BUBBLESTREAM WHISTLES ARE NOT REPRESENTATIVE OF A BOTTLENOSE DOLPHIN'S VOCAL REPERTOIRE

Abstract

Whistling bottlenose dolphins sometimes identify themselves with a concurrent bubblestream, and some researchers use these bubblestream whistles as their sole whistle sample. However, bubblestream whistles are not known to be representative of the entire repertoire. Bubblestreams and whistles were recorded from three captive female dolphins and their newborn calves. Bubblestreams were rare (0.13/min), with calves producing ten times as many as adults. Overall, 79% of bubblestreams were associated with whistles, but only 1 % of whistles were associated with bubblestreams. Bubblestream whistles were not independent: 49% occurred within 1 sec of another bubblestream, and 72% of these had the same contour as other bubblestream whistles in the bout. Bubblestream use was context-dependent: adults were more likely to bubblestream when caring for a calf (P < 0.001), and calves were more likely to bubblestream when other calves were present (P < 0.001). Bubblestreams were not associated with all whistle types. Bubblestream whistles were not evenly distributed across the clusters of a hierarchical cluster analysis of contour parameters using 300 randomly selected non-bubblestream whistles and 92 independent bubblestream whistles (10 clusters, P= 0.003). In conclusion, bubblestreams are rare visual cues that dolphins produce in association with certain whistles in certain contexts and are not representative of the dolphin's repertoire.