Horizontal Transmission of Call Features in Killer Whale Dialects (original) (raw)
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Is killer whale dialect evolution random?
Behavioural Processes, 2013
The killer whale is among the few species in which cultural change accumulates over many generations, leading to cumulative cultural evolution. Killer whales have group-specific vocal repertoires which are thought to be learned rather than being genetically coded. It is supposed that divergence between vocal repertoires of sister groups increases gradually over time due to random learning mistakes and innovations. In this case, the similarity of calls across groups must be correlated with pod relatedness and, consequently, with each other. In this study we tested this prediction by comparing the patterns of call similarity between matrilines of resident killer whales from Eastern Kamchatka. We calculated the similarity of seven components from three call types across 14 matrilines. In contrast to the theoretical predictions, matrilines formed different clusters on the dendrograms made by different calls and even by different components of the same call. We suggest three possible explanations for this phenomenon. First, the lack of agreement between similarity patterns of different components may be the result of constraints in the call structure. Second, it is possible that call components change in time with different speed and/or in different directions. Third, horizontal cultural transmission of call features may occur between matrilines.
Physical constraints of cultural evolution of dialects in killer whales
The Journal of the Acoustical Society of America, 2016
Odontocete sounds are produced by two pairs of phonic lips situated in soft nares below the blowhole; the right pair is larger and is more likely to produce clicks, while the left pair is more likely to produce whistles. This has important implications for the cultural evolution of delphinid sounds: the greater the physical constraints, the greater the probability of random convergence. In this paper the authors examine the call structure of eight killer whale populations to identify structural constraints and to determine if they are consistent among all populations. Constraints were especially pronounced in two-voiced calls. In the calls of all eight populations, the lower component of two-voiced (biphonic) calls was typically centered below 4 kHz, while the upper component was typically above that value. The lower component of two-voiced calls had a narrower frequency range than single-voiced calls in all populations. This may be because some single-voiced calls are homologous to...
Animal Behaviour, 2012
Keywords: acoustic repertoire call type dialect evolution killer whale Orcinus orca Although killer whale, Orcinus orca, dialects have been studied in detail in several populations, little attempt has been made to compare dialect characteristics between populations. In this study we investigated geographical variation in monophonic and biphonic calls among four resident populations from the North Pacific Ocean: Northern and Southern residents from British Columbia and Washington State, southern Alaska residents, and eastern Kamchatka residents. We tested predictions generated by the hypothesis that call variation across populations is the result of an accumulation of random errors and innovation by vertical cultural transmission. Call frequency contours were extracted and compared using a dynamic time-warping algorithm. We found that the diversity of monophonic calls was substantially higher than that of biphonic calls for all populations. Repertoire diversity appeared to be related to population size: in larger populations, monophonic calls were more diverse and biphonic calls less diverse. We suggest that the evolution of both monophonic and biphonic calls is caused by an interaction between stochastic processes and directional selection, but the relative effect of directional selection is greater for biphonic calls. Our analysis revealed no direct correlation between call repertoire similarity and geographical distance. Call diversity within predefined call categories, types and subtypes, showed a high degree of correspondence between populations. Our results indicate that dialect evolution is a complex process influenced by an interaction among directional selection, horizontal transmission and founder effects. We suggest several scenarios for how this might have arisen and the implications of these scenarios for call evolution and population history. Ó
Cultural evolution of killer whale calls: background, mechanisms and consequences
Behaviour, 2015
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 hypothes...
The Structure of the Discrete Call Repertoire of Killer Whales Orcinus Orca from Southeast Kamchatka
Bioacoustics, 2007
The problem of categorization arises in any classification system because classes should be discrete while the characteristics of most natural objects and aspects of nature are more or less gradual. In systematics, this problem usually is solved by creating several levels of categories, such as class, order, family, genus and species. In the existing killer whale discrete call classification, only two levels occur -call type and call subtype. In this paper we describe structural categories at a broader level than call type in the discrete sounds of killer whales and compare these categories between and within vocal clans in a community of resident killer whales from Southeast Kamchatka, Russian Far East, and also with killer whales outside this community. We found four main classes of discrete calls in the repertoire of resident killer whales from Southeast Kamchatka. The calls of Southeast Kamchatka transient killer whales and Sakhalin killer whales do not fall into these classes. This suggests that the resident killer whale community from Southeast Kamchatka has some rules defining the structure of calls which are typical for this community. Consequently, all resident killer whales from Southeast Kamchatka can be said to share the same vocal tradition.
Can Genetic Differences Explain Vocal Dialect Variation in Sperm Whales, Physeter macrocephalus?
Behavior Genetics, 2012
Sperm whale social groups can be assigned to vocal clans based on their production of codas, short stereotyped patterns of clicks. It is currently unclear whether genetic variation could account for these behavioural differences. We studied mitochondrial DNA (mtDNA) variation among sympatric vocal clans in the Pacific Ocean, using sequences extracted from sloughed skin samples. We sampled 194 individuals from 30 social groups belonging to one of three vocal clans. As in previous studies of sperm whales, mtDNA control region diversity was low (p = 0.003), with just 14 haplotypes present in our sample. Both hierarchical AMOVAs and partial Mantel tests showed that vocal clan was a more important factor in matrilineal population genetic structure than geography, even though our sampling spanned thousands of kilometres. The variance component attributed to vocal dialects (7.7%) was an order of magnitude higher than those previously reported in birds, while the variance component attributed to geographic area was negligible. Despite this, the two most common haplotypes were present in significant quantities in each clan, meaning that variation in the control region cannot account for behavioural variation between clans, and instead parallels the situation in humans where parent-offspring transmission of language variation has resulted in correlations with neutral genes. Our results also raise questions for the management of sperm whale populations, which has traditionally been based on dividing populations into geographic 'stocks', suggesting that culturally-defined vocal clans may be more appropriate management units.
Animal Behaviour, 2002
Cultural lineages are based on learned social traditions that are stable for several generations. When cultural lineages also reflect common ancestry and/or are shared by individuals that live together they are called clans. The existence of clans among killer whales has been previously proposed but has not been confirmed. Here, we show that clans exist among resident type killer whales, Orcinus orca, in southern Alaska. Resident killer whales live in stable matrilines from which emigration of either sex has not been observed. Matrilines that associate regularly (d50% observation time) are called pods. Pods are believed to consist of closely related matrilines and share a unique repertoire of discrete call types. Pods that share parts of their repertoire form what Ford (1991, Canadian Journal of Zoology, 69, 1454-1483) called an acoustic clan. Here, we identified discrete call types of seven pods from southern Alaska, using a method based on human discrimination of distinct aural and visual (spectrogram) differences. Mitochondrial DNA of members of each pod was also analysed. The repertoires of the seven pods were compared and two acoustically distinct groups of pods were identified. Each group was monomorphic for a different mitochondrial D-loop haplotype. Nevertheless, pods from different clans associated frequently. It thus appears that the acoustic similarities within groups, which we presume to be cultural, reflect common ancestry, and that these groups therefore meet the above definition of clans. We also argue that a combination of cultural drift and selection are the main mechanisms for the maintenance of clans.
acta ethologica, 2009
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.