Ross Sea killer whale distribution,behavior, color pattern, and

vocalizationsJ . A. THOMAS, S. LEATHERWOOD, W. E. EVANS,

and J . R. JEHL, JR.

Hubbs Sea World Research InstituteSan Diego, California 92109

F. T. AWBREY

Biology DepartmentSan Diego State UniversitySan Diego, California 92182

Objectives of this continuing project are to document(1) killer whale (Orcin us orca) distributions and behaviors nearRoss Island and elsewhere in the Antarctic, (2) geographic andinterpod variation in killer whale color patterns, and(3) geographic variability in killer whale vocalizations.

Searches for killer whales were made from shipboard in thefollowing areas: (1) in the Ross Sea, January 1981 (Leather-wood, Thomas, and Awbrey in press); (2) between McMurdoStation and Punta Arenas, Chile, Lyttleton, New Zealand, andWellington, New Zealand, January and February 1981 (Leath-erwood, Todd, Thomas, and Awbrey in press); and (3) betweenPort Hueneme, California, and Callao, Peru, December 1980.Searches also were made from land-based helicopters 5-26January 1980 in McMurdo Sound and from ship-based heli-copters 27 January-2 February 1980 off Franklin Island andnorthwestern Ross Island (total of 30 flights; approximately 50hours). On 28 occasions, ice-edge stations were maintained tocollect underwater recordings of whales and seals (approxi-mately 40 hours of recordings) (figure 1).

Killer whales were seen off Cape Adare, over Pennell Banks(approximately 170°O'E 75°0'S), and near King George Island,but were abundant only off Ross Island. As many as 152 whaleswere observed during a single flight, with an estimated 50 ina single herd. Whales were concentrated in some of the samefour or five areas on nearly ever flight. Calves, large adultmales (estimated at 9 meters in length), and numerous inter-mediate-sized animals were seen. Animals judged to be calvesof the season, less than half the length of an accompanyingadult, comprised 2.99 percent (52 of 1,789) of all animalssighted-3.66 percent (47 of 1,285) of those in McMurdo Soundand 1.00 percent (5 of 504) of those in more offshore areas.

Before the icebreakers arrived at McMurdo Sound, the killerwhales used the fast-ice edge. When the breakers began pre-paring the channel, they were accompanied by killer whales,which moved ahead of and behind the vessels into newlyforming cracks and holes. Once the channel was open, thewhales continued to use the newly opened water and adjacentcracks. In one instance, a group of eight was observed in acrack about 6 nautical miles from the icebreaker channel, nearthe Strand Moraines; the group was progressing slowly awayfrom open water such that individuals had to break 2.5-15.0centimeters of sheet ice to breathe. Bubble-blowing often pre-ceded the whales' contact with the ice. Preparation of breath-ing holes appeared purposeful. Whales, sometimes threeabreast, often surfaced in the newly opened holes.

Figure 1. Researcher recording vocalizations of killer whales In acrack west of the icebreaker channel In McMurdo Sound, 24 Jan-uary 1981. (Photo by J. Thomas)

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Figure 2. Comparison of selected vocalizations of killer whalesfrom Ross Island and Puget Sound, Washington: (A) Downsweptwhistle followed by rapid, suppressed, carrier FM burst. This Is oneof the most common sounds produced by McMurdo killer whalesand is most similar to the "ricochet" sound of Puget Sound animals(Dahlheim 1980). (B) Upswept whistle of Puget Sound killer whales(Dahlheim 1980). (C) Upswept whistle of McMurdo Sound killerwhale. Compare with (B). Sounds of McMurdo whales generallystart and end at higher frequencies than comparable sounds fromPuget Sound. Effective filter bandwidth for all three, 50 hertz.

1981 REVIEW 157

edly in front of the recording station after long dives. Theymade no movements that we regarded as aggressive.

