Fig. 1. Diagrammatic sample of whale spectrograms (also called sonagrams) indicating terminology used in describing songs. Frequency 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 hydrophonepreamplifier combination was flat in response (±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 Magnecorder, 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 Schevill and Watkins (9), apparently 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 observations by Watlington. By using binoculars, he was able, on several occasions, to observe whales blowing in the vicinity of the hydrophones during a recording of "whale sounds." On rare occasions, Watlington was able to verify 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 In addition to the tapes provided by 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 instance to be humpbacks; (ii) interposition 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 exceptionally loud series of sounds were correlated with blowing of a nearby humpback at the surface (several occasions) and with a breaching humpback (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 indicated. 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 (except 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 dynamite 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 find 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 spectrograms. Fig. 3. Whale II, recorded by Watlington in spring, 1963. At the end of line 4 the whale stopped briefly, and a small bit (just after it started singing again, line 5) was not taped. Note, however, that the whale resumed singing in proper sequence of the song. Sounds of a second and more distant whale are prominent on the spectrographic record midway through song 2. At the end of the second song, whale II stopped singing one of our few examples of the end of a song. 2 SECONDS Fig. 4. Whale III, recorded by Watlington in May 1963. The first song is much shorter than the second, which begins with an unusually long first theme. 2 די Fig. 5. Whale IV, recorded by Watlington 12 April 1961. This is an example of a different song type (type B) from the previous three examples. The poor signal-to-noise ratio of the recording caused the spectrograms for the highest frequency, lowest intensity signals to be quite faint. At the end of song 2, the whale stopped singing. This was actually the fourth and last consecutive song Watlington recorded from this whale on this occasion, and thus also indicates a true ending. while the pair were submerged. He was using no hydrophone, the sounds coming directly through the bottom of the boat. Observations such as these have removed most of our doubts that what we have been analyzing are humpback sounds; yet the great variability of the sounds still leaves us with residual reservations about ascribing to one species (the humpback) all of the sounds we are analyzing here. Analysis of Humpback Sounds On first hearing humpback vocalizations, one has the impression of an almost endless variety of sounds. Spectrographic analysis shows, however, that all prolonged vocalizations occur in long, fixed sequences and are repeated with considerable accuracy every few minutes. Because one of the characteristics of bird songs is that they are fixed patterns of sounds that are repeated, we call the fixed patterns of humpback sounds "songs." The principal differences between bird and humpback songs are that bird songs usually last for a few seconds, while humpback songs last for minutes; and one song of a bird is usually separated from the next by a period of silence, whereas humpback songs are repeated without a significant pause or break in the rhythm of singing. The term "song," as used in discussions of sounds made by animals, has received considerable attention. In one case, no fewer than nine pages of a comprehensive glossary by Broughton (see 11) are devoted to a detailed discussion of the many uses, misuses, and meanings of "song." Broughton finally arrives at three meanings, or categories of meanings, of the term "song," which he characterizes as sensu latissimo, sensu stricto, and sensu strictissimo. The median of these three (sensu stricto) is defined as "a series of notes, generally of more than one type, uttered in succession and so related as to form a recognizable sequence or pattern in time." By that definition (and by Broughton's other two as well), we feel justified in using the term "song" to describe repetitive sound patterns of humpback whales. In describing the humpback whale song, we will adhere to the following designations. The shortest sound that is continuous to our ears when heard in "real time" will be called a "unit." (Some units when listened to at slower |