476 



LCC 



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mil 



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PHRASE 



PIIISE 



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THEIE 



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son SESilOl 



Fig. 1. Diagrammatic sample of whale spectrograms (also called sonagrams) indicating terminology used in describing songs. Fre- 

 quency is given on the vertical axis, time on the horizontal axis. The circled areas are spectrograms that have been enlarged to show 

 the substructure of sounds which, unless slowed down, are not readily detected by the human ear. 



Harbour. Watlington's hydrophone- 

 preamplifier combination was flat in re- 

 sponse (±3 decibels) from 500 hertz 

 to 10 kilohertz, with an amplitude loss 

 of 6 decibels per octave below 500 

 hertz. A cable from this hydrophone 

 extended to Watlington's office, where 

 the sounds were taped by a Magne- 

 corder, type PT 6-AH, operating at 

 19.1 centimeters per second. Thus, 

 when whales uttered sounds within 

 range of the hydrophone, Watlington 

 was able to make recordings free of 

 the usual shipboard and cable noises, 

 with the assurance that the whales were 

 not being disturbed by the presence of 

 an observer. 



Evidence that Sounds Are 

 Correctly Ascribed to Humpbacks 



Schevill and Watkins (9), apparent- 

 ly referring to some of the same sounds 

 from the same Watlington tapes that 

 we have described here, have already 

 pointed out that the sounds come from 

 humpback whales. Additional evidence 

 that this is true comes from observa- 

 tions by Watlington. By using binoc- 

 ulars, he was able, on several occa- 

 sions, to observe whales blowing in the 

 vicinity of the hydrophones during a 

 recording of "whale sounds." On rare 

 occasions. Watlington was able to veri- 

 fy that these whales were humpbacks 

 by noting the prominent white flippers 

 when the whales breached. However, 

 such observations did not accompany 



all of the recordings analyzed in detail 

 here. 



In addition to the tapes provided by 

 Watlington, we have taken into con- 

 sideration several hundred hours of 

 recordings made by Payne, who has 

 studied humpback sounds and behavior 

 off Bermuda during the past five 

 springs (1967 to 1971). Payne and 

 Payne (10) have reviewed many of 

 these tapes by noting the form of the 

 sounds in a simple shorthand and, in 

 some cases, by spectrographic analysis. 

 All of our general conclusions about 

 songs are based on considerations of 

 both the Watlington and Payne record- 

 ings, but all spectrographic analyses 

 shown here are from the Watlington 

 recordings. 



The evidence that Payne's recordings 

 come from humpbacks is as follows: 

 (i) when the sounds (such as those 

 to be analyzed here) that were heard 



were loud and whales were visible in 

 the area, the whales proved in each in- 

 stance to be humpbacks; (ii) interposi- 

 tion of a motorboat's wake between 

 identifiable, nearby humpbacks and a 

 hydrophone reduced the intensity of the 

 sounds being recorded (the bubbles in 

 the wake presumably acted as a partial 

 screen); (iii) unfavorable orientation 

 of a hydrophone array in relation to a 

 visible group of humpbacks reduced 

 the intensity of the sounds recorded 

 (one occasion); (iv) pauses in an ex- 

 ceptionally loud series of sounds were 

 correlated with blowing of a nearby 

 humpback at the surface (several oc- 

 casions) and with a breaching hump- 

 back (one occasion); and (v) while 

 drifting in a boat on a very calm sea, 

 Payne went near a pair of clearly 

 identifiable humpbacks and heard one 

 whale emit a complete sequence of 

 sounds, of the sort described here. 



Fig. 2. Here, as well as in Figs. 3 to 5, the right side shows a machine spectrographic 

 analysis of two complete songs (labeled 1 and 2). Frequency and time scales are indi- 

 cated. The left side is a tracing of the spectrograms on the right, emphasizing loud 

 notes of the song and leaving out noise, echoes, distant whales, and all harmonics (ex- 

 cept in the case of pulsive sounds, which depend on their harmonic structure for the 

 effect they have on the human ear). The gap between spectrographs of songs 1 and 2 

 is designed to make the individual songs clear and is not indicative of any gap in time. 

 This figure shows two songs of whale I. recorded 28 April 1964 by F. Watlington of 

 the Palisades Sofar Station. St. David's, Bermuda. Note dynamile blasts occurring in 

 pairs every 10 minutes. These two songs are part of a series of seven from this whale, 

 and by comparison with earlier songs, lacking the dynamite blasts, we lind that the 

 blasts do not have any detectable effect on the whale's rendition of its song. We 

 have other examples of whales singing, without change in the form of the song, right 

 through loud underwater sounds generated by other research activities in the area. The 

 dashed line at about 500 hertz represents propeller noise from a passing freighter. 

 Echoes are prominent, making louder sounds appear three times on the original spec- 

 trograms. 



