12

NOAA Technical Report NMFS 12

Soviet-American Cooperative

Research on Marine Mammals.

Volume 1- Pinnipeds

Under Project V.6. Marine Mammals,

ofthe US-USSR Agreement on Cooperation

in the Field of Environmental Protection

Francis H. Fay and Gennadii A. Fedoseev (Editors)

September 1984

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service
NOAA TECHNICAL REPORTS NMFS

The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance

and geographic distribution offishery resources, to understand and predict fluctuations in the quantity and distribution of

these resources, and to establish levels for optimum use ofthe resources. NMFS is also charged with the development and implementation of policies for managing national fishing grounds, development and enforcement ofdomestic fisheries regulations, surveillance offoreign fishing offUnited States coastal waters, and the development and enforcement ofinternational

fishery agreements and policies. NMFS also assists the fishing industry through marketing service and economic analysis

programs, and mortgage insurance and vessel construction subsidies. It collects, analyzes, and publishesstatistics on various

phases of the industry"

The NOAA Technical Report NMFS series was established in 1983 to replace two subcategories of the Technical

Reports series: "Special Scientific Report-Fisheries" and ··Circular." The series contains the following types of reports:

Scientific investigations that document long-term continuing programs of NMFS, intensive scientific reports on studies of

restricted scope, papers on applied fishery problems, technical reports of general interest intended to aid conservation and

management, reports that review in considerable detail and at a high technical level certain broad areas of research, and

technical papers originating in economics studies and from management investigations.

Copies ofNOAA Technical Report NMFS are available free in limited numbersto governmental agencies, both Federal

and State. They are also available in exchange for other scientific and technical publications in the marine sciences. Individual copies may be obtained from: Publications Services Branch (E/Al 13), National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, 3300 Whitehaven

St., Washington, DC 20235.
NOAA Technical Report NMFS 12

Soviet-American Cooperative

Research on Marine Mammals.

Volume 1- Pinnipeds

Under Project V.6. Marine Mammals,

of the US-USSR Agreement on Cooperation

in the Field of Environmental Protection

Francis H. Fay and Gennadii A. Fedoseev (Editors)

September 1984

U.S. DEPARTMENT OF COMMERCE

Malcolm Baldrige, Secretary

National Oceanic and Atmospheric Administration

John V. Byrne, Administrator

National Marine Fisheries Service

William G. Gordon, Assistant Administrator for Fisheries
PREFACE

Some 25 to 30 yr ago, when we as students were beginning our respective careers and were

developing for the first time our awareness of marine mammals in the waters separating western North

America from eastern Asia, we had visions of eventually bridging the communication gap which existed

between our two countries at that time. Each of us was anxious to obtain information on the distribution,

biology, and ecological relations of "our" seals and walruses on "the otherside," beyond our respective

political boundari~s where we were not permitted to go to study them. We were concerned that the

resource management practices on the other side of the Bering and Chukchi Seas, implemented in

isolation, on a purely unilateral basis, might endanger the species which we had come to know and were

striving to conserve. At once apparent to both of us was the need for free exchange of biological

information between our two countries and, ultimately, joint management of our shared resources. In a

small way, we and others made some initial efforts to generate that exchange by personal correspondence and through vocal interchange at the annual meetings ofthe North Pacific Fur Seal Commission.

By the enabling Agreement on Cooperation in the Field of Environmental Protection, reached between

our two countries in 1972, our earlier visions at last came true. Since that time, within the framework of

the Marine Mammal Project under Area V of that Agreement, we and our colleagues have forged a

strong bond of professional accord and respect, in an atmosphere of free intercommunication and

mutual understanding. The strength and utility of this arrangement from the beginning of our joint

research are reflected in the reports contained in this, the first compendium of our work.

The need for a series ofsuch a compendia became apparent to us in 1976, and its implementation

was agreed on by the regular meeting ofthe Project in La Jolla, Calif., in January 1977. Obviously, the

preparation and publication of this first volume has been excessively delayed, in part by continuing

political distrust between our governments but mainly by increasing demands placed on the time ofthe

contributors. In this period of growing environmental concern in both countries, we and our colleagues

have been totally immersed in other tasks and have experienced great difficulty in drawing together the

works presented here. Much of the support for doing so was provided by the State of Alaska, through

funding for Organized Research at the University of Alaska-Fairbanks. For its ultimate completion in

publishable form we wish to thank Helen Stockholm, Director of Publications, Institute of Marine

Science, University of Alaska, and her staff, especially Ruth Hand, and the numerous referees narned

herein who gave willingly oftheirtime to review each ofthe manuscripts critically and to provide a high

measure of professionalism to the final product.

Francis H. Fay - United States

Gennadii A. Fedoseev - Soviet Union

ii
CONTENTS

MILLER, ROBERT Y. The US-USSR marine mammal project _ .

BURNS, JOHN J., FRANCIS H. FAY, and GENNADII A. FEDOSEEY. Craniological analysis of harbor and spotted seals of the

North Pacific region 5

BURNS, JOHN J., and VITALI N. GOL'TSEV. Comparative biology of .harbor seals, Phoca vitulina Linnaeus, 1758, of the

Commander, Aleutian, and Pribilof Islands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

BRAHAM, HOWARD w., JOHN J. BURNS, GENNADII A. FEDOSEEV, and BRUCE D. KROGMAN. Habitat partitioning by

ice-associated pinnipeds: Distribution and density of seals and walruses in the Bering Sea, April 1976 . . . . . . . . . . . . . . . . . . . 25

FEDOSEEV, GENNADII A. Use of nonmetrical characters of skulls of Bering Sea seals in a study of the phenotypic structure of

their populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

BUKHTIYAROV, YURII A., KATHRYN J. FROST, and LLOYD F. LOWRY. New information on foods ofthe spotted seal"Phoca

largha, in the Bering Sea in spring 55

DELYAMURE, SEMYON L., MIKHAIL Y. YURAKHNO, VALENTIN N. POPOV, LARRY M. SHULTS, and FRANCIS H. FAY.

Helminthological comparison of subpopulations of Bering Sea spotted 3eals, Phoca largha Pallas. . . . . . . . . . . . . . . . . . . . . . . 61

ESTES, JAMES A., and VITALI N. GOL'TSEV. Abundance and distribution of the Pacific walrus, Odobenus rosmarus divergens:

Results of the first Soviet-American joint aerial survey, autumn 1975 67

DeMASTER, DOUGLAS K. An analysis of a hypothetical population of walruses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

FAY, FRANCIS H., YURII A. BUKHTIYAROV, SAMUEL W. STOKER, and LARRY M. SHULTS. Foods of the Pacific walrus in

winter and spring in the Bering Sea. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

FAY, FRANCIS H., G. CARLETON RAY, and ARKADII A. KIBAL'CHICH. Time and location of mating and associated behavior

of the Pacific walrus, Odobenus rosmarus divergens IIli~er . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

HANSEN, LARRY J., WILLIAM F. PERRIN, ANATOLI S. SOKOLOV, and JAMES G. MEAD. A list of A erican and Soviet

institutIOns possessing collections of osteological specimens from pinnipeds and sea otters 101

The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any proprietary product or proprietary material

mentioned in this publication. No reference shall be made to NMFS, or

to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, reccmmends

or endorses any proprietary product or proprietary material mentioned

herein, or which has as its purpose an intent to cause directly or indirectly

the advertised product to be used or purchased because of this NMFS

publication.

iii
('
The US-USSR Marine Mammal Project

ROBERT V MILLER1

ABSTRACT

Tbe Marine Mammal Project was organized under Area V (Protection of Nature and tbe OrganizatiOll of

Preserves) of tbe US-USSR Agreement on Cooperation in tbe Field of Environmental Protection. From its

inception in 1973, tbis Project has sponored a wide variety of collaborative research efforts on tbe biology,

ecology, and population dynamics of pinnipeds and celaceans, principally of tbe Nortb Pacific region. Tbe

earliest activities involved joint and cooperative researcb on tbe seals and walruses of the Bering and Chukchi

Seas, and those studies are continuing to yield Information ofsubstantial value to botb countries for conservation and management of sbared resources. In conjunction witb tbem, tbe Project bas placed empbasis on

development of recommendations for a proposed international agreement on joint management and conservation of tbose resources. In recent years, the researcb program bas expanded into studies of tbe busbandry and

care of marine mammals in captivity; also implemented were several studies on morphology and taxonomy,

which are of prime importance for identification of populational units requiring separate management consideration. The measure of success of sucb a diverse program is the quantity and quality of reports and

publications evolving from it. A number of papers have been published separately, but tbis is the first

compendium oforiginal reports on the studies ofPinnipedia. A second compendium, on studies ofCetacea, is in

preparation.

PE310ME

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INTRODUCTION

On 23 May 1972 in Moscow, President Nixon of the USA and

President Podgorny of the USSR signed an "Agreement on Cooperation in the Field of Environmental Protection." That agreement

recognized the great importance placed by both countries on solving

mutual problems of environmental protection, and it expressed the

beliefthat progress could be made on their solution more effectively

through cooperative rather than through unilateral action. Among

the areas agreed on was cooperation in the "Protection of Nature

and the Organization of Preserves." This became Area V of the

Environmental Agreement and subsequently included a "Marine

Mammal Project" (Table 1).

The objective of our cooperative effort within the Marine Mammal Project has been to develop collaborative research on the

biology, ecology, and population dynamics of marine mammals of

'Deputy Director. National Marine Mammal Laboratory, National Marine

Fisheries Service. NOAA. 7600 Sand Point Way NE., Seattle, WA 98115, USA.

interest to both countries, thereby contributing to sound management and conservation of those animals. This need for better scientific information, with which to achieve better management of

marine mammals, was recognized and enunciated from the

beginning.

From that initial step, a vigorous program of cooperative and

joint research on marine mammals evolved between our two countries. The first formal meeting between Soviet and American scientists under this program took place in January 1973, during the

organizational meeting for development of Area V. In those initial

discussions, guidelines were established that have continued to

influence our progress. All species ofmarine mammals were recognized as being of mutual concern, in any geographic area of the

world. Nonetheless, the most appropriate areas for concentrated

cooperative effort were recognized as those of the North Pacific

region, particularly the Bering and Chukchi Seas, because of our

common interests and common borders there. A few species, such

as northern fur seal and polar bear, were excluded from consideration by the Project, because each already was included under other

ongoing international programs.
Table I.-Organization of activities under the US-USSR Environmental Protection Agreement. The program is administered by

*

Joint Committee, made up of American and Soviet Chairmen and Executive Secretaries.

Area

I Prevention of air pollution

II Prevention of water pollution

III Prevention of pollution associated with agricultural

production

IV Enhancement of the urban environment

V Protection of nature and the organization of preserves ---------1

VI Protection ofthe marine environment from pollution

VII Biological and genetic effects of environmental

pollution

VIII Influence of environmental changes on climate

IX Earthquake prediction

X Arctic and subarctic ecological systems

XI Legal and administrative measures for protecting

environmental quality

Projects

I. Conservation of wild species of flora and fauna

2. Protection of northern ecosystems

3. Reclamation and revegetation ofdisturbed land

4. Biosphere reserves

5. Arid ecosystems·

6. Marine mammals

7. Plant and animal ecolllgy

8. Ichthyology and aquaculture

Generally speaking, the US-USSR Marine Mammal Project consists of four levels of activity:

I) Exchange of published information. In the USA, a full set of

exchanged materials is deposited in the library of the National

Marine Mammal Laboratory in Seattle, Wash.; and duplicates are

distributed to institutions involved in the subject research.

2) Continuous exchange of unpublished data resulting from

cooperative research efforts. These data are available to both sides

and usually are exchanged on a scientist-to-scientist basis.

3) Coordination of research conducted under national programs.

This has involved standardization of methods, formats, and scope,

and cooperative or joint analysis of resultant data.

4) Joint research expeditions. Scientific personnel of both countries have worked together on joint and complementary research in

the field.

The third and fourth levels have been the substantive parts of the

Project.

Operationally, the Project involves development of proposals by

each side for collaborative work, which are discussed at Project

meetings. Those meetings take place at 18-mo intervals, alternately

in the USA and the USSR. On the US side, a 7-man Steering/

Planning Committee reviews proposals made by scientists throughout the marine mammal research community and assists in developing a coherent package to put forward at the Project meetings. The

Steering Committee also makes recommendations on policy and

direction of-the program. After agreement is reached at the Project

level, those proposals are reviewed by the Joint Committee of the

overall Environmental Agreement. If approved by that body, they

become binding commitments on the two sides.

The following is a resume of activities of the Project, from its

inception in 1973 to the end of its first 6-yr segment in 1978.

PINNIPED RESEARCH

The earliest efforts within the Project involved joint studies of

pinnipeds in the Bering and Chukchi Seas. Those studies were

initiated because of recognition that unilateral efforts, while contributing to the information base on the biology and ecology of

walruses and seals, only addressed part of the problem. Both sides

recognized that the populations of walruses, ringed, ribbon, spotted, harbor, and bearded seals occur over wide areas of the Bering

and Chukchi Seas, generally corresponding to the movement ofthe

pack ice and transcending political boundaries. The same populations are harvested by both countries, at least for subsistence purposes by native peoples. Therefore, management of those species,

to be effective, must be based on understanding and consideration

of the total data base, including harvests and other impacting factors

from both sides.

A highly successful initial effort was the pinniped research cruise

on the RV Alpha Helix during July-August 1973. Two Soviet and

eight American scientists participated in that cruise, on which

studies were conducted of morphology, physiology, taxonomy, and

distribution of walruses and several species of seals in the eastern

Bering Sea and throughout the Chukchi Sea. Some results from that

cruise were reported earlier by Burns and Fay (1974)3, Halasz et al.

(1974), and Hammel et al. (1977). Others are reported in this volume

(Burns and Gol'tsev 1984).

In 1974, two American scientists visited several marine mammal

laboratories in the Soviet Union to study extensive collections of

osteological specimens and to work with Soviet colleagues on the

taxonomy of walruses and phocid seals. The data accruing from

those studies contributed toward clarification of the taxonomic

status of seals of the North Pacific region, as reported by

Shaughnessy and Fay (1977) and in the paper by Burns et al. (1984).

During the autumn of 1975, the first cooperative SovietAmerican aerial census of walruses was conducted in the Bering

and Chukchi Seas. The Soviet surveys covered the regions west of

the International Date Line, and the American surveys, the eastern

regions. Some ofthe results and statistical problems associated with

the American surveys were reported earlier by Estes and Gilbert

(1978); the combined results are reported for the first time in the

paper by Estes and Gol'tsev (1984).

In January 1976, a special conference on the biology of walruses

and ice-associated seals was held in Moscow. The conference reviewed much of the currentstate ofknowledge ofthose animals and

developed preliminary plans for long-range research, calling for 1)

increased emphasis on studies at the community and ecosystem

levels, 2) evaluation of current aerial survey methods, and 3)

development ofjoint studies in Alaska and Chukotka on population

dynamics, herd structure, and activity patterns. An exchange of

information on systems of standard measurements for pinnipeds

was discussed at the conference, and consideration of the question

of standardization of cetacean measurements was proposed as a

subjectfor discussion at future project meetings. The measurements

'Bums, J: J., and F. H. Fay. 1974. New data on taxonomic relationships among

North Pacific harbor seals, genusPhoca (sensu stricto). IAbstr.] Trans·. First Int.

TherioL Congr. 1:99. Nauka, Moscow.
used by Soviet and American biologists have not been entirely

comparable, but with increasing collaborative efforts, a unified

system may eventually be implemented.

Another major item discussed at the conference was the need for a

convention for joint Soviet-American conservation of walruses and

ice-associated seals in the Bering and Chukchi Seas. Recognizing

that unilateral protective measures occasionally may succeed in

reversing downward trends of populations, the consensus of the

meeting was that closer communication and joint management of

these pinnipeds would be of greater mutual value to our two countries. Of particular concern was the potential environmental degradation resulting from increasing human populations and commercial development of the continental shelf. The scientists involved

identified a list of basic management and conservation principles

that could form the basis for such a convention, and agreed on a

proposal to carry this forward in exploratory discussions within

their respective governments.

In spring 1976, three American and four Soviet scientists participated in a research cruise on the ZRS Zagoriany in the southeastern

Bering Sea. New information was obtained on distribution, population structure, and biological characteristics of walruses and of

spotted and ribbon seals. Some results ofthat work were reported by

Fay et al. (1977)4, Gol'tsev (1978)5, Yurakhno (1978)6, Fay (1982),

and Fay and Furman (1982); others are included in several papers in

this volume, for example on helminthology of spotted seals

(Delyamure et al. 1984), on time and place of mating by walruses

(Fay, Ray, and Kibal' chich 1984), and on feeding habits of walruses

(Fay, Bukhtiyarov, Stoker, and Shults 1984) and spotted seals

(Bukhtiyarov et al. 1984).

At the same time as the Zagoriany expedition in April 1976, three

coordinated aerial surveys of pinnipeds in the pack ice of the Bering

Sea were conducted by Soviet and American scientists. This was the

most thorough coverage of the region ever completed. Some results

of the American surveys were reported earlier by Burns and Harbo

(1977)7 and Krogman et al. (1979)8. The combined results, reported

in this volume by Braham et al. (1984), provide a comprehensive

view of distribution and density of walruses and ice-associated seals

in the Bering Sea pack ice.

Later in 1976, an American and two Soviet scientists studied

ringed and bearded seals at Wainwright, Alaska, and visited several

museums in the United States. New concepts ofthe systematics and

biology of those species and of spotted and ribbon seals in the

Bering Sea were developed as a result of the visits, some results of

which are reported by Fedoseev (1984).

'Fay, F. H., R. A. Dieterich, and L. M. Shults. 1977. Morbidity and mortality of

marine mammals - Bering Sea. In Environmental assessment of the Alaskan continental shelf. Annual reports of principal investigators for the year ending March

1977, Vol. I, p. 161-188. NOAA Environ. Res. Lab., Boulder, Colo.

'Gol'tsev, V. N. 1978. Materials on reproduction of the Pacific walrus. Abstracts

7th All-Union Conf. Marine Mammals, p. 89. Ministerstvo Rybnogo Khozyaistva

SSSR, Moscow.

'Yurakhno, M. V. 1978. Toward the study of the helminth fauna of pinnipeds

inhabiting the eastern part of the Bering Sea. Abstracts 7th All-Union Conf. Marine

Mammals, p. 363-364. Ministerstvo Rybnogo Khozyaistva SSSR, Moscow.

'Burns, J. J., and S. J. Harbo, Jr. 1977. An aerial census of spotted seal, Phoca

vitulina largha, and walruses, Odobenus rosmarus, in the ice front of Bering Sea. In

Environmental assessment of the Alaskan continental shelf. Quarterly reports of

principal investigators, April-June 1977, Vol. I, p. 58-132. NOAA Environ. Res.

Lab., Boulder, Colo.

"Krogman, B. D., H. W. Braham, R. M. Sonntag, and R. G. Punsly. 1978. Early

spring distribution, density, and abundance of the Pacific walrus (Odobenus rosmarus) in 1976. Final report, R.U. 14,47 p. Outer Continental ShelfEnvironmental

Assessment Program, NOAA Environ. Res. Lab., Boulder, Colo.

3

Two cruises, one American and one Soviet, were conducted in the

Bering and Chukchi Seas in 1978 with joint scientific participation.

Both cruises studied the distribution and biology of walruses and ice

seals in their respective areas of deployment, contributing further to

the data base on these species and adding to the foundation of

knowledge so important to our two nations.

CETACEAN RESEARCH

Studies of cetaceans were initiated within the Project somewhat

later than those on pinnipeds. American and Soviet scientists participated jointly in a research expedition abOard the whale-catcher

KS Vnushitelny from February to April 1975 in the eastern and

central tropical Pacific. Activities included "Discovery-marking"

and extensive observation of distribution and behavior of large and

small cetaceans in a region hitherto little explored by cetologists.

Approximately 2,000 large whales were sighted during the cruise

and 179 sperm whales were marked. Particularly noteworthy was

the sighting of several groups of blue whales between Mexico and

the Galapagos Islands and of a group of more than 100 blue whales

near the California coast. Also of interest was the finding that sei

and Bryde's whales occur together in the same habitat. The data

obtained on distribution and behavior of large whales during that

cruise, as well as during the Zharkii cruise in 1977, are of major

significance to the work of the International Whaling Commission.

Of especial importance will be the ultimate findings from the

Discovery-marking.

More than 6,000 delphinids were sighted during the Vnushitelny

cruise. They included 10 species of the genera Stenella, Steno,

Tursiops, Peponocephala, Grampus, Orcinus, Lagenodelphis, and

Globicephala. The information gained on distribution, herd size,

and abundance was of direct value to the American porpoise/tuna

program, which is monitoring the status and trends of populations

of porpoises in connection with the eastern tropical Pacific yellowfin

tuna fishery.

Exchanges of scientists during 1975, 1976, and 1977 enabled

collaboration on a series ofmorphological studies of large and small

cetaceans. One study compared the arrangement of blood vessels

and muscle weights in the flukes and dorsal fins ofseveral species of

delphinids to better define the morphological basis for the hydrodynamic attributes of these animals. Another study compared the

ontogeny of two species of delphinids. A major, continuing study is

examining the color patterns of several species of large and small

cetaceans, primarily sperm and killer whales. The major task of

cataloguing the cetacean specimens in Soviet and American

museums also was begun during these exchanges.

The scope of cetacean work within the Project has broadened in

recent years to include joint participation in field tests of radio-tags

remotely applied to humpback whales and cooperative studies of

bowhead or Greenland whales. Scientists from both countries are

studying the population characteristics and dynamics of Black Sea

dolphins and comparing them with those in the eastern tropical

Pacific. The information gained from these studies may have significant implications for management programs in both countries.

THE FUTURE

In other areas, joint work is planned or underway on a wide

variety of subjects. For example, there is interest in expanding

information exchange on husbandry, care, and maintenance of

marine mammals in captivity, the plans for which originated during

an exchange of scientists who visited oceanaria in both countries in
1977 and 1978. American and Soviet scientists are studying the

physiology and population dynamics of the Baikal seal, in an effort

to gain better understanding of that species. Agreement has been

reached to undertake joint studies on the community relationships

of sea otters in Alaska and the Commander Islands. New work on

walruses, northern sea lions, harbor seals, and ringed seals in

Alaska and the Soviet Far East is concentrating on life history,

ecology, and population status. Finally, the two governments are

continuing exploratory discussions concerning an agreement for

mutual conservation of walruses and ice-associated seals in the

Bering and Chukchi Seas.

Thus far, the Project has been remarkably successful in implementing exchanges of people and information, but not always

smoothly. Major problems have arisen in achieving sufficiently

advanced communications regarding cruise schedules, personnel

exchanges, travel schedules, visa acquisitions, etc. In this age of

almost instantaneous communication by satellite and other sophisticated means, transmission of a single "yes" or "no" between

continents sometimes is impossible to arrange in less than a week's

time.

A more substantive impact on the joint research has been the

restriction of access to key areas ofmarine mammal concentrations,

principally in the Soviet Far East. This problem, which has not yet

been solved, has retarded our research efforts on some species,

notably walruses, gray whales, and ringed seals. Nonetheless, we

are optimistic that options for collaborative work in several desirable locations will emerge, with continuing efforts at both the

Project and Joint Committee levels. To fulfill our goals, access to

key areas for joint marine mammal research must continue to

improve.

At the same time, a lack of effort on some subjects, such as

obtaining statistics on subsistence catch of seals, on the part of the

United States, causes continued uncertainty in determining the

impact of total harvest on the populations of these species.

From a modest beginning, the Project has developed a broad

scope of research, which now addresses not only the biology of

Bering-Chukchi pinnipeds, but cetacean and pinniped morphology,

systematics, and population dynamics, as well as technological

exchanges on methods for husbandry and maintenance of marine

mammals in captivity. It also has advanced the development of

recommendations for international agreement on conservation and

management of marine mammal resources of mutual concern to

both countries.

The research on pinnipeds thus far has resulted in numerous

reports and publications, but this is the first compendium of joint

work under the US-USSR Marine Mammal Project. A second

volume, on cetacean research, is in preparation for subsequent

publication. With further growth ofthe Project and improvement in

communications, we anticipate increasing opportunities for additional collaborative work and publications of this type, to the

mutual benefit of our two countries.

4

LITERATURE CITED

BRAHAM, H. w., J. J. BURNS, G. A. FEDOSEEV, and B. D. KROGMAN.

1984. Habitat partitioning by ice-associated pinnipeds: Distribution and den·

sity of seals and walruses in the Bering Sea, April 1976. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 12:25-47.

BUKHTlYAROV, Y. A., K. J. FROST, and L. F. LOWRY.

1984. New information on foods of the spotted seal, Phoca largha, in the

Bering Sea in spring. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 12:

55-59.

BURNS, J. J., F. H. FAY, and G. A. FEDOSEEY.

1984. Craniological analysis of harbor and spotted seals of the North Pacific

region. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 12:5-16.

BURNS, J. J., and V. N. GOL'TSEY.

1984. Comparative biology of harbor seals, Phoca vitulina Linnaeus, 1758,

of the Commander, Aleutian, and Pribilof Islands. U.S. Dep. Commer.,

NOAA Tech. Rep. NMFS 12:17-24.

DELYAMUR:E, S. L., M. Y. YURAKHNO, V. N. POPOV, L. M. SHULTS, and

F. H. FAY.

1984. Helminthological comparison of subpopulations of Bering Sea spotted

seals, Phoca largha Pallas. U.S. Dep. Commer., NOAA Tech. Rep. NMFS

12:61-65.

ESTES, J. A., and J. R. GILBERT.

1978. Evaluation of an aerial survey of Pacific walruses (Odobenus rosmarus

divergens). J. Fish. Res. Board Can. 35: 1130-1140.

ESTES, J. A., and V. N. GOL'TSEY.

1984. Abundance and distribution of the Pacific walrus, Odobenus rosmarus

divergens: Results of the first Soviet-American joint aerial survey, autumn

1975. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 12:67-76.

FAY, F. H.

1982. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens lIliger. North Am. Fauna 74, 279 p. U.S. Fish Wildt. Serv.,

Washington, D.C.

FAY, F. H., Y. A. BUKHTIYAROV, S. W. STOKER, and L. M. SHULTS.

1984. Foods of the Pacific walrus in winter and spring in the Bering

Sea. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 12:81-88.

FAY, F. H., and D. P. FURMAN.

1982. Nasal mites (Acari: Halarachnidae) in the spotted seal, Phoca largha

Pallas, and other pinnipeds of Alaskan waters. J. Wildt. Dis. 18:63-68.

FAY, F. H., G. C. RAY, and A. A. KIBAL'CHICH.

1984. Time and location of mating and associated behavior of the Pacific

walrus, Odobenusrosmarusdivergens Illiger. U.S. Dep. Commer., NOAA

'!echo Rep. NMFS 12:89-99.

FEDOSEEV, G. A.

1984. Use of nonmetrical characters ofskulls of Bering Sea seals in a study of

the phenotypic structure of their populations. U.S. Dep. Commer., NOAA

Tech. Rep. NMFS 12:49-54.

HALASZ, N. A., R. ELSNER, R. S. GARVIE, and G. T. GROTKE.

1974. Renal recovery from ischemia: a comparative study of harbor seal and

dog kidneys. Am. J. Physiol. 227:1331-1335.

HAMMEL, H. T., R. ELSNER, H. C. HELLER, J. A. MAGGERT, and C. R.

BAINTON.

1977. Thermoregulatory responses to altering hypothalamic temperature in

the harbor seal. Am. J. Physiol. 232:RI8-R26.

SHAUGHNESSY, P. D., and F. H. FAY.

1977. A review of the taxonomy and nomenclature of North Pacific harbour

seals. J. Zool. 182:385-419.
Craniological Analysis of Harbor and Spotted Seals

of the North Pacific Region

JOHN J. BURNS,l FRANCIS H. FAY,2 and GENNADII A. FEDOSEEy3

ABSTRACT

We reexamined the taxonomic status of the geronimensis, richardsi, and stejnegeri forms of harbor seals,

Phoca vitulina, in the North Pacific Ocean by comparing the cranial differentiation among them with the

differentiation of P. vitulina from its sibling species P. largha, the spolled seal. This assessment was based

primarily on the results of three discriminant analyses and a Q-mode cluster analysis, for which we used both

measurements and nonmetrical characters ofskulls. The results showed tbat the differentiation of vitulina from

largha is greater tban that among the three Pacific forms of vitulina. Within vitulina, the geronimensis form in

southern California and Mexico is not clearly differentiated from richardsi. The stejnegeri form, conversely,

has become differentiated sufficiently for subspecific status. The "boundary" between stejnegeri and richardsi

is not in Near Strait as proposed earlier; instead, it seems to be in the vicinity ofthe eastern Aleutian Islands and

Alaska Peninsula. A firm conclusion on that point cannot be reached, however, without study of additional

specimens from that region.

PE310ME

HaM" np08c~eH T8KCOHOMHlfecKJtH CT3TyC palHOBH,ll,HOCTeii Ot)blKHoBelllloro HOJleUM: [Ph. vitulina]

geronimensis, richards; I' stejnegeri B ceBepHoii '-taCT" Tnxoro OKeaHa nyTeM cpaBHeHHH KPSHHOilorHlfeCKHX

pa3Jnt1.J"" Cpe,ll,H ...IX It CUX BH,Il,OM jl80HHIIKOM nHTHHCTbli\1 TlOneHeM [Ph.larghaj. 3nl HCCne./l,OBaHHH OCH003HItI

r.r1301lb1M 06palOM U3 pelynbT3T3X ,O,ItCKpItMllHaHTHoro II KJlHCTepUoro «Q·mode)) 3H3nH10B C HCnOJlb30B3HHeM

MeTpHl.IeCK;'IX It HeMeTpw·tecKHX npltlU3KOB lfepenOB. Pe]YJ1bTaTl~1 nOKala!lH, "ITO ,Qltlllcl»epeH"'Ha ...ItA Mem,QY

vitulina H largha 60JlhWe, ~eM Cpel-lit Tpex TItXOOKeaHCKnx pa3HOBlt,QHOCTeH 06blKHoBeHHoro TlOneHA [vitulinaJ.

