A male sperm whale can grow in length up to 60 feet.
Photo: Chris Johnson
March 18, 2001
The Acoustic Realm of the Sperm Whale - Part II
This is Genevieve Johnson speaking to you from the Solomon Sea in Papua New Guinea.
One would be hard pressed to encounter a more impressive animal than the adult male sperm whale, by any measure it is a most magnificent animal. The largest predator in the sea, he may reach lengths of over 60 ft (18m), he has nothing to fear and is the undisputed king of his ocean home. Sperm whales are extremely vocal, with acoustics being their most important sense in an environment where visibility can often be poor and communication over long distances is necessary. These animals emit clicks for most of the time spent below the surface, with the loud vocalizations and resonant clicks of the male sperm whales being particularly powerful.
Benjamin Kahn discusses the essential role of acoustics in the life of the male sperm whale.
[ sound recording of a large group of sperm whales ]
A different vocalization among sperm whales are the clicks of the males, the mature males or bulls. These are perhaps the most impressive sounds when in the company of sperm whales. The loud metallic 'clangs' from the mature males visiting tropical breeding grounds are really a joy to hear.
[ sound recording of a large group of sperm whales with a male 'clang' sound ]
We have heard several of these in the Bismarck Sea, indicating that we are looking at a breeding ground, a calving ground, perhaps even a mating ground in this Kimbe Bay area. This has been a very significant find, something that we didn't really expect. We have been seeing 'bachelor schools', four males neatly tied together in a group, codaing and clanging away. It has been quite an exciting event to see so many bachelor schools in a relatively small area.
The 'Clangs' have a metallic quality to them, and are most likely forms of acoustic display, a mating call perhaps. The males appear to do little or no feeding at all in these low latitudes, compared to their favorite haunts, the cold waters of the temperate and polar zones. The males are highly migratory and only come into the warm waters of the tropics during the mating season.
Although we don't really know the precise function of these 'clangs', or male vocalizations, we can speculate a little bit as to what the function may be. For instance it could attract receptive females, or at the same time it could dissuade other males from coming into the area. We do know that the characteristics of the coda relate to the size of the animal making the sounds. In that respect it could be a sizing up, an acoustic challenge if you like, of another whale.
Another interesting facet of encountering such a relatively high number of medium size males, is the fact that the waters North of here, the North Pacific waters off Japan for instance, were some of the most heavily hunted waters in the 1960's. So the numbers of large, sexually and socially mature males, have been substantially reduced. This would mean that we could be looking at the next generation of breeding bulls, somewhat reduced in size, but none the less exploring the tropics and finding their way toward females.
It is always a joy to hear the metallic 'clangs' beaming into the bridge via the hydrophone speakers, while tracking and studying these migratory creatures. Their movements and activities are certainly a research priority.
The RV Odyssey has been outfitted with a bioacoustic system that allows us to digitally record whale vocalizations directly to a computer hard disk, and file them into a database. This data will tell us whether the acoustic censusing of populations is possible, as well as allowing us a greater understanding of the acoustic behaviors of sperm whales.
Log by Benjamin Kahn & Chris Johnson
Gordon, J. 1991. Evaluation of a method for determining the length of sperm whales (Physeter catadon) from their vocalizations. J. Zool. 224: 301-314.
Gordon, J. 1998. Sperm whales. Voyager Press, USA. 72pp.
Kahn, B., H. Whitehead and M. Dillon. 1993. Indications of density-dependent effects from comparisons of sperm whale populations. Mar. Ecol. Prog. Ser. Vol. 93: 1-7.
Watkins, W. 1977. Acoustic behavior of sperm whales. Oceanus Vol 20 (2):50-58.