The Whale-Watching Web: CONTEXT/The contextual sound

Preliminary, insight into the acoustic sound repertoire of the short-finned pilot whale (Globicephala macrorhynchus) off Tenerife, Canary Islands.

Michael Scheer Bianka Hofmann Peter Behr
Projekt CONTEXT
Vor dem Steintor 92, 28203 Bremen, Germany
Tel.:+49-421-73187 Fax:+49-421-76482

INTRODUCTION

Many delphinids live in long-lasting stable units (Bigg et al. 1989, Scott et al. 1990). Data of the social structure of short-finned pilot whales off Tenerife seems support this tendency (Heimlich- Boran and Heimlich-Boran 1992, and Heimlich-Boran 1993. Kasuya and Marsh 1984 for Globicephala macrorhynchus off the Pacific coast of Japan). The phenomena of high-developed social structures often correlates with a complex communication (Ford 1989, Ford 199 1, dos Santos 1990). As reported in spinner dolphins /Stenella longirostris) this might reach a cultural level.

Concerning short-finned pilot whales nearly nothing is known about the acoustic communication system (some information in Poulter 1968 and Schevill 1964). Most acoustic work done with Globicephala has been resulting from recordings of Globicephala melaena (Taruski 1979, Poulter 1968. Evans 1987). Acoustic data on Globicephala in general is available in Dreher and Evans (1 964) and Thomas et al. (1986).

To get a deeper insight into the communicative skills of short-finned pilot whales and furthermore the possible transmitted semantic content of the emitted signals the sound emissions have to be categorized.

During a two-month field study in February and March 1994 acoustic samples of Globicephala macrorhynchus were taken.

MATERIAL AND METHODS

The study area was around 28'N and 17.45'W off the Southwest coast of Tenerife on the Canary Islands. Observations were conducted from a 7m' Fiberglas boat with a 65PS engine. Acoustic recordings were made with an Uher 4200 Monitor tape recorder and a self-made hydrophone. We recorded in a depth of 7m. The sound was analysed on Avisoft.

In this study eve didn't pay attention on the context of the vocalisations but tried to record the variety of the whale's acoustic emissions in general.

RESULTS AND DISCUSSION

During a total of 13 sightings (each about 4h) conducted from February 23 through March -'10 in 1994 a total of 4,5h of audio recordings were collected. The acoustic categories can be. generally devided into two main groups: pulsed and non-pulsed sounds. These are several types of click, trains (echolocation clicks, grunts, cries) representing pulsed sounds and several "s of whistles (calls, several high-frequency whistles) for the group of non-pulsed sounds. Sometimes whistles are s superimposed with clicks (as reported in Poulter 1968). This results from the fact that delphinids probably produce clicks and whistles simultaneously (Lilly 1962 for Tursiops). The following monograms are a small insight into the variety of the short-finned pilot whale's acoustic emissions. 1. Click. trains. a) Typical echolocation clicks. As reported in Taruski (1979) the whistle-frequency ranges from 2-12 kHz. Preliminary this can be confirmed. Taruski also suggests the possibility of the existence of a signature-character of specific calls for Globicephala melaena. Probably the whistles shown in sonogram 2 a) and b.) might have the same function because they were repeated very often per sequence. Due to the fact that the animals of one pod often swim less cohesive these sounds probably serve as an acoustic @ among them.

As suggested in Brownlee (unpubl.data, Ph.D.-dissertation) for spinner dolphins whistles act for different social communicative functions to identify the individual caller, to locate the individual in space and to assess the emotional state, alertness and preparedness of the school to behave co- operatively.

Finally it can be said that the short-finned pilot whales have a high social level which suggests a complex communication system. Furthermore it is suspected that these whales might have geographic variations in their vocalizations as observed in killer whales (Thomas et al. 1986). Much more work has to be done, first of all an emphasis on the context in which acoustic signals are transmitted.

LITERATURE

Bigg. M. A., Olesiuk. P. F., Ellis, G. M. Ford, J. K. B., Balcomb, K. C. 1990. "Social organisation and genealogy of resident killer whales in the coastal waters of British Columbia and Washington State". In: Hammond, P. S., Mizroch, S. A., Donovan, G. P. (eds. ). "Individual recognition of cetaceans". Rep. Int. Whal. Commn. (Special Issue 12), Cambridge, pp. 383-406.

dos Santos, M. E., Caporin, G., Moreira, H. O. Ferreira, A. J., Coelho, J. 1990. "Acoustic behavior in a local population of bottlenose dolphins". In: Thomas, Kastelein (ed. ). "Sensory abilities of cetaceans". Plenum Press, New York, pp. 585-598.

Dreher, J. J., Evans, W. E. 1964. "Cetacean communication". In: Tavolga, W. N. (ed. ). "Marine Bioacoustics". Pergamon Press, Oxford, pp. 373-393.

Evans, P. G. H. 1987. "The natural history of whales and dolphins". Christoffer Helm, London.

Ford, J. K. B. 1989. "Acoustic behavior of resident killer whales off Vancouver. Island, British Columbia". Can. J. Zool. 67: 727-745.

Ford, J. K. B. 1991. "Vocal traditions among resident killer whales (Orcinus orca) in coastal waters of British Columbia". Can. J. Zool. 69: 1454-1483.

Heimlich-Boran, J. R., Heimlich-Boran, S. L. 1992. "Social structure of short-finned pilot whales off Tenerife, Canary Islands". In: Evans, P. G. H. (ed. ). European Research on Cetaceans 6, pp. 154-157.

Heimlich-Boran, J. R., Heimlich-Boran, S. L. 1993. "Pilot whale pods: mating groups or feeding groups?". In: Evans, P. G. H. (ed. ). European Research on Cetaceans 7. pp- 12-15.

Kasuya, T., Marsh, H. 1984. "Life history and reproductive biology of the short-finned pilot whale off the Pacific coast of Japan". Rep. Int. Whal. Commn. Special Issue 6, Cambridge, pp. 259-310.

Lilly, J. C. 1962. "Vocal behavior of the bottlenose dolphin". Proc. Am. Phil. Soc., Vol. 106, No. 6, pp. 520-529.

Poulter, T. C. 1968. "Marine Mammals". In: Sebeok, T. A. (ed. ). "Animal Communication". Indiana University Press, Indiana, pp. 405-465.

Schevill, W. E. 1964. "Underwater sounds of cetaceans". In: Tavolga, W. N. (ed. ). "Marine Bioacoustics", Pergamon Press, Oxford, pp. 307-316.

Scott, M. D., Wells, R. S., Irvine, A. B. 1990. "A long-term study of bottlenose dolphins on the west coast of Florida". In: Leatherwood, S., Reeves, R. R. (eds. ). "The bottlenose dolphin". Academic Press, San Diego, pp. 235-244.

Taruski, A. G. 1979. "The whistle repertoire of the north Atlantic pilot whale (Globicephala melaena) and its relationship to behavior and environment". In: Winn, H. E. and Olla, B. C. (eds. ). "Behavior of Marine Animals". Vol. 3: Cetaceans. Plenum Press, New York, pp. 345-368.

Thomas, J. A., Fisher. S. R. Awbrey, F. A. 1986. "Use of acoustic techniques in studying whale behavior". In: Donovan, G. P. (ed. ). "Behavior of whales in relation to management". Rep. Int. Whal. Commn. (Special Issue 8. ), Cambridge, pp. 121-138.

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