ИСТИНА

Killer whale groups have repertoires of stereotyped calls stable over the years. Some of these calls contain an overlapping high-frequency component, which is thought to enhance recognition and indicate the caller’s direction of movement. These calls are usually referred to as biphonic calls. It was shown previously that the diversity of monophonic calls was substantially higher than the diversity of biphonic calls in four populations of fish-eating (resident) killer whales in the North Pacific. In this study we compared the diversity of call contours within and between mammal-eating (transient) and several populations of fish-eating killer whales. We used the recordings of mammal-eating killer whales from False Pass (Eastern Aleutian Islands), British Columbia (Canada) and Kamchatka (Russia), and recordings of fish-eating killer whales from British Columbia, Alaska and Kamchatka. Call frequency contours were extracted and compared using dynamic time-warping algorithm. Diversity of monophonic and biphonic calls in mammal-eating killer whales followed the pattern revealed previously for the fish-eating populations: median similarity for monophonic calls (57.97%) was lower than the median similarity for biphonic calls (68.27%). Inter-population comparison showed that mammal-eaters’ repertoire of monophonic calls differed almost equally from all four fish-eating populations. On the contrary, biphonic calls compared by the low-frequency component were the most similar to Alaskan fish-eating population, while biphonic calls compared by both the low- and the high-frequency components were the most similar to Southern Vancouver Island fish-eating population. Our results suggest that monophonic and biphonic calls in both fish-eating and mammal-eating killer whales may evolve following different rules and the low- and the high-frequency components of biphonic calls may have different patterns of similarity across populations.