Pa3HOBitAHOCTII OOblKHOBeHHoro TlOneHA geronimensis 10mHO" Kamt£llopHHH It MeKCHKH nnoxa

JI."<!><!>epe"u"pOBa"bl OT richardsi. <l>opMa stejnegeri "anpOT"B JJ.H<!><!>epe"lI"pOBaJlBCb " OTBe'lBeT CTaTYCY

nOABH,Q3.

CaMbl" 60nbWO" palpblB B rpaAHeHTe Mop4JOJlOrW"leCKHX palJlH~H" KameTCR B COCeJl,HHX paHOHax

BOCTOI"IHO" 'faCTH AneyTcKltx OCTPOBOB H nonyocTpoBa AJlHCKa.

8 l3KnlO"Iem·te OTMe-rHM, 'fTO HlJlO>KeHHaa TO'lK3 lpeHHR He MomeT 6bITb OKOH'faTeJlbHOH 6e3

,QonO.IlIlI:tTenbllbIX HccneAooalntH )THX nO)l,BII,UOB 8 YK3l3HHbiX paltOH3X.

INTRODUCTION

A series of recent works on the taxonomy of seals of the genus

Phoca (in the strict sense) of the North Pacific region by Chapskii

(1955, 1960, 1967, 1969), Belkin (1964), Mohr (1965), McLaren

(1966), Bigg (1969, 1981), Naito and Nishiwaki (1972, 1975), and

Shaughnessy and Fay (1977), has led to worldwide recognition of

the sibling species, P. largha Pallas, lhe spotted or larga seal of the

",easonal pack ice, and P. vitulina Linnaeus, the harbor or common

seal of the coasts and islands. The taxonomic status of two other

forms, described earlier by Allen (1902) and Doutt (1942) as P.

stejnegeri of the Commander Islands and eastern Asia and P. v.

geronimensis of southern California and Mexico, still remains

unsettled. The stejnegeri form was redescribed by Inukai (1942) as

P. okhotensis kurilensis and later by Belkin (1964) as P. insularis. At

present it is regarded as rare and endangered in both Japan and the

Soviet Union; for that reason alone, its taxonomic status needs to be

resolved.

I Alaska Department of Fish and Game, 1300College Road. Fairbanks, AK 99701,

USA.

'Institute of Marine Science, University of Alaska. Fairbanks, AK 99701, USA.

3Magadan Branch, Pacific Research Institute of Fisheries and Oceanography

(MoTINRO), Nagaevskaya 51, Magadan 685013. USSR.

5

Shaughnessy and Fay (1977) reviewed the information on harbor

and spotted seals of the North Pacific region and concluded (as had

Mohr 1965; Chapskii 1969; Bychkov 1971; Burns and Fay 1974;4 and

Kosygin et al. 19755 ) that the coastal harbor seals of the North

Pacific region, from northern Hokkaido in the west to Baja California in the east, appeared to comprise only one polytypic taxon, P.

vilt/lina richardsi (Gray), rather than two or three. The concept of a

single subspecies of P. vitulina in the North Pacific, however, has

not been popular. To test that taxonomic theory with somewhat

greater rigor than before, we statistically examined both the differences and the similarities among a large series of crania of those

seals, collected throughout the North Pacific region. This work,

begun in 1970, has been continued since 1973 in the context of the

US-USSR Marine Mammal Project.

METHODS

We examined skulls of 435 Pacific harbor and spotted seals, the

'Burns. J. J., and F. H. Fay. 1974. ew data on taxonomic relationships among

North Pacific harbor seals, genus Phoca (sensu stricto). [Abstr.] Trans. First Int.

Theriol. Congr. 1:99. Nauka, Moscow.

'Kosygin, G. M., A. E. Kuzin. and E.!. Sobolevskii. 1975. Systematic position,

morphology, and ecology of the Kuril seal. III Marine mammals. Materials 6th

all-union conf. 1:151-153. [Abstr.] Naukova Dumka, Kiev.
majority of which were adult animals. These were drawn from 21 of

the major osteological collections in the Northern Hemisphere

(Appendix I).

For each specimen, insofar as possible, we recorded 37 cranial

characters, including 29 measurements and 8 nonmetrical attributes

(Figs. 1,2), in addition to date and location of collection, sex. and

relative age. Those characters were selected in part on the basis of

universal mammalogical methods and in part on the basis uf our

mutual experience and our interpretations of Chapskii's (\967,

1969) contributions. Relative age of each specimen was determined

from the degree of closure of eight cranial sutures (after Doutt 1942):

Occipito-parietal, squamoso-parietal, interparietal, fronto-parietal.

interfrontal, basiocci pital- basis phenoidal. basis phenoidal1-----4----1

1----5--~

presphenoidal, and intermaxillary. The degree of closure of each

suture was assessed visually and assigned a numerical score from I

to 4. The minimal value of 1was given for sutures which were open

wide; the maximum of 4 was given for those fully ankylosed.

Females with total scores of 28 to 32 and males with total scores of

30 to 32 were regarded as adults, usable in the analysis. Skulls with

lower scores were not included in the analyses because most of the

crani:i1 measurements tend to increase with age during the juvenile

and subadult stages of growth.

Each variable was measured to the nearest 0.1 mm; each nonmetrical character was ranked and assigned a numerical score, based on

our judgement of its conformity to one of the diagrams in Figure 2.

The rank-order of those nonmetric characters is debatable in some

t----- 6 ----~

-

Figure I.-Dorsal and ventral views of the skull (upper) and lateral views of the skull and mandible (lower) ofseals of the Phoca vitulina-P. Iargha type, showing 26 of

the measurements used in this study: 1) condylobasallength, 2) palatal length, 3) length of upper tooth row, 4) greatest width at mastoids, 5) greatest width of cranium,

6) greatest zygomatic width, 7) height of cranium, 8) length ofmandible, 9) height ofmandible at coronoid process, 10) length oflower tooth row, 11) height ofmandible

behind the molar, 12) overall length of nasals, 13) length of maxillo-frontal suture to anterior end of nasals, 14) width of nasals at maxillo-frontal suture, 15) maximal

width of external nares, 16) width ofsnout at canines, 17) least interorbital width, 19) width of palate behind first molars, 20) least width of palate at pterygoid hamuli,

21) width of bulla from notch anterior to auditory process to middle of carotid foramen, 22) greatest length of bulla, 23) greatest width at condyles, 26) length ofsnout

from anterior edge of nasals, 34) presence of sagittal crest, 35) greatest length of jugal, 36) width or bulla from tip of auditory process to anterior edge of carotid

foramen.

6
instances and obviously not continuous in any. We recognized the

weaknesses of combining such discontinuous data with the continuous data from the measured variables, but we did so initially

because the emphasis in earlier taxonomy of these seals had been

heavily on those categorical attributes. Ultimately, they mostly

were not found to be powerful as discriminators.

The skulls of largha were from specimens taken in the pack ice of

the Okhotsk, Bering, and Chukchi Seas. Those of vitulina were

from coastal areas in the North Pacific Ocean and southern Bering

Sea. Each of those coastal areas was given a numerical code, as

shown in Figure 3. Skulls of the three forms of vitulina were from

specimens taken in the following geographical areas, approximately conforming to the limits originally described by Allen

(1902): Areas 100-150 = stejnegeri, areas 160-280 = richardsi, and

areas 300-310 = geronimensis.

Males and females were treated separately because of differences

in size'and proportions, as shown by Fisher (1952), Bishop (1967),

Chapskii (1967), Bigg (1969), Naito and Nishiwaki (1972), Burns

and Fay (footnote 4), Pitcher and Calkins (1979),6 and Burns and

·Pitcher, K. w., and D. G. Calkins. 1979. Biology of the harbor seal, Phoca

vitulina richardsi, in the Gulf of Alaska. Final report, R.U. 229, 72 p. Outer

Continental Shelf Environmental Assessment Program, NOAA Environ. Res. Lab.,

Boulder, Colo.

37

29 32

A

fT\

33

A 3

30

31

Figure 2.-Cranial measurements and nonmetrical characters in skulls ofseals of the Phoca vitulina-P. /argha type used in this study: 18) greatest anterior-posterior

length ofsecond upper premolar, 24) greatest width offoramen magnum, 25) greatest height of foramen magnum, 27) distance from posterior end of vomerine septum

to medial edge of palate, 28) shape ofjugo-squamosalsuture, 29) extent ofnaso-premaxillary contact, 30) shape of palatal margin, 31) angle ofsecond upper premolar

relative to tooth row, 32) shape of pterygoid hamuli, 33) shape of bulla and auditory process in anterior view (skull inverted), 37) shape of anterior nares.

7
Gol'tsev (1984). Because many of the skulls were'partly broken, the

full suite of 37 characters was not available from all. For that

reason, sample sizes varied among analyses, depending on which of

the characters were being compared and the type of statistical

treatment employed.

The data were analyzed in four ways. In the first, a set of 11 ratios

of cranial dimensions which had been pointed out by Chapskii

(1967) as being useful for discrimination between largha and vitulina were used in a discriminant analysis (Nie et al. 1975). Those

ratios were of measurements 2, 3,4, 12, 13, 22, and 35 relative to

condylobasal length, of measurements 6, 16, and 17 relative to

greatest width at mastoids, and of measurements 25/24 (see Figs. I,

2). For that analysis, a sample of 39 specimens of largha (21 males

(M), 18 females (F» was compared with 229 specimens of Pacific

vitulina (87M, 142F).

In the second procedure, we also employed discriminant analysis, but instead of ratios, we used all 37 of the metrical and

nonmetrical characters. Our objective was to compare the discrimination between largha and vitulina with that among the three

Pacific forms of vitulina. All samples were smaller than in the

previous analysis (largha 14M, I2F; stejnegeri 8M, 12F; richardsi

38M, 74F; geronimensis 3M, IF), because of the requirement that

each specimen have the full suite of 37 characters.

For our third treatment, we excluded the largha phenotype and

performed a factor analysis (Nie et al. 1975) of all 37 characters for

all of the vitulina seals. Resultant factors with an eigenvalue>1.0

were considered. Ten factors for males accounted for 77% of the

variance; eight factors for females accounted for ,80%. From a

varimax rotation, we selected characters with high loadings in the

individual factors. For each sex, we chose 14 nonredundant and, as

far as possible, nonlinked characters.

After selecting the 14 characters for each sex, we performed a

discriminant analysis with the entire series of vitulina samples,

subdividing them into five geographical groups, as follows: 100-150

(Hokkaido to Commander Islands), 170-190 (Aleutian and Pribilof

Islands), 200-220 (Bristol Bay and Alaska Peninsula to Kodiak

Island and Cook Inlet), 230-280 (Prince William Sound to Washington), and 300-310 (California to Mexico). In the discriminant analysis, the objective is to optimize the statistical descriptors of difference among groups; the similarity among groups is not emphasized

analytically.

In the final treatment, we performed a Q-mode cluster analysis

(Parks 1970), with a simple distance function as a measure of

similarity among specimens of the vitulina sample. Variables were

the 14 selected by factor analysis for males and females. In the

Q-mode cluster analysis, distance coefficients were weighted according to percent of total variance accounted for by each principal

component. This procedure re-sorts the individual specimens into

clusters on the basis of their similarities, rather than differences.

RESULTS

Discriminant Analysis with Measurement Ratios:

vitulina vs. largha

The II ratios of cranial dimensions identified by Chapskii (1967)

as being useful for discriminating largha from vitulina were not

adequate in themselves to classify correctly all of the specimens.

I

•. I

180'- ., .....1'

I

120 135 150

North

165

Bering

Sea

Pocific

10

Oceon

165 150 135

----

120

60

45

Figure 3.-Numerical codes and boundaries (dashed lines) of geographical sampling areas for harbor seals in the North Pacific region. Not shown is code 160, which

was assigned to a single specimen from an unspecified locality in "southeastern Bering Sea."

8
The results of the discriminant analysis were that only 205 (76%) of

the 268 skulls were correctly classified on the basis of those II

ratios; the rest of the specimens were misclassified. Thus, the ratios

alone are not as powerful in discrimination as Chapskii had implied,

though they clearly have some value.

The discrimination of harbor seals collected in areas bordering

the Okhotsk and Bering Seas showed a very strong tendency for

greater success (84.5% correct) than did discrimination of harbor

seals collected in western North America, from the Gulf of Alaska

to Mexico (73.0% correct) (87/103 vs. 92/126, X2 =3.708:

0.05<P <0.06). Spotted seals of the Okhotsk Sea also tended to be

classified correctly more often than were those of the Bering Sea

(Table I), but the samples were small and the difference between

them was not significant (X2 = 1.22, P>0.25).

Table I.-Percent of Pacific harbor, Phoca vilulina and

spotted, P. Iargha, seal skulls correctly and incorrectly identi·

fied by discriminant analysis, based on II ratios of cranial

measurements.·

Actual taxon

largha vitulina

Predicted Okhotsk Bering Eastern Western

taxon (N=12) (N=27) (N=103) (N=126)

largho 83 59 16 27

viluJina 17 41 84 73

'Ralios identified by Chapskii (1967) as diagnostic of the largha

phenotype.

Table 2.-Group means and standard deviations of ratios of skull measurements for male and female spotted and harbor seals.'

P.largho P. vilulina

Ratio of Male Female Male Female

cranial (N=21) (N=18) (N=87) (N=142)

measurement mean:!: SO mean:!:SO mean:!:SO mean:!:SO

2/I:Palatallength/CBL' 36.4:!: 18.1 41.2:!: 10.4 38.6:!: 16.3 39.2:!: 14.1

3/1 :Length upper tooth

row/CBL 27. I:!: 13.5 32.8:!: 0.8 29.2:!: 12.4 30.7:!: 10.2

4/I:Mastoid width/CBL 45.0:!:22.4 54.7:!: 13.8 47.5:!:22.7 51.1 :!:20.2

12/1 :Nasal iength/CBL 19.1:!: I I. I 23.7:!: 1.9 20.6:!: 9.9 21.5:!: 8.8

13/I:Nasal width from

maxillo-frontal suture/

CBL I I. I:!: 5.7 12.8:!: 1.4 II.O:!: 5.4 JI.2:!: 4.7

22/1 :Length bulla/CBL 15.1:!: 7.5 19.0:!: 0.6 15.7:!: 7.0 16.6:!: 6.2

35/ I:Length jugal/CBL 21.9:!: 10.9 25.6:!: 6.5 24.5:!: 10.4 25.0:!: 9.0

25/24:Height/width foramen

magnum 65.1 :!:28.0 72.2:!: 18.6 63.5:!:31.8 67.8:!:29.0

6/4:Zygomatic width/

mastoid width 91.0:!:38.4 97.6:!:24.8 89.4:!:41.2 90.3:!:35.9

16/4:Snout widlh/mastoid

widlh 28.8:!: 12.3 28.8:!: 7.5 29.8:!: 13.4 28.7:!: 11.1

17/4:lnterorbital width/

mastoid width 8.8:!: 5.2 IO.7:!: 2.9 IO.O:!: 4.7 9.6± 3.6

I All ratios are (A x 100)/B.

'CBL = Condylobasal length.

In this analysis, a single discriminant function accounted for all

of the discriminating power of the factor matrix for each sex_ For

males, the eigenvalue of that function was 0.22802; for females, it

was 0.13453. Three of the ratios contributed significantly to that

function for both sexes (jugal length/ condylobasal length; nasal

length from maxillo-frontal suture/condylobasallength; interorbital

width/ mastoid width); two contributed nothing (mastoid width/

condylobasal length; length upper tooth row/condylobasal length);

each of the other ratios contributed in one sex but not in both. The

means and standard deviations of all ratios are shown in Table 2.

Discriminant Analysis-37 Characters:

largha vs. vitulina

With the full suite of 37 metrical and nonmetrical characters, the

discriminant analysis correctly distinguished all of the harbor seals

from the spotted seals. Within sexes, it also distinguished 98% of

the three forms of harbor seals from each other (Table 3). The

distinction of the three forms was less effective among sexes;

significant overlap developed between richardsi and geronimensis,

though not with stejnegeri (Fig. 4). Among the three harbor seal

forms, richardsi was most similar to largha.

For males, two discriminant functions accounted for 90.8% of

the relative power to discriminate among the four forms. Within the

first function (70.5% relative; eigenvalue 12.35458), the seven

variables with the largest standardized coefficients were 10 (length

lower tooth row), 27 (length vomerine septum), 16 (width ofsnout),

.4

GE

/---.., ! '

r . GE

\

'. .1

N

>0

U

-I

-2

-~·~4----~3-----::2----+I---:!:0---•..&,I---+~2:---.-!:3:--.....J.4

C. v.

Figure 4.-Distribution of samples of male (dashed circles) and female (solid

circles) seals of the largha (LA), geronimensis (GE), richardsi (RI), and sle}negeri (ST) forms on the first two canonical variates (CVI and CV2). Circles

enclose 95% of the plotted values for each taxon.

Table 3.-Percent of seal skulls correctly and incorrectly identified to taxon by discriminant

analyses, based on 37 cranial characters.

AClUaltaxon

largha richardsi sle}negeri geronimensis

Predicted Male Female Male Female Male Female Male Female

(axon (N=14) (N=12) (N=38) (N=741 (N=8) (N=12) (N=3) (N=I)

largllll 100 100 0 0 0 0 0 0

richardsi 0 0 100 96 0 0 0 0

slejneger; 0 0 0 4 100 100 0 0

geronimens;s 0 0 0 0 0 0 100 100

9
7 (height of cranium), 8 (length of mandible), 19 (width of palate),

and 22 (length of bulla). In the second function (20.3% relative;

eigenvalue 3.55208), the three variables with the largest coefficients were 16, 22, and 15 (width of nares).

For females, also, the first two discriminant functions accounted

for more than 90% of the relative discriminating power. Within the

first function (71.4% relative; eigenvalue 6.45098), the seven most

significant characters were 3 (length upper tooth row), 28 (jugosquamosal suture), 21 (width of bulla), 9 (height at coronoid), 22,

36 (width bulla at auditory process), and 32 (pterygoid hamuli). In

the second function (23.0% relative; eigenvalue 2.07899), the three

most significant characters were I (condylobasallength), 2 (palatal

length), and 16.

Factor Analysis: vitulina Polytype

In this test, from which largha was excluded, the 14 most significant cranial characters were sel,cted for each sex in vitulina

(Table 4). For the males, these were chosen from six ofthe first eight

discriminant factors, which accounted for 79.5% of the sample

variation. For the females, the 14 most significant variables were

selected from 9 ofthe first 10 discriminant factors, which accounted

for 77.4% of the sample variation. For both sexes, selection of

characters was based on their having the largest coefficients in the

varimax rotated factor matrix. Ten ofthe variables were the same for

both sexes; four were specific to each sex.

Table 4.-Principal diagnostic characters selected by factor analysis from the

set of 37 metric and nonmetric characters ofskulls of Pacific harbor seals.

Percent of

Sex Factor variation Principal diagr.ostic characters'

Male 45.7 1,2,6,8,9,10,11,16,35 (condylobasal, palatal,

mandibular, lower tooth row, and jugal length;

zygomatic and snout width; height of mandible

at coronoid and behind the molar)

3 6.0 24 (width of foramen magnum)

4 4.7 31 (angle of second upper premolar)

6 4.9 37 (shape of anterior nares)

7 3.6 29 (extent of premaxillary-nasal contact)

8 3.1 32 (shape of pterygoid hamuli)

Female 40.4 1,2,6,8,9,16 (condylobasal, palatal, and mandibular length; zygomatic and snout width;

coronoid height)

2 8.0 24 (width of foramen magnum)

3 4.8 14 (width of nasals)

4 4.4 25 (depth of foramen magnum)

5 4.1 31 (angle of second upper premolar)

7 3.3 28 (shape of jugo-squamosal suture)

8 3.1 32 (shape of pterygoid hamuli)

9 2.9 22 (length of bulla at auditory process)

10 2.8 37 (shape of anterior nares)

I Refer to Figures I and 2.

Discriminant Analysis: vitulina5 Geographical Groups

Using the 14 variables selected by the factor analysis for each sex,

we compared five geographical groups of the vitulina samples by

discriminant analysis. The geographical boundaries between

groups were drawn arbitrarily, mainly with the objective of comparing the variation among regional samples of richardsi with that

between richardsi and the stejnegeri and geronimensis samples. In

effect, group I was stejnegeri as defined by Allen (1902), groups 2,

10

3, and 4 were regional samples of richardsi from Alaska to Washington, and group 5 included some richardsi from California and all

(5) of the available geronimensis. The sexes were analyzed separately; the results are combined in Table 5. The classification function coefficients for each group are given in Table. 6.

The discrimination among the five groups was moderate to high.

About two-thirds to four-fifths of the specimens were correctly

placed in their respective geographic groups. The highest proportions of correct placements were at each end of the series: 82% in

group I, 75% in group 5. Ofthe specimens in group 5, only three

(60%) of the geronimensis from southern California and Mexico

were correctly placed, compared with nine (82%) of the richardsi

from central and northern California. This difference, however, was

not significant (X2 =0.097, P>0.25).

The clinal nature of the morphological variation among geographical groups was shown clearly by this analysis, but a discontinuity in the cline also was indicated. Whereas in most instances

Table 5.-Percent of harbor seal skulls classified to the correct geographical region by discriminant analysis, based on the 14 most diagnostic characters for each sex. Vertical lines connect regional groups

with closest aflinities,

Actual region of originl

Predicted 100-150 170-190 200.2202 230·280 300-310

region (N=38) (N=28) (N=50) (N=47) (N=16)

100-150 18~ I I~~ I 0 0 6

170-190 6 2 0

200-220 3 4

I~I I~~ I

6

230-280 3 7

300·310 5 4 I~; I 1Refer to Figure 3.

21ncludes one specimen from "southeastern Bering Sea," for which location was not specified.

Table 6,-Classification function coefficients (Ftslter's linear discriminant functions) resulting from discriminant analyses ofskulls of male and female I'itulilUl,

grooped by geographical areas.

Geographical group'

Sex Variable' 100-150 170-190 200-220" 230-280 300-310

Males (N=16) (N=13) (N=II) (N=20) (N=9)

I 0.616 0.608 0.556 0.574 0.596

2 -0.242 -0.240 -0.171 -0.189 -0.235

9 -0.293 -0.299 -0.282 -0.295 -0.250

16 -0.288 -0.267 -0.314 -0.302 -0.323

24 0.861 0.838 0.844 0.785 0.774

29 -0.152 -0.025 -0.207 -0.132 -0.090

31 0.214 0.101 0.188 0.141 0.334

35 0.409 0.395 0.412 0.376 0.381

Constant -700.551 -676.579 -628.634 -604.483 -637.337

Females (N=22) (N=15) (N=39) (N=27) (N=7)

2 0.146 0.164 0.184 0.187 0.194

14 0.479 0.384 0.365 0.396 0.405

16 0.240 0.189 0.135 0.126 0.177

22 1.022 1.045 0.970 0.936 0.875

24 0.765 0.741 0.691 0.675 0.717

25 0.593 0.546 0.572 0.556 0.571

28 0.932 1.014 1.074 0.960 1.034

31 0.802 0.689 0.664 0.666 0.815

32 1.092 1.176 1.026 1.012 0.997

37 -8.823 -7.571 -6.449 -6.576 -7.482

Constant -601.158 -575.862 -528.916 -507.420 -531.924

,Refer to Figures I and 2.

2Refer to Figure 3.

'Includes one specimen from "southeastern Bering Sea," for which location was

not sPecified further.
Cluster Analysis: vitulina Polytype

affinity between adjacent groups was indicated by about 10 to 20%

of incorrect placements, this did not occur between groups 2 and 3.

That is, the seals from Hokkaido to the eastern Aleutian Islands

appeared to be acraniologically interrelated unit, divergent from the

other interrelated unit in the Gulf of Alaska to Mexico. This appeared to confirm Chapskii's (1967, 1969) predictions that the delimitation of stejnegeri from richards; would be found at or near the

eastern end of the Aleutian Islands.

Similarity -

e

WITHIN-GROUP SIMILARITY INDEX

m

I

I

I

I

Decreasing p

o Sample r--------I-------

A

B

D

c

IT

I

Cluster

of North America, between southern Alaska and Washington State,

were poorly represented in primary cluster I, but they made up most

of primary cluster II for both sexes. Included in cluster II were 38

(79%) of the specimens from localities between Cook Inlet and the

coast of Washington (areas 220-280) and both of the specimens

from Mexico (area 310); Asian and Aleutian specimens were very

poorly represented. The specimens from the Pribilof Islands and

Bristol Bay (areas 170, 200) had questionable affiliations. All ofthe

females from the Pribilofs and the males from Bristol Bay were

placed in primary cluster I with the Asian-Aleutian group, whereas

the one Pribilof male and most of the Bristol Bay females we placed

in primary cluster II with the North American group.

WITHIN-GROUP SIMILARITY INDEX

ZllO 1------'

Decreasing Similarity---- p p Sample 0r-- ---f _

A

B

C

D

IT

Cluster

Using the 14 variables identified by the factor analysis for each

sex, we submitted vitulina to a cluster analysis, which grouped the

individual specimens by similarity. For each sex, the specimens

tended to be clumped into two primary clusters (1 and II), each of

which was made up of two secondary clusters (A-B and CoD), as

shown in Figures 5 and 6. The compositions ofthe clusters, in terms

of specimens drawn from each of the geographical areas, were

similar between sexes but not identical (Table 7).

For the sexes combined, the larger (1) of the primary clusters

included 58 (92%) of the specimens from eastern Asia and the

Aleutian and PribilofIslands(areas 100-190), but they also included

17 (71 %) of the specimens from the southern coast of the Alaska

Peninsula to Kodiak Island (area 210) and 13 (93%) of those from

California (area 300). Specimens from the rest of the western coast

Figure 5.-Dendrogram ofresults ofQ-mode cluster analysis of66 male seals of

the Phoca vitulina group in the North Pacific region. The individual specimens

making up the primary clusters (I and II) and secondary clusters (A to D) are

listed along the vertical axis by the numerical code for the area where they were

collected (see Fig. 3).

Figure 6.-Dendrogram of results of Q-mode cluster analysis of 104 female

seals of the Phoca vitulina group in the North Pacific region. The individual

specimens making up the primary clusters (I and II) and secondary clusters (A

to D) are listed along the vertical axis by the numerical code for the area where

they were collected (see Fig. 3).

11
Thble 7.-Numbers of specimens per sex/area making up the

two primary clusters of Pacific harbor seals, as indicated by the

cluster analysis.

Primary cluster I Primary cluster II

Area' Male Female Male Female

100 4 5 0 0

110 2 4 0 0

140 I I 0 0

150 7 10 1 I

160 0 I 0 0

170 0 4 I 0

180 8 8 I 0

190 2 I 0 I

200 5 4 0 10

210 3 14 I 6

220 0 0 I I

230 2 0 9 5

240 0 0 0 I

260 0 0 3 2

270 I I I 4

280 0 6 4 7

300 8 5 0 I

310 0 0 I I

,Refer to Figure 3.

In the secondary clusters, the specimens from the coast of Asia

(areas 100-140) were placed mainly in cluster B, whereas those from

the Commander and Aleutian Islands (areas ISO, 180, 190) were

about equally distributed in A and B (Table 8). The majority from

the Pribilof Islands (area 170), Bristol Bay (area 200), and the

Alaska Peninsula-Kodiak area (210) were split about 60/40 between

clusters A and D, respectively. The majority of specimens from

Cook Inlet to Washington (areas 220-280) were placed in cluster D.

A minority of the Alaskan specimens (220-260) was placed in

cluster C, and of British Columbia-Washington specimens (270,

280), in cluster A. Accordingly, most of the specimens from

California and Mexico (areas 300, 310) were placed in clusters D

and A.

These results, like those from the discriminant analyses, further

describe the clinal nature of craniological variation within the

vitulina polytype. They indicate that the Commander-Aleutian seals

are most uniform, and that the boundary between the stejnegeri and

richardsi phenotypes definitely is not in Near Strait, as supposed by

Allen (1902); neither does it appear to be in the vicinity of Kamchatka Strait. The representation of geographical samples in the

Table 8.-Relation of the three forms of Pacific harbor seals (as

originally defined) 10 the composition of the secondary clusters,

as indicated by the percent of specimens from the regional

samples in each cluster.

Percent in

secondary clusters

Phenotype! Area code2 N A B C 0

slejnegeri 100,140 17 18 82 0 0

150 19 47 42 0 10

richardsi 180,190 21 48 43 0 9

, 170,200,210 49 57 6 6 ~I

220·260 24 8 0 29 63

270,280 24 29 4 8 58

300 II 82 18 0 0

geronimensis 300,310 5 20 20 0 60

'As defined by Allen (1902) and Doutt (1942).

'Refer to Figure 3.

'Includes one specimen from ·southeastern Bering Sea," for

which the exact locality was not specified.