Although present during most recording sessions, Weddellseals were not vocalizing. Their silence may have been aresponse to the presence of killer whales, or it may reflecttermination of mating activities. Killer whale activity levelsincreased in the evening, corresonding with peak underwateractivity of Weddell seals.

This research was sponsored by National Science Founda-tion grant DPP 77-12646. We thank personnel of rrr, McMurdoStation, and the officers and crew of USCGC Polar Star, USCGCGlacier, AVDET 82, Mobile, Alabama, and VXE-6, McMurdo.

References

Figure 3. A killer whale feeding on an antarctic cod (Dissostichusmawsonl) near the Ice edge In McMurdo Sound. (Photo by S.Drelschma n)

Evans and Yablokov (1978) reported regionally distinct colorpatterns for killer whales. Bigg, MacAskie, and Ellis (1976) andChandler, Goebel, and Balcomb (1977) similarly distinguishedpods and individuals. Ross Island killer whale patternsobserved in 1981 were indistinguishable from those seen therein 1980 (JehI et al. 1980). One large male seen in 1980 and inother years since 1976 was re-identified in 1981 from its saddlepattern and its distinctively shaped and notched dorsal fin.Many individuals had light, yellowish to brownish patches;these are presumed to be algal concentration.

Killer whale regional populations (Jehl et al. 1980), pods(Ford 1980), and individuals (Dahlheim 1980) also can be dis-tinguished acoustically. Sounds of Ross Island killer whalesrecorded in 1981 were indistinguishable from those recordedthere in 1980. However, all antarctic killer whale sounds (figure2), other than clicks, are different from those of Pacific North-west killer whales.

Killer whales were observed feeding on antarctic cod (Dis-sostichus mawsoni) (figure 3) and pursuing Adelie penguins.On one occasion, a killer whale swimming in an ice-leadstopped at locations where emperor penguins had been feed-ing, hyperventilated, proceeded directly to the next penguinfeeding area, and again hyperventilated. The whales wereaware of our presence on the ice and often investigated thehydrophone, "spy-hopping" in front of us or surfacing repeat-

Bigg, M. A., MacAskie, I. B., and Ellis, C. 1976. Abundance and move-ments of killer whales off eastern and southern Vancouver Island withcomments on management (Preliminary unpublished report). Ste.Anne de Bellevue, Quebec: Arctic Biological Station.

Chandler, R., Goebel, C., and Balcomb, K. C. 1977. Who is that killerwhale? Pacific Search, 11(7), 25-35.

Dahiheim, M. E. 1980. A classification and comparison of vocalizationsof captive killer whales (Orcinus orca). Unpublished masters thesis,San Diego State University.

Evans, W. E., and Yablokov, A. V. 1978. Intraspecific variation of thecolor pattern in the killer whale(Orcinus orca). In V. E. Sokolov andA. V. Yablokov (Eds.), Advances in studies of cetaceans and pinnipeds.Moscow: "Nauka" Publications. (English summary)

Ford, J . 1980. Group specific vocalizations of the killer whale (Orcinusorca). Paper presented at the 146th national meeting of the AmericanAssociation for the Advancement of Science, San Francisco, 3-8January 1980.

Jehl, J . E., Jr., Evans, W. E., Awbrey, F. T., and Dreishman, W. S.1980. Distribution and geographic variation in killer whale (Orcin usorca) populations of the antarctic and adjacent waters. AntarcticJournal of the U.S., 15(5), 161-163.

Leatherwood, S., Thomas, J . A., and Awbrey, F. T. In press. Minkewhale response to a transiting survey vessel (Report of the InternationalWhaling Commission, 32, presented at the thirty-first meeting ofthe International Whaling Commission, Cambridge, England).(Document SC/JN81IMIS9)

Leatherwood, S., Todd, F., Thomas, J . A., and Awbrey, F. T. In press.Incidental records of cetaceans in southern seas January and February1981 (Report of the International Whaling Commission, 32, pre-sented at the thirty-first meeting of the International Whaling Com-mission, Cambridge, England). (Document SC133/010)

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