In the emperor penguin courtship call, male vocalizations are composed of long, slow bursts with lower frequency tones than the female version. But calls of SeaWorld San Diego male penguin E-79 defied this binary. Also unusual was this penguin's male companion, E-81. The pair 'kept company' and sometimes exhibited ritual courtship displays. Researchers studied the courtship calls of E-79 and E-81, recording the birds in their below-freezing enclosure and refining the usual technique for analyzing the bursts.