12

clusters suggests that a steepening ofthe cline between the comparatively stable Aleutian-Asian series and the highly variable North

American series takes place between the eastern Aleutian Islands

and the Alaska Peninsula. A significant discontinuity in relationships is shown in that area also by the pair-matrix of specimens in

the clusters (Fig. 7). Specimens from Asia and the Commander and

Aleutian Islands (ACA) were paired in the clusters very significantly

more often with specimens from that same region than with those

from farther east, on the Pribilof Islands and the North American

continent (PNA) (ACA=39/57, PNA=I1/113; XZ =46.48, df=l,

P<O.ool).

AREA OF ORIGIN

<t

w

~--t'.c...c..<t---t-+..L..t--+--h~-r7l-:77t--+-+---t-+-i

I

--+-i7'

o

w

--+-+--+-+---11--- 11.

SAMPLE SIZE

o 1-10 11-20 21-30 )30

PERCENT OF SAMPLE

Figure 7.-Pairing frequenCy matrix from duster analysis(both sexes) ofNorth

Pacific Phoca vitulina. Shading indicates comparative percentages of specimens from each geographic sample tIult were paired (as most similar) with

specimens from their own or other localities.

Discriminant Analysis ofSecondary Clusters

We performed a discriminant analysis on the four secondary

clusters for each sex to identify the characters that contributed the

most to their grouping. The most powerful variables in the first

function for females were (in descending order of importance)

numbers 16 (snout width), 22 (bulla length), 2 (palatal length), and

8 (mandible length); for males, they were 16,8,9 (coronoid height),

and 35 Uugallength).

The clusters tended to be ordered by size (Table 9). For both the

males and the females, the largest skulls were those from the

Asian-Commander-westem Aleutian seals (cluster B); the smallest

(cluster C) were mostly from sealstaken in Prince William Sound to

southeastern Alaska. A comparable geographical trend in size was

shown by Burns and Gol'tsev (1984) for body length.
Table 9.-Means and standard deviations (mm) of the four principal diagnostic variables

in the first discriminant function for each sex among the secondary clusters A to D, shown

in Figures 5 and 6.

Sex

Male

Female

Secondary clusters

A B C 0

Principal (N=29MAOF) (N= 14M,24F) (N=6M,6F) (N= 17M,34F)

characterl mean±SD mean±SD rnean±SD mean±SD

16 471.5±30.7 531.0±25.8 390.3.t 14.8 4278± 19.6

8 1,5345±51.4 1.624.7±36.1 1,3735±29.1 1,447.6±44.7

9 737.4.t47.4 793.5:d7.4 618.3± 19.1 655.0±28.1

35 658.3±30.7 705.5±23.9 584.5±42.9 610.9±22.4

16 409.8± 17.4 446.5±22.4 356.2± 15.6 375.5± 17.9

22 399.5±20.6 415.3±21.5 367.0.t 97 381.2± 13.0

2 935.2±34.3 969.4±33.0 843.3±28.4 883.3±44.3

8 1,392.2±39.8 1,463.0±44.9 1,271.0±53.5 1,325.9±44.2

'Refer to Figures 1 and 2. 16=5noul widlh, 8=lenglh of mandible, 22=lenglh of bulla,

9=coronoid height, 2=palatallength.

DISCUSSION

The harbor or common seals of the North Pacific Ocean were

divided by Scheffer (1958) into two taxa, Phoca vitulina richardsi of

western North America and P. v. largha of eastern Asia, essentially

following the conclusions of Doutt (1942). Those two taxa were

believed to adhere to the coasts and be isolated to some degree from

each other in the North Pacific and Bering Sea by the broad expanses

of open water in Near and Bering Straits, respectively, where the

political boundaries lie between the Soviet Union and Alaska. The

anatomical, physiological, and ecological differences between the

two forms were not well understood at that time, and the fact that

each taxon crossed one of those boundaries and "intruded" into the

geographical range of the other was not yet appreciated.

Understanding of the differentiation and geographical distribution of Pacific harbor and spotted seals has been advanced greatly in

recent years. We now know that I) the center of abundance of the

spotted seal is in the Okhotsk Sea, whereas that of the Pacific harbor

seal is in the Gulf of Alaska, 2) these two taxa are widely sympatric

in the southern parts of both the Bering and Okhotsk Seas, even

more than was shown by Bigg (1981, fig. I), and 3) each form

maintains its identity clearly in those areas of sympatry. Although

both forms haul out at the same time in several of the same locations, even during their respective breeding seasons, they ordinarily

do not mix but tend to stay in discrete groups. That they do not

interbreed freely is indicated by the scarcity of specimens identifiable as intergrades. Where the two forms coexist in the eastern

Bering Sea, parasitological findings also indicate that they are

socially and nutritionally divergent (Fay and Furman 1982; Delyamure et al. 1984).

Our analyses of the II ratios of cranial measurements selected by

Chapskii (1967) for discrimination of harbor from spotted seals

showed that vitulina tends to be most divergent cranially from

largha in areas where the two species coexist; it is least divergent

where vitulina occurs alone. That is, cranial differentiation of

Pacific harbor seals from the spotted seals appears to have been

enhanced by sympatry. As Shaughnessy and Fay (1977) observed,

the same enhancement has taken place in the color of the pelage and

in the timing of reproduction and molt.

Thus P. vitulina and P. largha are now recognizable as sibling

species. Superficially, they are very similar and obviously closely

related; nevertheless, upon closer inspection they are found to be

morphologically, ecologically, socially, and reproductively distinct.

13

Because oftheir sibling status, their slight craniological differentiation is ideally suited as the standard for comparison with that among

the three North Pacific forms of vitulina (i .e., richardsi, stejnegeri,

and geronimensis).

Our goal from the outset of this study was to reach a firm, final

decision about the taxonomic rank of those three forms. Doutt

(1942), Scheffer (1958), Chapskii (1960, 1967, 1969), and Mohr

(1965) were unable to weigh enough ofthe evidence needed to reach

such a decision because none ofthem had access to all ofthe world's

collections. Shaughnessy and Fay's (1977) approach was mainly

through review of the literature, but they also had already surveyed

most of the world's collections, as well as viewed the living seals in

many of the different habitats around the North Pacific. Because of

insufficient information, however, they were obliged to take the

conservative view in concluding that geronimensis was just the

southern end of a north-south gradient of increasing frequency of

dark pelage in P. v. richardsi. Likewise, they conservatively concluded that stejnegeri might qualify for subspecific status under P.

vitulina, but it did not appear to meet the requirements for full

specific rank because of extensive primary intergradation with

richardsi. Our conclusions here are similar.

Our analyses indicated that the cranial differentiation among the

three forms of Pacific harbor seals was less than that between

vitulina and largha, and that richardsi showed the poorest differentiation from largha. The specimens from California and Mexico,

which included geronimensis, were discriminated well by the 37-

character analysis, but the samples were too small (3M, IF) to give

reliable results. Slightly larger samples (9M, 7F) from that region

were 75% correctly discriminated in the 14-character analysis of

geographic groups, but only five of those specimens (2M, 3F) were

from the range described by Allen (1902) for geronimensis in

southern California and Mexico; the rest were from central and

northern California, which is within the described range of

richardsi.

Inthe cluster analysis, the five specimens of geronimensis were

paired with some from Hokkaido, Bristol Bay, Kodiak, Prince

William Sound, and California. The specimens of richardsi from

central and northern California were paired with a similarly broad

geographical series. The relationships of both forms were so diverse

and so similar that no discreteness was indicated. Hence, we feel

that even with larger samples, geronimensis probably would not

qualify as a subspecies; it appears to be simply the terminal

ecomorph in a long, unbroken cline of richardsi in western North
America. Certainly, geronimensis is much less divergent from.

richardsi than is stejnegeri, and the laller's differentiation appears

to be of no more than subspecific rank.

The skulls of stejnegeri (Commander Islands to Hokkaido)

showed differentiation from richardsi nearly as great as that between richardsi and largha, mainly in size. Belkin (1964), McLaren

(1966), and Naito and Nishiwaki (1972, 1973) argued for recognition of the large, black seals of the Kuril Islands as a full species,

Phoca insularis or P. kurilensis (=stejnegeri), primarily on the

basis of marked differentiation from P. largha of the Okhotsk Sea.

Not necessarily in disagreement but with a broader biogeographical

overview, Mohr (1965), Chapskii (1969), Burns and Fay (footnote

4), Kosygin et al. (footnote 5), and Shaughnessy and Fay (1977)

responded that the Kuril seal appeared to be conspecific with P. v.

richardsi and possibly was just the western end of a cline of

morphological variation that extends from the Gulf of Alaska to

Hokkaido.

The relationship of the Kuril seal to the Pacific harbor seal of

western North America is no longer a point of contention. but the

degree of that relationship is a question thdt has not yet been

answered to the satisfaction of all parties concerned. In this study,

every analysis that we conducted confirmed that the Kuril seal

(stejnegeri) is well enough differentiated from the harbor ~eals of

western North America (richardsi) to qualify for subspecific rank,

but in our opinion the requirements for a full species were not met.

Although typically large, dark stejnegeri of the Kuril Islands may

be quite different in appearance from the typically small, pale

richardsi of Prince William Sound, e.g., they live 111 similar

habitats, behave in similar ways, and both are clearly identifiable as

"harbor seals" from their anatomical conformity (in about equal

degrees) with Phoca vitulina of the North Atlantic Ocean.

The typical stejnegeri and richardsi are allopatric, but they are

not isolated. In the 6,000 km between them is a long series of freely

interbreeding populations, in which the diagnostic characters of

those two phenotypes vary clinally in degree and/or frequency of

occurrence, from the one extreme to the other. Our discriminant

analyses appeared to define some sort of "discontinuities" in the

cline between the two phenotypes, on the one hand in Near Strait (as

assumed by Allen 1902) and on the other in the vicinity of Unimak

Pass (as predicted by Chapskii 1967). The discontinuity in Near

Strait certainly was not a natural break in the gradient; it was the

product of our choice of a potential boundary between stejnegeri

and richardsi, based on Allen's (1902) diagnosis and Shaughnessy

and Fay's (1977) assessment of geographic barriers. The other

discontinuity, in the vicinity ofUnimak Pass, was partly attributable

to our grouping of samples, but it was more strongly expressed than

any other in the discriminant analyses.

The best indicator of natural discontinuities in the east-west cline

was the cluster analysis, because it was not biased by our geographical compartmentalization of the samples. For both sexes, the

specimens sorted out into essentially four clusters, which bore some

resemblance to the previous geographical groups. More than 90% of

the Hokkaido-Kuril-Commander-Aleutian specimens were contained in the first primary cluster; the second primary cluster held

about two-thirds of those from the North American coast. Least

distinctive were the specimens from the intervening region, the

southeastern Bering Sea and Alaska Peninsula, which were almost

evenly distributed between the two primary clusters. This intermediacy suggested a point of demarcation between the eastern and

western forms in the vicinity of the eastern Aleutians-Alaska Peninsula. A strong discontinuity in that region was indicated also by the

makeup of the secondary clusters and was strongly confirmed

14

further by the matrix of paired specimens in th~ clu>ters. Because

the cline in ratio of color phases also appears to be much steeper in

the eastern Aleutians than elsewhere (Shaughnessy and Fay 1977,

fig. 3), we suggest that this is the most probable location for a

genetic "boundary" between P. v. stejnegeri (Allen 1902) and P \'.

richardsi (Gray 1864), if such a boundary exists.

We are skeptical still about the existence of that boundary, because the present series ofspecimens is not uniformly representative

of seal populations throughout the region. That is, we cannot rule

out the possibility that the perceived discontinuity is simply the

result of uneven sampling. In these analyses, the specimens from

area 180 (western Aleutians) were mostly (16/17) from Amchitka

and Adak Islands, some 800 to 1,100 km west of Unalaska Island,

where most (3/4) of the specimens for area 190 (eastern Aleutians)

were taken. For areas 200 and 210, the samples were principally

from Port Heiden (12/19) and Tugidak Island (24/24), respectively,

which are about 700 to 800 km east of Unalaska. Thus, the largest

samples were from localities 1,500 to 1,900 km apart, and the

genetic discontinuity indicated by them may, in actual ity,. be

nonexistant. The whole range of morphologically intermediate

forms could be present in that 1,500 to 1,900 km gap. In our opinion,

study of many additional specimens from that region wi II be needed

before a firm decision can be reached about the boundary between

richardsi and stejnegeri.

ACKNOWLEDGMENTS

We thank especially the many colleagues and curatorial personnel

of the museums and smaller collections who generously made

available to us more than half of the specimens used in this study.

Many of the rest were collected by us, by K. W. Pitcher of the

Alaska Department of Fish and Game, and by other co-workers,

with logistic support principally from the Alaska Department of

Fish and Game, the United States Coast Guard, the U.S. National

Science Foundation, and the Soviet Ministry of Fisheries. We are

grateful for advice on statistical procedures received from I. y.

Frohne, and from S. J. Harbo, Jr., D. B. Hawkins, A. A. Hoover, I.

A. McLaren, and E. H. Miller, who also assisted us by critically

reading an earlier draft of this paper. Computer programming sel'-

vices were provided by G. Hanson, L. R. Miller, and J. A. Venable.

Our work was sponsored in part (Burns and Fay) by the Alaska Sea

Grant Program, the U.S. Marine Mammal Commission, the Alaska

Department ofFish and Game, and the University of Alaska, and in

part (Fedoseev) by the Soviet Ministry of Fisheries, Pacific Research Institute of Fisheries and Oceanography, Magadan Section.

LITERATURE CITED

ALLEN, J. A.

1902. The hair seals (family Phocidae) of the North Pacinc Ocean and Bering

Sea. Bull. Am. Mus. Nat. Hist. 16:459-499.

BELKIN, A. N.

1964. A new species of seal from the Kuril Islands-Phoca insularis sp.

n. Ookl. Akad. Nauk SSSR 158:1217-1220.

BIGG, M. A.

1969. The harbour seal in British Columbia. Fish. Res. Board Can., Bull.

172.33p.

1981. Harbour seal Phoca viwlina Linnaeus, 1758 and Phoca /argha Pallas,

1811. In S. H. Ridgway and R. J. Harrison (editors). Handbook of marine

mammals, Vol. 2 Seals, p. 1-27. Acad. Press. Lond.

BISHOP, R. H.

1967. Reproduction. age determination. and behavior of the harbor seal.

Phoca dIu/ilia L., in the Gulf of Alaska. M.S. Thesis, Univ. Alaska,

Fairbanks. 121 p.
BURNS. J. J.• and V. N. GOL·TSEV.

1984. Comparalive biology of harbor seals. Phoca vitulina Linnaeus. 1758.

of the Commander. Aleutian. and Pribilof Islands. U.S. Dep. Commer.,

NOAA Tech. Rep. NMFS 12:17-24.

BYCHKOV. V. A.

1971. Review of the status of pinnipeds of the fauna of the USSR. In L. K.

Shaposhnikov, V. A. Borisov. L. V. Zhirnov, and N. V. Shkarban (editors),

Scienlific elements of nature conservation, p. 59-74. Ministerstvo

Sel'skogo Khozyaistvo, Moscow.

CHAPSKII, K. K.

1955. An allempt at revision of the systematics and diagnostics ofseals of the

subfamily Phocinae. Tr. Zool. Inst. Akad. Nauk SSSR 17: 160-199.

1960. Morphologie systematique, differenciation intra-specifique et

phylogenese du sous-genre Phoca sensu stricto. Mammalia 24:343-360.

1967. Morpho-taxonomic characteristics of the pagetoda form of the Bering

Sea larga. In K. K. Chapskii and M. Y Yakovenko (editors), Investigations

of marine mammals, p. J47-176. Polyarnaya Pravda, Murmansk.

1969. Taxonomy .of seals of the genus Phoca sensu stricto in the light of

contemporary craniological data. In V. A. Arsen'ev, B. A. Zenkovich, and

K. K. Chapskii (editors), Marine mammals, p. 294-304. Nauka. Moscow.

DELYAMURE, S. L., M. V. YURAKHNO, V. N. POPOV, L. M. SHULTS, and

F. H. FAY.

1984. Helminthological comparison ofsubpopulations of Bering Sea spoiled

seals, Phocalargha Pallas. U.S. Dep. Commer., NOAA Tech. Rep. NMFS

12:61-65.

DOUTT,J. K.

1942. A review of the genus Phoca. Ann. Carnegie Mus. 29:61-125.

FAY, F. H., and D. P. FURMAN.

1982. Nasal mites (Acari:Halarachnidae) in the spoiled seal, Phoca largha

Pallas, and other pinnipeds of Alaskan waters. J. Wildt Dis. 18:63-68.

FISHER, H. D.

1952. The status of the harbour seal in British Columbia, with particular

reference to the Skeena River. Fish. Res. Board Can., Bull. 93, 58 p.

APPENDIX I

Sources and Acquisition Numbers ofHarbor and Spotted

Seal Specimens Used in These Analyses

Harbor Seals

Alaska Department of Fish and Game (ADF&G), Anchorage and

Fairbanks, Alaska, USA. (The transfer of specimens to the Geist

Museum, University of Alaska, Fairbanks, is in progress.)

Males: 66-20, S-OO, S-33, B-4, B-5, B-41, PWS-73-3, PWS-16-75,

PWS-19-75, PWS-26-75, PWS-32-75, PWS-76-75, PWS-78-75,

PWS-82-75, PWS-107-75, 12-6-65, AH-17-72, AH-IO-73, AH39-73, AH-52-73, AH-56-73, AH-9-74, AH-9a-74, JNO-2-72,

JNO-l2-72, JNO-l3-72, JNO-18-72, JNO-19-72, HS-72-I, HS-72-

3, HS-72-6, HS-72-15, N-7-68, CR-3-75, CR-23-75.

Females: 66-12, 66-21, 66-22, 66-23, 66-25, 66-29, 66-30, 66-31,

66-34,66-39, A-7, A-26, A-27, A-34, A-36, B-1, B-12, B-15, B-16,

B-17, B-18, B-27, B-28, B-29, B-30, B-32, B-35, B-37, B-39,

PWS-73-l3, PWS-73-15, PWS-14-75, PWS-85-75, AH-6-68,

AH-21-72, AH-2-73, AH-II-73, AH-23-73, AH-28-73, AH-33-73,

AH-35-73, AH-36-73, TU-I-7I, TU-2-71, HS-72-4, HS-72-5,

JNO-I-68, JNO-20-72, AMC-I-69, N-IO-68, CR-2-75, NAN-4-73,

KSK-27-73, ADF&G-I, 019, 020, 100, 101, 102, 103, 104, 105,

106.

All-Union Research Institute of Fisheries and Oceanography

(VNIRO), Moscow, USSR.

15

lNUKAI, T.

1942. Hair seals from the northern waters of Japan. [In Jpn.) Shokubutsu

Oyobi Dobutsu 10:927-932, 1025-1030. (Eng!. transl., Marine Mammal

Div., Northwest Alaska Fish. Cent., Seallle, Wash.)

McLAREN, I. A.

1966. Taxonomy of harbor seals of the western North Pacific and evolution of

certain other hair seals. J. Mammal. 47:466-473.

MOHR,E.

1965. Uber Phoca vitulina largha Pallas, 1811 und weissgeborene

Seehunde. Z. Saeugetierkd. 30:273-287.

NAITO, Y., and M. NISHIWAKl.

1972. The growth of two species of the harbour seal in the adjacent waters of

Hokkaido. Sci. Rep. Whales Res. Inst. Tokyo 24: 127-144.

1973. Kurile harbour seal (Phoca kuri/ensis). In Seals: Proceedings of a

working meeting of seal specialists on threatened and depleted seals of the

world, held under the auspices of the Survival Service Commission oflUCN,

p. 44-49. Int. Union Conserv. Nature Nat. Resour. Publ., n.s., Suppl.

Pap. 39.

1975. Ecology and morphology of Phoca vitulina largha and Phoca kuri/ensis

in the southern Sea of Okhotsk and northeast of Hokkaido. In K. Ronald and

A. W. Mansfield (editors), Biology of the seal, p. 379-386. Rapp. P.-V.

Reun. Cons. Int. Explor. Mer 169.

NIE,N. H.,C. H. HULL,J.G.JENKINS,K. STEINBRENNER, and D. H. BENT.

1975. Statistical package for the social sciences. 2d ed. McGraw-Hili Book

Co., N.Y., 675 p.

PARKS,J. M.

1970. Fortran IV program for Q-mode cluster analysis on distance"function

with printed dendrogram. Kansas Geol. Surv. ComputerContrib. 46, 32 p.

SCHEFFER, V. B.

1958. Seals, sea lions, and walruses; a review of the Pinnipedia. Stanford

Univ. Press, Stanford, Calif., 179 p.

SHAUGHNESSY, P. D., and F. H. FAY.

1977. A review of the taxonomy and nomenclature of North Pacific harbour

seals. J. Zool. (Lond.) 182:385-419.

Females: 3484, 29112.

Black Douglas Mammal Collection (BDM), National Marine

Fisheries Service, National Marine Mammal Laboratory, Seattle,

Wash., USA.

Females: BDM-l272.

California Academy of Science (CAS), San Francisco, USA.

Males: 5,411,413.

Females: 527, 530, 15934.

Carnegie Museum (CMP), Pittsburgh, Pa., USA.

Female: 18738.

Fisheries Research Board of Canada (FRBC), Arctic Biological

Station, Ste. Anne de Bellevue, Quebec, Canada.

Male: HS8.

Geist Museum, University of Alaska (GMUA), Fairbanks, USA.

Males: 3409,7265, 7304.

Females: 3702,7264.

Los Angeles County Museum (LACM), California, USA.
'Females: 9539.

Museum of Comparative Zoology (MCZ), Harvard University,

Cambridge, Mass., USA.

Male: 6157.

Female: .11455.

Museum of Vertebrate Zoology.(MVZ), University of California,

Berkeley, USA.

Males: 101090, 114778, 140849, REJ-439.

Females: REJ-454, REJ-681.

National MuseumofNatural History (USNM), Smithsonian Institution, Washington, D.C., USA.

Males: 81515, 140401, 140402, 140403, 146430, 146432, 147700,

253045,273532, 274152, 274155, 275176.

Females: 81517, 81518, 146433, 146434, 147680, 219868, 219873,

219874, 245915, 250712, 250713, 253042, 253043, 253046,

261781, 274146, 276362, 276365.

Ocean Research Institute (ORI), University of Tokyo, Japan.

Males: 69-6, 70-186, 70-208, 70-223, 70-228.

Females: 69-NE3, 70-13, 70-20, 70-35, 70-155, 70-168, 70-187,

70-222.

Pacific Research Institute of Fisheries and Oceanography (TINRO),

Magadan, USSR.

Males: 57-1964, 80-1964, 26-1975, 33-1975, 34-1975, 35-1975,

39-1975,47-1975.

Females: 225, 389, 1-1964, 27-1%4, 43-1964, 83-1964, 86-1964,

3-1975, 10-1975, 11-1975, 13-1975, 14-1975, 18-1975, 20-1975,

24-1975,27-1975,28-1975,29-1975,40-1975, 45-1975, 46-1975.

Males: 01, 22799.

Vertebrate Museum, University of British 'Columbia (VMUBC),

Vancouver, Canada.

Males: 1470, 7339.

Females: 2159, 2167, 2168, 9530, 9539,9540,9541.

Zoological Institute, Academy of Sciences (ZIAS), Leningrad,

USSR.

Males: 835, 2679, 26977.

Zoological Museum, University of Moscow (ZMUM), USSR.

Male: 45050.

Spotted Seals

ADF&G

Males: D-55-65, N-IO-66, N-30-67, D-191-67, AH-63-73, AH-I74, AH-2-74.

Females: N-12-66, N-17-66, N-51-67, G-9-69, N-26-72, AH-27-72,

AH-28-72, NAN-3-73.

CMP

Male: DC-1586.

FRBC.

Female: PV-41O.

GMUA.

Male: 1529.

Puget Sound Museum of Natural History, University of Puget Sound ORI.

(UPSMNH), Tacoma, Wash., USA.

Males: 69-42, 69-49, 70-69, 70-107.

Males: 15182, 16040, 16043, 16103, 16430.

Females: 70-50, 70-56, 70-58.

Females: 15211, 15274, 16039, 16041, 16044, 16054, 16096.

TINRO.

Dr. Robert L. Rausch (RLR), University of Washington, Seattle,

USA.

Male: 39716.

Hemales: 39715, R1I332.

Charles A. Repenning, United States Geological Survey, Menlo

Park, Calif., USA.

Male: 6842.

Santa Barbara Museum of Natural History (SBMNH), California,

USA.

Females: 251, 258, 1895.

University of Arizona (UAZ), 'fucson, USA.

16

Females: 7-1975,41-1975.

USNM.

Males: 219885, 290655.

Females: 219865,290653.

ZIAS.

Males: 3487, 3491, 29117.

ZMUM.

Males: 10095,45024,69371.

Females: 29925, 45025.
Comparative Biology of Harbor Seals,

Phoca vitulina Linnaeus, 1758,

of the Commander, Aleutian, and Pribilof Islands

JOHN J. BURNSl and VITALI N. GOL'TSEV2

ABSTRACT

Harbor seals, Phoca vitulina, of the Aleutian Ridge and Pribilof Islands were studied through field

observation and examination ofanimals(173 seals, IS fetuses) collected in four areas: The Commander, western

Aleutian, eastern Aleutian, and Pribiloflslands. Spotted seals, Phoca Iorgha, were not analyzed. in this study.

Habitats .were similar in these four areas and seals were present at all locations visited. Differences in pelage

coloration between seals of the Aleutian and Commander Islands were not significant, but there was a trend

toward more dark colored seals in the western islands. Growth in relation to age ofseals from the four areas was

similar, as was fetal growth. Mating was found to occur in July to early August, implantation in November,

birth in early June to mid-July, and weaning of pups by mid-August. Some females (33%) first ovulated at age 3.

First pregnancy also occurred in some 3-yr-olds; all females had been or were pregnant by age 6. The incidence

of pregnancy in sexually mature animals was 75%. Similarities among seals of the Aleutian Ridge include

timing of eventsin the reproductive cycle, size/age relationships including fetal growth, food habits, and habitat

utilization. Harbor seals ofthe North Pacific region vary in size and coloration in an apparentiy c1inal manner

over their linearly continuous range from Mexico to Japan.

PE310ME

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HB npH6"'JIOBCKHX OCTpoBOX. JIBprB, Phoca largha He BKJIIO'IBJIBCI. Bno HCCJIeI\OBBHHe. Cpel\a OliHTBHHB

CXOAH8 80 Bcex 4 palloHsx, H TIOJleHH OTMf'laJlHCb B Kam)J.OM Hl HKX. PalHHQW R oKpacKe Mexa Me>KjQ'

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AJIeyTcKo-KoMBHl\opcKoii rpBI\'" npoB8J1BeTCB a penpOI\YKI\HOHHOM I\HKJIe, BpBlMepHO-BOlpBCTHOM COCTBae

paJBHTHH lM6pHOHOB, nUTaHHH H eCTeCTBeHHoil cpe~e 06HTaHHR. 06wKHoBeHHwe TIOJleHH ceBepHoii '1aCTH

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H1MeH'IHBOCTb 8 palMepax Tena H OKpaCKe.

INTRODUCTION

In an evaluation of the taxonomy and nomenclature of North

Pacific harbor seals, Shaughnessy and Fay (1977) reviewed the three

taxa recognized at that time: 1) The ice-associated "spotted" or

"larga" seal, Phoca largha Pallas 1811, of the Bering, Chukchi,

Okhotsk, Japan, and Yellow Seas; 2) the eastern Pacific harbor seal,

P. vitulina richardsi (Gray 1864), distributed from northwestern

Mexico to the Gulf of Alaska and westward through the Aleutian

and Pribilof Islands; and 3) the western Pacific harborseal or insular

seal, P. v. stejnegeri (Allen 1902), of northern Japan (Hokkaido),

eastern Kamchatka, and the Kuril and Commander Islands.

Spotted seals are sympatric with harbor seals about eastern Hokkaido (Inukai 1942; Naito and Nishiwaki 1972; Naito 1974, 1976),

I Alaska Department ofFish and Game, 1300College Road, Fairbanks. AK 99701,

USA.

'Magadan Branch, Pacific Research Institute of Fisheries and Oceanography

(MoTINRO), Nagaevskaya 51, Magadan 685013, USSR.

]7

the Kuril Islands, eastern Kamchatka, and the Commander Islands

(Belkin 1964; Marakov 1967; Voronov 1974; Kosygin et al. 1975a,3

1975b;4 Heptner et al. 1976). They are sympatric also in the southeastern Bering Sea from the estuary of the Kuskokwim River south

to the Alaska Peninsula, the Pribilof Islands, and, to a limited

extent, the eastern Aleutian Islands (Burns 1970; Burns and Fay

1974;5 Shaughnessy and Fay 1977; Burns and Fay unpubl. data).

There is evidence based on skull characteristics ofsome intergradation between largha and stejnegeri in the Okhotsk Sea and

between largha and richardsi in the southeastern Bering Sea (Burns

3Kosygin. G. M., A. E. Kuzin, and E. I. Sobolevskii. 1975. Systematic position.

morphology, and ecology of the Kuril seal. In Marine mammals. Materials 6th

all-union conf. 1:151-153. [Abstr.] Naukova Dumka, Kiev.

4Kosygin. G. M., A. E. Kuzin, and V. A. Petrova. 1975. The larga of the Kuril

Islands. In Marine mammals. Materials 6th all-union conf. 1:149-151. [Abstr.]

Naukova Dumka, Kiev.

'Burns, J. J., and F. H. Fay. 1974. New data on taxonomic relationships among

North Pacific harbor seals, genus Phoca (sensu stricto). [Abstr.] Trans. First Int.

