fatty acids, protein, carbohydrate, electrolytes, osmolarity) tosupplement the small amount of published data on milk com-position in this species.

Field support for this work was supplied by the NationalScience Foundation, for which we are deeply grateful. Wethank D. Griffiths for assistance in the field studies.

References

Green, B., and Newgrain, K. 1979. Estimation of the milk intake ofsucklings by means of 22Na. Journal of Mammalogy, 60, 556-559.

Macfarlane, W. V., Howard, B., and Siebert, B. D. 1969. Tritiatedwater in the measurement of milk intake and tissue growth of rum-inants in the field. Nature, 221, 578-579.

Tedman, R. A. 1981. Lactation in the Weddell seal, Leptonychotes wed-delli (Lesson). Doctoral thesis, University of Queensland.

Tedman, R. A., and Bryden, M. M. 1981. The mammary gland of theWeddell seal, Leptonychotes weddelli (Pinnipedia). 1. Gross andmicroscopic anatomy. Anatomical Record, 199, 519-529.

Wright, D. E., Jones, B. A., and Gentry, K. C. 1974. Measurement ofmilk consumption in young ruminants using tritiated water. Pro-ceedings of the New Zealand Society for Animal Production, 34,145-150.

Population dynamics of Weddellseals in eastern McMurdo Sound

J. W. TESTA, J. L. BENGTSON, and D. B. SINIFF

Department of Ecology and Behavioral BiologyUniversity of Minnesota

Minneapolis, Minnesota 55455

We investigated the population dynamics of Weddell seals(Leptonychotes weddelli) near McMurdo Station from 22 Octo-ber to 5 December 1980. Our main objective was to maintainthe continuity of census and reproductive data for a long-termresearch project initiated in 1970.

Seals on the fast ice adjacent to Ross Island between CapeEvans and McMurdo Station were reached by tracked vehiclesfrom late October through early December. Tagging pups andretagging adult females in pupping colonies along traditionaltide cracks at Hutton Cliffs, Turks Head, and the DelbridgeIslands (166°25'E 77°40'S) were priorities early in the season.Tagging of pups was intensive enough to allow a completecount of parous females and pups. Numbers of males andnonparous females were estimated by Jolly-Seber analysis ofresightings. Censuses of seals were conducted seven timesfrom 11 November to 2 December. Pups at the Hutton Cliffscolony were weighed weekly to evaluate their growth andcondition at weaning, providing a basis for comparison withprevious years.

The total population of Weddell seals in the fast-ice area wasestimated to be 930. There were at least 830 individuals (this

figure includes those seen during a census period plus taggedseals known to be alive but not sighted). Adult and subadultfemales accounted for approximately 80 percent of the popu-lation. Pup production had increased from a low of 257 in 1976(DeMaster 1978; Thomas et al. 1980) to a high of 457 in 1980.The proportion of known adult females pupping (76 percent)was as high as that of any of the last 10 years (Siniff in press).However, total population size has not recovered from the1976 decline. Growth and condition of the pups at HuttonCliffs in 1980 were good.

Future work will concern ecological relations between Wed-dell seals and antarctic cod (Dissostichus mawsoni) and the sea-sonal movements and mortality factors affecting juvenile Wed-dell seals. Preliminary work on these aspects was begun in1979 (Thomas et al. 1980).

This research was sponsored by National Science Founda-tion grant DPP 78-21713801.

References

DeMaster, D. P. 1978. Estimation and analysis of factors that control apopulation of Weddell seals (Leptonychotes weddelli) in McMurdoSound, Antarctica. Unpublished doctoral thesis, University of Min-nesota.

Siniff, D. B. In press. Antarctic seal population dynamics and ecology.Proceedings of the Ross Sea Symposium (Royal Society of New Zea-land).

Thomas, J. A., Keuchie, V. B., Ross, M. J., and Eagle, T. C. 1980.Satellite tracking and automatic position/activity monitoring tech-niques for the antarctic cod and Weddell seal. Antarctic Journal ofthe U.S., 15(5), 153-154.

Late summer dives of Weddell seals In early January 1981, studies of the diving behavior ofWeddell seals began near Scott Base and near White Island.This late-summer investigation continued until late February,when all summer personnel departed. By the end of the sum-mer field season 20 dive recorders had been attached to sealsand 19 had been recovered.

