In a recent study, some emperor penguins wore digital electrocardiogram recorders when they dove deep into the waters of McMurdo Sound in Antarctica. Using these devices for the first time on penguins, researchers were able to record heart rate data beat by beat.

Among some surprises: in one lengthy dive, the penguin’s heart beat only six times per minute over a five-minute period. Another penguin’s heart was racing at 256 beats per minute when it returned from a dive.

 The purpose of this study by the Scripps Institution of Oceanography was to gather information about the bird’s adaptations to low-oxygen during diving, which may help humans, and to a changing climate. Heart attacks and strokes cause low levels of oxygen in humans and can damage human tissues.  The research took place at a special research camp called Penguin Ranch, designed for studying penguins’ underwater behaviors. In the 1990s, researchers from Scripps and National Geographic attached miniaturized cameras in backpacks on the animals, providing the first live footage of emperor penguins hunting for fish under the Antarctic ice. Segments of this appeared in the film March of the Penguins. Other research has recorded time and depth of the birds’ dives—underwater stays of 30 minutes at a time and dives over 1,500 feet.