Theriol. Congr. 1:99. Nauka, Moscow.
and Fay unpubl. data). Nevertheless, spotted seals are for the most

part clearly differentiated morphologically, physiologically, and

ecologically from those two forms (Chapskii 1960, 1967, 1969,

1975;6 Mohr 1965; Burns 1970; Burns and Fay footnote 5, unpubl.

data). Shaughnessy and Fay (1977) concluded that the larga

phenotype should be regarded as a separate species, Phoca largha

Pallas, 1811, as proposed by Chapskii (1967). For that reason,

spotted seals have been excluded from the present analysis.

The validity of subspecific distinction for the richardsi and

stejnegeri phenotypes is in question. Their range is linearly continuous along the shores of all suitable land masses around the North

Pacific Ocean, from northern Mexico to northern Japan. In the area

of their presumed discontinuity, the Aleutian-Commander Ridge,

harbor seals occur on all of the islands. The respective ranges of

stejnegeri and richardsi in that area have not been clearly defined.

Some authors have included the Aleutian and PribilofIslands within

the range of stejnegeri (Chapskii 1967; Belkin et al. 1969; Heptner

et al. 1976); others have included those islands within the range of

richardsi (Burns and Fay 1973; Shaughnessy and Fay 1977). As

pointed out by Shaughnessy and Fay (1977), a real possibility exists

that the two subspecies comprise a single, trans-Pacific cline as

suggested also by Mohr (1965), Chapskii (1969), Bychkov (1971),

Burns and Fay (footnote 5), and Kosygin et al. (footnote 3).

In this paper we compare the physical and biological characteristics of harbor seals from the Commander and Aleutian Islands. Data

from a few seals taken on the PribilofIslands are compared as well.

THE STUDY AREA

The Commander and Aleutian Islands are physiographically

similar, comprising the emergent portions of the Aleutian Ridge

(Fig. 1). According to Wahrhaftig (1965:33): "The Aleutian Islands

are a chain of islands surmounting the crest of a submarine ridge

1,400 miles long, 20-60 miles wide, and 12,000 feet high above the

sea floor on either side. An arcuate line of 57 volcanoes ofQuarternary age, 27 reported active, rises 2,000-9,000 feet above sea level

along the north side of the Aleutian Islands. Other topography in the

Aleutian Islands is of two types: (a) wave-cut platforms less than

600 feet above sea level, bordered by low sea cliffs, and (b) in-

·Chapskii, K. K. 1975. Taxonomy of seals of the genus Phoca sensu stricto. In

Marine mammals. Materials 6th all-union conr. 2:159-162. [Abstr.] Naukova

Dumka, Kiev.

tensely glaciated mountainous islands 600·3,000 feet above sea

level, indented with fiords and bordered by cliffs as high as 2,000

feet ....Broad level intertidal platforms border some islands; they

were probably produced by frost weathering."

The Commander Islands are the westernmost emergent parts of

the Aleutian Ridge. They include two large islands, Bering and

Copper. The Commander Islands are 156 km (97 mi) from Kamchatka and 290 km (180 mi) from Attu Island, the westernmost of

the Aleutian Islands.

The PribilofIslands are volcanic extrusions from the continental

shelf of the Bering Sea (Wahrhaftig 1965). They include two large

islands, St. Paul and St. George, two small islands, Otter and

Walrus, and an islet, Sea Lion Rock. These islands are mainly of

undissected topography, consisting of Cenozoic basalt flows and

pyroclastic debris interbedded with some sediments. Cinder cones

are present.

In most aspects, the rocky shores and islets occupied by harbor

seals in the Commander, Aleutian, and PribilofIslands are similar.

Cobble and pebble beaches are present in protected bays and fjords,

and sandy beaches occur at the mouths of a few of the short, swift

streams. Muddy shores are nearly absent in these islands.

MATERIALS AND METHODS

Most of the materials utilized in this study were obtained by the

authors in the course of four expeditions: Cruises of the RV Alpha

Helix in Aleutian and Pribilof waters during 1968 (Bums), 1972

(Burns), and 1973 (Burns and Gol'tsev), and of the hunting vessel

Sanzar in Commander Island waters in 1974 (Gol'tsev). Specimens

were collected by shooting with a high-powered rifle. Some additional materials, mainly from the western Aleutian and Pribilof

Islands, were made available by biologists of the Alaska Department of Fish and Game and the University of Alaska.

Seals collected by the authors were sexed, weighed, measured,

photographed (skins wet), and necropsied. Measurements included

standard length and axillary girth. Weights were of whole seals

(with no correction for blood loss) and of the hide and attached

blubber. For studies of growth, data from males and females were

treated separately because of sexual dimorphism in size. Skulls

were prepared for taxonomic studies reported elsewhere (Bums et

al. 1984). Lower canine teeth were extracted, decalcified, and

sectioned longitudinally to determine age, based on the number of

annuli in the cementum (Bigg 1969a).

500 N

0LI...J-.L.....II~I -,590 1111••

Figure 1.-Map orthe North PIlcIfic: rePH showing die lec:ation or

the study area,

4S0N

1700 E

o

I

lIOO lim I I , 500 N

18

ISOOW 1700 W 1600 W ISOOW 4S0N
Reproductive tracts were obtained from most females collected in

Alaskan waters. These were preserved in 10% Formalin7 for later

study, at which time the uterine horns were externally examined for

signs of current or previous pregnancy, indicated by external size,

form, and degree of rugosity. Uterine horns were opened and

examined for placental scars, fetuses, or other indications of recent

pregnancy, including condition of the uterine walls, presence of

hemorrhagic tissue, and kind and amount of debris in the lumen.

Ovaries were serially sectioned longitudinally with a scalpel, in

sections 1-2 mm thick. Each section was examined macroscopically

for vesicular follicles, corpora lutea, and corpora albicantia. On the

basis of the findings, females were classified as nulliparous,

primaparous, or multiparous.

Our sample included 173 seals and 15 fetuses. Fifty-one of the

seals were from the Commander Islands, 74 were from the Rat and

Andreanof Islands of the central and western Aleutians, 35 were

from the Islands of Four Mountains and Fox Islands of the eastern

Aleutians, and 13 were from the Pribilof Islands (Fig. I). For

various reasons, we were unable to obtain all of the data desired

from each seal; sample sizes for each data set are indicated where

appropriate.

RESULTS

Habitat

Harbor seals were present in the nearshore waters of all parts of

the study area. Their abundance tended to be greatest in protected

inlets, bays, and fjords of the larger islands and least along simple,

exposed coasts and around the smaller islands. One exception was

Otter Island in the Pribilofs, where harbor seals were abundant

around its exposed coast.

In the protected bays and fjords of the Aleutian Islands, seals

usually were found in small groups on narrow boulder beaches or on

nearshore rocky islets. In less protected areas they tended to haul out

on the wider, more gently sloping beaches composed ofsmall stones

or gravel. The general size of groups on those beaches was much

larger than that of groups on boulder beaches and islets. Where

broad, gently sloping beaches occurred adjacent to rocky islets and

boulder beaches, the seals hauled out mostly on the broad beaches.

Sandy beaches also were utilized but are not common in the study

area.

Abundance and Composition

Seals were least numerous around the Islands of Four Mountains,

in the eastern Aleutians. During a census via small boat on 7 August

1973, we saw only seven seals along 7.2 km (4.5 mi) of the north

side of Yunaska and 57 seals along approximately 22.5 km (14 mi)

of Chuginadak. Although these densities are high in comparison to

those in many other parts of the range of harbor seals, they were the

lowest encountered by us in the Aleutian Islands. There were no

protected embayments on those two islands.

Because the beaches utilized by seals in the study area usually

were of black or dark volcanic rock, and because the seals also were

mostly of dark coloration, assessment of their abundance required

very close inspection. On several occasions when no seals or very

few were seen from the ship anchored I to 2 km offshore, we found

'Reference to trade names does not imply endorsement by the National Marine

Fisheries Service, NOAA.

19

them actually to be numerous on closer inspection, when we walked

the beaches or traveled very close to them in small boats.

Nearly two-thirds ofthe animals older than pups that we collected

were females (48:82). In instances where several adult seals were

taken from a group on shore, the animals commonly were all of one

sex. Males predominated (7:1) in the seals taken in the water

adjacent to large hauled out groups during July-August 1973.

Pelage

Shaughnessy and Fay (1977) summarized the data available on

frequency of occurrence of light and dark color phases in harbor

seals ofthe North Pacific region, including the four areas considered

here. In their samples, dark phase seals occurred with a frequency of

about 90% on the Commander Islands (N=I,500+), 80% on the

western Aleutian Islands (N=37), 30% on the eastern Aleutian

Islands (N=348), and 30% on the PribilofIslands (N=I,643).

Most of our regional samples were smaller, being the number of

animals actually collected. In these samples, the percentage frequency of dark phase seals was: Commander Islands, 59% (N=51);

western Aleutians, 70% (N=43); eastern Aleutians, 50% (N=IO);

and PribiiofIslands, 40% (N=5). The proportion of dark seals on

the Aleutian Islands was not significantly different from the proportion on the Commander Islands (X2 =0.58, P > 0.25). However,

dark phase seals tended to occur more frequently in localities on the

western part of the Aleutian Ridge than on the eastern part and the

Pribilof Islands. This gradient continues to the west, with the

highest proportion of dark phase seals on Hokkaido Island (Naito

1973; Shaughnessy and Fay 1977).

Age and Growth

The length/age and weight/age relationships for harbor seals

collected in this study are presented in Tables 1and 2. The probability of differences in size among the four samples was tested by the

Kruskal-Wallis test (analysis of variance by ranks: Zar 1974), the

results of which are shown in Table 3. In all cases, the null

hypothesis was not rejected. This test was not applied to pups,

because the times of sampling in each area were different, and

growth in pups is rapid.

Since no differences in size were demonstrated among areas, data

from seals in all areas were pooled. These suggest that about 70% of

growth is achieved by age 6 or 7 (Figs. 2, 3). Length/age correlation

is a better indicator of growth than weight/age in these seals, since

there are large seasonal variations in weight, associated with pregnancy, lactation, and molt.

The average standard length of adult males 11 yr and older was

176.25 cm. The largest male, 191.0 cm (age and weight unknown),

was from Amchitka Island. The heaviest male, 140.5 kg, was 14 yr

old and was collected at Atka Island. The average standard length of

adult females II yr and older was 161.82 cm; the maximum was

175.8 cm in a 25-yr-old female taken near Adak Island. This animal

was lactating and had recently ovulated, as indicated by the presence of a developing corpus luteum; she weighed 122.4 kg. The

heaviest female, 125.5 kg, was collected near Amchitka Island. She

was 19 yr old and was carrying a near-term fetus weighing 13.6 kg.

Comparison with sizes of adult seals from other areas around the

North Pacific (Fig. 4) indicates that the Commander-AleutianPribilof seals are not unusual.

Laws (1956) indicated that, in pinnipeds, the average length of

females at puberty is about 86% of adult length. In our sample,

females reached the 86% level at age 4. This corresponds well with
Table I.-Standard length/age relationship for harbor seals, Phoca vitulinD, from the Commander, western Aleutian,

eutem Aleutian, and Pribilor Islands.

Commander is. W. Aleutian Is. E. Aleutian Is. Pribilof Is.

Age SL(cm) SL(cm) SL(cm) SL(cm)

Sex (yr) N Mean Range N Mean Range N Mean Range N Mean Range

Male Pup 4 106.7 100.0-112.0 5 105.6 96.8-115.0 2 109.8 109.2-110.5 0

I 0 1 112.0 I 125.0 0

2 2 124.5 121.0-128.0 0 2 131.7 126.6-136.8 0

3 1 130.0 0 3 145.9 140.3-154.9 0

4 0 0 0 0

5 I 147.0 0 1 147.3 0

6 2 170.0 167.0-173.0 1 158.0 0 0

7 4 158.7 156.0-163.0 2 162.0 162.0 1 157.5 0

8 0 3 171.7 166.0-180.3 2 162.6 153.7-171.5 I 166.0

9 I 174.0 0 2 166.6 161.3-172.0 0

10 I 160.0 2 167.6 166.3-169.0 I 160.7 0

11+ 3 176.0 168.0-184.0 7 180.4 166.0-191.0 3 166.8 159.1-171.4 0

Female Pup 4 107.0 100.0-114.0 9 103.1 87.6-119.0 4 112.3 104.5-119.0 1 123.1

I 2 118.5 117.0-120.0 3 118.8 116.2-122.2 2 117.2 113.7-120.7 0

2 I 128.0 I 127.6 I 127.0 I 123.8

3 5 126.8 119.0-131.0 3 139.9 135.2-143.0 0 0

4 4 132.7 127.0-137.0 3 143.3 138.0-146.0 2 145.7 135.2-156.2 0

5 4 146.2 140.0-155.0 5 139.8 121.0-152.4 I 144.8 0

6 3 151.0 144.0-155.0 5 149.3 132.0-162.5 1 146.0 1 148.5

7 4 144.7 142.0-147.0 I 141.7 4 148.0 140.0-160.0 0

8 3 151.0 146.0-157.0 2 158.4 154.9-161.9 0 1 155.5

9 0 1 153.0 I 137.5 0

10 0 1 150.4 0 0

11+ 2 165.0 158.0-172.0 16 161.5 148.1-175.8 0 'I 160.5

'From Scheffer (1977).

Table 2.-Weight/age relationship for harbor seals, Phoca vitulina, from the Commander, western Aleutian, eastern

Aleutian, and Pribilof Islands.

Commander Is. W. Aleutian Is. E. Aleutian Is. Pribilof Is.

Age Weight (kg) Weight (kg) Weight (kg) Weight (kg)

Sex (yr) N Mean Range N Mean Range N Mean Range N Mean Range

Male Pup 4 29.7 26.0-31.0 5 29.2 24.1-34.0 2 30.1 26.8-33.5 0

I 0 2 43.3 38.6-48.0 I 44.4 0

2 2 51.5 48.0-55.0 0 2 54.0 52.6-55.5 0

3 I 59.0 0 3 59.3 55.5-66.2 0

4 0 0 0 0

5 I 72.0 0 I 68.2 0

6 2 101.0 96.0-106.0 I 88.6 0 0

7 4 93.5 78.0-120.0 2 82.9 77.3-88.6 I 87.3 0

8 0 2 105.4 95.2-115.6 2 91.1 75.0-107.3 1 88.4

9 I 103.0 0 2 105.5 100.0-111.1 0

10 I 104.0 2 117.6 117.3-117.9 I 84.1 0

11+ 3 113.0 92.0-125.0 5 125.4 107.7-140.5 3 100.5 87.0-123.6 0

Female Pup 4 28.5 24.0-32.0 10 29.1 15.9-38.5 5 31.4 24.1-39.9 I 35.3

I 2 38.5 33.0-40.0 2 36.2 34.5-38.0 2 37.0 30.5-43.6 0

2 I 53.0 I 40.8 I 45.3 I 38.5

3 5 45.6 33.0-54.0 3 54.7 47.6-62.7 0 0

4 4 50.0 41.0-60.0 I 68.0 2 59.6 53.5-65.7 0

5 4 63.7 54.0-78.0 3 65.8 47.6-81.6 1 76.4 0

6 3 73.3 72.0-76.0 4 71.1 50.7-84.3 1 54.5 . I 63.4

7 4 74.2 65.0-86.0 I 63.4 4 70.0 60.0-86.8 0

8 3 75.3 64.0-84.0 2 71.1 63.4-78.9 0 1 79.3

9 0 0 I 54.0 0

10 0 I 68.0 0 0

11+ 2 91.0 78.0-104.0 16 94.4 56.2-125.5 0 'I 106.2

'From Scheffer (1977).

20
o

Age

o o 0

o 0

o

o

o 5 10

• , ..-----

.- ~cf0 -

o /' 0

:~~O0 0 0 0 0

o o 0 00

Age Critical

class Calculated table value' Null

Areas compared (yr) Sex H value (P = 0.01) hypotheSIS

1 x 2 x 3 I F o 18 9.21 accepted

I x 2 .>< 3 4 F 4.00 6.44 accepted

Ix2":'.><4 6 F 0.36 11.34 accepted

Ix2x4 11+ F 7.28 9.21 accepted

2 x 3 x 4 8 M 0.81 9.21 accepted

Ix2x3x4 11+ M 2.43 11.34 accepted

200

'Critical values are from tables of Critical Values of the Kruskal-Wallis H, or

Critical Values of the Chi-Square Distribution, as appropriate, depending upon

sample size (Zar 1974).

Table 3.-Results of Kruskal·Wallis analysis of variance by ranks, as applied

to length/age correlations per sex from the four sample areas: I = Commander

Islands, 2 =western Aleutians, 3 =eastern Aleutians, and 4 =Pribilof Islands.

The hypothesis tested is that the groups compared are similar (null hypothesis).

Figure 2.-Standard length per age of harbor seals, Phoca vi/ulina, from the

Commander, Aleutian, and Pribilof Islands. Curve was fitted visually.

our findings from the reproductive organs, as described below. The

standard length (SL) of pups taken in late July and early August was

61 % (males) and 66% (females) of the mean adult length (11 yr and

older).

Axillary girths (sexes combined) were 66.9% SL in pups (range

58.6-75.8%, N=21) and 64.3% SL in animals II yr and older (range

56.1-78.9%, N=28). The seasonal samples are small but show

trends in variation similar to those of percentage weight of skin and

blubber (Table 4).

The percentage of total body weight made up by skin and blubber

varied seasonally among age classes (Table 4). In July and August,

pups (near and recent weanlings) had the highest mean percentage

N

-+- 5

--+- 8

8

I 17

26

47

10

19

49

59

-+- 8

-t- 8

+ 2

--+- 6

-+ 5

-+- 6

5

22

'--'_-'-_-'--'-_-'----J----lto to to 11) to to to r0 <;j" to (!) ro O'l

Standard Length (cm)

Southeast Alaska· Juneau Burns (iJnpublished)

Tugidak I.

Bishop {1967}

Yakutat 8 Icy Bays Pi!chtlr and Calkins (ted footno'e I (J J

Kuril Is. Be/kin eto/. (1969)

British Columbia Fisher (1952), 8igg (19690)

Commander, Aleutian, Pribilof Is. This study

Kodiak I.

Pilcher('ndColkins (text footnote fO)

Prince William Sound Pilcher ond Calkins (tellt footnote 10)

Hokkaido I. Naito and Nishiwoki (1975)

Figure 3.-Body weight per age of harbor seals, Phoca vi/ulina, from the

Commander, Aleutian, and Pribilof Islands. Curve was fitted visually.

Figure 4.-Maximum, minimum, and mean standard lengths of harbor seals,

Phoca vi/ulina, from the North Pacific region. Males were 8 yr and older,

females 6 yr and older. Values were derived from the best approximations of

growth curves, tables, or texts of Ihe indicaled sources.

20 25 30

o 00

o

10 15

Age (yeors)

o 5

Table 4.-Perccnt of lolal body weighl made up of SKin and blubher, and axillary girlh/slanda,-d length x 100 (coefficient of condilion) in harbor seals, Phoca vi/ulina, from Aleutian, Commander, and Pribilof Islands.

Collection Age Skin and blubber as % body weight AG/SL x 100 (coeff. cond.)

Area period group N Mean Range N Mean Range

Aleutian Is. 22 July-II Aug. pup II 47.1 36.3-55.8 6 71.2 67.5-75.8

I yr 3 40.7 36.7-45.5 3 66.4 64.4-67.8

;;.2 33 34.9 22.9-53.4 35 63.3 56.1-73.2

Nov.-Apr. pup 3 33.0 25.9-37.3 7 64.3 58.6-71.0

I yr I 37.4 2 66.9 63.6-70.3

;;.2 II 41.1 32.8-59.1 28 63.7 56.6-69.9

Commander Is. 15-30 Aug. pup 8 40.6 31.2-52.9 8 66.1 62.1-72.0

I yr 2 35.1 30.3-40.0 2 65.0 64.2-65.8

;;.2 41 32.8 24.0-38.2 41 64.2 55.5-74.1

Pribilof Is. 12 Aug. ;;.2 4 30.9 27.7-35.5 4 63.4 61.2-65.6

21
of hide and blubber. Seals 2 yr old and older had the lowest 'values;

those I yr old were intermediate. This trend was the same in the

Aleutian, Commander, and Pribilof Islands. In November to April

the ranking was reversed.

Reproduction

Reproductive tracts were obtained from 76 females taken in the

Aleutian and PribilofIslands. Of these, 15 were from pups, B were

from animals between ages I and 5 that had not yet ovulated, .md 48

were from females between ages 3 and 25 that had ovulated at least

once.

In the second half of July, only 4 (29%) of 14 sexually mature

females had ovulated, but by the first half of August, IO (77o/c) of 13

had ovulated (Table 5). These findings indicate that the br~eding

(mating) period of harbor seals in the Aleutian-Pribilof area extends

from at least mid-July to mid-August, probably with a peak in early

August.

Table 5.-Condition of ovarian structures in 27 sexually mature female harbor

seals, ages 4 and older, taken between 12 July and 12 August on the Aleutian

and Pribilof Islands.

Enlarged Corpus luteum

follicles Recent Corpus luteum completely

only ovulation partly formed formed

Time period N No. % No. % No. % No. %

12-31 July 14 10 71.4 2 14.3 7.1 I 7.1

1-12 August 13 3 23.1 3 23.1 23.1 4 30.7

Three females taken in October had a large corpus luteum but no

implanted fetus. Two taken on 6 November exhibited slight enlargement of implantation sites, indicating that implantation had

just taken place. In each ofthese , the embryo was < I mm long. One

female taken on 8 December contained an 11.4 g fetus, 8.2 em in

crowiJ-rump length. These data indicate that implantation takes

place early in November, about 3 mo after mating. Lengths and

weights of 16 fetuses and one newborn pup from the Aleutian and

Pribilof Islands are presented,in Table 6.

Time of birth was determined on the basis ofthe latest occurrence

of near-term fetuses and the earliest occurrence of recently postpartum females. The latter were identified from the condition of the

uterus, in which one horn still was distended and in some cases

filled with blood and debris from a very recent birth. Each of two

females, taken on 2 June at Amchitka Island, supported a near-term

fetus, 13.6 and 1l.8 kg. One taken on 5 July appeared to have given

birth very recently. Each of nine females taken between 24 and 31

July showed signs ofrecent birth; at least four of these probably had

given birth within the previous 2 wk.

Thus, the birth period in the Aleutian area seems to extend at least

from mid- or late June to mid-July, with the majority of births

presumed to occur in late June to early July. Murie (1959) reported

newborn pups in the Aleutians in mid-June. On the Commander

Islands, births occur to the end of June (Marakov 1967). Johnson

(1974)8 found births taking place on the Pribilof Islands in June and

July with the greatest number in late June-early July. Scheffer (1977)

indicated mid-May to mid-July as the birth period on the Pribilofs,

but some of the pups reported by him could have been P. largha.

"Johnson, B. W. 1974. Otter Island harbor seals: a preliminary report. Unpubl.

manuscr., 20 p. Alaska Dep. Fish Game, Fairbanks, AK 99701.

22

Table 6.-Standard length and weight offetal and newborn

harbor seals, Phoca Vi/alina, from the Aleutian and Pribilof

Islands, Alaska.

Standard

Weight length

Dalc Locati·.)n Sex (g) (cm)

6 Nov. Amchitka 01 I I

b Nov. Amchilka ?' I I

8 Dec. Amchitka M 11.4 8.2

2~ Jan. Amchitka F 614.0 27.0

4 Mar. Unalaska f 2.526.5 48.3

15 Mar. Adak F 3,292.0 55.0

10 Apr. Unalaska F 5,421.5 65.1

13 Apr. Unalaska F 5,875.5 68.6

11 Apr. Otter M 5,023.0 66.9

13 Apr. Otter M 6,560.0 72.4

13 Apr. Otter M 5,763.0 68.3

4 May Tanaga 9.070.0

b May Tanaga 8,620.0

2 June Amchitka F 13,620.0 88.0

2 June Amchitka F 11,804.0 76.0

10 June Otter M' 11,100.0 89.8 (newborn)

15 June SI. Paul F' 13,800.0 91.5

'Specimens provided by R. L. Rausch.

'From Scheffer ( 1977).

Of 16 sexually mature females collected during November to

early June, 12 (75%) were supporting an apparently healthy fetus.

Of the remainder, one taken in March showed no indications of

recent pregnancy; another in March contained a partly resorbed

ktus; and two taken in April had recently aborted. Of 12 adult seals

taken in July, 9 (75%) had recently given birth; the others showed no

indication of recent pregnancy.

Age at tirst ovulation was from 3 to 5 yr (Table 7). All females 6

yr old and older had ovulated at least once. The youngest seals in our

Table 7.-lncidence of ovulation in 21 harbor seals,

ages 2 to 7 yr, taken on the

Aleutian and Pribilof Islands during JUly-August.'

Age N Ovulated %

2 3 0

3 3 33

4 5 60

5 3 67

6 5 100

7 2 100

1An animal was considered

to have ovulated if a corpus

IUleum, a corpus albicans, or

a foil icle larger than 13 mm

was present.

sample which were successful in pregnancy were 5 yr old. One of

these contained a near-term fetus on IO April; the other had given

birth not long before it was collected (24 July). The latter also had

been pregnant in the previous year, judging from the presence of a

placental scar in the opposite uterine horn and presence of a large

corpus albicans in the adjacent ovary.

Feeding Habits

Remains of food were found in 16 of 51 seals taken on the

Commander Islands between 15 and 30 August. Fourteen of these

contained only beaks of octopus, one contained octopus and uniden-
tified fishes, and one contained squid beaks. Similar prey were

reported for harbor seals about the Kuril Islands (Panina 1966).

Since cephalopod beaks may accumulate from several feedings,

their presence is not representative ofthe proportion of cephalopods

in the diet (Pitcher 1980). Fishes, cephalopods, and shrimps were

indicated by Marakov (1967) as the prinicpal foods of harbor seals

near the Commander Islands.

Food remains were found in 17 of 43 seals taken in the western

Aleutian Islands between 25 July and 6 August. Four of these were

nursing pups, the stomachs of which contained only milk. Most of

the remaining I3 seals had fed on only one type of prey. Three

stomachs from weaned pups and two from older animals contained

mysids; four contained pandalid shrimps; three contained remains

of octopus; and one contained a combination of crangonid shrimps

and fishes (Pacific cod, Gadus macrocephalus, and unidentified

sculpin). The prey of 18 harbor seals from Amchitka Island, as

reported by Wilke (1957) and Kenyon (1965), included mainly

octopus; Atka mackeral, Pleurogrammus monopterygius; and

greenling, Hexagrammos sp.

Our findings in the pups indicate that the time of weaning is in

late July to early August, and suggest that the pups' first solid food

in this area may be mysids. These organisms were very abundant in

dense swarms within the kelp beds, where they probably are readily

available to the pups.

The stomachs of three seals from the eastern Aleutians contained

food. These were collected at Unalaska Island, between 10 and I3

April. Walleye pollock, Theragra chalcogramma, was the dominant prey, comprising 98% of the total volume. Pacific cod comprised the remaining 2% (Lowry et al. 1979).

Stomachs of eight seals from the Pribilof Islands contained food.

These were obtained in mid-April. Data from these seals were

pooled and treated as a single sample. The mean volume ofstomach

contents per seal was 166.2 ml. Fishes, principally walleye pollock

and cods (Gadus spp.), comprised 63.5% of the total volume.

Octopus made up 28.7% of the volume. 9

DISCUSSION AND CONCLUSIONS

The differences among harbor seals from the Asian coast, the

Aleutian-Commander Ridge, and the North American coast are not

inconsistent with predictions for a relatively sedentary species

exhibiting essentially linear distribution over an elongate, coastal

range. Based on the values reported by other investigators (see Fig.

4), growth of harbor seals from the Asian and North American

coasts appears to be comparable with that of seals from the

Commander-Aleutian area. The Asian and Commander-Aleutian

seals tend to be larger and more often of dark pelage than those from

most of North America. North American seals tend to be smallest

and palest in the northern part of the Gulf of Alaska and in northern

British Columbia (Fig. 4 and see Shaughnessy and Fay 1977).

Perhaps the larger size ofseals occupying the Aleutian-Commander

and Kuril-Kamchatka Ridges may be a phenotypic expression of the

richness of their environment, which includes some of the most

productive marine habitats in the world.

A study of the genetics of North Pacific harbor seals has

suggested that the basic dark and light color phases are controlled by

a single pair of autosomal alleles, with light phase dominant, and no

correlation with sex or size within local populations (Kelly 1981).

Investigation of cranial characteristics has indicated that differences

0L. F. Lowry. Game Biologist II, Alaska Dep. Fish Game, Fairbanks, AK 99701,

pers. commun. October 1979.

23

between groups in skull size parallel those of body length, and that

proportional relationships ofskull measurements among groups are

similar (Burns et al. 1984).

From Hokkaido to the eastern Aleutians, differences between

regional groups in the timing of events in the breeding cycle are

small and apparently c1inal (Bigg 1969b, 1973). In eastern Hokkaido, implantation ofthe fetus takes place appreciably earlier than

was found in our study. Naito and Nishiwaki (1972) reported fetuses

3.9,8.4,8.5, and 9.5 cm long in females collected during October

from the Nemuro Peninsula, whereas our findings suggest attainment of such size no earlier than November. They indicated further

that birth takes place in May and June, and that weaning is completed by late June-early July (Naito and Nishiwaki 1972, 1973),

both about I mo earlier than in our study area. Time of birth on the

Kuril Islands apparently is similar to that on Hokkaido (Belkin

1964; Belkin et al. 1969; Velizhanin 1967). On islands in the Gulf of

Alaska also, implantation and birth take place somewhat earlier

than on the Aleutian Islands. Bishop (1967) and Pitcher and Calkins

(1979)tO observed that implantation takes place in late August to

early October and birth primarily in May and June, at least 2 wk

earlier than in our study area. Shaughnessy and Fay (1977) summarized the available information from other areas farther south on

the North American coast and suggested, as did Bigg (1973), that

the observed variation in birth dates may be correlated with local

availability of certain prey during the period when pups are weaned.

