SOUNDS FROM BRYDE, BALAENOPTERA EDENI, AND 

 FINBACK, B. PHYSALUS, WHALES IN THE GULF OF CALIFORNIA 



William C. Cummings, 1 Paul 0. Thompson, 2 and 

 Samuel J. Ha 3 



ABSTRACT 



Low-frequency moaning sounds were recorded from Bryde whales, Balaenoptera edeni, off Loreto, Mex- 

 ico, in the Gulf of California. These utterances averaged 0.4 s in duration with most of the sound energy 

 at about 124 Hz. Elsewhere in the Gulf, we recorded about 1,300 low-frequency moans from at least 35 

 feeding finback whales, B. physalus. The finbacks' most outstanding sound was a long moan with a 1.9-s 

 component at 68 Hz and a 1.6-s component at 34 Hz. Overall sound source levels in the effective band- 

 widths ranged between 152 and 174 dB re 1 jiPa (1 m) for Bryde whales, and 159 to 183 dB for finback 

 whales. Short "20-Hz signals" that are typically associated with finback whales were not present in these 

 recordings, apparently because of seasonal or behavioral differences. 



The main objective of this study was to describe 

 underwater sounds from two species of mysticete 

 whales— the Bryde whale, Balaenoptera edeni, and 

 the finback whale, B. physalus. We also wanted to 

 compare the presently described finback sounds with 

 those recorded elsewhere. 



Contrasted with the typical whistles, squeals, and 

 clicks of odontocetes, we continue to find that 

 mysticetes utter mostly low-frequency sounds. How- 

 ever, exceptional and rare sounds of higher frequency 

 have been reported (Cummings and Thompson 1971; 

 Beamish and Mitchell 1971, 1973; Beamish 1978). 

 The combination of low frequencies (Hz), long wave- 

 lengths, and high source levels of mysticete whale 

 sounds enables their detection at distances up to 100 

 km or more, even with standard signal processing. 



Low-frequency sounds (40-75 Hz, 1-s long, and 

 others) have been recorded from finbacks in the 

 North Atlantic (Schevill and Watkins 1962; Edds 

 1981). Short, powerful "20-Hz signals" have also been 

 recorded from this species (Schevill et al. 1964). 

 Watkins (1981) categorized underwater finback 

 sounds as 20-Hz pulses, ragged broadband low-fre- 

 quency pulses, low-frequency rumbles, higher fre- 

 quency sounds, and broadband impulses. 



We have long been interested in "20-Hz signals", 

 having worked with many categories from wide- 

 spread areas of the world (Cummings and Thomp- 

 son 1966 4 ; Northrop et al. 1968, 1971), and the pros- 

 pects of recording them from the more accessible 



^ceanographic Consultants, 5948 Eton Court, San Diego, CA 

 92122. 

 2 4256 Sierra Vista, San Diego, CA 92103. 

 3 Millersville University, Millersville, PA 17551. 



finbacks in the Gulf of California also was an impor- 

 tant objective. 



We are unaware of any other descriptions (except 

 for 20-Hz pulses) of sounds from Pacific finbacks. 

 Underwater sounds from the Bryde whale were 

 unknown, this being the original description except 

 for a brief abstract of the present work in 1969 

 (Thompson and Cummings). 



MATERIAL AND METHODS 



An expedition took place in June 1969, aboard the 

 27 m yawl, Saluda. The ship left La Paz (southeast 

 Baja peninsula, Mexico) sailed northward to Mulege, 

 across the Gulf of California to Guaymas on the Mex- 

 ican mainland, northward past Isla San Esteban, 

 around Isla Angel de la Guarda, and southward to 

 Santa Rosalia— a distance of about 1,500 km (Fig. 

 1). Except for Contact 3, all of the sounds recorded 

 in the presence of unidentified large whales were 

 generally the same as those that we determined to 

 be from finbacks. However, we were not always cer- 

 tain which balaenopterid was being recorded, 

 especially at long distances. Consequently, if an iden- 

 tification of a balaenopterid whale was questionable, 

 the "contact" was noted simply as "Balaenoptera sp". 



The water's surface varied from Sea State to 2, 

 and currents usually were minimal. The ship's oper- 

 ating equipment was shut down during all record- 

 ings. The instrumentation included a hydrophone- 



4 Cummings, W. C, and P. O. Thompson. 1966. 20-Hz signals 

 in the northeast Pacific Unpubl. Rep., 17 p. Navy Electronics 

 Laboratory, San Diego, 92152. 



Manuscript accepted July 1985. 



FISHERY BULLETIN: VOL. 84, NO. 2, 1986. 



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