Premilinary results of the effects of SURTASS-LFA sonar on singing humpback whales

Abstract

Abstract : The singing behavior of humpback whales exposed to SURTASS-LFA sonar was monitored in Hawaii during March 1998. An observation vessel towing a hydrophone array followed individual singers continuously recording their songs and the received level of the sonar near the whale. At least 2 complete songs were recorded before commencing a 60 min 42s long playback, which consisted often 42s signals transmitted every 6 min. by a U.S. Navy vessel. Observations continued into the post-exposure period. Song spectrograms were broken into themes and phrases using visual analysis and aural scoring. 23 focal follows were conducted; 5 were control follows with no playback. In 9 follows the whale sang throughout the playback, in 4 the whale stopped singing when it joined another whale and in 5 it stopped presumably in response to the playback. We recorded at least one complete song in all three experimental conditions from six individuals. These singers sang longer songs during (13.75 min) than before (10.68 min) or after (10.58 min) the playback (model III ANOVA, p = 0.047, n = 6). No differences were found in theme order (X(exp 2)2 = 3.273, p = 0.195). Song cessation and song duration responses did not scale with sonar received level. High variability in individual responses may indicate that some males were more sensitive to the sonar than others.