William A. Watkins

Sperm whale codas

Short series of 3 to 40 or more clicks are produced by sperm whales, Physeter catodon, in stereotyped repetitive sequences or codas. The temporal click patterns in codas appear to be unique to individual whales over at least a few hours. It is suggested that sperm whale codas serve as a means of individual acoustic identification. An apparent exchange of codas between two animals was analyzed and acoustical locations calculated for the four‐hydrophone array data that changes in underwater meovement coincided with changes in the coda sequences.

Aerial Observation of Feeding Behavior in Four Baleen Whales: Eubalaena glacialis, Balaenoptera borealis, Megaptera novaeangliae, and Balaenoptera physalus

Distinct behavioral differences were noted from aerial observations of four species of baleen whales ( Eubalaena glacialis , right whale; Balaenoptera borealis , sei whale; Megaptera novaeangliae , humpback whale; Balaenoptera physalus , finback whale) feeding together on 30 April and 1 May 1975. The right and sei whales fed together on patches of plankton. Right whales fed steadily with mouths open in the densest areas, while the sei whale followed a faster but more erratic path through the patches, alternately opening and slowly closing its mouth with slight throat distension at each closing. Humpback and finback whales fed together on dense schools of fish associated with the patches of plankton. The humpback fed by rushing, generally from below the schools of fish, while finback feeding was by more horizontal passes sometimes characterized by sharp turns and rolls within the fish schools and often with enormous throat distension.

Sound source location by arrival-times on a non-rigid three-dimensional hydrophone array

Abstract Three-dimensional locations of underwater biological sound sources were accomplished by arrival-time-difference measurements on a four-hydrophone array. Accuracy of the locations depended on proximity of the source to the array, demonstrating that the arrival-time-difference method of location inherently is accurate only for nearby sources. A system of concurrent calibration periodically reassesses the hydrophone positions and makes practical the use of flexible non-rigid arrays at sea. Sources located by the array included passing ships, other artificial sources, whales, and porpoises. Direction to a sound source may be reliably indicated even though the source is too distant for useful location. In coastal waters in springtime, the sound levels varied drastically on identical hydrophones separated by only 30 m, presumably largely an effect of shallow-water propagation.

Right Whale Feeding and Baleen Rattle

Surface and subsurface feeding behavior of right whales, Eubalaena glacialis (Borowski, 1781), has been observed in Cape Cod waters since 1956. During surface feeding the whales follow discrete rows of concentrated plankton, and in subsurface feeding they also appear to be feeding on specific patches of food at particular depths and localities. No purposeful underwater sounds are heard during feeding, but the rattle of baleen is often audible during surface feeding and appears to be an adventitious sound. Baleen rattles only when it is held so that some of the forward plates are out of the water while others are partly immersed and subject to movement by passing waves. The rattle is a low level, highly variable sound, composed of sporadic sequences of two to 10 broad bandwidth pulses at uneven repetition rates and widely varying levels. Dominant frequencies are usually between 2 and 4 kHz.

Acoustics and the Behavior of Sperm Whales

The first good recordings of underwater sperm whale sounds that we have were made 27 years ago (22 April 1952, R/V Caryn at 38°29′N, 69°29′W) and five years later the sounds were identified definitely and described (Worthington and Schevill 1957). At every opportunity since then, we have stopped with these whales and listened underwater (Watkins 1977). Repeated observations have gradually sorted out many of the sounds. The overlapping clatter of click series that are usually heard in the presence of these whales have given way with time to acoustic sequences that apparently have characteristics identifiable with individuals. The unorganized welter of sound can be simplified to series of pulses that are related and that can sometimes be traced for hours. Whales underwater have been located and tracked by their own sounds. Yet with all this, the sounds are still not well enough correlated with the whales’ actions to provide anything but glimpses into the role that acoustics plays in the behavior of sperm whales.

Underwater Sounds of Pinnipeds

Descriptions and analyses are presented of underwater sounds made by six species of seals in captivity, Zalophus californianus, Phoca vitulina, P. (Pusa) hispida, P. (Pagophilus) groenlandica, Halichoerus grypus, and Cystophora cristata. The suitability of these very faint sounds for echolocation is discussed.

Listening to Hawaiian Spinner Porpoises, Stenella cf. Longirostris, with a Three-Dimensional Hydrophone Array

A three-dimensional array of hydrophones was anchored for 6 days (8 to 13 May 1971) in Kealakekua Bay on the island of Hawaii in order to listen to the underwater sounds of a resident population of spinner porpoises, Stenella cf. longirostris (Gray, 1828). Arrival-times for individual porpoise sounds were measured, and source locations were calculated to provide a three-dimensional indication of position for calling animals. Most sounds originated at depths less than 10 meters, and many of them were exchanges of sounds by porpoises within 10 to 15 meters of each other. Source level calculations indicated a wide range of levels that suggest intentional control of sound level. The three-dimensional array provided information that would not have been available by single hydrophone listening.

Sperm whales (Physeter catodon) react to pingers

Abstract Sperm whales, Physeter catodon , temporarily interrupted their own sound production in reaction to underwater pulses produced by our calibration sound sources (pingers). All seven whales that passed close to the hydrophone array at different times reacted the same way. They remained silent for at least 2 min, and some of the more distant ones quieted for shorter periods. Acoustic tracking of the sounds indicated that these whales moved underwater at a speed of about 2 knots and downward at a slope of 10–15°, in the general direction of other clicking sperm whales.

Radio tracking of finback (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales in Prince William Sound, Alaska☆

Abstract Finback whales ( Balaenoptera physalus ) and humpback whales ( Megaptera novaeangliae ) were tracked by radio tags in Prince William Sound, Alaska during June, 1978. Tracks of the whales show details of their movements. The tag remained implanted for over 16 days in humpbacks and for over 17 days in a finback (24 days tracking of one whale, visually and by radio). The whales appeared to be undisturbed by the tags. During the tracking, both species had distinct shifts in behavior, their activities were often in unison with conspecific companions, and they had shorter dive times during the dark. The finbacks returned periodically to the same area and the humpbacks roamed for as much as 100 km in a day. The radio tags provided positive individual identification needed for continous tracking and for detailed behavioral observation.

Distinctive characteristics of underwater calls of the harp seal, Phocagroenlandica, during the breeding season

Underwater calls of the harp seal, Phoca groenlandica, from the early March whelping and breeding season (1967, Gulf of St. Lawrence) were analyzed. Seventy‐five percent of the seal calls were characterized by increasing amplitude and/or increasing frequency (Hz) components. In addition, 94% of the calls were repetitive. These features contrasted sharply with the general features of ambient noise, and provided a distinctive quality to the harp seal calls that could be used to recognize the reproductive herd at a distance.