Social complexity and cultural transmission of dialects in killer whales

Abstract

Many social animals have cultural traditions that may shape their societies while the social structure can in turn influence how the culture is acquired. Killer whales possess culturally transmitted dialects. The divergence of dialects was thought to occur simultaneously and consistently with the gradual fission of matrilines. In this paper we compare the social associations across matrilineal units, Bayesian phylogeny of dialects and similarity of particular syllables to test whether dialects affect social structure and whether associations or common origin define similarity of call types. We found that neither phylogeny of dialects nor similarity of syllables was correlated to associations between matrilineal units, but similarity of syllables was correlated to phylogeny of dialects for four of the six syllables analysed. The complexity and fluidity of social ties between matrilineal units and the variation in cultural transmission patterns produce a complex relationship between the social network and the socially learned vocalizations.

Independent acoustic variation of the higher- and lower-frequency components of biphonic calls can facilitate call recognition and social affiliation in killer whales

“…This can happen if the components evolve with different speed. Variation in the rates of cultural evolution of different elements of killer whale vocal repertoire has been reported previously: Deecke et al [25] showed that different call types can change with different speed, and Filatova et al [5] found that different syllables within calls diverge with different speed, including syllables of both the lower-and higher-frequency components. Yurk [55] performed McDonald-Kreitman test for positive selection and found different selective pressures for the lower-and higher-frequency components.…”

“…Each R-type killer whale pod shares the same dialect; new pods form gradually through the split of an ancestral pod, and the dialects of the splitting pods slowly diverge in time due to changes in call structure. This provides the complex system of dialects with varying degrees of similarity to each other that more or less reflect the degree of relatedness between the corresponding pods [5,6].…”

A comparison of Northeast Atlantic killer whale (Orcinus orca) stereotyped call repertoires

“…Various terminologies have been used to describe subunits of killer whale calls. The terms part, segment, component, or syllable have been used to refer to abrupt shifts in pulse repetition rate (Filatova, Ivkovich, Guzeev, Burdin, & Hoyt, 2017; Ford, 1991; Strager, 1993). Yurk et al (2002) distinguished between elements (separating parts of a call marked by abrupt shifts) and segments (parts of a call separated by silent intervals).…”

“…Due to variation in call quality, not all parameters were measured from all calls. The measurements were made using a custom routine in MATLAB R2017a (The MathWorks, Natick, MA (Filatova, Ivkovich, Guzeev, Burdin, & Hoyt, 2017;Ford, 1991;Strager, 1993). Yurk et al (2002) distinguished between elements (separating parts of a call marked by abrupt shifts) and segments (parts of a call separated by silent intervals).…”

Crowd intelligence can discern between repertoires of killer whale ecotypes

“…Different populations normally have completely different call sets and can include one or more clans. Calls change over time through learning errors and innovations (Ford, 1991;Deecke et al, 2000), and consequently the repertoires of closely related, recently diverged groups are generally more similar, than in the more distantly related groups (Ford, 1991;Yurk et al, 2002;Filatova et al, 2017).…”