Usage of any items from the University of Cumbria's institutional repository 'Insight' must conform to the following fair usage guidelines.Any item and its associated metadata held in the University of Cumbria's institutional repository Insight (unless stated otherwise on the metadata record) may be copied, displayed or performed, and stored in line with the JISC fair dealing guidelines (available here) for educational and not-for-profit activities provided that• the authors, title and full bibliographic details of the item are cited clearly when any part of the work is referred to verbally or in the written form• a hyperlink/URL to the original Insight record of that item is included in any citations of the work • the content is not changed in any way• all files required for usage of the item are kept together with the main item file. You may not• sell any part of an item• refer to any part of an item without citation • amend any item or contextualise it in a way that will impugn the creator's reputation• remove or alter the copyright statement on an item.The full policy can be found here. Alternatively contact the University of Cumbria Repository Editor by emailing insight@cumbria.ac.uk. Island residents, southern Alaska residents, and eastern Kamchatka residents. We tested 37 predictions about call variation across populations which are due to an accumulation of random 38 errors and innovations by vertical cultural transmission. Call frequency contours were extracted 39 and compared using a dynamic time-warping algorithm. We found that the diversity of 40 monophonic calls was substantially higher than the diversity of biphonic calls for all populations. 41 Call diversity in the NorthRepertoire diversity appeared to be related to the population size: in larger populations, 42 monophonic calls were more diverse and biphonic calls were less diverse. We suggest that the 43 evolution of both monophonic and biphonic calls is caused by an interaction between stochastic 44 processes and directional selection, but the relative effect of directional selection is greater for 45 biphonic calls. Our analysis revealed no direct correlation between call repertoire similarity and 46 geographical distance. Call diversity within pre-defined call categories -types and subtypes -47 showed a high degree of correspondence between populations. Our results suggest that dialect 48 evolution is a complex process influenced by an interaction between directional selection, 49 horizontal transmission and founder effects. We suggest several scenarios for how this might 50 have arisen and the implications of these scenarios for call evolution and population history. 51Keywords: dialect, killer whale, acoustic repertoire, evolution, call type. in vocal repertoires is common among both bird and mammalian populations (e.g., Krebs & 61 Kroodsma 1980;Slobodchikoff et al. 1998; Mitani et al. 1999). In this study we examined geographical variation in monophonic and biphonic calls 140 among four resident populations from the North Pacific Ocean...

Killer whale discrete calls include types containing an overlapping high-frequency component (biphonic calls) and types without an overlapping high-frequency component (monophonic calls). In the resident killer whales of the Northeast Pacific, biphonic discrete calls exhibit higher source levels than monophonic calls, which suggests different active space and consequently different functions for monophonic and biphonic call types. In this study we investigate the potential communicative functions of monophonic and biphonic discrete calls produced by killer whales from Kamchatka (Northwest Pacific). We analyze how the usage of these calls depends on the number of pods present in the area and type of activity. Our results show that the usage of monophonic and biphonic calls in Kamchatkan killer whales depends on the number of pods in the area and is less dependent on the type of activity. Biphonic calls are more common when more than one pod is present in the area and could therefore function as markers of pod and matriline affiliation, serving mainly as cohesion signals. Monophonic calls dominated the vocalizations when a single pod was present, while in the presence of more than one pod both categories were used in equal proportions.

Cultural evolution is a powerful process shaping behavioural phenotypes of many species including our own. Killer whales are one of the species with relatively well-studied vocal culture. Pods have distinct dialects comprising a mix of unique and shared call types; calves adopt the call repertoire of their matriline through social learning. We review different aspects of killer whale acoustic communication to provide insights into the cultural transmission and gene-culture co-evolution processes that produce the extreme diversity of group and population repertoires. We argue that the cultural evolution of killer whale calls is not a random process driven by steady error accumulation alone: temporal change occurs at different speeds in different components of killer whale repertoires, and constraints in call structure and horizontal transmission often degrade the phylogenetic signal. We discuss the implications from bird song and human linguistic studies, and propose several hypotheses of killer whale dialect evolution.