Biological studies of seals inpack ice habitat

D. DEMASTER, J . THOMAS, and S. STONE

Department of Ecology and Behavioral BiologyUniversity of Minnesota

Minneapolis, Minnesota 55455

D. ANDRIASHEK

Canadian Wildlife ServiceEdmonton, Alberta, Canada

From 25 October through 22 November 1978, leop-ard seals (Hydrurga leptonyx), crabeater seals (Lobodon car-cinophagu.c), Weddell seals (Leptonychotes weddelli), andRoss seals (Ommatophoca rossi) were studied from abroadthe iJv Hero. We conducted these studies in pack iceareas from King George Island south to Anvers Island,including Bransfield and Gerlache Straits and Bismarck,Dallmann, and Flandres bays, between latitude 61°-65°Sand longitude 58°-65°W.

Our primary objectives were to estimate the numberof each species, based on daily counts of all seals seenon ice floes; to locate female leopard seals with pups forbehavioral observations and documentation of the ap-proximate time of parturition; to collecTTiIleopardand crabeater seals for preservation of reproductivetracts, stomach contents, toenails, and skeletal material;to document the underwater vocal repertoire of thesepack ice seals; and to determine the patterns of leopardseal activity using radio telemetry.

Nineteen days of census in good pack ice habitat wereconducted during this field period. Tallies were madefrom the ice house of the nlv Hero from approximately0400 through 2200 hours each day. For each seal, wenoted the species, sex, age, behavior, location, and sizeof floe on which it was located.

A total of four leopard seal pups were observed on icefloes between 7 and 13 November. Two near-term fe-tuses were collected, on 4 and 14 November. We wereable to take weights and body measurements on threeleopard seal pups and a second series of weights andmeasurements on two of the three pups. In addition, wecollected a newborn Ross seal pup on 14 November. Theunfrozen afterbirth indicated recent parturition. Theonly other documented observation of a Ross seal pupwas made by Soviet scientists (Tikhomirov, 1975). Incontrast, most crabeater pups observed during this pe-riod were newly weaned juveniles.

To investigate reproductive parameters, food habits,and age structure, our collection efforts were concen-trated on female leopard and crabeater seals (See table1). The entire reproductive tract (ovary, uterus, cervix,and part of the vagina) was collected to document re-productive histories. By correlating this informationwith age determinations based on toenails and teeth, it

will be possible to estimate age-specific reproductive suc-cess. In addition, we will determine the stage of estrusduring this time of year. Stomach contents from cap-tured leopard seals indicated that crabeater seal, pen-guin, fish, squid, and krill were all part of the leopardseal diet. In contrast, crabeater stomachs contained al-most exclusively krill.

Underwater recordings of vocalizations were made todocument the vocal repertoire of pack ice seals and in -vestigate vocalization rates as a measure of diurnal ac-tivity patterns. Recordings of seal vocalizations weremade with sonobuoys (model AN/SSQ-41B), whichtransmitted information to an onboard receiver, andwith crystalline-timer controlled cassette recorders hou-sed in Coleman coolers with R-130 hydrophones, whichwere left on ice floes overnight. Both recording systemsperformed well in the pack ice habitat.

We marked and recaptured leopard seals with twotypes of tags, plastic cattle ear tags and radio transmitters(table 1). Two sets of plastic tags were attached to therear flippers of all seals handled and released. Adultfemale leopard seals with pups were restrained with abag (Stirling, 1969), as were all the Weddell, Ross, andcrabeater seals that were tagged and released. All otherleopard seals were immobilized with Sernylan and Val-ium (Hofman, 1975). Initially, Sernylan dosages of 0.3milligram per kilogram were used, with variable andunpredictable results. We found that lower dosages ofSernylan (0.1-0.15 milligram per kilogram) with 5 mil-ligrams of Valium immobilized the seal sufficiently fora bag to provide satisfactory restraint for attaching ra-dios. Four radio tags were successfully attached to leop-ard seals, and three of the four radio-tagged animalswere relocated. These relocated animals seem to havebeen passively moving with the drift of the pack ice. Wealso tested various stomach-pumping techniques on bothcrabeater and leopard seals. The best results were ob-tained with a standard veterinary stomach pump, anevacuation bottle, and lubricated 1/2-inch surgical tub-ing. Stomach specimens of krill from crabeater sealstomachs were particularly easy to sample in this way.

