and calm seas made recording condi- 

 tions ideal. The first clicks, shown in 

 Figure 4F, began 1 mm after the 

 whale started a 3-min-J!5-sec-long dive. 

 at a distance of 50 to 70 m from the 

 hydrophone. Additional click trains 

 (Figure 4G) occurred simultaneously 

 with the first exhalation after the 

 dive. Twenty sec later, noise from an 

 unseen boat began and continued for 

 95 sec. A third click train was emit- 

 ted 50 sec after the boat noises ceased 

 and 50 sec prior to the next blow. By 

 then, the whale was 80 to 100 m from 

 the hydrophone and the received level 

 of the clicks was 5 to 7 dB lower than 

 the level of the clicks recorded when 

 the whale was half that distance from 

 the hydrophone. 



On 18 August 197.^. the click train 

 shown in Figure 4H was recorded 

 from a single feeding gray whale at 

 0900 hr. The whale was about 600 m 

 from shore in 4 m of water. The sur- 

 face was calm with about a Im swell. 

 At the time the click train was emitted, 

 the whale v\as 100 to 150 m from the 

 hydrophone. Twenty min later a sin- 

 gle harbor porpoise, Phocoena pho- 

 coena. was observed in the area. 



About 5 hr of recordings uere 

 made in the presence of the gray 

 whales in Wickaninnish Bay and 

 much additional monitoring was done 

 without recording. Although at times 

 nearly continuous very faint clicking 

 could be heard, only about 250 of the 

 recorded clicks had good signal-to- 

 noise ratios. The number of clicks per 

 train varied from I to 96 with repeti- 

 tion rates of 8 to 40/sec. The principal 

 energy of these clicks occupied a band 

 from about 2 to 6 kHz. centered at 

 3.5 to 4.0 kHz. The average click 

 duration was a little under 2 msec. 



DISCUSSION 



striction (similar to the sound of air' 

 escaping from a scuba regulator un- 

 derwater). Since this whale sound 

 generally was not associated with ex- 

 halation or blowhole movement, if it 

 were, in fact, generated by escaping 

 air. the air must have passed from one 

 internal chamber to another. No bub- 

 bles v\ere observed coming from the 

 mouth or blowholes. 



Although the possibility exists that 

 another species of marine mammal 

 could have produced the clicks re- 

 corded when Gigi was released off 

 San Diego and the clicks recorded in 

 the presence of gray whales in Wick- 

 aninnish Bay. we think the evidence 

 indicates that the clicks did come from 

 the gray whales. The acoustic param- 

 eters of the clicks recorded from the 

 geographic areas are nearly identical. 

 The only marine mammals, other 

 than gray whales, observed in either 

 recording area was the single Phocoena 

 phocoeiw observed a half hour after 

 the recording was made on 18 August 

 1973 in Wickaninnish Bay and a 

 small group of Dclphiniis dclphis. 

 about 2 km awa\ from the site of 

 Gigi's release a half hour before she 

 was released. Phocoena phocoena. 



however, has not been observed off 

 San Diego, and clicks of Delphinits 

 have a much higher frequency content 

 than described in this report. Also, 

 the level of the clicks recorded in the 

 presence of Gigi was too high for the 

 sounds to have come from the Del- 

 phinits as the clicks appeared to origi- 

 nate from a single source rather than 

 from a group of animals. 



We have no evidence that the clicks 

 recorded in the presence of gray 

 whales have an echolocation function, 

 but if the\ do. their frequency range 

 (2 to 6 kHz) probably would be too 

 low for the sounds to be useful for 

 locating small individual food organ- 

 isms. However, they could be helpful 

 for finding dense concentrations of 

 organisms or for ranging off the bot- 

 tom to feed or navigate. Despite four 

 seasons of recording in the presence 

 of hundreds of migrating gray whales 

 off San Diego, Naval Undersea Center 

 personnel have never recorded similar 

 clicks from the whales. But. accord- 

 ing to most authorities, gray whales 

 do not feed on their long migrations 

 (Rice and Wolman. 1971). If the 

 clicks were associated with feeding, 

 we consequently should not expect to 



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We do not know how any of the 

 sounds discussed in this paper were 

 actually produced by the gray whales. 

 The ""metallic-sounding pulsed signal" 

 produced by Gigi at Sea World sound- 

 ed like air bubbles escaping from an 

 area of high pressure through a con- 



Fjgure 3. — Hydrophone suspension system used to record underwater sounds in Wickaninnish 

 Bay, Vancouver Island, Canada. 



43 



