Results

Using data collected during the Operation WhaleSonic, partly funded by experiment.com, we have conducted an investigation into the biphonic calls of killer whales. These are vocalizations in which killer whales produce two independent sounds (a high frequency component and a low frequency component) at the same time. We investigated the extent of systematicity in these biphonic calls, testing whether certain combinations occur more often than expected by chance. We also tested whether certain components re-occur across multiple combinations. We identified 22 categories of high and low-frequency components. We found 14 types of combinations that occur at a frequency above chance, thus denoting systematic combinations. Further, 12 of these types contain components that are also re-used across other combination types, denoting a strong tendency for recombining acoustic elements. Overall, we have described the kinds of biphonic combinations produced by Norwegian killer whales, hinting at the capacity of these animals to produce a vast repertoire of sounds by both combining components into combinations as well as recombining components across combinations.