Fig. 2.

Allometric comparisons for resting metabolic rate and heart rate in mammals. In A, basal and resting metabolic rates for terrestrial mammals from rodents to elephants (black symbols) and marine mammals from sea otters to killer whales (blue symbols) are compared. Measurements for marine mammals were taken as the animals rested on the water surface. Data, regressions and references are compiled in Davis (Davis, 2019). In B, resting heart rates of marine mammals lying sedentary on the water surface (cyan circles, heart rate = 260.6body mass ^−0.21, r² = 0.69, p < 0.0001) or submerged/gliding (dark blue circles, heart rate = 105.1body mass ^−0.22, r² = 0.54, p = 0.0016) are compared to the predicted values for terrestrial mammals (red line) from Stahl (Stahl, 1977). Lines in both panels are least squares regressions through the data points for each group plotted in relation to body mass. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)