The recorders were of two types, a time-depth recorder (TDR)

and a depth histogram recorder (DHR). Both are described else-where (Kooyman 1981; Kooyman, Billups, and Farwell inpress). The TDR, which records every dive over a 2-week

GERALD L. KOOYMAN, MICHAEL A. CASTELLINI,

and RANDALL W. DAVIS

Physiological Research LaboratoryScripps Institution of OceanographyUniversity of California, San Diego

La Jolla, California 92093

1981 REVIEW 153

period, has been used in previous studies of Weddell seals(Kooyman et al. 1979). The DHR, which analyzes the frequencyof dives to a preset depth threshold, records every dive overa 1-month period. This was the first time it had been used inthe Antarctic, but it has been used previously in studies ofking penguins in the subantarctic (Kooyman, Davis, and Costa1980).

The recorders were on the seals from 2 to 21 days. A total of4,000 dives were recorded. Data on these dives now are beinganalyzed for similarities and differences from previous years,as well as for comparisons between McMurdo Sound andWhite Island seals. Analyzed will be such variables as thediving intensity (number of dives per unit of time and amountof time spent underwater), preferred depths, and preferredtime of diving.

Simultaneous with the dive studies, a field site for overwin-tering was being set up at White Island (figure). The site

---.-

_t--I

includes an ice hole cut through 15 meters of sea and plateletice. The hole is being used for biological and oceanographiccollections and observations through the winter.

The White Island site is of special interest because it islocated about 25 kilometers south of the edge of the Ross IceShelf and is one of the few localities where seals live yeararound within the ice shelf. The ice in this location is stablethroughout the year, and we are taking advantage of thiscondition to study the seals throughout the winter. Similarwinter studies will be done at McMurdo as soon as ice con-ditions permit.

Such studies will yield information about how foragingbehavior of seals differs between summer and the harsherwinter conditions. We also will look for differences in feedingbehavior between seals diving under thin sea ice and thosediving under thick shelf ice. Ice thickness under the shelfranges from an estimated 15 to 70 meters. Dives under thethick ice will provide data on orientation abilities of sealswhen they dive to depths where no astronomical light sources(such as the sun, moon, or stars) are available.

This work was supported by National Science Foundationgrant DPP 79-23623. Many assisted in the fieldwork; we wouldlike to give special acknowledgment to the Weddell seal fieldteam of M. Davis, M. Horning, R. Maue, and W. Stockton.

References

.;'•

A south-facing, oblique, aerial photograph of White island taken25 January 1981 from an altitude 011,525 meters. The arrow Indi-cates the overwintering field camp. There were open water leadsup to 10 meters wide In the three ice rifts nearest the island. Therifts are about 10 meters deep. (Photograph by G. L. Kooyman)

Kooyman, G. L. 1981. Weddell seal: Consummate diver. Cambridge,England: Cambridge University Press.

Kooyman, G. L., Billups, J. 0., and Farwell, W. D. In press. Tworecently developed recorders for monitoring diving activity ofmarine birds and mammals. In A. C. MacDonald and P. C. Priede(Eds.), Experimental biology at sea. New York: Academic Press.

Kooyman, C. L., Castellini, M. S., Costa, D. P., Billups, J. 0., andPiper, S. J. 1979. Diving characteristics of free-ranging Weddellseals. Antarctic Journal of the U.S., 14(5), 176.

Kooyman, G. L., Davis, R. W., and Costa, D. P. 1980. Behavior andenergetics of diving in king penguins. Aptenodytes patagonicus. Ant-arctic Journal of the U.S., 15(5), 158-159.

Minke whales oft northwesternRoss Island

S. LEATHERWOOD and J . A. THOMAS

Hubbs Sea World Research InstituteSan Diego, California 92109

F. T. AWBREY

Biology DepartmentSan Diego State UniversitySan Diego, California 92182

The first objective of our study was to quantify responses ofminke whales (Balaenoptera c.f. B. acutorostrata) to a surveyvessel passing nearby. This information is needed to deter-

mine whether a correction term is necessary for ship transectmodels used to estimate population sizes of minkes and otherlarge whales (Tillman in press). Joint helicopter and ship sur-veys totaling 8 hours 8 minutes were conducted at seven loca-tions in open water in the southwestern Ross Sea (figure 1).Observed minke whale swimming directions, grouped by dis-tance and bearing relative to the ship, were tested for uniform-ity (Batschellet 1972). If the whales were not responding to thevessel, one would expect a uniform distribution of swimmingdirections, irrespective of the whales' positions relative to theship. We found that swimming directions were unaffected bythe ship (Leatherwood, Awbrey, and Thomas in press) andconcluded that no correction factor would be necessary toestimate minke whale density from data collected on boardUSCGC Polar Star. However, we recommended to the Interna-tional Whaling Commission (IwC) that similar studies be con-ducted with aircraft and the actual research vessels used byiwc in censuses of antarctic minke whales.

Our second objective was to describe the distribution, size,and behavior of the Ross Island segment of minke whale pop-

154 ANTARCrIc JOURNAL