Call Types and Acoustic Features Associated with Aggressive Chase in the Killer Whale (Orcinus orca)

Instances of aggressive chase over a 5-mo period were investigated in captive killer whales (Orcinus orca). Such episodes were found to be quite rare, occurring only eight times in 1,872 h of observation. A consistent vocal pattern was found to be associated with agonistic episodes that differed markedly from the pattern recorded during non-aggressive, time-matched control periods. In general, vocalizations associated with aggressive chase were characterized by amplitude and frequency modulated pulses of approximately 190 ms in duration. In addition, three specific call types were found to occur only during chase events. As a whole, these particular call types and associated features are offered as an acoustic signature of agonism in the killer whale. It is hoped that these sounds might aid researchers in interpreting heretofore enigmatic killer whale vocalizations recorded from wild populations.