Figure S1. Received levels and calculated source levels of walrus claps from Walruses produce intense impulse sounds by clap-induced cavitation during breeding displays

Received level of 158 clap impulses as a function of recording distance d (panel a), and source level of the same clap impulses following calculation based on propagation loss of 20 log d (panel b), a conservative measure of propagation loss in this environment. Mean back-calculated source level (at 1 m) of clap impulses is 203 dB peak-to-peak re. 1 μPa. An independent analysis showed that animal orientation (0° towards hydrophone, 90° towards window, 180° away from hydrophone) did not influence received level of clap impulses (ANOVA, F(2,153)=2.004, p=0.14); thus, the apparent source levels measured at body orientations of 0° to 180° approximate the true source levels of these signals.