardiogram; emperor penguin; heart rate; pinniped.

Figure 1

Beat-to-beat heart rate profiles of emperor penguins diving either at an experimental isolated dive hole in McMurdo Sound, Antarctica, or during foraging trips at sea from Cape Washington, Antarctica. Heart rate profiles were characterized by an immediate decline from high pre-dive levels [200–240 beats min⁻¹ (bpm)], a continued gradual decline to below-resting levels over the initial 1 to 2 min, and then a further progressive decline as dive duration increased. In the bottom phase of long dives and deep dives, heart rates could be as low as 5–10 bpm. Ascents were characterized by a gradual increase in heart rate. Heart rate profiles were characterized by abrupt oscillations in heart rate throughout the dive. Heart rate at rest was about 72 bpm. Adapted from the data of Meir et al. (2008) and Wright et al. (2014).

Figure 2

Beat-to-beat heart rate profiles of four dives of a blue whale in Monterey Bay, CA. Heart rates were typically 4–8 beats min⁻¹ (bpm) during the bottom phases of both shallow and deep dives. Oscillations in heart rate were not uncommon. Pre- and post-dive heart rates after deep dives were near 35 bpm; for shallow, short duration dives, surface heart rates were typically 25–30 bpm. The allometrically predicted resting heart rate of a 70,000 kg blue whale was 15 bpm. Gaps in the heart rate profile were due to artifact in the ECG record. Adapted from the data of Goldbogen et al. (2019).