CUMMINGS and THOMPSON: GRAY WHALES 



Besides no playback, used in the 1969 exper- 

 iments, random noise and pure tone served as 

 additional controls in 1970. 



Gray whales come by Point Loma at any time 

 during the migration season, day or night, as 

 individuals or in small groups of two to five 

 animals. However, for the total of 5 weeks 

 at sea, we had to work in bright daylight, 0830 

 to 1630 hr, because of earlier difficulty in seeing 

 the whales in subdued light. Undisturbed whales 

 moved along in a southerly course at average 

 speeds of 10 km/hr, blowing from one to three 

 times every 1 to 14 min. We have also seen 

 killer whales off Point Loma. 



Migrating gray whales produce underwater, 

 low-frequency moaning sounds in a band from 

 20 to 150 Hz (Cummings, Thompson, and Cook, 

 1968) . These sounds last 1.0 to 1.7 sec. 



We began an experiment upon seeing an on- 

 coming whale or group of whales that was not 

 encumbered with small boat traffic. Playbacks 

 were generally started when the whales were 

 150 to 450 m away, toward the north. The ex- 

 periments were alternated so that successive 

 contacts would not encounter the same situation. 

 Sessions lasted 30 to 100 min, after which the 

 whales had passed the ship or disappeared. 

 There were 77 experiments (77 contacts) in- 

 volving a total of 132 gray whales. The ap- 

 pearance of "whale-watching" or fishing boats 

 invalidated our work with numerous other con- 

 tacts. They not only interfered with the whales' 

 progress, but their underwater sounds consider- 

 ably reduced the playback signal-to-noise ratio. 



EXPERIMENTAL RESULTS 



The reactions of gray whales to the projected 

 killer whale sounds were spectacular. Blowing 

 whales, or those running at the surface, imme- 

 diately swirled around and headed directly away 

 from the killer whale sound source. We have 

 no idea of how quickly the submerged whales 

 reacted, but subsequent surfacings were away 

 from the killer whale sound source. 



Most whales fled towards the north. How- 

 ever, if their previous southerly course had taken 

 them seaward of the ship and the sound source, 



they turned and swam toward the open sea. 

 Gray whales coming from the general direction 

 of the kelp, or those very close to it, fled into 

 this heavy growth and stayed in one general lo- 

 cation until we stopped the killer whale stimulus. 



Whales came about and resumed a southerly 

 course for Mexico 5 to 30 min after the killer 

 whale sound stopped. If we renewed the play- 

 back, before the whales passed by, they again 

 fled northward from the sound source. On sev- 

 eral occasions, we repeated the experiments on 

 the same contact up to three times, each with 

 similar results. 



Of the 36 contacts principally involving killer 

 whale playback, 30 avoided the sound source, 

 3 were questionable because we never saw them 

 after playback, and 3 passed the ship as normal, 

 without an apparent avoidance (Table 1) . How- 

 ever, one of the last-mentioned was a single 

 whale that had already come very close to the 

 east-west line arbitrarily set on the projecting 

 transducer. This whale could have just as easily 

 avoided the sound source by swimming to the 

 south. 



Table 1. — Reaction of gray whales contacted on 77 



occasions to various stimuli. 



[1-4 whales in a contact; 132 whales in all.] 



Random 

 noise 



Pure 

 tones 



No 

 ploybock 



Killer 



whole 



"screams" 



Avoidance 

 No ovoidance 

 Questionable 





 21 

 



30 

 3 

 3 



All 21 contacts not encountering an intended 

 stimulus (no playback) moved along towards 

 the south in normal fashion. Two contacts of 

 the 10 that received pure tone avoided the sound 

 source. However, 1 of these 2 turned only mo- 

 mentarily. It then resumed the southerly course, 

 still in the presence of the playback stimulus. 

 Of the 10 contacts presented with random noise, 

 2 avoided by turning towards the north for a 

 very short distance. However, both of these 

 gray whales seemed to be startled only for the 

 moment; then quickly turned a second time and 

 swam down past the random noise sound source. 



Two of the 8 contacts that did not avoid 

 random noise and 2 of the 8 that did not avoid 



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