The Commander-Aleutian Ridge is of particular zoogeographic

importance to marine mammals because it extends across the entire

northern end of the North Pacific Ocean and supports continuous

North American-Asian distributions of such species as the sedentary sea otter, Enhydra lutris, the more wide-ranging Steller sea

lion, Eumetopias jubatus, and harbor seals. For the seals, the

habitats utilized, size/age relationships, timing of events in the

annual breeding cycle, and feeding habits appear to be essentially

the same throughout this area as well as on the Pribiloflslands. Only

pelage coloration appears to vary, but in an east-west c1inal manner.

Thus, to the extent that our investigations compared them, we found

no significant biological or ecological differences among the seals of

the Aleutian-Commander region. Instead, our results indicate a

single, linearly distributed form of harbor seals in this region, as

predicted by Mohr (1965), Chapskii (1969), Bychkov (1971), Burns

and Fay (footnote 5), Kosygin et al. (footnote 3), Shaughnessy and

Fay (1977), and Burns et al. (1984).

Harbor seals in the Aleutian and Pribilof Islands are unexploited

and, for the most part, undisturbed. Their populations probably

exist in balance with the natural carrying capacity of their environment. For this reason, we believe that the various biological characteristics described in this study are those of stationary populations,

in which birth and death rates have been equal for a long time. These

are of considerable significance for comparative purposes. For

example, the pregnancy rate (75%) for sexually mature females in

our study area is markedly lower than that of a heavily exploited and

declining population (95%) in eastern Canada (Boulva and

McLaren 1979) and of an exploited population (97%) in British

Columbia (Bigg 1969a). Pitcher and Calkins (footnote 10) found a

pregnancy rate of 92% for adults in the Gulf of Alaska, where the

population is presumed to be increasing following earlier intensive

harvests.

I·Pitcher, K. w., and D. G. Calkins. 1979. Biology of the harbor seal, Phoca

vitulina richardsi. in the Gulf of Alaska. Final Report, R.U. 229, 72 p. Outer

Continental Shelf Environmental Assessment Program. NOAA Environ. Res. Lab.,

Boulder, Colo.
ACKNOWLEDGl\1ENTS

We wish to express our appreciation to J. Vania, K. B. Schneider,

K. W. Pitcher, K. J. Frost, L. F. Lowry, L. M. Shults, and R. L.

Rausch for making specimens available to us. L. F. Lowry

examined the food remains in seals from the Aleutian and Pribilof

Islands. K. W. Pitcher provided unpublished data about harborseals

in south-central Alaska. F. H. Fay was especially helpful, providing

enlightening discussions and critical reviews ofthis paper. M. Bigg,

K. W. Pitcher, and J. Coady also kindly reviewed the manuscript,

D. Borchert prepared the figures, and K. Valentine typed the several

drafts. The research vessels MY Alpha Helix, operated by the

Scripps Institution of Oceanography, USA, and the KS Smwu,

operated by the Pacific Research Institute ofFisheries and Oceanography (TINRO), USSR, provided the principal logistic support. We

are indebted to the officers and crews of these vessels. R. Elsner,

Chief Scientist during the 1973 cruise of the Alpha Helix, was

particularly accommodating and helpful. Financial support was

provided by TINRO (Gol'tsev) and by Federal Aid in Wildlife

Restoration, Projects W-17-R, and the Alaska Sea Grant Program

(Burns).

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24

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possible dispersal of pups. Sci. Rep. Whales Res.lnst. Tokyo 28:175-185.

:-IAITO, Y., and M. NISHIWAKI.

1972. The growth of two species of the harbour seal in the adjacent waters of

Hokkaido. Sci. Rep. Whales Res. Inst. Tokyo 24: 127-144.

1973. Kurile harbour seal (Phoca kurilellsis). III Seals: Proceedings of a

working meeting of seal specialists on threatened and depleted seals of the

world, held under the auspices of the Survival Service Commission of

IUCN. Int. Union Conserv. Nature Nat. Resour. Publ., n.s., Suppl. Pap.

39:44-49.

1975. Ecology and morphology of Phoca vitulina largha and Phoca kurile1lSis

in the southern Sea of Okhotsk and north east of Hokkaido. In K. Ronald and

A. W. Mansfield (editors), Biology of the seal, p. 379-386. Rapp. P.-V.

Reun. Cons. Int. Explor. Mer 169.

PANlNA, G. K.

1966. On the feeding of the sea lion and hair seals on the Kurillslands. Izv.

T1NRO 58:235-236.

PITCHER, K. W.

1980. Stomach contents and feces as indicators of harborseal, Phoca vi/ulina,

foods in the Gulf of Alaska. Fish. Bull., U.S. 78:797-798.

SCHEFFER, V. B.

1911. Newborn harbor seals on the Pribilof Islands, Alaska. Murrelet

58:44.

SHAUGHNESSY, P. D., and E H. FAY.

1977. A review of the taxonomy and nomenclature of north Pacific harbour

seals. J. Zool. (Lond.) 182:385-419.

VELIZHANIN, A. G.

1967. A new species of seal. Priroda 1967(7):76-79.

VORONOV, B. G.

1974. Mammals oftheKurillslands. Akad. NaukSSSR, Leningtad, 162 p.

WAHRHAFT[G, C.

1965. Physiographic divisions of Alaska. U.S. Geol. Surv. Prof. Pap. 482,

52 p.

WlLKE,E

1957. Food of sea otters and harbor seals at Amchitka [sland. J. Wildl.

Manage. 21:241-242.

ZAR,J. H.

[974. Biostatistical analysis. Prentice-Hall, Englewood Cliffs, N.J., 620 p.
Habitat Partitioning by Ice-Associated Pinnipeds:

Distribution and Density of Seals and Walruses

in the Bering Sea, April 1976

HOWARD W. BRAHAM,· JOHN J. BURNS,2 GENNADII A. FEDOSEEV,a and BRUCE D. KROGMAN!

ABSTRACT

Aerial surveys were conducted over the Bering Sea pack ice in April 1976 to assess the distribution and

density of five ice-associated pinnipeds. Results from those surveys support the hypothesis that walruses,

ringed, ribbon, spotted, and bearded seals partition the available ice habitat by distributing themselves

differentially according to north-south and east-west gradients. Partitioning is believed to be the result of

selection for specific ice types and, perhaps, availability of different prey. All species exhibited a clumped

distribution. \\\llruses were most abundant near St. Lawrence Island and in outer Bristol Bay, as had been

observed in previous surveys during April. Ringed seals were widely dispersed, and their presence in considerable numbers in the southeastern sector of the pack is reported for the first time. Ribbon seals were most

abundant in the west-central ice front. Densities ofspotted seals were highest in the ice front, east and west ofthe

major concentration ofribbon seals as well as in outer Bristol Bay. Bearded seals were nearly ubiquitous on the

pack ice but with higher densities in the northern than in the southern sectors. The pack ice in April 1976

extended nearly to its southern maximum, hence the data collected during this study allowed a comparison of

the spatial relationship among the ice-associated pinnipeds in a year of maximal dispersal.

PE310ME

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INTRODUCTION

In winter and early spring, much of the Bering Sea is covered

with ice floes, which are used as haul out areas by several species of

pinnipeds: The Pacific walrus, Odobenus rosmarus divergens; the

ringed seal, Phoca hispida; the ribbon seal, Phoca fasciata; the

spotted or larga seal, Phoca largha; and the bearded seal, Erignathus barbatus. These pinnipeds use the ice as a subslrate on which

to give birth to their young, to molt, and to rest. To some extent also,

the moving ice serves as a means for passive dispersal of these

mammals into seasonal feeding areas, especially during its southward advance in autumn and its northward retreat in spring (Burns

1970; Fay 1974). Harbor seals, Phoca vitulina, and northern sea

'National Marine Mammal Laboratory, National Marine Fisheries Service,

NOAA, 7600 Sand Point Way NE., Seattle, WA 98115. USA.

2 Alaska Department of Fish and Game, 1300College Road, Fairbanks, AK 99701,

USA..

3Magadan Branch, Pacific Research Institute of Fisheries and Oceanography

(MoTlNRO), Nagaevskaya 51, Magadan 685013, USSR.

25

lions, Eumetopiasjubatus, also rest on floes in the southern edge of

the pack during the spring, particularly when it extends far into the

southwestern and southeastern Bering Sea. The centers of abundance for those two pinnipeds, however, lie farther to the south, in

ice-free areas such as the Aleutian and Commander Islands and the

Alaska and Kamchatka Peninsulas. Their use of the pack ice,

therefore, is irregular and opportunistic.

Pack ice generally is present over most of the continental shelf of

the Bering Sea from December to June (Shapiro and Burns 1975;

McNutt 1981). In most years, the pack reaches ils maximum in

extent during late March, when its extreme southern limit coincides

approximately with the 200 m isobath (Burns and Harbo 19774 ). In

years of extreme icing, however, the maximum is attained in April

'Burns, J. J., and S. J. Harbo, Jr. 1977. An aerial census ofspolted seal, Phoca

vitu/ina /argha, and walruses, Odobenus rosmanlS in the ice front of Bering Sea. /n

Environmental assessment of the Alaskan continental shelf. Quarterly reports of

principal investigators, April-June 1977, Vol. I, p. 58-132. NOAA Environ. Res.

Lab., Boulder, Colo.
and extends farther south. This was its condition in April 1976

(Fig. 1).

The spring distribution of pinnipeds in parts of the Bering Sea

pack ice had been investigated previously, for example by Kenyon

(19605,19726 ), Krylov et al. (1964), Tikhomirov (1964), Fedoseev

(1965), Shustov (1965, 1969), Kosygin (1966), Burns (1970), and

Fay (1974), but no single study had investigated distribution

throughout the pack ice, as we were able to do in April 1976. April is

the optimal month for such an investigation, for the greatest proportion of the species occurring there at that time is likely to be lying

out on the ice, where they can be seen from the survey aircraft.

Three separate aerial surveys were conducted over the Bering Sea

pack ice in April 1976, with the common objective of describing the

distribution and density of the several species of pinnipeds residing

there. Surveys were conducted over 1) the eastern Bering Sea by the

National Marine Fisheries Service (H. W. Braham), 2) the ice front

in the southeastern and southcentral Bering Sea by the Alaska

Department of Fish and Game (1. J. Burns), and 3) the western

Bering Sea by the Pacific Institute of Fisheries and Oceanography

(G. A. Fedoseev). Although these surveys were conducted independently of each other, they were coordinated for purposes of

obtaining maximal areal coverage and compatible data. Because the

ice cover was more extensive than normal, we hypothesized that the

distribution of the pinnipeds also would be near its maximum in

extent. The aerial surveys conducted at that time offered an unusual

opportunity to test that hypothesis. The purpose of this paper is to

report on the combined results.

NATURAL mSTORY OF THE

SPECIES SURVEYED

The distribution and movements of the ice-associated pinnipeds

in the study area are closely linked with the advance and retreat of

the pack ice (Burns 1970; Fay 1974). A major part of the Pacific

walrus population migrates from the Bering Sea into the Chukchi

Sea from April to June; they return to the Bering Sea in October to

December (Belopol'skii 1939; Nikulin 1941; Fay 1982). In winter,

the entire population is distributed throughout the Bering pack ice,

but tends to concentrate in outer Bristol and Kuskokwim Bays and in

the north-central Bering Sea near S1. Lawrence Island (Kenyon

footnotes 5, 6). Because they feed mainly on bivalve mollusks,

walruses normally remain in waters <100 m deep, which coincides

with the usual distribution of pack ice over the continental shelf.

The young are born mainly in May, during the northward migration.

Ringed seals occur throughout the pack in the Bering Sea, with

highest densities in areas ofshore-fast ice (Fedoseev 1965; Johnson

et al. 1966; Burns 1970, 19737 ). This is the smallest of the iceassociated pinnipeds and it generally is solitary, congregating only

during the molt in May-June. The subadults which have wintered in

the Bering Sea begin to migrate northward in April; the adults and

pups migrate later (Burns 1970, unpubl. data). During the winter,

the highest concentrations of breeding adults occur 5-40 km

offshore in the fast ice zone; juveniles and subadults tend to occur

farther offshore (Tikhomirov 1966a; Burns 1970, footnote 7). The

pups usually are born in the first week of April in snow lairs on fast

'Kenyon, K. W. 1960. Aerial surveys of marine mammals in the Bering Sea, 23

February to 2 March 1960 and 25-28 April 1960. Unpubl. rep., 39 p. U.S. Bur. Sport

Fish. Wildl., Seattle, WA 98115.

"Kenyon, K. W. 1972. Aerial surveys of marine mammals in the Bering Sea, 6-16

ApriL 1972. Unpub!. rep., 79 p. U.S. Bur. Sport Fish. Wild!., Seattle, WA 98115.

'Burns, J. J. 1973. Marine mammal report. Project report, Fed. Aid Wild!.

Restor., Vo!. XlIl, 44 p. Alaska Dcp. Fish Game, Juneau, AK 99802.

26

ice, stable pack, or in pressure ridges (McLaren 1958; Burns 1970;

Smith and Stirling 1975), hence the pups and attendant adults

generally are not visible from the air during April.

Ribbon seals are unique to the North Pacific, occurring mainly in

the Bering and Okhotsk Seas (Shustov 1965). Two "reproductive

groups" in the Bering Sea were identified tentatively by Fedoseev

and Shmakova (19768 ), one in the western and the other in the

eastern zone. Nevertheless, Fedoseev's (1984) craniological comparison suggests that considerable intermixing ofthese groups takes

place. In April, ribbon seals characteristically occur on floes in the

ice front, where they give birth to their pups from western Bristol

Bay to within 50 km of the Soviet coast (Shustov 1965; Tikhomirov

1966a, b; Burns footnote 7; Fay 1974). Late spring concentrations

have been reported in Anadyr Gulf and near S1. Lawrence Island

(Tikhomirov 1966a).

The spotted or larga seal, an ice-associated relative of the coastal

harbor seal, frequents the ice front during winter and spring, with

the greatest numbers within 25 km of the irregular southern edge of

the pack. This seal is the most abundant species of the ice front in

southeastern Bering Sea (Tikhomirov 1964). Although present

throughout the front, the adults tend to congregate in eastern,

central, and western zones. During April, the adults occur as

isolated pairs, each with a single pup (Tikhomirov and Kosygin

1966; Burns et a1. 1972); later, during the molt, they congregate in

small herds and move northward to coastal and estuarine habitats in

the northern Bering and Chukchi Seas.

Bearded seals are widely distributed throughout the Bering Sea

pack ice in winter and spring, occurring principally in-waters <200

m deep, wherever polynyas, leads, and thin ice persist (Burns 1970).

In April, most bearded seals are solitary, except for females with

pups; occasionally several seals may rest on the same floe. Highest

densities in the pack ice have been reported near S1. Lawrence

Island, southeast of S1. Matthew Island, south of Nunivak Island,

and in Anadyr Gulf (Kosygin 1966). Local abundance may be

related to availability of food (Tikhomirov 1964). The northward

migration of bearded seals is underway in April (Bums 19679); they

later move northward into the Chukchi Sea with the retreating ice.

METHODS

Eastern Bering Sea Pack Ice Survey

The National Marine Fisheries Service (NMFS) survey covered

the northeastern Bering Sea on 13, 15, 19-23 April and southeastern

Bering and Bristol Bay on 6,8,9,12,13, 15, 17-19 April 1976 (Fig.

2). Strip census methods were applied, as described in Eberhardt

(1978). Initially, the survey was stratified using randomly selected

strips along lines of latitude 3 nmi (5.6 km) apart. Subsequently,

strips were chosen systematically and the surveys flown to delineate

further the areas of animal abundance (Krogman et al. 19781°).

Stratification methods were used in the analysis to reduce the

variance when estimating abundance.

'Fedoseev, G. A., and G. G. Shmakova. 1976. Some results of investigations of

spatial structure of ribbon and larga seals of the Bering Sea. Unpub!. rep., 9 p.

Special Meeting Marine Mammal Project, US-USSR Environmental Protection

Agreement, Moscow.

'Burns, J. J. 1967. The Pacific bearded seal. Alaska Dep. Fish Game, Juneau,

66 p.

IOKrogman, B. D., H. W. Braham, R. M. Sonntag, and R. G. Punsly. 1978. Early

spring distribution, density, and abundance of the Pacific walrus (Odobenus rosmarus) in 1976. Final report, R.U. 14,47 p. Outer Continental Shelf Environmental

Assessment Program, NOAA Environ. Res. Lab., Boulder, Colo.
The survey aircraft were the turbo-jet powered Grumman

Goose ll (N780) and the long-range Lockheed Neptune P2Y

(N48347). The P2Y was used only on 13 and 15 April. Airspeed

generally was 120-140 1m at survey altitudes of 100-350 m; most

surveys were flown at about 135 m. A crew of four people was used

for most surveys; there were two observers, one recorder, and one

alternate. Crew members changed jobs hourly to reduce observer

fatigue. The alternate observer periodically surveyed from the rear

of the aircraft to test for observer bias (e.g., for the number of

animals missed by forward observers or to validate species identification).

Information recorded included species, number of adults and

pups, local time of sighting, position to I nmi2 (obtained from an

onboard Global Navigation System, model GNS500), perpendicular angular distance from aircraft to animal (taken with an optical

clinometer, model Pm-5/360 PC, Suunto Instruments, Helsinki),

animal activity, and environmental conditions, including weather,

visibility, ice type, and ice cover.

Sighting angles were recorded during surveys and were later

converted to distance of the animal from the aircraft. When large

concentrations of animals were encountered, their occurrence

within different "sectors" of a strip transect were noted. Each of

those sectors was 0.25 statute mile wide (0.4 km), as follows: A =

0-0.25 mi; B = 0.25-0.5 mi; C = 0.5-0.75 mi; D = >0.75 mi.

Since observers could not see directly below the aircraft, sector

boundaries were offset to each side of the aircraft (approximately

ISO) during flights made in the Grumman Goose. Sector boundaries

for all flights were delineated by the clinometer. In this report,

density estimates of pinnipeds other than walruses were based upon

only those sightings made within the first 0.25 mi strip on each side

of the aircraft; total strip width therefore equaled 0.5 mi (0.8 km).

For walruses, strip width equaled I mi (1.61 km).

Southern Bering Sea Ice Front Survey

The Alaska Department of Fish and Game (ADF&G) surveys

were restricted to the ice front (Fig. 3). Their primary purpose was

to determine the distribution and relative abundance of spotted

seals. Flights were conducted on 8, 9, 11, 17, 19, 20, 21, and 23

April 1976. The aircraft used was the P2Y which had a large

Plexiglas observation compartment in the nose. A crew of three

persons usually occupied this compartment during the surveys; two

were primarily observers, but one also recorded. The third person

acted as a back-up observer whose function was to determine the

proportion of seals not seen by the primary observers, to verify

inclusion or omission of animals at the limit of transects, and to

replace primary observers when fatigued. On most flights, a primary observer counted on one side of the aircraft for 2 h, then

counted on the other side for 2 h, then rested for up to I h. Forward,

lateral, and downward visibilities from the observation compartment were excellent.

Survey procedures involved use of strip transects 0.5 nmi (0.93

km) wide on each side of the aircraft, for a total strip width of I nmi

(1.85 km). Angle indicators were mounted on each side of the

observation compartment to limit the outer boundaries of the strip.

The survey aircraft was equipped with a GNS500. To the extent

possible, survey altitude in the P2Y was maintained at 91 m. Lower

altitudes were flown when necessitated by weather. Flight speed

averaged 160 kn.

11Reference to trade names does not imply endorsement by any agencies represented by the authors.

27

Information recorded included species and number of animals

sighted, group size, animal activities, ice types, weather, local

time, and navigational information. Animal sightings were recorded continuously in I min time intervals.

The P2Y flight strips on 8, 9, and II April were selected at

random. Those surveys on 17 and 19 April were along preselected

flight lines designed to achieve a replicate, stratified, random sample in the recognized area of highest seal density. Systematic surveys, flown mainly in an east-west direction, covered the southern

portion ofthe ice front on 20 April and the northern part on 21 April.

Western Bering Sea Survey

The Pacific Institute of Fisheries and Oceanography (TINRO)

surveys involved extensive flights over the ice-covered regions of

north-central and northwestern Bering Sea. Survey lines generally

were oriented north-south and covered all ice types from the front to

Bering Strait. Surveys were flown on 12-15, 17, 19, and 21-26 April

1976. The aircraft employed was a Soviet UL-14 equipped with

standard navigation instruments.

Marine mammals were observed from the left side of the aircraft

by a single observer (Fedoseev) viewing through a bubble-type

window installed in the compartment aft of the flight deck. This

bubble window provided both vertical and horizontal visibility. The

observer also was the recorder.

Flight altitude was 200 m, with occasional descents to 100 m. A

strip transect equal in width to the altitude of the aircraft was used.

The outer limit of the transect was maintained by sighting a 45°

angle from the observation window. All animals observed were

recorded, but only those animals sighted within the strip were

included in the analysis.

Observation periods varied in duration, usually lasting I to 1.5 h,

followed by a short rest period. Information recorded for each 5-min

survey period included start and end time, start and end coordinates, distance covered, transect width, area surveyed, and kind and

number of animals sighted. Ice type was recorded by a hydrologist,

also on board the aircraft.

Accuracy of the Counts and Identifications

Only the animals sighted on the ice were included in the analyses,

since pinnipeds in the water are difficult to identify from aircraft.

Because the ability of the observers to sight animals on the ice was

recognized as being impaired by fog and snow, the segments of

survey strips covered during such periods of poor visibility were

routinely deleted from the analyses.

Walruses are easier to see from low-flying aircraft than are any of

the other pinnipeds surveyed, but because they tend to congregate

on the ice in dense herds, they are more difficult to count. In these

surveys, most ofthe small groups « 20) were believed to have been

counted accurately, but the numCers in the larger groups mostly

were estimated in round numbers.

The sightings of ringed seals probably were the least precise

because these seals are the smallest and the most shy (i.e., most

disturbed by aircraft) of any of the pinnipeds surveyed. Even under

the best of conditions, the numbers sighted on the ice in April

probably will be only a very small fraction of the numbers present,

since many of the animals (particularly females and pups) at that

time haul out in lairs under the snow, where they cannot be seen

from the air.

Ribbon seals usually react only slightly to the presence of aircraft, frequently remaining on the ice, even when the plane passes
directly overhead. They are easily identified by their characteristic

method of locomotion, as well as by their distinctive coloration.

During April, most of the ribbon seals sighted on the ice probably

are adult females and pups; adult males tend to remain in the water at

that time. The pups are more difficult to sight thim are the adults

because of their small size and white coloration.

Spotted seals also are easily identified by their locomotion, coloration, and the fact that the adults in April generally occur as pairs

on the ice, usually with a white-coated pup. These seals are more

disturbed by the aircraft than are the ribbon seals, hence tend to

move more rapidly and in a straight line to the water. Because ofthis

motion, the pups usually can be seen, despite their small size and

coloration.

Bearded seals are readily seen and identified from the air, because

oftheir large size. They usually are not frightened, often remaining

on the ice even when the aircraft passes directly over them. Most of

those sighted in April probably are subadults, which occur singly,

and adult females with pups; adult males tend to be in the water at

that time.

. where S2 = group size variance.

Abundance estimates with 95% confidence intervals were generated for each region covered by the NMFS surveys. Confidence

intervals were calculated as:

(7) T ± t.05(2)V VV(T).

The notation t.05(2)V refers to the critical value of t where alpha (u)

= .05 (I-u = .95) based upon a two-tailed test with V degrees of

freedom. Degrees of freedom were calculated as the total number of

survey strips minus the number of strata.

RESULTS

Analytical Methods

whereSi = variance ofR

n = number of survey strips

In the northern Bering Sea, walruses were concentrated to the

west and north of St. Lawrence Island, in a pattern suggesting

movement through Anadyr Strait (between St. Lawrence Island and

the Chukchi Peninsula), toward Bering Strait (Figs. 4, 5). The

numbers north of St. Lawrence Island apparently were greater than

had been reported previously in this month by Kenyon (footnotes 5,

6). Kenyon's April surveys showed the highest concentrations in

this region to be southwest of St. Lawrence Island and in Anadyr

Strait. The overall density of animals in the St. Lawrence Island

area in April 1976 was 2.77 ±O.77 (mean ± SD) individuals/nmi2

(Table I, unstratified estimate). Data from the TINRO surveys in

that area suggest that the abundance estimate from the NMFS

surveys of 25,320±9,744 (mean ± 95% confidence interval) animals was conservative (Krogman et aI. footnote 10).

Walruses were conspicuously absent in the central Bering Sea

from lat. 59° to 63°N, as well as in Norton Sound and north of lat.

65°N. The ice in those areas was considerably more compact than it

was to the north and west ofSt. Lawrence Island and in Bristol Bay.

Walruses were found in the southeastern part of the Bering Sea,

particularly from the Pribilof Islands to Bristol Bay. Highest densities were found I) around the Pribilof Islands, 2) east of the

Pribilofs, approximately 10-40 Ian north of the ice front, 3) southwest of Cape Newenham, and 4) in outer Bristol Bay (Figs. 4, 6).

Walruses were nearly absent from inner Bristol Bay, including

Round Island, a traditional summer haulout site. Densities also were

lower along the ice front than deeper in the pack, indicating that

walruses prefer the heavier pack.

Walruses were most dispersed in Bristol Bay (Table 2) than near

St. Lawrence Island (Table I}. The density estimate (unstratified)

for Bristol Bay was 0.82±0.22 animals/nmi2• An abundance estimate of 30,358±13,933 (95% CI) was derived from the NMFS

survey area (Table 2), to which an additional 1,319 animals should

be added for the areas covered exclusively by the ADF&G surveys

(Krogman et al. footnote 10).

Ringed Seals

animal abundance in stratum

total area of stratum

density of animals per square nautical mile

number of animals in the ith survey strip

area of the ith survey strip

where 1),

A

whereR

Yi

Xi

(3) 1), = iu

(4) V(1),) = A(A - IXi)Sk

where V(1),) = variance ofTy.

Data from the TINRO surveys were computer-plotted directly as

numbers of animals sighted per 5-min time segment of each transect. Data from the NMFS and ADF&G surveys were plotted as

numbers of animals sighted per I-min of time within each 10' x 10'

(0.3 Ian x 0.3 km) block of latitude and longitude. Where more

than one survey strip crossed a 10' x 10' (0.3 km x 0.3 km) block,

the data were averaged to give equal weight to the survey effort in all

blocks.

The data were stratified by the method developed experimentally

by Krogman et al. (footnote 10). Estimates of regional density and

abundance were computed only from the NMFS surveys by

"Method I" of Estes and Gilbert (1978):

Average group size was calculated as;

(5)G = IYi / IOi

whereG

0;

average group size in stratum

number of observations (= groups in the ith survey

strip)

In the northern Bering Sea, ringed seals were found to be most

closely associated with shorefast and dense pack ice, except just

west of St. Lawrence Island (Figs. 7, 8). Along the Soviet coast,

they were most abundant in the ice ofthe eastern Chukchi Peninsula

and were numerous also in the southwestern Anadyr ice massif,

where the pack ice is characteristically very dense, and in

28
Table I.-Walrus statistics from NMFS aerial surveys conducted 13·23 April 1976 in northern Bering Sea. Data were treated by stratified and unstratified methods.

Estimated

Stratum I Percent No. of walruses counted Average group size total/stratum

Density area of area No. of Individuals Animals Groups/nmi' No. of Variance

stratum (nmi') sampled lran:'lCcts Total per nmit Variance pt;r group Variance No. groups Variance walruses (x 10')

I 6.683 5.00 12 32 0.10 >0.00 6.40 21.71 O.oJ >0.00 641 0.12

2 394 14.57 6 12 0.21 0.01 3.00 I 83 007 >0.00 82 >0.00

3 315 19.28 3 66 1.09 0.59 4.13 3.03 0.26 0.03 342 0.05

4 3,945 10.90 13 698 1.62 020 8.13 3.12 0.20 >0.00 6,401 2.74

5 1,343 5.44 3 267 3.66 0.82 20.54 124.92 0.18 >0.00 4.908 1.40

6 133 14.63 2 254 13.09 195.59 18.14 88.27 0.72 0.45 1.736 2.Q4

7 86 8.69 2 250 33.30 1,102.89 125.00 625.00 0.27 0.07 2,876 7.51

8 44 17.40 2 451 59.39 3,522.23 56.37 1,765.64 1.05 1.11 2,592 5.54

9 87 1306 3 750 65.69 425.86 83.33 600.00 0.79 0.07 5,742 2.83

Total

stratified 13,030 46 2,780 25,320 2313

Unstratified 12,878 7.80 17 2,780 2.77 0.60 17.94 12.05 0.15 >0.00 35.622 91.96

1Areas were approximated by straight line integration, thus minor discrepancies exist between sum of strata and total unstratified region.

Table 2.-Walrus statistics from NMFS aerial surveys conducted 6·15 April 1976 in southeastern Bering Sea. Data were treated by stratified and unstratified methods.

