484 



four grunts (units 5, 6, and so on). 

 This phrase Is usually repeated quite 

 exactly ten or more times. An interest- 

 ing sound that is sometimes superim- 

 posed on the grunts may represent the 

 audible component of a train of ultra- 

 sonic pulses, but this possibility must 

 await recordings on equipment sensi- 

 tive to ultrasound. 



Song type B (as shown by whale 

 IV) resembles type A in themes 1, 2, 

 and 3, but by theme 4 the parallel is 

 less clear. The series of descending 



notes shown on line 4 of Fig. 5 is not 

 comparable to anything in song type A, 

 unless it could be thought of as a 

 series of units similar to those in theme 

 4, but with the duration of the units, 

 and the silences between them, being 

 much greater. The subsequent very 

 short and rapidly delivered notes are 

 certainly unlike type A songs. At the 

 end of its first and second songs, whale 

 IV emits sustained notes that are fol- 

 lowed by a low grunt. In a broad 

 sense, this is quite similar to the basic 



phrase of theme 6 in song type A. 

 However, in type A the sustained notes 

 differ markedly in pitch, whereas they 

 arc delivered at roughly constant pitch 

 in song type B. In some ways, type B 

 is intermediate between type A and the 

 very different song type C. (We have 

 various examples of type C from 1969, 

 but they will not be discussed here.) 

 Since variability within a fixed gen- 

 eral pattern is such a prominent feature 

 of humpback songs, it may be worth 

 taking a detailed look at some of the 



Fig. 9. Themes 5 (left) and 6 (right). The starting moments of the first unit in each phrase are aligned at the left margin of the 

 column. Note the very regular duration and spacing of these sounds. 



I 



