Total avoidance (i.e., all whales1eavingtheobservationarea)occurredat 1.3,7.2,3.5and2.9km,withcorrespondingsoundlevelsof152, 165,178and165dB.Thesimilarities among experiments reported here support the conclusion that short-term behavioral changes occur when bowhead whales are exposed to airgun blasts from approaching geophysical vessels at ranges < 10 km. Partial avoidance (Le., some whales leaving the observation area while others remained) occurred at ranges of 3.5 and 7.6 km, with sound levels of 142 and 158 dB respectively. responses occurred at 3.5 and 8.2 km with received airgun noise levels of 142 and 157 dB respectively (all levels in dB re 1pPa). Behavioral responses included shorter surfacing and dive times, fewer blows per surfacing, longer blow intervals and subtle to overt changes in surface behaviors. The responses of bowhead whales to controlled approaches by geophysical vessels producing airgun blasts were observed during the course of four field experiments conducted in the Alaskan Beaufort Sea in September 1984. We know of no other non-human animal for which such dramatic non-reversing changes appear in the display pattern of an entire population as part of their normal behavior. We do not understand the significance of changing songs. Such analysis demonstrates inter– and intra– individual variability, none of which is as great as the variation between songs of consecutive years. An analysis of the songs sung by groups of whales shows that normal singing continues even when whales are close enough, presumably, to hear each other. We present some basic characteristics of the song form and consider the nature and extent of changes in content as a function of time. All the songs showed basic structural similarities so that it is possible to define a song form which characterizes songs from many years. However, the song was changing conspicuously and progressively with time so that songs separated by a number of years were very. In each year's sample, all whales were singing basically the same song. One of these reaches 65 km inland to Strathcona Provincial Park, another to the sawmilling community of. From a cluster of forested islands near the mouth of the sound, three deep inlets (Tahsis, Tlupana and Muchalat) penetrate inland. 163 songs of humpback whales (Megaptera novaeangliae) recorded near Bermuda during April and May of 13 years between 19 have been analysed as continuous sound spectrograms and compared. Nootka Sound, BC, is an inlet on Vancouver Island 's western coast, 270 km northwest of Victoria.
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