Estimated

Stratum l Percent No. of walruses counted Average group size total/stratum

Density area of area No. of Individuals Animals Groups/nmi' No. of Variance

stratum (nmi') sampled transects Total per nmi 2 Variance per group Variance No. groups Variance walruses (x 106 )

I 1,472 5.32 3 0 0.00 0.00 0.00 0.00 0

2 1,772 5.62 7 I 0.01 >0.00 1.00 >0.00 18 >0.00

3 8,037 6.27 15 13 0.03 >000 1.86 0.31 0.01 >0.00 207 0.00

4 18.063 8.82 37 298 0.19 >0.00 5.05 1.83 0.04 >0.00 3,378 1.54

5 3,895 14.09 36 712 1.30 0.06 3.61 0.21 0.36 >0.00 5,054 0.81

6 652 9.67 4 124 1.97 0.65 2.70 0.18 0.73 0.07 1,282 0.25

7 272 6.97 2 81 4.28 13.20 4.05 1.38 1.06 2.15 1,163 0.91

8 556 5.02 2 273 9.80 46.46 21.00 120.21 0.47 0.05 5,441 13.64

9 370 6.22 2 302 13.12 37.72 20.13 73.20 0.65 0.05 4,854 4.84

10 167 8.71 2 344 23.99 284.42 IC.42 35.85 2.30 0.78 3.947 7.03

II 110 5.78 2 290 45.72 1,791.73 1813 27.59 2.52 5.45 5,014 20.30

Total

stratified 35,364 112 2,438 30,358 49.32

Unstratified 35,230 8.40 32 2,438 0.82 005 599 0.63 0.14 >0.00 29,014 58.80

1Areas were approximated hy straight line integration. thus minor discrepancies exist between sum of strata dod total unstratified region.

Karaginskii Gulf (Fig. 8). Ringed seals were not numerous

offshore, except to the west of St. Lawrence Island (Fig. 7), where

many were seen in a rather narrow band associated with thin ice.

The mea!] group size (± 95% CI) north of lat. 600

N was 1.20±0.08

(Table 3).

In southeastern Bering Sea, ringed seals were present from north

of the Pribilof Islands to outer Bristol Bay, mainly well north of the

ice front (Figs. 7, 8,9). Densities were low and group size south of

lat. 600N was 1.04±0.02 (Table 3). Those seen 15 to 50 km offshore

probably were immature or nonbreeding animals. These animals

probably move southward with the advancing pack ice in late

winter, away from the preferred breeding habitat in the north.

Ribbon Seals

Apparently, ribbon seals were absent north of lat. 61 oN. except in

one location southwest of St. Lawrence Island (Figs. 10, II) but

were abundant from the Pribilof Islands west to Olyutorskii Bay

(Fig .. 12). Most of these were situated from the ice edge to about 100

km north. The distribution appears to have been continuous, with

Table 3.-Comparative statistics for ribbon and ringed seals from MFS aerial surveys conducted 6-23 April in northern and southeastern Bering Sea.

Estimated

Stratum Percent No. "I' seals counted Average group size total/stratum

Species and area of area No. of Individuals Seals Groups/nmi' No. of

stratum (nmi') sampled transects Total per nmi 2 Variance per group Variance No. groups Variance seals Variance

Ribbon seals.

southeastern 35.441 4.21 32 9 0.006 >0.00 1.13 0.016 0.005 >0.00 214 5,236

Ribbon seals.

nort~ern 13,547 3.76 18 0 0000 0.00 0 0.000

Ringed seals,

southeastern 35,441 4.21 32 25 0.017 >0.00 1.04 0.002 0.016 >0.00 594 66,549

Ringed seals,

northern 13,547 3.76 18 30 0.059 0.002 1.20 0.040 0.049 0.01 799 326,959

29
no major clumping of breeding groups into eastern and western

segments, as suggested by Fedoseev and Shmakova (footnote 8).

Density estimates generated from the NMFS surveys were extremely low (Table 3). No estimates were generated for areas covered by the ADF&G and TINRO surveys.

Spotted Seals

Although virtually absent from the northern Bering Sea, spotted

seals were widely distributed in the ice front from Bristol Bay to

Karaginskii Gulf (Figs. 13, 14, 15). The highest densities were in I)

outer Bristol Bay, 2) central Bering Sea from about long. 175°W to

180°, and 3) Karaginskii Gulf. Density estimates (stratified) from

the NMFS surveys in the Bristol Bay region ranged from about 0.05

to 6.3 seals/nmi2, with a mean (not stratified) of 0.37 ±0.06 (Table

4). Densities clearly were greatest in the ice front, decreasing

northward into the pack ice. Seals collected by Burns (unpubl. data)

in the Bristol Bay concentration in March 1976 were principally

subaduits, ~uggesting that there is some age-segregation at that

time. The larger groups there also included a few harbor seals,

which are abundant in the nearshore zone of that area.

Bearded Seals

These seals were nearly ubiquitous in the Bering Sea pack ice but

apparently were concentrated in three or four areas: I) To the west

and north of St. Lawrence Island, 2) in southwestern Anadyr Gulf,

3) about 40 to 60 km north of the ice front in the central Bering Sea,

and 4) in the area between the PribilofIslands and Bristol Bay (Figs.

16, 17, 18). A few were sighted also along the Koryak coast and in

Karaginskii Gulf. Densities computed from the NMFS surveys were

higher in the northern than in the southern areas (Tables 5, 6).

Overall Relative Abundance

As is apparent from the foregoing descriptions of the distribution

of each species, the pinnipeds of the Bering Sea pack ice were not

uniformly distributed. Each species tended to be most abundant in a

slightly to extremely different part of the pack ice than did the

others, presumably because of different habitat requirements and,

perhaps, interspecific competition for food or space. For walruses,

ringed seals, and bearded seals, the centers of abundance were well

Table 4.-Spotted seal statistics from NMFS aerial surveys conducted 6-15 April 1976 in southeastern Bering Sea. Data were treated by stratified and unstratified

methods.

Estimated

Stratum' Percent No. of spotted seals counted Average group size Groups/nmi' total/stratum

Density area of area No. of Indi viduals Variance Seal; Variance Variance No. of Variance

stratum (nmi') sampled transects Total per nmi2 (X 10-3) per group (X 10-3) No. groups (X 10-3) seals (x 106)

I 5,872 3.34 12 9 0.046 0.1 1.50 11.7 0.03 >0.0 269 0.02

2 8,475 4.03 22 18 0.053 >0.0 1.20 1.1 0.04 >0.0 446 0.03

3 14.762 402 30 41 0.06-) >0.0 1.58 1.6 0.04 >0.0 1.020 0.08

4 382 5.05 3 2 0.121 1.0 1.00 0.0 0.12 1.0 40 >0.00

5 217 17.08 6 7 0.189 0.8 1.40 6.0 0.14 0.4 41 >0.00

6 581 3.41 2 7 0.354 4.8 1.75 22.9 0.20 0.9 206 0.02

7 240 4.55 2 4 0.366 I.7 1.33 11.1 0.28 0.3 88 >0.00

8 214 8.60 4 7 0.380 2.7 1.40 6.0 0.27 1.1 81 >0.00

9 2,530 6.45 19 84 0.515 1.0 1.59 1.0 0.33 0.3 1,302 0.06

10 733 3.74 2 27 0.985 1.0 1.23 0.8 0.80 0.2 722 >0.00

II 108 9.60 4 12 1.161 54.2 2.40 6.0 0.48 7.3 125 >0.00

12 476 2.97 3 27 1.909 106.9 2.08 5.7 0.92 11.2 909 0.24

13 385 3.92 2 54 2.577 241.9 1.46 2.0 2.45 113.6 1,377 0.34

14 666 6.06 8 254 6.290 492.4 4.62 74.6 1.36 15.9 4.190 2.05

Total

stratified 35,587 119 553 10,876 2.84

Unstratified 35,441 4.21 32 552 0.370 3.3 2.21 4.4 0.17 0.3 13.125 39.79

'Areas were approximated by straight line integration. thus minor discrepancies exist between sum of strata and total unstratified region.

Table S.-Bearded seal statistics from NMFS aerial surveys conducted 12-23 April 1976 in northern Bering Sea. Data were treated by stratified and unstratified methods,

Estimated

Stratum' Percent No. of bearded seals counted Average group size Groups/nmi' total/stratum

Density area of area No. of Individuals Variance Seals Variance Variance No. of Variance

stra!um (nmi') sampled transects Total per nmi2 (X 10-') per group (X 10- 3) No. groups (X 10- 3) seals (x 10') ._._--_..._.

I 3.580 5.66 18 7 0.035 >0.0 1.00 0.0 0.04 >0.0 124 1.6

2 6,642 2.13 9 II 0.078 0.1 1.10 1.0 0.07 0.1 516 43.3

3 2.738 3.96 8 14 0.129 0.3 1.17 1.3 0.11 0.2 354 26.6

4 189 2.40 2 2 0.440 407.8 1.00 0.0 0.44 407.8 83 142.3

5 43 8.70 2 2 0.537 0.0 1.00 0.0 0.54 0.0 23 0.0

6 221 8.80 2 8 0.822 6.6 2.00 100.0 0.41 1.7 182 3.1

7 86 6.53 3 5 0.893 3.1 1.67 11.1 0.54 0.0 77 0.2

8 131 5.81 3 7 0.918 41.6 1.75 22.9 0.53 13.6 120 6.8

9 129 4.34 2 6 1.067 >0.0 1.50 8.3 0.71 1.6 138 >0.0

10 43 8.70 2 10 2.682 260.2 2.00 10.0 1.34 65.0 115 4.4

Total

stratified 13.802 51 72 1,732 228.3

Unstratified 13,547 3.76 18 72 0.141 0.1 1.35 1.0 0.10 >0.0 1,917 186.6

JAreas were approximated by straight line integration, thus minor discrepancies exist between sum of strata and total unstratified region.

30
Thble 6.-Bearded seal statistics from NMFS aerial surveys conducted 6-15 April 1976 in southeastern Bering Sea. Data were treated by stratified and unstratified

methods.

Estimated

Stratum' Percent No. of bearded seals counted Average group size Groups/nmi' total/stratum

Density area of area No. of Individuals Variance Seals Variance Variance No. of Variance

stratum (nmi') sampled transects Total per nmi' (X 10-3) per group (X 10-3) No. groups (X 10-3) seals (X 10")

I 14.040 4.07 34 12 0.021 >0.0 1.20 1.8 0.02 >0.0 295 29.4

2 5,974 3.71 27 5 0.023 >0.0 1.00 0.0 0.02 >0.0 135 2.7

3 5,883 3.44 19 5 0.025 >0.0 1.00 0.0 0.03 >0.0 145 5.6

4 4,586 4.15 18 9 0.047 >0.0 1.13 1.6 0.04 >0.0 217 6.6

5 382 11.45 II 4 0.091 0.2 1.00 0.0 0.09 0.2 35 0.3

6 269 14.01 6 6 0.159 0.3 1.20 4.0 0.13 0.2 43 0.2

7 165 5.90 2 2 0.205 4.0 2.00 0.10 34 1.0

8 1,535 7.40 18 24 0.211 0.3 1.09 0.8 0.19 0.3 324 7.4

9 471 3.87 2 4 0.219 0.7 1.00 0.0 0.22 0.7 103 1.4

10 218 6.34 2 4 0.289 7.4 1.33 11.1 0.22 2.7 63 3.3

II 322 7.28 4 7 0.298 0.4 1.17 2.8 0.26 0.3 96 0.4

12 110 4.98 2 2 0.365 10.3 1.00 0.0 0.37 10.3 40 1.2

13 641 8.19 II 21 0.400 1.5 1.17 0.8 0.34 1.1 256 5.7

14 495 4.35 2 9 0.418 2.2 1.00 0.0 0.42 2.2 2m 5.1

15 374 4.35 6 8 0.491 1.1 1.14 2.0 0.43 1.4 184 1.5

16 157 2.91 2 8 1.748 308.4 2.67 277.8 0.66 43.4 275 71.8

Total

stratified 35,622 166 130 2,452 145.9

Unstratified 35,441 4.21 32 124 0.083 >0.0 1.16 0.3 0.07 >0.0 2,948 367.6

I Areas were approximated by straight line integration, thus minor discrepancies exist between sum ofstrata and total unstratified region.

inside of the pack ice; those of the ribbon and spotted seals were in

the ice front itself.

Within the ice front, the spotted seals showed essentially three

centers of abundance, in the southeastern, central, and southwestern sectors, whereas the ribbon seals were centered primarily in the

west-central front zone (Fig. 19). In the inner pack ice, walruses

were centered in the southeastern and north-central sectors, as had

been shown previously by Kenyon (footnotes 5, 6).

The ringed seals were abundant in patches in the southwestern,

northern, and southeastern sectors, mainly outside of the areas

inhabited by the walruses. Bearded seals were most abundant in the

southeastern, central, and northern sectors in and around the areas

occupied by both the walruses and the ringed seals.

Compartmenting the surveyed area into six sectors, in which the

survey effort was approximately comparable, we find that the

ringed and bearded seals and walruses all showed their greatest

abundance within the same (north-central) sector, and that both the

ribbon and the spotted seal were most abundant in the west-central

sector (Table 7). Although walruses and spotted seals were the two

most frequently sighted species in the southeastern sector, each was

more abundant in another part of the Bering Sea pack ice; similarly,

Table 7.-Comparative abundance of pinnipeds sighted (no./min.) in relation

to location in the Bering Sea pack ice, April 1976.'

Sector of pack ice'

South· East- West· South· North· North·

Pinniped eastern central central western central western

Walrus 1.2·76.0 1.2-8.2 0.2- 1.0 0 0.6-197.5 0.4-1.3

Ringed seal 0.2- 1.6 0.2-0.8 0.2 0.2- 1.0 0.2- 4.4 0.2-0.6

Ribbon seal 0.2- 0.6 0.2-0.9 0.2- 6.0 0.2- 1.2 3.0 0

SJXlued seal 0.4-22.0 0.4-7.0 0.4-24.5 0.5-11.9 0 0.4

Bearded seal 0.2- 2.2 0.2-0.9 0.2- 3.0 0.5- 1.0 0.2- 5.0 0.2-3.0

'Data from all surveys, combined.

'Southeastern = long. 160° to 168°W, south of lat. 61°N; East-central = long.

168° to 174°W, south of lat. 61°N; West-central = long. 174°W to 176°E, south

of lat. 61°N; Southwestern = long. 176° to 162°E; North-central = long. 168° to

I76°W, north of Jat. 61°N; Northwestern = long. J76°W to J78°E, north of lat.

61°N.

31

ribbon and ringed seals showed centers of abundance in the southwestern sector, but each was more abundant elsewhere.

DISCUSSION

The winter pack ice of the Bering Sea is by no means a uniform

covering over the water, nor is the marine environment beneath it of

uniform physical or biotic composition (Hood and Calder 1981). A

wide· variety of ice and aquatic habitats is available here, as is

indicated by the unusual diversity of marine mammals inhabiting

this region (Fay 1974). Because the margin of the ice was exceptionally far south in April 1976, extending to the edge of the continental

shelf in the eastern Bering Sea and well beyond it in the west, the

variety of habitats available to these mammals was even greater than

normal. The partitioning of those habitats among the fi ve species of

ice-associated pinnipeds, therefore, probably was about maximal at

that time.

The actual densities of pinnipeds in each sector of the ice certainly were greater than could be estimated from the counts along

the survey strips, for only the animals that were lying on the ice were

included in the computations. At all times, some proportion of the

animals is in the water, swimming, feeding, or courting, where only

a small proportion of them can be seen from the air. For this reason,

each of the estimates of abundance certainly is very conservative,

and the degree of conservatism differs greatly between species. For

example, the probability is very high that a much lower proportion

of the ringed seals than of any other species was on the ice, and a

much higher proportion of walruses and spotted seals. Therefore,

comparison of estimated densities among the five species within

any given region or overall is not a reliable indicator of their relative

abundance. Nevertheless, the estimated densities of a given species

in different areas probably can be relied on as approximations of

that species' relative abundance in each area.

Nearly all of the walruses which were sighted during the several

aerial surveys described in this and earlier reports were situated in

the north-central sector near St. Lawrence Island, and in the southeastern sector, between Bristol Bay and the PribiiofIslands. During

the winter, these are major areas of ice formation and divergence,
where leads and polynyas are plentiful (Burns et al. 198012), and the

benthic food supply presumably is adequate. Ringed and bearded

seals, like the walruses, also were situated for the most part well

north of the southern border of the pack ice, but they were more

widely distributed, presumably because of their greater ability to

make and maintain breathing holes in even the denser parts of the

pack. The distribution of the bearded seal~, in general, overlapped

those of both the walruses and the ringed seals to a high degree but

extended also into a broad sector of the western ice where neither of

the other two species was sighted. Earlier, Braham et al. (197713 )

had indicated that the mean group size of bearded seals in the

northern Bering Sea was significantly larger than in the southeastern

sector, implying that more of the northern animals were pairs of

adults. Reevaluation of those data, however, indicates no difference

between sectors.

Most ofthe ringed sealssighted during our surveys probably were

immature or nonbreeding individuals, for the breeding adults in this

month (April) mainly inhabit the shorefast ice and haul out only in

lairs beneath the drifted snow (Fedoseev 1965; Burns 1970; Smith

and Stirling 1975). The presence of these seals in considerable

numbers in the southeastern sector of the Bering Sea pack ice is

reported here for the first time. Previous information from that

region by Kosygin (1966) from shipboard surveys in April 1962 and

1963, indicated that they were absent there. Their regular presence

was confirmed, however, by several shipboard sightings from the

icebreaker CGC Glacier in April 1971 (1. J. Burns, unpubl. data)

and by numerous shipboard sightings from the ZRS Zvyagino in

February-March 1981, during joint Soviet-American investigations

of marine mammals.14

The predominant inhabitants of the outer 200 km of the pack, all

across the Bering Sea, were the ribbon and spotted seals, whose

preferred pupping habitat appears to be in the "front" zone, just

inside the southern edge of the pack ice (Burns et al. 1972, footnote

12). The front is made up of more or less rectangular floes, about 10

to 20 m in diameter, which are formed from larger fields ofice by the

action ofsea swells. Ribbon seals were found throughout the front,

from Bristol Bay to Karaginskii Gulf, but were most abundant in the

west-central sector, over deep waters south of the continental shelf.

Spotted seals also were widely distributed in the front but tended to

be concentrated only in those parts which were situated over waters

about 200 m or less in depth, i.e., along the Koryak-Kamchatka

coast, in the central sector, and in southern Bristol Bay. A high

proportion of those in Bristol Bay appeared to be immature and

nonbreeding animals, with which were mixed a few harbor seals.

Pinnipeds were scarce to absent in the ice over most ofthe eastern

Bering Sea shelf, north of lat. 60o

N, as noted in previous surveys by

Kcnyon (footnotes 5, 6). That region, which comprises most of the

inner shelf oceanographic domain, appears to be shunned in part

because of its dense, heavy ice cover (McNutt 1981); it may be little

used also because of poor secondary production of zooplankton,

ichthyoplankton, and benthos on which forage fishes and the pinnipeds themselves might feed (Alton 1974; Motoda and Minoda

1974; Waldron 1981).

"Burns, J. J., L. H. Shapiro, and F. H. Fay. 1980. The relationships of marine

mammal distributions, densities, and activities to sea ice conditions. Final report.

R.U. 248/249,172 p. Outer Continental Shelf Environmental Assessment Program,

NOAA Environ. Res. Lab., Boulder, Colo.

I3Braham, H. w., R. D. Everitt, B. D. Krogman, D. J. Rugh, and D. E. Withrow.

1977. Marine mammals of the Bering Sea: Preliminary analysis of distribution and

abundance, 1975-76. Processed rep., 90 p. Northwest and Alaska Fisheries Center,

National Marine Fisheries Service, NOAA, Seattle, WA 98115.

"F. H. Fay, Associate Professor, Institute of Marine Science, University of

Alaska, Fairbanks, AK 99701, pers. commun. April 1981.

32

ACKNOVVLEDG~ENTS

Robert Everitt participated in all phases ofthe NMFS surveys and

is especially thanked for his significant contributions. Samuel J.

Harbo, Jr. assisted in the design of surveys conducted by the

ADF&G, and David James participated in all flights. Vitali N.

Gol'ts¥v was an observer'during I d ofthe TINRO surveys. National

Marine Mammal Laboratory personnel who provided valuable assistance were: Teresa Bray, Clifford Fiscus, Leola Hietala, Richard

Punsley, and Ronald Sonntag. We also thaitk James A. Estes, U.S.

Fish and Wildlife Service, and Francis H. Fay, Institute of Marine

Science, University of Alaska, for their suggestions and discussions

during the initial stages ofthe research. Appreciation is extended to

Douglas G. Chapman, University of Washington, and to Michael F.

Tillman, National Marine Mammal Laboratory, for statistical consultation. Ian Stirling contributed valuable suggestions and reviewed'the manuscript.

While in Nome we received invaluable assistance from Carl

Grauvogel and Ed Muktoyuk, and in King Salmon from Jim Faro

and Nick Steen, all with the Alaska Department of Fish and Game.

Aircraft logistics for the NMFS and ADF&G surveys were provided

by the Office of Aircraft Services, U.S. Fish and Wildlife Service,

Anchorage, Alaska.

We also wish to express our gratitude to A. A. Visnevskii, Y. M.

Malyshev, and V. F. Omel'chenko, hydrologists from the Kolymsk

section of the Hydrometeorological Service, Magadan, USSR, for

their help during the TINRO surveys.

Support for the NMFS and ADF&G research came, in part, from

contracts administered by the Alaska Outer Continental Shelf Environmental Assessment Program Office, NOAA, Juneau, through

an interagency agreement with the Bureau of Land Management,

U.S. Department of the Interior.

LITERATURE CITED

ALTON, M. S.

1974. Bering Sea benthos as a food resource for demersal fish populations. In

D. W. Hood and E. J. Kelley (editors), Oceanography of the Bering Sea, p.

257-277. Institute of Marine Science, Univ. Alaska, Fairbanks.

BELOPOL'SKll, L. O.

1939. On the migrations and ecology of reproduction of the Pacific walrus

(Odobaenus rosmarus divergens llliger). ZooI. Zh. 18:762-774.

BURNS, J. J.

1970. Remarks on the distribution and natural history of pagophilic pinnipeds

in the Bering and Chukchi Seas. J. Mammal. 51:445-454.

BURNS, J. J., G. C. RAY, F. H. FAY, and P. D. SHAUGHNESSY.

1972. Adoption of a strange pup by the ice-inhabiting harbor seal, Phoca

vi/ulina largha. J. Mammal. 53:594-598.

EBERHARDT, L. L.

1978. Transect methods for population studies. J. Wildl. Manage. 42: 1-31.

ESTES, J. A., and J. R. GILBERT.

1978. Evaluation of an aerial survey of Pacific walruses (Odobenus rosmarus

divergens). J. Fish. Res. Board Can. 35: 1130- I 140.

FAY, F. H.

1974. The role of ice in the ecology of marine mammals of the Bering Sea. In

D. W. Hood and E. J. Kelley (editors), Oceanography of the Bering Sea, p.

383-399. Institute of Marine Science, Univ. Alaska, Fairbanks.

1982. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens lIliger. North Am. Fauna 74, 279 p. U.S. Fish Wildl. Serv.,

Washington, D.C.

FEDOSEEV, G. A.

1965. Comparative characteristics of populations of the ringed sea'l of coastal

waters of the Chukchi Peninsula. Izv. TlNRO 59: 194-212.

1984. Use of nonmetrical characters ofskulls of Bering Sea seals in a study of

the phenotypic structure of their populations. U.S. Dep. Commer. , NOAA

Tech. Rep. NMFS 12:49-54.

HOOD, D. w., and J. A. CALDER (editors).

1981. The eastern Bering Sea shelf: oceanography and resources. Vols. 1and

2, 1339 p. Univ. Washington Press, Seattle.
JOHNSON, M. L., C. H. FISCUS, B. T. OSTENSON, and M. L. BARBOUR.

1966. Marine mammals. In N. J. Wilimovsky and J. N. Wolfe (editors),

Environment of the Cape Thompson region, Alaska, p. 877-924. U.S. At.

Energy Comm., Wash., D.C.

KOSYGIN, G. M.

1966. Distribution and some features of the biology of pinnipeds of the

Bering Sea (spring-summer period, 1963). Izv. T1NRO 58:117-124.

KRYLOV, V. I., G. A: FEDOSEEV, and A. P. SHUSTOV.

1964. Pinnipeds of the Far East. Pischevaya Promyshlennost', Moscow,

58 p.

McLAREN, I. A.

1958. The biology of the ringed seal (Phoca hispit!a Schreber) in the eastern

Canadian arctic. Fish. Res. Board Can., Bull. 118,97 p.

McNUTT, S. L.

1981. Remote sensing analysis of ice growth and distribution in the eastern

Bering Sea. In D. W. Hood andJ. A. Calder(editors), The eastern Bering Sea

shelf: oceanography and resources, Vol. I, p. 141-165. Univ. Washington

Press, Seattle.

MOTODA, S., and T. MINODA.

1974. Plankton of the Bering Sea.ln D. W. Hood and E. J. Kelley (editors),

Oceanography of the Bering Sea, p. 207-241. Institute of Marine Science,

Univ. Alaska, Fairbanks.

NIKULlN, P. G.

1941. Chukchi walrus. Izv. TINRO 20:21-59.

SHAPIRO, L. H., and J. J. BURNS.

1975. Satellite observations ofsea ice-nlovement in the Bering Strait region.

In G. Weller and S. A. Bowling (editors), Climate of the Arctic, p. 379-

386. Geophysical Institute, Univ. Alaska, Fairbanks.

33

SHUSTOV, A. P.

1965. The distribution of ribbon seal (Histriophocafasciata) in the Bering

Sea. In E. N. Pavlovskii, B. A. Zenkovich, S. E. Kleinenberg, and K. K.

Chapskii (editors), Marine mammals, p. 118-121. Nauka, Moscow.

1969. Test of a quantitative aerovisual survey of seals in the north-western

part of the Bering Sea. In V. A. Arseniev, B. A. Zenkovich, and K. K.

Chapskii (editors), Marine mammals, p. 111-116. Nauka, Moscow.

SMITH, T. G., and I. STIRLING.

1975. The breeding habitat of the ringed seal (Phoca hispida). The birth lair

and associated structures. Can. J. Zool. 53:1297-1305.

TIKHOMIROV, E. A.

1964. On the distribution and biology of pinnipeds of the Bering Sea. In P. A.

Moiseev, A. G. Kaganovskii, and I. V. Kisevetter (editors), Soviet fisheries

investigations in the northeastern part of the Pacific Ocean, Pt. 3, p. 277-

285. Pischeveya Promyshlennost', Moscow.

1966a. Identifying the species of Far Eastern seals from an airplane. Izv.

T1NRO 58:163-172.

1966b. Development and variation of coloration in the pelage of the ribbon

seal. Izv. TINRO 58:239-240.

TIKHOMIROV, E. A., and G. M. KOSYGIN.

1966. Prospects for commercial sealing in the Bering Sea. Rybn. Khoz.

42(9):25-28.

WAlDRON, K. D.

1981. Ichthyoplankton.ln D. W. Hood and J. A. Calder(editors), The eastern

Bering Sea shelf: oceanography and resources, Vol. I, p. 471-493. Univ.

Washington Press, Seattle.
,." "Ii I •

OCEAN

St. Lawrence I.

CHUKCHI SEA

Is.

• ~. 111"_ ~-­

St. Matthew 1...

Aleutian

(:)Wrangell.

".0 •

"

••

PA CIFIC

1700 E

USSR

d ~,~~ Ie r Koroginskii ~~ E

Gulf :/ .....~~~~~ ~()

JOI

./ BERING SEA

Commander

'\ Is.

Figure I.-Study area in wbicb cooperative Soviet-American aerial surveys were conducted. Ice edge is approximate maximum in Bering Sea in April 1976.

34
65

176 172 168

u./"

. . . . . .. :..

164 160

·.r·

~'"..'

."

65

63 63

59

61

'.. ,If

:::'- '~....

Bering Sea

57 c;J

57

""

+11 .

•

55 55

176 172 168 164 160 156

59

61

Figure 2.-Computer plot of aerial survey stripsflown over eastern Bering Sea by NMFS scientists in April 1976. Dots depict corners of 10 x 10 minute latitude

by longitude cells which were overflown by the aircraft.

35
179 177 173 169 165 161 157

59

57

173 169 165 161 157

Bering Sea

179 177

59

55 r-t:11 II II II II II II II II II II II I I II I I II I I II II II II II I I II I I Ii I I II I I II I I I, I I II I ' I, !"'Flft ,'fer' I II II'f!", I , , I II , I II I55

57

w

0'>

Figure 3.-Computer plot of aerial survey strips flown in southeastern Bering Sea by ADF&G scientists in April 1976. Dots depict corners oflO x 10 minute latitude by longitude cells which were overflown by

the aircraft. The southern limit of surveys marks the southern edge of the pack ice; the northern limit of surveys approximates the inner margin of the ice front.
176 172 168 164 160 156

59

65

57

156

.

•

.. ..,

·.r·

~.~ . . ... .

160

,

63

" ... " oA ". ", . ,~

,0

61

.-

168 164

<:)

··:::::.. :··..·.. ::::1::: . ········::::1: . ........... '1" ...... ·T.. ~A

......... 1.1". ..:::::.. III:III::I:::::I :I::I::I:::::::::::::::.::.:::::: ..::::::::::::::::I:::I 11111: :;.::I::::::::.:::::: .