Table 1. List of seals taken during Antarctic Peninsulastudy, 1978

SpeciesCategory Leopard Crabeater Weddell Ross

Tagged & ReleasedAdult males481Adult females4*218Pup males300Pup females100

Total 121019

CollectedAdult males220Adult females1650Pup males 1**00Pup females 00

Total 2070Grand Total321719

* = radio transmitters attached**collected in utero

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Future investigations will concentrate on other seg-ments of the reproductive cycle and behavior of leopardseals in order to improve our understanding of popu-lation dynamics.

The energetic and responsive support of our effortsby the captain and crew of it/v Hero was a decisive con-tribution to our program and integral to our findings.This research has been supported by National ScienceFoundation grant DPP 77-21946.

References

Hofman, R. J . 1975. Distribution patterns and populationstructure of Antarctic seals. Ph.D. thesis, University of Min-nesota.

Stirling, I. 1966. A technique for handling live seals.Journal ofMammology, 47: 543-44.

Tikhomirov, E. A. 1975. Biology of the ice forms of seals in thePacific section of the Antarctic. Rapp. P-v. Reun. Cons. mt.Explor. Mer., 169: 409-12.

Observations of two genera ofsmall odontocete cetaceans

(Orcinus and Globicephala) inantarctic and adjacent waters

WILLIAM E. EVANS, JOSEPH R. JEHL, JR., MERRILL

J . WHITE, JR., and JAMES R. HOLBROOK

HubbslSea World Research InstituteSan Diego, California 92109

During the cruise of i'/v Hero from 25 February to 5April 1979, we made observations, as opportunitiesarose, on killer whales (Orcinu.s orca) and pilot whales(Globicephala sp.). Although similar in size, and overlap-ping in range, these small cetaceans exhibit marked dif-ferences in abundance (the pilot whale is much less com-mon), biology, social behavior, and vocalizations. Further,although both are top predators feeding on fish andsquid, Orcinus also preys on warm-blooded vertebrates.

Our observations form part of a larger study of thebiology of these and other small odontocetes in the RossSea and Palmer Peninsula areas and in the coastal watersof southern South America. We seek to understand theecological role of these whales in antarctic and subant-arctic ecosystems.

Our research plans call for comparative studies ofdensity and distributional patterns to assist in determin-ing the size of current stocks and ecological factors thatmay affect distribution. In addition, we are documentingvariations in color pattern. Recent studies of largewhales (Physeter, Megaptera) and some deiphinids haveindicated that such variation can be used to distinguish

regional stocks, family groups, and even individuals.Variations in Globicephala color pattern may also clarifyspecies limits. Further, we are comparing color patternsin killer whales and pilot whales to determine if theymigrate seasonally from the Antarctic to southern SouthAmerica. We are also recording vocalizations to inves-tigate possible regional and/or pod differences in dia-lects, and we are measuring physical characteristics ofambient noise in areas of apparent high productivity.

We made our initial observations during Wv Hero'scruise that began in Ushuaia, Argentina, and followeda route that took us to Palmer Station, the Weddell Sea,the South Orkney Islands, and the Shetland Islands.

We sighted five pods of Orcinus during the cruise, butno Globicephala. Color-pattern variations were docu-mented photographically and vocalizations were re-corded using U.S. Navy-type AN/SSQ-41B sonobuoys,a DEl broadband receiver, and a Nagra SJS portable au-dio recorder. To gather additional data on whale sight-ings, we distributed color-pattern observation forms toscientists working at research bases on the Palmer Pen-insula and to the Wv Hero crew.

Analysis of cruise data is in progress, including com-parison with information already compiled for northernhemisphere populations of Orcinus and Globicephala. Theduration and structure of Orcinus vocalizations recordedduring the Hero cruise are being compared with othersrecorded in British Columbia, Newfoundland, and ant-arctic locations.

Although Wv Hero was well equipped for acoustic rec-ording, weather conditions and the animals' swimmingbehavior often prevented effective field observations.

In future studies, we plan to use smaller, high-speedboats (Zodiac or Avon inflatables) and increase the areathat can be surveyed by flying transects with an airplaneor helicopter.

This work has been supported by National ScienceFoundation grant DPP 77-21646 to the Hubbs/Sea WorldResearch Institute.

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