Orchestration : the movement and vocal behavior of free-ranging Norwegian killer whales (Orcinus orca)

Abstract

Studying the social and cultural transmission of behavior among animals helps to identify patterns of interaction and information content flowing between individuals. Killer whales are likely to acquire traits culturally based on their population-specific feeding behaviors and group-distinctive vocal repertoires. I used digital tags to explore the contributions of individual Norwegian killer whales to group carousel feeding and the relationships between vocal and non-vocal activity.Periods of tail slapping to incapacitate herring during feeding were characterized by elevated movement variability, heightened vocal activity and call types containing additional orientation cues. Tail slaps produced by tagged animals were identified using a rapid pitch change and occurred primarily within 20m of the surface. Two simultaneously tagged animals maneuvered similarly when tail slapping within 60s of one another, indicating that the position and composition of the herring ball influenced their behavior.Two types of behavioral sequence preceding the tight circling of carousel feeding were apparent. First, the animals engaged in periods of directional swimming. They were silent in 2 of 3 instances, suggesting they may have located other foraging groups by eavesdropping. Second, tagged animals made broad horizontal loops as they dove in a manner consistent with corralling. All 4 of these occasions were accompanied by vocal activity, indicating that this and tail slapping may benefit from social communication. No significant relationship between the call types and the actual movement measurements was found.Killer whale vocalizations traditionally have been classified into discrete call types. Using human speech processing techniques, I considered that calls are alternatively comprised of shared segments that can be recombined to form the stereotyped and variable repertoire. In a classification experiment, the characterization of calls using the whole call, a set of unshared segments, or a set of shared segments yielded equivalent performance. The shared segments required less information to parse the same vocalizations, suggesting a more parsimonious system of representation.This closer examination of the movements and vocalizations of Norwegian killer 3 whales, combined with future work on ontogeny and transmission, will inform our understanding of whether and how culture plays a role in achieving population-specific behaviors in this species. 4 ACKNOWLEDGEMENTS

Impacts of Whale Watching on the Behavior of Humpback Whales (Megaptera novaeangliae) in the Coast of Panama

“…The number of slap behaviors increased when the number of boats declined. This observation supports the theory that if a whale is close to another group, they will communicate through slapping behavior (Shapiro, 2008). Whales of both sexes slap their fins to communicate or gain attention when seeking a mate.…”

Comparing call-based versus subunit-based methods for categorizing Norwegian killer whale, Orcinus orca, vocalizations

“…The prospect that killer whales build their calls from smaller subunits is reinforced by the observation that compound calls can be constructed from whole stereotyped calls (Strager 1993(Strager , 1995Shapiro 2008). This suggests a nested system of vocal production in which similar rules of flexible sequencing assemble subunits into call types, which can then be assembled into compound calls.…”

“…Research on birdsong, killer whale calls and human speech has used silent periods and abrupt spectral shifts to define subunit boundaries. Similarly, in this study we designated subunit boundaries whenever there was at least a 0.1s span of silence or a 500 Hz spectral jump occurring within 0.25s ( Figure 2; see Shapiro 2008 for the contour traces of all calls). The LFC and HFC of a call were often divided into subunits at different time points.…”

Killer whale call frequency is similar across the oceans, but varies across sympatric ecotypes

“…For the False Pass transient population, call categorization was performed based on audible characteristics of calls and visual inspection of spectrographic features. For Icelandic and Norwegian killer whales, we have modified and updated existing classifications (Strager, 1995;Shapiro, 2008;Duc, 2011). The herding calls of Icelandic killer whales (Simon et al, 2006) were not included in the analysis.…”