... ::: 1.1.::::. '1: :lfl,I1p1'11,:1.11. Ja·: '1:'" ...... :.. : :. IJ .. .. .. rT IT· I'I"T' . q

.:::: :::1. ::1:f.rll'l:rl.l:I:I:: .::1 ::i::::1 J :1'1 :'::1':' ::I:h

:

r :'. .. .u-, ..,.. ,: .:.: .... I ,'n:II'-T\::" . "",' . . .• . .•.. '" q

·::·.IU1 :::: 1;;·

..

(>

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. II 1'1' 'I'j' ..1.

1

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IP~::··"""." . .::

.JJJ¥:I~I ':1:::::"::"::1:

I::::::::::::::::::

:: 1I:::::::1J:::::::::1

WFlLRUS

SIGHTINGS PER MINUTE

I 7.238

I 21.598

I 35.959

I 50.320

m 69.500

I 75.167

B 76.000

II 83.333

B 88.750

B 197.500

61

63

57

59

65

Figure 4.-Computer plots of walrus density from NMFS aerial surveys 6-23 April 1976.

37
67

65

64

63

.... .. 61

60

59

58

57

56

55

1~ 164 162 180

..' .

:~ Bering Sea

170 172 174 176 1~ 180 1~ 176 174 172 1M 168

64

63

62

61

60

59

58

57 < . .. .

56

55

160 162 184 1~ 1~

IIl.RUS SIOHTED PER FIVE I1Itm'fS

* ... 0 • 67 3O.rol

66 * 15.059

65

* 6.522

• 3.107

~1~ 1~ 1~ 1~ 1M In 1~ 1~ 1~ 1~ m 1~ 1~ In lMl~ 1~ 1~~

Figure 5.-Computer plots of walrus density in relation to aerial survey strips from TINRO aerial surveys, 12-26 April 1976. Star symbols are centered on positions

where walruses were observed.

179 177 173 165 161 157

57

59

179 177 173 169 165 161

SIGHTI~L~~ M~~~~~"::::::: ::::::::::::::::: ::1:1:':1: :::::1::: :: :::::::::::: ::. Bds~o1 .. ::' ....::.::::: :: ::: :I ••

I 1.230 I II····' . . ay J........... :. :~~: :::::;::::::::; :r~: :::: :;::~; :::: :: ::: :: .::.. n :: :: :: :.. .. ..L.. :::': :1: ::1: .. . ..

1 B.233 .1.1..1. ..I· ..· · , 11.111 '1" .1.1.,..\•.•1.1. ·1· .. '· ·1·lt·I""'j"I.I.·· IiJ 9.556 ···I·· .. ·.. ·.. ·v····· .. ·.. ·.. ········ .. ·I·I·I·I·······,·,~· ........ la 12.300 .... .. .... :::: ..:::::::::::::::·::::11::::::::::::::·: .. ::::'" q

a 21.750 .:::: ::: : : :: ::

Bering Sea

59

57

Figure 6.-Computer plots of walrus density from ADF&G aerial surveys, 8-23 April 1976.

38
59

61

63

57

65

156

•

•

."

,

'"

'.v· tCS "•.

. .-.~.

160

160

_. e. •

'4It?

.0

.

,". .....

164

168 164

168

:....,.:..r..r,.n.9

1

: .....

,..'....1.1""1'"1' 'II" '.. '

...••:••..:•..•. , ••••••• ) •••:••••••.•• .-."."•• L •••

::::II: . ... '1:[ .'1.1\.\1\: .(1/ ]'1' 'I: .\[. ...:.:.:\1\ .:.::::::

172

172

. :::::::::::::::::::.. .T

. I·····:1:.···:::::::::::·····:::I::::::I:..

]l ••:~ ••

'::::::::"::":::1::

:J:::::::::::::::::::::::

176

176

RINGED SEAL

SIGHTINGS PER MINUTE

J 0.580

I 1.557

I 2.534

I 3.511

61

59

63

57

65

Figure 7.-Computer plots of ringed seal density from NMFS aerial surveys, 6-23 April 1976.

39
160 162 164 166 168 170 172 174 176 178 180 178 176 174 172 170 168 166 164 162 160

68 68

RINGED SEALS SIGHTED PER FIVE MINUTES

* ,. 0

67 22.00 67

66 * 11.09 66

65

* 4.86 65 lIE 2.37

0.96

64 64

'" 63 63 r ,

62 62

61 61

60 60

59 59

58 58

57 57

56 56

55 55

160 162 164 166 168 170 172 174 176 178 180 178 176 174 172 170 168 166 164· 162 160

Figure S.-Computer plot of ringed seal density from TINRO aerial surveys, U-26 April 1976.

179 177 173 169 165 161 157

59

57

·:::::::::::::::::1:1::::::::... RINGED SEAi.·······:::::::::::::::::::::::::I::::···············I I'"

SIGHTINGS PER MINUTE .. . " .. . .. .

I 0.153 .....::::::::::::::::::. .. .. :::::: ...

I 0.395::::::: :::::::: ::: ::::::: :::::: .:::: ::::: :: .... I 0.637

I 0.879

Bering Sea

59

57

179 177 173 169 165 161 157

Figure 9.-Computer plot of ringed seal density from ADF&G aerial surveys, 8·23 April 1976.

40
:::...::::::1:::::::::::::::::::::::::::::::::::

II:

63

61

59

57

RIBBON SEAL

SIGHTINGS PER MINUTE

I 0.181

1 0.319

I 0.458

1 0.597

176

172

.•

172

168

"::::::::::1.::

168

164

164

160

.

.... . -. -.

:1:1::

II

160

..,

I

•

156

156

63

61

59

57

Figure lO.-Computer plot of ribbon seal densily from NMFS aerial surveys, 6-23 April 1976.

4l-
179 177 173 169 165 161 157

179 177 173 169 165 161 157

Figure H.-Computer plot or ribbon seal density rrom ADF&G aerial surveys, 8-23 April 1976.

160162164166168170172 174 176 178 180 178 176 174 172 170 168 166 164162160

56

57

58

59

61

60

63

62

65

67

66

64

14.84

6.18

2.71 • 0.76

*

RIBBON SEALS SIGHTEo~PER FIVE ~INUTES

30.00

*

*

59

58

56

57

60 .

62

61

63

64

67

66

65

160 162 164 166 168 170 172 174 176 178 180 178 176 174 172 170 168 166 164 162 160

Figure 12.-Computer plot or ribbon seal deBlty rrom TINRO aerial surveys, 12-26 April 1976.

42
176 172 168 164 160 156

59 SPOTTED SEAL

SIGHTINGS PER MINUTE

:I 0.642

1 1.792

I 2,942

• 4.092

57 111 5.333

Il 7,071

a 22.000

65

63

61

'.1' ' ~'" . . .... ~.

,.,

.. :::~ :. ....... .. .... . ( .. ...... .., .... ..

.

... . "'\ ...,

'OIt?.0

IO

L":'n,'IlIf[[ . .. 11

"" ·1 ..111·1·1·1··[ ..1·1.. ·' 1· .. · ·.. · ·· 1..'1"'" ..

.. ,,•• 'n:":.':: '',,:;I!;~~:I:i;:': ]~j[;I J••• '•• .. TITIllBlrlillTI TITI TI' .I. . ........ ···········T····

¥UEI::. II: :r:~' •

•

65

63

61

59

57

176 172 168 164 160 156

Figure B.-Computer plot of spotted seal density from NMFS aerial surveys, 6-23 April 1976.

43
179 177 173 169 165 161 157

57

59

161 157

··IT··I·····I·T··· hr'::':':'II::'1 ... :: 1::.. Bering Sea

.......... :::I:,:JIWHJlUI1..lr.:.... . d';. '. ':.: .. ::.

SPOTTED SEAL ..fIrt:-:-: .... ~1·1. 1'111[ 1"11 . ITr" ·:::·1::· .. ::: ... SIGHTINGS PER MINUTE ....11.... :u:· r" .. ... . .I .... I. ..

I 0.410 .,..,.,. '''::LI:I~·I1I,:· .. '1······:11'.· ..,. .. I· TT'" . I 1.150 .... · .. ·.. ·..1· II· .... ·'.. ·.. ]· ..... ." ... 1.. ... :: ... .... T.. · .. ·.... ···lr][[···.. ~I ,

: ~.~;~ ": •.1" :'::I::I':~:'I:::"I:':l":""I'::':::::Il'~"'":''' .!' ... ::::':.1:.'1:' • .. , T.. ·.... ·.. T.. ·.. ·...... T.. ·.. "I"·.I....·+ ..· .. n .. ·.. ·.. · . : ;:~~~ :.:.: :::: .. :"\;\: I.': :,:: :,:':'::.:.: :'I"~I:I.I.. .I .... :,. :I:d::::': ::1::':' q

Ii 4.294 I.............. .. ... 1.1. .... II 5.000 . ..... .... .. ".

S 5.750 .

B 7.000

59

57

Figure .4.-Computer plot ofspotted seal density from ADF&G aerial surveys, 8-23 April 1976.

160 162 164 166· 168 170 172 174 176 178 180 178 176 174 172 170 168 166 164 162 160

68 68

SPOTTED SEALS SIGHTED PER FIVE MINUTES

* . '0 . 67 121.00 67

66 * 59.66 66

65

* 24.64 65• 10.62

2.74

64 64

63 63

62 62

61 61

60 60

59 59

58 58

57 57

56 56

55 55

160 162 164 166 168 170 172 174 176 178 180 178 176 174 172 170 168 166 164 162 160

Figure IS.-Computer plot of spolled seal density from T1NRO aerial surveys, U-26 April 1976.
176 172 168 164 160 156

59

61

57

63

65

•

•

• 'f

,

'"

'.'1 . ~'" . • ft. J>.

.

'.. • -=\ ..-.

.~

0

0

•.

U.S.S.R.

::::::::~I~::I:::::::~f:

J

I

I

rl <) :::.1::......... I

········T···T1'n

....[.•.•.....••••• IIII,,;[.(:;,'I•.•••••••••••S".:.{ ••••11 ~:: .

.. ::::: 11:: ~III: .1.11: *1:1: 1I:IJ J: J :11'::'::.'I':II.' J

q J ..I.. JI. .I L.'1' .. '1"1 . . T' J ..

.......•... :::::11.1.1. '1' ::.:::1.1: .1]1 J T:.,: ::r: ::I:IJ .::: .

"<7 ···UT·II"T····TTI·T·····T···

" ".".. ... .".::/r:::II ... <I~ ... qte> ..'1'

:::::: ]~I:' ~~I: ::1::':: ' :

T··DTf·T····!·····················

"I" ..

"1'.1... "I"I~:: ., .. ...... .... ' ..

••••• •••• o'

I::::::::::::::':1:1::

::: ::: ::11:::::11: 1:

0.275

0.768

1.261

1.754

2.250

5.000

I

][

I

I

iii

Iil

BEARDED SEAL

SIGHTINGS PER MINUTE

59

61

63

57

65

176 172 168 164 160 156

Figure 16.-Computer plot of bearded seal density from NMFS aerial surveys, 6-23 April 1976.

4S
160 162 164 166 168 170 172 174 176 178 180 178 176 174 172 170 168 166 164 162 160

7.90

58

57

56

59

65

64

60

61

63

62

66

67

68

3.84

2.22

1.30

BEARDED SEALS SIGHTED PER FIVE MINUTES

*. #' 0

15.00

*

*

68

67

65

66

Fipft 17.-C_.... platcf......... deulty ..... T1Nm ........-ys, 11-26 April 1976.

179 177 173 169 165 161 157

.1::::::::::::::::::::.... 59

57

179 177 173

Bering Sea

169 165 161

59

57

Figure 18.-Computer plot of bearded seal density from ADF&G aerial surveys, 8-23 April 1976.

46
lZJ Walrus

• Ringed Seal

Ribbon Seal

Spotted Seal

o Bearded Seal ..-,

~_J NS, Not Su rveyed

NS

• 4

".0 •

""

NS

"Ii •

Figure 19.-Centers of abundance of ice-associated pinnipeds in the Bering Sea pack ice, based on numbers sighted per minute during NMFS, ADF&G, and TINRO

aerial surveys, 6-26 April 1976. Areas indicated for walrus and spotted seal include only those where at least 2/mi" were sighted, and for ringed, ribbon, and bearded

seal, at least O.S/min.

47

Use of Nonmetrical Characters of Skulls of

Bering Sea Seals in a Study of the

Phenotypic Structure of Their Populations

GENNADII A. FEDOSEEyl

ABSTRACT

Analysis of the phenotypic composition of Bering Sea ribbon, Phocafasciata, and spotted, Phoca largha,

seals shows that these seals differ in degree of differentiation of their populations. The spotted or larga seal

shows the greatest differentiation and can be considered as comprising three geographical populations:

Karaginskii Gulf, Anadyr Gulf, and eastern Bering Sea. The difference between the Karaginskii and Anadyr

groups has been demonstrated previously by their comparative helminth faunas and cranial dimensions. The

ribbon seal shows a higher degree of uniformity than does the spotted seal. Ribbon seals residing in the eastern

and western Bering Sea are weakly differentiated, indicating a low degree of isolation and high degree of

panmixia. In the interest of maintaining stable stocks of these two species, the harvest of each should be evenly

distributed among all of its groups.

PE310ME

AHaJlHl <!IeHoTHnH'IeCIWrO COCTaaB KPblJlaTKH [Phoca fasciatal H JlaprH [Po mrghal IiepHHroaa MOpR

nOKBlBJI, 'ITO lTH TIOJleHH HMelOT PBlHYIO CTeneHL ",H<!I<!IepeHI\HBI\HH HX nonYJlRI\HiI. JIBprB no aceil

aepoRTHoCTH 06pBlyeT TpH JlOKBJlLHble nonYJlRI\HH: KBparHHcKylO, BHa",L'pcKylO H aOCTO'lHO6epHHroaoMopcKylO. PBlJlH'IHe Me",iI.Y KapBrHHCKoil H BHB"'b1pcKOil Jlaproii 6b1J1o nOKBlaHO pBHLlUe npH

cpaBHeHHH HX reJlLMHHTo<!laYHbI H pBlMepHblX npH3HBKOB '1epena. KpLIJlaTKB HMeeT 60JlLlUYlO CTeneHL

cxo",CTaB, '1eM Jlapra. CJla6aR Mop<!lOJlOrH'IeCKaR ",H<!I<!IepeHI\HaI\HR KpblJlaTKH, 06HTBIOU\eii B BOCTO'lHOii H

lanaJUlOH "t3CTHX 6epHHr003 MOpA, YK31blBaeT Ha HH1KYIO CTeneHb HlOiU.","" It BbiCOKYIO CTeneHb naHMHKCHH. B

HHTepecax co~paHeHHA cTa6HnbHhlX 3anaCOB ')THX ~BYX BHAOR, Heo6xo.QHMO paBHOMepHO pacnpe)\enHTb

...06L1'1y Me",...y KB"''''L1MH rpynnoBKaMH.

INTRODUCTION

Study of the population as a basic structural unit in the evolution

of species occupies a central place in contemporary biology.

Knowledge of the phenotypic structure of each populational unit has

particular significance in the management of animal populations

and their protection, since an understanding of their geographical

boundaries, degree of intermixing, mutual relationships, and

ecological roles determines to a great extent the approach to solution

of fundamental management problems.

The identification of separate populations requires detailed

ecological and morphological description of the animals within the

boundaries of each geographical region or ofthe entire species-area.

In developing such a description, it is important to bear in mind that

one population may not differ from a neighboring one in specific

morpho-physiological features that are common to all individuals in

it. Instead, they may tend to differ in gene frequency, i.e., in the

quantitative expression of various alleles as phenotypes (Yablokov

and Yusufov 1976). Genetic analysis ofseal populations, as in many

other animals, is very difficult. However, a phenotypic approach to

the spatial distribution of populations is possible, using discrete

elemental features or phenes (Timofeev-Resovskii et al. 1973). The

nonmetrical characteristics of the skulls are such features (Berry

1963, 1968).

I Magadan Branch. Pacific Research Institute of Fisheries and Oceanography

(MoTlNRO). Nagaevskaya 51. Magadan 685013. USSR.

49

Definite morphological and ecological differences between seals

of the Okhotsk and Bering Seas have been demonstrated previously

by Fedoseev (1967),2 Shustov (1970), and Kosygin and Potelov

(1971). Recently, a more detailed study of polymorphism in seals of

the Okhotsk Sea was conducted by Fedoseev et al. (1979). In the

Bering Sea, morphological differentiation has been demonstrated

between the larga or spotted seal, Phoca largha, populations of the

Karaginskii and Anadyr Gulfs (Gol'tsev et al. 19753).

The present work is a continuation of the studies cited above. In

it, I have analyzed the nonmetrical characters of skulls of spotted

seals and of ribbon seals, Phocafasciata, from the eastern Bering

Sea, east of long. l74°W, and from the central Bering Sea, west of

long. 176°W, and in Anadyr Gulf. This was made possible by

Soviet-American collaboration in the study of pinnipeds, in which

the craniological collections of American and Soviet colleagues

were utilized.

METHODS

Skulls of 196 ribbon seals were examined and scored for eight

nonmetrical morphological characters (Figs. 1,2): 1) The locations

'Fedoseev. G. A. 1967. Comparative morpho-ecological characteristics of ringed

seals of the Okhotsk Sea and the coastal waters of the Chukchi Peninsula. Avtoreferat

Disserlatsii. Magadan.

3Gol'tsev, V. N., V. N. Popov, and M. V. Yurakhno. 1975. On the localization nf

stocks of Bering Sea largas. In Marine mammals. Materials 6th all-union conf.

1:100-102. [Abstr.1 Naukova Dumka, Kiev.
d

c

b

f

m---f~---\

n

Figure I.-Nonmetrical characters of seal skulls: a) Position of palatine foramina, b) pterygoid vacuities, c) central

vacuity in basioccipital, d) vacuities in condyloid fossae of exoccipitals, e) edge of hard palate, f) ventral border of

foramen magnum, g) lateral processes of nasals, i) mid-ventral ridge on intermaxillary suture, j) basioccipitalb8!iisphenoidalsuture, k) interparietalsuture, I) nuchal crest, m) marginal ridges on temporal fossae, and n) margins of

temporal fossae on the frontals.

v

"\I

c. 2 V

l~

2

a b d e

50

Figure 2.-Variations in form of nonmetrical characters ofseal skulls: a) Ventral edge of foramen magnum in ribbon

seals, b) posterior edge of hard palate in ribbon seals, c) edges of temporal fossae in spotted seals, d) opening of

mandibular foramen, and e) edge of hard palate in spotted seals.
RESULTS

applying Yates' correction for small samples to P 1 and P 2' The

standard error of each sample was estimated as .JP(l-P) .

N

The comparison of ribbon seals from the central Bering Sea and

Anadyr region with those from the eastern Bering Sea on the basis of

nonmetrical characters ofthe skull revealed the following (Table I).

In the central and Anadyr ribbon seals, significant differences

were found between males and females in two characters: I) The

ventrolateral vacuities in the exoccipital bones were absent more

often in females than in males (this tendency was reversed in the

eastern sample), and 2) the ventral edge of the foramen magnum

was more often V-shaped in females than in males (as it tended to be

also in the eastern sample).

In the eastern ribbon seals, significant sexual dimorphism was

evident in only one character: The central vacuity in the basioccipital bone was more often absent in females than in males (not so in

the central sample); when it was present, it tended to be larger in

females than in the males (similar tendency in the central sample).

Several other dimorphic trends, suggested mutually by the data

from both samples, could have been due to chance.

Significant differences among female ribbon seals between the

two regions were identified in three nonmetrical characters: I) The

pterygoid vacuities were absent more often in the central than in the

eastern sample, 2) the central vacuity in the basioccipital bone was

absent more often and tended to be smaller in the central than in the

eastern sample (not so in the males), and 3) the shape of the

posterior edge of the hard palate was more often notched as in "type

I" in the central than in the eastern sample.

Among the male ribbon seals, the central and eastern samples

differed significantly in four characters: I) The palatine foramina

were less often ahead of and more often within the maxillo-palatine

suture in the central than in the eastern sample, 2) the shape of the

edge of the hard palate was less often of "type 4" and more often of

"type 6" in the central sample, 3) the shape ofthe ventral edge ofthe

foramen magnum tended to be more often of "type 2" in the central

animals, and 4) the mandibular foramen was less often rounded and

more often acute in the central than in the eastern males.

In the spotted seals from central and eastern Bering Sea, somewhat more sexual dimorphism was evident, and the differentiation

between regional samples was expressed much more strongly than

in the ribbon seals (Table 2). In the central and Anadyr sample,

females differed significantly from males in five characters: I) The

pterygoid vacuities were more often well expressed in females, 2)

the exoccipital vacuities were more often absent bilaterally in

females, 3) the nuchal crest was more strongly expressed in females

than in males, 4) the ridges along the dorsal margins of the temporal

fossae were better expressed in males than in females, and 5) those

same ridges tended to converge on the frontal bones, forming a crest

more often in the males. In the eastern sample, the degree ofridging

along the upper edges of the temporal fossae, and the tendency for

convergence into a crest on the frontals also tended to differ between

sexes, but in both characters the trend was toward greater expression

in females than in males.

Both sexes of central spotted seals differed from the eastern

sample in having I) palatine foramina more often ahead of than

behind the posterior edges of the 5th postcanines, 2) the central

vacuity in the basioccipital bone more irregular in shape, and 3)

better expression of ridging on the upper edges of the temporal

fossae. The central males (but not the females) also showed 4) more

frequent presence of the exoccipital vacuities, and 5) of the central

vacuity in the basioccipital bone, as well as 6) a greater tendency for

the temporal ridges to form a crest on the frontals, than in the eastern

sample.

In the eastern spotted seals, the females showed significantly

greater tendency for ridging on the ventral intermaxillary suture,

and both sexes showed greater I) expression of the pterygoid vacuities, 2) opening of the basioccipital-basisphenoidal suture, 3)

presence of an interparietal suture, and 4) tendency for the mandibular foramina to be wedge-shaped. In the males (but not in the

females), the nuchal crest was better expressed than in the central

sample. In most instances, the probability of these differences

having been due to chance was <0.1 %.

( =

the proportion in sample I

the proportion in sample 2

the estimated standard error of Pi

the estimated standard error of P 2

where Pi

P2

SP1 =

SP 2 =

of the palatine foramina relative to the maxillo-palatine suture, 2)

the absence or presence and size of the vacuity at the junction of the

pterygoid bones with the basisphenoid-presphenoidal suture (i.e.,

in the area of the pterygoid canal), 3) the absence or presence and

size of the mid-ventral vacuity in the pharyngeal tubercle of the

basioccipital bone, 4) the absence or presence of the ventro-Iateral

vacuities in the condyloid fossae of the exoccipital bones, 5) the

shape of the posterior edge of the hard palate, 6) the shape of the

ventro-anterior edge of the foramen magnum, 7) the relative length

of the lateral and medial anterior processes of the nasal bones, and

8) the form of the opening of the mandibular foramen. •

Skulls of 123 spotted seals were scored on the basis of 12 characters (Figs. 1,2): 1) Location of the palatine foramina relative to an

imaginary line between the posterior edges of the roots of the fifth

post-canine teeth, 2) the absence, presence, and degree of development of the vacuities in the vicinity of the pterygoid canals, 3)

absence or presence of the vacuity in the pharyngeal tubercle of the

basioccipital bone, 4) absence or presence of the vacuities in the

condyloid fossae of the exoccipitals, 5) the shape of the posterior

edge of the hard palate, 6) the shape of the opening of the mandibular foramen, 7) the absence and extent when present of the ridge

along the mid-ventral suture between the maxillary bones, 8) the

condition ofthe basioccipital-basisphenoidal suture, 9) condition of

the interparietal suture, 10) degree of expression ofthe nuchal crest,

11) degree of expression of the ridges along the medial margins of

the temporal fossae, and 12) the convergence or divergence of those

margins anteriad, on the frontals. This scheme was modified from a

preliminary one kindly provided by A. V. Valetskii and A. V.

Yablokov. Some modification of their scheme was required, inasmuch as some of their suggested characters were found to vary with

the age of these seals.

The sample proportions (P) ofindividuals having the character in

question (number having character/total number in sample) were

compared I) between sexes within regional samples and 2) within

sexes between regional samples. Assuming binomial distribution,

the probability of significant differences between the compared

samples was determined by estimation of the (-variate, using the

formula (Rokitskii 1961):

51
Table I.-Percentage frequency of occurrence of nonmetrical morphological characters in skulls of ribbon seals of central and eastern Bering Sea, with probability of

signiflcant interpopulatlooal differences.

Probability of

Central area Eastern area difference' between

Females Males F:M' Females Males F:M' central and eastern

(N=55-59) (N=65-69) difference (N=15-17) (N=50-51) difference Females Males

O1aracter %/ %/ (t) %/ %/ (t) (t) (t)

Location of palatine foramina (Fig. Ia)

Ahead of maxillo-palatine suture 25.4 24.6 0.12 31.2 47.1 1.02 0.63 2.61·

Behind maxillo-palatine suture 18.6 7.2 1.94 25.0 11.8 1.31 0.73 0.88

Within maxilio-palatine sulUre 55.9 68.1 1.44 43.8 41.2 0.33 0.58 2.83··

Pterygoid vacuities (Fig. Ib)

Absent 11.9 11.6 0.74 0.0 5.9 1.14 2.28· 1.07

Large 61.0 68.1 0.85 68.8 70.6 0.30 0.42 0.26

Small 27.1 20.3 0.92 31.2 23.5 0.76 0.49 0.45

Central vacuity in basioccipital (Fig. Ie)

Absent 20.3 21.7 0.18 0.0 28.0 4.10"· 3.48··· 0.82

Large 55.9 47.8 0.74 82.4 56.0 2.11· 2.16· 0.70

Small 23.7 30.4 0.84 17.6 16.0 0.33 0.37 1.86

Vacuities in exoccipitals (Fig. Id)

Absent 47.3 29.0 2.13· 29.4 43.1 0.90 1.23 1.63

Present, right 52.7 59.4 0.77 58.8 49.0 0.42 0.30 0:95

Present, left 52.7 58.0 0.61 64.7 52.9 0.73 0.74 0.58

Shape, edge of hard palate (Figs. Ie, 2b)

lYpel 16.9 7.6 1.60 0.0 6.0 1.21 3.03·· 0.29

1Ype 2 3.4 7.6 1.02 0.0 6.0 1.21 0.55 0.29

1Ype 3 22.0 24.2 0.28 11.8 20.0 0.65 0.85 0.51

1Ype4 8.5 6.1 0.53 23.5 24.0 0.12 1.57 2.70··

1Ype 5 25.4 24.2 0.17 52.9 38.0 0.79 1.77 1.62

1Ype6 23.7 28.8 0.64 5.9 6.0 0.28 1.97 3.47···

Shape, ventral edge foramen magnum (Figs. If, 13)

lYpel 35.1 15.9 2.51· 33.3 29.4 0.46 0.05 1.77

1Ype2 22.8 37.7 1.83 20.0 17.6 0.41 0.03 2.51·

lYpe3 42.1 46.4 0.47 46.7 52.9 0.13 0.49 0.52

Anterior processes of nasals (Fig. Ig)

Lateral processes longest 52.7 60.0 0.83 53.3 68.0 1.18 0.12 0.87

Lateral nI medial processes equal in length 47.3 40.3 0.79 46.6 32.0 1.17 0.12 0.90

Shape of mandibular foramen (Fig. 2d)

Roonded 62.7 50.7 1.36 70.6 2.24·

Acute 37.3 49.3 1.36 29.4 2.24·

'·P<.05, ··P<.OI, ···P<.OOL

DISCUSSION

Shustov (1970) noted that ribbon seals localize in two main areas

in the northern Bering Sea in spring: An eastern area, in the vicinity

of St. Matthew, St. Lawrence, and King Islands, and a west-central

area in Anadyr Gulf and along the Koryak coast. In his analysis of

the dimensions of the body and skull, he found no significant

differences between the animals from these two groups. On that

basis, he concluded that the eastern and west-central groupings of

Bering Sea ribbon seals are not independent, but appear to be

panmictic.

The comparison of those groups on the basis of nonmetrical

characters reported here indicates that there is some phenotypic and

probably weak genetic differentiation of ribbon seals in the eastern

and central Bering Sea. Some distinctive differences in the direction

of natural selection in the eastern and central areas are to be

expected, inasmuch as the living conditions of these seals are not

identical in the two areas. The eastern area is shallower and is

exposed to the greater warming effect of the Pacific Ocean waters,

which results in a unique biocoenosis in that region (Natarov 1963;

Moiseev 1964). The central zone is much colder and deeper and

supports a distinctly different biocoenosis.

Although there is a tendency toward ecological and genetic differentiation of eastern and central ribbon seals, apparently there is at

52

the same time enough exchange (probably of young animals) between them to minimize their differentiation. Possibility for exchange appears to be greatest in years ofless than average ice cover,

when the breeding habitat is most restricted. The close similarity of

the ribbon seals of the eastern and central Bering Sea indicates that

they are not evolutionarily independent but compromise a single

geographical population.

In winters with average ice cover, the spotted seal population of

the Bering Sea tends to be distributed in three major areas during the

breeding season I) to the southwest, in Karaginskii Gulf, 2) centrally, from Cape Navarin to about long. 176°W, and 3) to the

southeast, from the Pribilofs to Bristol Bay. The central group

apparently moves northward into Anadyr Gulf in spring. The results

of comparisons ofsamples from the Karaginskii and Anadyr groups

have shown great morphological differentiation, as well as differences in the composition of their helminth faunas (Gol'tsev et al.

footnote 3). Their differences are great enough to allow consideration of these groups as independent, local populations. The high

degree of phenotypic difference between samples ofthe Anadyr and

southeastern Bering Sea groups also indicates great differentiation.

