ИСТИНА

Some killer whale sounds include an overlapping high-frequency component usually referred to as biphonation. Biphonic calls are suggested to be long-range signals used as pod markers, and monophonic calls are thought to be close-range intra-group contact signals, which should obviously influence the diversity of these categories. In this study we estimated the diversity of biphonic and monophonic calls in the repertoires of two killer whale populations: Northern Resident population from the Northeast Pacific (British Columbia, Canada) and resident population from the Northwest Pacific (Kamchatka, Russia). We extracted frequency contours from call spectrograms using an algorithm in MATLAB. We used one call per each call type. In total, 59 calls from Kamchatka population (31 biphonic and 28 monophonic) and 33 calls from British Columbia population (22 biphonic and 11 monophonic) were used in this analysis. Categorization of calls was performed using MATLAB algorithm that incorporates dynamic time-warping and an adaptive resonance theory neural network. The algorithm has divided biphonic and monophonic calls from Kamchatka into 6 and 17 categories respectively (mean calls per category: biphonic 5.17, monophonic 1.65), and biphonic and monophonic calls from Canada into 9 and 10 categories respectively (mean calls per category: biphonic 2.44, monophonic 1.1). Mean amount of calls per category differed significantly between Kamchatka biphonic and monophonic calls (Mann-Whitney test, p=0.04) and between British Columbia biphonic and monophonic calls (Mann-Whitney test, p=0.003). There were no significant differences in the mean number of calls per category between Kamchatka and British Columbia biphonic calls, and between Kamchatka and British Columbia monophonic calls. We conclude that monophonic calls are more diverse than biphonic calls in both populations. Since these populations do not contact, this similarity obviously result from the specific functions of monophonic and biphonic calls rather than cultural transmission between populations.