The available information on the ecology of the spotted seal

characterizes this as an adaptable species, capable of inhabiting a

wide variety of biocoenoses, from oceanic to estuarine. Conversely,

the ribbon seal is wholly pelagic in the oceanic environment. The
Table 2.-Percentage frequeJKy of occurrence of nonmetrical morpbological cbaracters in skulls of spotted seals of central and eastern Bering Sea, witb probabUlty .,

significant interpopulational differences.

Probability of

Central area Eastern area difference' between

Females Males F:M' Females Males F:M' central and eastern

(N=31-36) (N=44) difference (N=20-U) (N=18-24) difference Females Males

Character %/ %/ (/) %/ %/ (/) (/) (I)

Location of palatine foramina (Fig. la)

Ahead of posterior edges 5th postcanines 63.9 70.4 0.38 9.5 8.7 0.12 4.93*** 6.45***

Behind posterior edges 5th postcanines 36.1 29.5 0.65 90.5 91.3 0.12 4.94*** 6.47***

Ridge along intermaxillary suture (Fig. Ii)

Present on full length 0.0 2.3 0.89 14.3 4.3 1.17 2.00* 0.63

Present on some part 31.4 47.7 1.47 61.9 69.6 0.55 2.02* 1.52

Absent 68.6 50.0 1.68 23.8 26.1 0.16 3.37** 1.74

Pterygoid vacuities (Fig. lb)

Well expressed 34.3 13.6 2.20* 66.7 78.3 0.88 2.19* 6.12***

Weakly expressed 48.6 56.8 0.50 19.0 17.4 0.16 2.38* 3.32**

Absent 17.1 29.5 1.29 14.3 4.4 1.15 0.18 2.97**

Basioccipital-basisphenoidal suture (Fig. Ij)

Open 0.0 2.3 0.91 9.1 13.0 0.41 1.63 1.59

Partly closed 13.9 13.6 0.07 63.6 69.6 0.43 3.91*** 4.84***

Absent 86.1 84.1 0.22 27.3 17.4 0.81 4.96*** 6.58***

Vacuities in exoccipitals (Fig. Id)

Absent. both sides 22.8 6.8 2.02* 14.3 27.3 1.06 0.72 2.12*

Present, left only 2.8 2.3 0.22 14.3 9.1 0.54 1.53 1.21

Present. right only 5.7 6.8 0.15 9.5 4.5 0.66 0.63 0.20

Present, both sides 68.6 84.1 1.65 61.9 59.1 0.18 0.58 2.21*

Central vacuity in basioccipital (Fig. Ic)

Absent 14.3 18.2 0.43 31.8 40.9 0.63 1.59 1.99*

Round or oval 25.7 22.7 0.34 50.0 40.9 0.30 1.59 1.58

Irregular form 60.0 56.8 0.26 18.2 18.2 0.00 3.26** 3.17**

Large 57.1 54.5 0.00 18.2 31.8 0.70 3.00** 1.55

Small 28.6 27.3 0.16 50.0 27.3 1.27 1.35 0.00

Interparietal suture (Fig. Ik)

Present 44.4 45.5 0.08 90.0 100.0 1.54 3.91*** 7.27***

Nuchal crest (Fig. II)

Well expressed 41.7 4.5 4.26*** 36.4 34.8 0.12 0.34 3.01**

Weakly expressed 58.3 88.6 3.21** 59.1 65.2 0.43 0.01 2.22*

Absent 0.0 6.8 1.72 4.5 0.0 1.04 1.22 1.52

Ridging, margins of temporal fossae (Fig. 1m)

Well expressed 2.8 31.8 3.81*** 0.0 4.4 1.00 0.70 3.24**

Weakly expressed 91.7 63.6 3.24** 63.6 33.3 1.84 2.17* 2.25*

Absent 5.6 4.5 0.31 36.4 62.5 1.53 2.89** 5.28***

Temporal margins on frontals (Figs. In,2c)

Convergent. forming crest 23.5 .47.7 2.28* 25.0 0.0 2.62* 0.21 6.20***

Shape of mandibular foramen (Fig. 2d)

Rounded, right only 50.0 '63.6 1.25 15.0 15.0 0.00 2.70** 4.17***

Rounded, left only 50.0 54.5 0.42 10.0 11.1 0.14 3.38** 3.74***

Wedge-shaped right 50.0 36.4 1.00 85.0 85.0 0.00 2.94** 4.17***

Wedge-shaped left 50.0 45.5 0.18 90.0 88.9 0.14 3.64*** 3.74***

Shape. edge of hard palate (Figs. le,2e)

Type I 3.2 0.0 1.16 14.3 0.0 1.89 1.44 0.00

Type 2 9.7 0.0 1.91 4.8 0.0 1.05 0.58 0.00

Type 3 0.0 0.0 0.00 4.8 0.0 1.05 1.19 0.00

Type 4 3.2 0.0 1.16 0.0 0.0 0.00 0.77 0.00

Type 5 0.0 0.0 0.00 4.8 4.5 0.06 1.19 1.28

Type 6 64.5 61.4 0.23 42.9 59.0 0.76 1.28 0.28

Type 7 19.4 38.6 1.83 28.6 36.4 0.54 0.82 0.08

'*P<.05, **P<.OI. ***P<.OOI.

differentiation of populations ofspotted seals probably is favored by congregating in traditional sites. As a rule, such relationships

their adaptability and, especially, by their social behavior. Whereas between individuals of gregarious species tend to favor genetic

the ribbon seal is a solitary animal, seldom congregating in pods differentiation among groups (Haldane 1932; Hinde 1975). The

under any circumstances, the spotted seal forms very stable family wide dispersal and wholly pelagic existence of the solitary ribbon

groups during the breeding season and congregates in pods and seal, however, apparently tends to favor panmixia.

larger herds immediately thereafter, for the rest of the spring,

summer, and autumn. Such pods and herds congregate traditionally

at certain estuaries and other feeding areas each year, and they haul CONCLUSION

out traditionally on certain reefs and islands. Those behaviors

suggest the possibility of long-term social and, perhaps, genetic The ribbon seals in eastern and central Bering Sea are weakly

relationships among the members of the pods and even of the herds differentiated morphologically, indicating a low degree of isolation

53
and high degree of mixing. Conversely, the phenotypic analysis of

Bering Sea spotted seals has shown quite the reverse: Strong differentiation and apparentsemi-isolation ofthe Karaginskii, Anadyr,

and southeastern groups. From the aspect of resource management,

the ribbon seals of the Bering Sea appear to be manageable as a

single stock, spanning both the Soviet and the American economic

zones. The spotted seal population, however, probably should be

treated as three stocks: Western, central, and eastern. In the interest

of preservation ofstable reserves of those three stocks, each probably should be managed separately on the basis of its own distinctive

populational and environmental parameters. Each stock inhabits a

different biocoenosis, which is affected by a different set of environmental forces. Nevertheless, the harvests should be distributed

as evenly as possible among these stocks, in order to maintain their

balance and genetic diversity.

ACKNOWLEDGMENTS

The author expresses his sincere acknowledgment and gratitude

to A. P. Shustov, V. M. Gol'tsev, G. G. Shmakova, F. H. Fay, J. J.

Burns, and A. A. Hoover for their help in this work and for the

opportunity of using their craniological collections, as well as to A.

V. Yablokov and A. V. Valetskii for their valuable advice in discussing nonmetrical features of the skulls ofseals. For their helpful

comments on an earlier draft ofthis paper, the author is grateful to J.

J. Burns, F. H. Fay, and B. P. Kelly.

54

LITERATURE CITED

BERRY, R. J.

1963. Epigenetic polymorphism in wild populations of Mus musculus. Genet. Res. 4: 193·220.

1968. The biology of non-metrical variation in mice and men. In D. R.

Brothwell (editor), The skeletal biology of earlier human populations, p.

103-133. Pergamon Press, Lond.

FEDOSEEV, G. A., Yu. A. BUKHTlYAROV, and G. G. SHMAKOVA.

1979. Comparative analysis of craniological characters of the Okhotsk Sea

seals with respect to the structure of their populations. Zoo!' Zh. 58:570-

581.

HALDANE, J. B.

1932. The causes of evolutIOn. Longmans, Lond., 235 p.

HINDE, R.

1975. Behavior of ammals. Mir, Moscow, 147 p.

KOSYGIN, G. M., and V. A. POTELOV.

1971. Age, sex, and populational variability of craniological characters of

the bearded sea!. In V. A. Arsen'ev and E. A. Tikhomirov (editors), Marine

mammals (fur seals and hair seals), p. 266-288. OtdelNauchnoTekhnicheskoi Informatsii, Moscow.

MOISEEV, P. A.

1964. Some results of investigations during a Bermg Sea scientific harvest

expedition. Tr. VNIRO 48:7-29.

NATAROV, V. V.

1963. On the water masscs and currents of the Bering Sea. Tr. VNIRO

47: 11-133.

ROKITSKII, P. F.

1961. Basic varIational statistics fur biologists. Belorus. Gos. Univ.,

Minsk, 329 p.

SHUSTOV, A. P.

1970. Geographic variability of the ribbon seal. Izv. T1NRO 70: 138-148.

T1MOFEEV-RESOVSKll, N. V., A. V. YABLOKOV, and N. V. GLOTOV.

1973. Outline of the study of populations. Nauka, Moscow, 277 p.

YABLOKOV, A. V., and A. G. YUSUFOV.

1976. Evolutionary science. Vysshaya Shkola, Moscow, 335 p.
New Information on Foods of the Spotted Seal,

Phoca largha, in the Bering Sea in Spring

YURI A. BUKHTIYAROV/ KATHRYN J. FROST,2 and LLOYD F. LOWRy2

ABSTRACT

Information on foods ofspotted seals was obtained by analysis ofstomach contents from specimenstaken in

spring in Karaginskii Gulf, Anadyr Gulf, and southeastern, central, and northern Bering Sea. Pollock was the

major prey in central Bering Sea and ranked second in Anadyr Gulf. Capelin was the major food in

southeastern Bering Sea and ranked second in northern Bering Sea. Arctic cod was the major food in Anadyr

Gulf and northern Bering Sea. Sand lance was the major food in Karaginskii Gulf. Most ofthe fishes eaten were

<20cm in length and <50 g in weight. A comparison ofthe lengths of Arctic cod eaten by spotted seals and those

caught in trawls in northern Bering Sea suggests that the seals may select the larger individuals of that species.

Pups ate mostly small crustaceans. Older animals ate mostly fishes, shrimps, and octopus. Maximal quantities

of food per stomach ranged from 2.7 to 5.9% of the seal's body weight.

PE310ME

,llaHHble 0 "UTaU"" JlaprH 8H811HJUp008JlHCb no CO~epiK"MOMY iKeny,l:tKOB iKHBOTHbIX, 83J1TblX BeCHO~ B

KaparHHCKoM, AHaAblpcKOM 3aJlHB8X HBIOro-BocTO'tHOii, l\eHTpaJlbHOii HceBepHoii 'taCTliX J)epHHroBa MOpli.

MHHT8ii HBJUlllCH r Jl8Bl-lblM HCTO"lHHKOM nH11I;" B ueHTpanbHoH qaCTH liepHHroB8 Mopa H l8HHMaeT BTopoe

MeCTO B AHa,[tblpcKoM 18nHoe. Motia8 COCT8BJlRn8 oenaRy n"TaHHA B IOro-OOCTOl.JHOH "IaCYH, H JaHHM8n8 BTopoe

MeCTO B ceaepHoii 'taCTH l>epHHroBa MOpli. CaiiKa npe06J1BAaJla BnHll\e B AHaAblpcKoM 3aJlHBe H BceaepHoii

"lacy" 6epHHr008 MOpS. neC'I8H1<:a 6bUl3 rn80HbiM HCTOIJHHKOM nHl1(H B KaparHHCKOM JaJJHBe. I)OJlI.WHHCTBO

CbeAeHHblX Pbll) 6b1J10 MeHbwe 20 CM. BAJlHHY H BeCHJlO MeHbwe SO rp. CpaBHeHHe AJlHHbI caiiKbI, CbeAeHHoii

naprOH H nOHM8HHOH TpanOM B ceBepHOH "IaCTH 6epHHrOB8 MOpR, .naeT OCHOBaHHe npe.unonaraTb, 'ITO noneHH

Bb.6Hpa1OT 60Jlee KpynHylO caiiKy. J1aprH-ceroJJeTKH nHTaJlHCb rJlaBHb.M 06pa30M MeJlKHMH paKo06pa3Hb'MH.

B3pOCilbie iKHBOTHble nHTailHCb 8 OCHOBHOM pbl6aMH, KpeBeTKaMH H OCbMHHoraMH. B pa'lHblX npo6ax

MaKCHMailLHoe KOJlIf'ICCTBO H:!H,lleHHOH nHmH B iKeny.nKax naprH Kone68JJoCb OT 2,7 .no 5,9 npo~eHTOB Beea TeJI8.

INTRODUCTION

The spotted or larga seal, Phoca largha, is one of several species

of phocine seals which frequent the waters ofthe Soviet Far East and

Alaska. The natural history of this species has been discussed by

Burns (1970), Burns et al. (1972), and Shaughnessy and Fay (1977).

During February to May, these seals are found in the ice front of the

Bering Sea. This is a broad swath of small, dispersed and moving

floes in the southern part of the seasonal pack ice, which extends

from Alaska to the Siberian coast. Spotted seals give birth, nurse

their young, and mate in the ice front. The exact geographical

position ofthe front varies widely between years, but usually is over

the continental shelf. As the Bering Sea pack ice begins to break up

in May and June, spotted seals concentrate on the remaining ice,

where they molt and spend much of their time basking. After the

Bering Sea ice has melted, these seals are found near shore, especially in and near estuaries.

The only previous information on the food of spotted seals was

from studies in the Okhotsk Sea by Wilke (1954), Fedoseev and

Bukhtiyarov (1972)3, and Nikolaev and Skalkin (1975) and in the

'Magadan Branch. Pacific Research Institute of Fisheries and Oceanography

.MoTINRO), Nagaevskaya 51, Magadan 685013, USSR.

2Alaska Department of Fish and Game. 1300 College Road, Fairbanks. AK 99701,

USA.

'Fedoseev, G. A.• and Y. A. Bukhtiyarov. 1972. Food ofse.ls oft:'e Okhotsk Sea.

Abstracts 5th all-union conf. stud. marine mammals. 1:110-112. Makhachkala.

55

Bering Sea by Gol'tsev (1971). The results presented in this paper

supplement and extend Gol'tsev's pioneering work.

MATERIALS AND METHODS

We collected information on the foods of spotted seals in March

to June. Materials were obtained from seals collected in Karaginskii

Gulf and Anadyr Gulffrom Soviet research vessels in 1972 and 1973

and from seals collected in southeastern, central, and northern

Bering Sea from American research vessels in 1976-78 (Fig.I).

Stomachs and intestines were obtained from seals collected in

waters <200 m deep over the continental shelf. Stomachs were slit

open longitudinally and the contents removed. In some cases, the

contents were examined and analyzed immediately; in others, they

were preserved for later analysis. For analysis, the contents were

gently sieved on a fine mesh screen and sorted by species. Each

component was quantified by weight in Soviet analyses and by

volume in American analyses. Weight and volume can be considered identical, since the densities ofthe prey involved are all close to

I g/ml. The number of each species (or higher taxon) in each

stomach was determined by counts of intact food items or representative hard parts, such as otoliths and other skeletal parts of fishes

and beaks of cephalopods. In American studies, otoliths and

cephalopod beaks were obtained also from the small intestine,

which was slit longitudinally (primarily for parasitological studies)

and washed in a pail of water. The contents were allowed to settle

and otoliths and beaks were separated from other materials. Counts

of otoliths from stomachs and small intestines were combined in
U.S.s.R.

...

-'-

Figure I.-Map of the Bering Sea showing areas in which spotted seals were collected.

analyses of the data. In some instances the lengths offresh otoliths

were measured to the nearest 0.1 mm with vernier calipers, as

indices of size of the fishes.

In areas where seals were collected by American investigators,

samples of available prey were collected by means of a 5.8 m

headrope, semiballoon otter trawl. The contents of trawl catches

were sorted, identified, and weighed. For fishes, the fork length,

weight, and the length of the otoliths were measured. Otolith size/

fish size relationships were calculated by means ofregression analysis (Frost and Lowry 1980, 1981).

Common and scientific names of fishes are from Bailey et al.

(1970).

RESULTS

Soviet Studies

Stomachs of over 500 spotted seals were examined, 110 of which

contained food remains taken for analysis. Of the samples, 68 were

from Karaginskii Gulf and 42 from Anadyr Gulf. A list of the

species of prey found in the stomachs is given in Table 1.

In Karaginskii seals, the major food item was sand lance, which

comprised 32.4% of the total weight of stomach contents. Other

important foods included herring (13.2%) and octopus (10.3%).

Unidentifiable fish remains accounted for 14.7%. Nine of the 18

species of prey were shrimps. However, crustaceans in total comprised < 5% of the stomach contents and only Pandalus hypsinotus

was commonly represented. The largest number of items in a single

stomach included 323 sand lance and 9 octopus.

In seals from Anadyr Gulf, fewer species of crustaceans were

found, and these did not include large crangonid shrimps. Instead,

brachyuran crabs (Chionoecetes opilio and Hyas coarctatus) and

small shrimps of the family Hippolytidae were well represented. As

in Karaginskii Gulf, crustaceans comprised < 5% of the total

weight of food consumed. Arctic cod (29.5%), pollock (13.6%),

and sand lance (9.1%) were the major prey. Remains of octopus

occurred in 40% of the stomachs containing food.

56

Nine of 11 species of prey in stomachs of pups of the year were

crustaceans (Table 2). Shrimps of the family Hippolytidae and

immature shrimps ofthe families Pandalidae and Crangonidae were

most commonly eaten. Sand lance occurred in approximately onefourth, and algae occurred in more than one-half, ofthe stomachs of

the seals in this age class.

Fishes and larger shrimps were present in greater quantities than

small crustaceans in seals 1 to 4 yr old. Octopus occasionally were

present; algae occurred rarely. The average weight of the food mass

in this age group was 250 g/stomach with a maximum of 2,300 g.

In sexually mature animals, fishes made up the greatest proportion of the stomach contents. Analysis of the skeletal remains

indicated that most of these were large individuals. Crabs as well as

shrimps occasionally were present. Octopus occurred more often

than in the younger animals.

American Studies

Of 51 seals collected, 31 from the central (n =5), southeastern

(n=14), and northern (n=12) Bering Sea contained food remains in

the stomach and/or intestine. The species of prey identified are

given in Table 1.

Fishes comprised more than 95% ofthe stomach contents ofseals

from all areas; octopus comprised 2% in central and 3% in northern

Bering Sea. Shrimps were found in only two seals from the northern

Bering Sea and amounted to < 1% of the total stomach contents. In

central Bering Sea, pollock and eelpout were the major foods; in

southeastern Bering Sea, capelin was the major prey, followed by

pollock and herring (Table 3). In northern Bering Sea, Arctic cod,

capelin, and saffron cod were found most frequently and in the

largest numbers.

Four of the spotted seals taken in southeastern Bering Sea were

collected from a single locality (lat. 57°40' N, long. 165°01' W) on

20 April 1977. Partially digested remains of 55 capelin and otoliths

from two pollock were found in the seal stomachs. In a 20-min tow

with an otter trawl at this location, the fishes caught included 28

capelin, 16 pollock, 28 sculpins, and 4 fishes of other species.
Table 1.-Prey taxa identified in spotted seal stomachs in the Bering Sea.

Karaginskii Anadyr Northern Central Southeastern

Prey Gulf Gulf Bering Sea Bering Sea Bering Sea

Invertebrates

Neomysis ray; X

Thysanoessa sp. X

Paralhemislo libellu/a X

Panda/us hypsinolus X

Panda/opsis /amelligera X

Sc/erocrangon boreas X X

Sclerocrangon sa/ebrosa X

Sclerocrangon intermedia X

Argis (=Neclocrangon) far X

Argis (=Neclocrangon) crassa X

Crangon sp. X

Lebbeus groen/andica X X

Eua/us gaimardii X

Pagurus sp. X X

Chionoeceles opi/io X X

Hyas coarclalUs X

Bivalve mollusk X

Octopus sp. X X X X

Fishes

C/upea harengus X X X X

(Pacific herring)

MallolUs villosus X X

(capelin)

Boreogadus saida X X X X

(Arctic cod)

E/eginus gracilis X X X X

(saffron cod)

Theragra cha/cogramma X X X X

(walleye pollock)

Lycodes sp. X X

(eelpoul)

Lumpenus sp. X

(prickleback)

Ammodyles hexaplerus X X X

(Pacific sand lance)

Hexagrammos sp. X

(greenling)

Family Conidae X

(sculpins)

Gymnocanthus sp. X

lee/us sp. X

Myoxocephalus sp. X X

Trig/ops sp. X

Family Pleuronectidae X X X

(flatfish)

Algae X X

Most of the fishes eaten by spotted seals in northern Bering Sea

were < 20 em in length and < 50 g in weight (Table 4). Larger

fishes, particularly large sculpins, are sometimes eaten, but in such

cases, the head of the fish may not be eaten.4 Therefore, the otoliths

of such fishes would not be present in the stomach or intestine. In

our studies we did not find skeletal remains of fishes larger than

those shown in Table 4.

The fresh condition of the stomach contents in 13 of the seals

collected in southeastern Bering Sea indicated that they were actively feeding at the time of collection. In these, volumes of

stomach contents ranged from 45 ml in a seal that had eaten capelin

to 1,535 ml in a seal that had eaten herring. The mean volume of

stomach contents in these seals was 491.5 ml, amounting to about

0.9% of the total body weight of the seals (range 0.08 to 2.7%).

'J. J. Burns, Game Biologist tV. Alaska Department ofFish and Game, Fairbanks,

AK 99701, pers. commun June 1979.

57

The range in size of Arctic cod caught by the otter trawl compared

with those caught by the seals was very similar (Fig. 2). The cod

eaten by the seals, however, tended to be slightly longer (~= 14.9

cm, n =326) than those caught in the trawls (~= 14.2 cm, n = 121).

Of the Arctic cod caught in the trawls, 38/121 (31.4%) were < 12 cm

long, while only 33/326 (13.5%) of those eaten by the seals were <

12 cm long. These differences in proportions are highly significant

(X2 =21.353, P< 0.01) and indicate that the I-yr-old Arctic cod

(7-12 cm long), which were strongly represented in the trawl

catches, were not commonly eaten by the seals.

DISCUSSION

At least 18 species of invertebrates and 155pecies of fishes were

identified from the stomach and intestinal contents of spotted seals

collected in the Bering Sea in spring. Sixteen of the invertebrate

species were crustaceans, 10 of which were shrimps. The number of

prey species identified from seals collected in central and southeast-
Table 2.-Percentage frequency of occurrence of prey taxa in stomachs of

spotted seals in relation to age class.

Age class of seal,

Pups 1104 yr 5 or more yr

Prey n=27 n=21 n=35

Thysanoessa sp. 2.8

Decapod crustaceans 4.8

Pandalus hypsinotus 7.4 4.8 5.7

Pandalus sp. 3.7 14.2 14.2

Pandalopsis lamelligera 4.8

Sclerocrangon boreas 2.8

Sclerocrangon salebrosa 2.8

Sclerocrangon intermedia 3.7

Sclerocrangon sp. 3.7 2.8

Argis (=Nectocrangon) lar 4.8

Argis .<=Nectocrangon) crassa 3.7

Crangon sp. 3.7

Family Hippolylidae 7.4

Lebbeus groenlandica 4.8

Pagurus sp. 3.7

Chionoecetes opilio 3.7 8.5

Hyas coarCIQlus 2.8

Bivalve mollusks 4.8 2.8

Octopus sp. 9.5 31.4

Unidentified fishe£ 14.2 25.7

Clupea harenglls 9.5 14.2

Ammodytes hexuptuu; 25.9 38.0 25.7

Eleginus gracilis 2.8

Boreogadus saida 4.8 11.4

Theragra chalcogramma 2.8

Family Cottidae 2.8

Family Pleuronectidae 4.8

Hexagrammos sp. 2.8

Algae 51.8 4.8

Table 4.-Size characteristics of fishes eaten by spotted seals in northern

Bering Sea.

Size of fishes estimated

from otol ith length

No.

otoliths Length (em) Weight (g)

Prey measured Mean Range Mean Range

Boreogadus saida 326 14.9 7.6·20.5 24.9 2.2- 7~.9

Eleginus gracilis 131 16.7 6.2-25.1 36.4 1.4-144.6

Theragra chalcogramma 21 10.9 8.0-15.0 8.4 3.3- 20.0

Lycodes sp' 6 27.3 22.3-30.9 73.4 38.0-103.1

Family Conidae' 19 10.0 3.3-16.5 14.5 0.3- 44.1

Mallotus villosus' 9.0-14.2 10.\ 4.5- 16.1

Clupea harengus' 8.6-27.2 12.5 5.0-180.0

Ammodytes hexapterus' 6.6-1\.9 2.3 0.5- 4.S

'Based on otolith length to fish length and weight relationships for Lycodes

palearis.

'Based on otolith length to fish length and weight relationships for Myoxocephalus sp.

'Based on sizes of fishes caught by otter trawl in the area in which seals were

collected.

&0

FROM SEALS

50

40

30

20 25

FROM TRAWLS

15

FORK LENGTN -eM

10 O+---'---==~,..------_r-----_,.--JI..--=:::L--~ 5

Figure 2.-Length-frequency distribution of Arctic cod, Boreogadus saida,

obtained from trawl samples and from stomachs of spotted seals in tbe same

areas of northern Bering Sea. Fork lengths of fisbes from seal stomachs were

estimated from otolith lengths.

10

.20

•

c

....

:: 10

;;

!

:: 0t---'="----,.------,..---------r-L.-----j

•

•:0

Z 20

ern Bering Sea was less than in other areas. The largest number of

prey species was identified in samples from Karaginskii Gulf. In

general, the number of species identified was positively correlated

with sample size. In northern Bering Sea, however, 14 prey species

were found in 12 seals examined, while in southeastern Bering Sea

only 8 prey species were found in 14 seals.

In spring in the Bering Sea, fishes, shrimps, and octopus comprised most ofthe food ofspotted seals in all areas, butthe principal

species eaten differed among areas. Pollock was the major food in

central Bering Sea and ranked second in Anadyr Gulf. Pollock have

been reported to be the main prey of these seals in the Okhotsk Sea

(Wilke 1954; Fedoseev and Bukhtiyarov footnote 3). Capelin was

the primary food in southeastern Bering Sea and ranked second in

northern Bering Sea. Arctic cod was the major prey in Anadyr Gulf

and northern Bering Sea. Sand lance was the major food in

Table 3.-Fishes identified from otoliths in stomachs and intestines of spotted seals taken in the Bering Sea.

Central Bering (n=5) Southeastern Bering (n= 14) Northern Bering (n= 12)

Total number Frequency of Total number Frequency of Total number Frequency of

of fishes occurrence of fishes occurrence of fishes occurrence

Species (%) (%) (%) (%) (%) (%)

Theragra chalcogramma 88 80 5 43 2 8

Boreogadus saida 7 51 92

Eleginus gracilis 7 15 42

Clupea harengus 5 14 4 25

Mallotus vil/osus 89 86 19 42

Ammodytes hexapterus 4 25

L)'codes spp. \I 80 8

Lumpenus sp. 20

Family Conidae 20 21 5 42

Family Pleuronectidae 7 25

'Less than 1%.

58
Karaginskii Gulf. Herring was of minor importance in all areas.

Herring and rainbow smelt, Osmerus mordax, are major foods of

spotted seals in southeastern Chukchi Sea in early summer and

autumn (Frost and Lowry unpubl. data), as well as along southwestern Seward Peninsula in autumn (J. J. Burns footnote 4). In general,

the regional and seasonal differences in foods of spotted seals

appear to be related to the seasonal distribution and abundance of

the principal species of forage fishes.

The comparison of seal stomach and otter trawl contents from

southeastern Bering Sea suggests that selection of prey does occur.

Capelin comprised 36.8% of the number of fishes caught in the

trawl, while pollock and sculpins accounted for 21.0 and 36.8%,

respectively. Since no pollock or sculpin bones were found in the

stomachs, we concluded that the seals were feeding selectively on

capelin when collected. Spotted seals sometimes eat pollock and

sculpins in appreciable quantities (Table 3), but in this instance they

apparently had selected for capelin or against pollock and sculpins.

Most of the fishes eaten by these seals are swallowed whole. The

results in Figure 2 indicate that, given access to fishes of different

sizes, the seals selected certain size classes, possibly those most

easily caught and swallowed.

The quantity of food found in each stomach usually was small,

relative to the weight ofthe seals. The maximal quantity from Soviet

samples was about 4.1 % of the average body weight and from the

American samples, only 2.7%. Go!'tsev (1971) reported a

maximum of 3,300 g, which would be about 5.9% of the body

weight of a medium-sized seal. Keyes (1968) reported that phocid

seals in captivity eat 6-10% of their body weight per day. AshwellErickson et al. (1979) reported that the food intake of two captive

spotted seals declined from 13% of the body weight per day during

the first year of life to 3% at age 9 yr. The quantity of food in the

stomach of a seal at any given time varies widely and does not

appear to be directly related to the daily food requirement. More

information is needed on the rate of food consumption, amount of

time spent feeding, and rate of food passage through the stomach.

The differences found in this study between age classes in kinds

of prey consumed were similar to those reported by Gol 'tsev (1971)

and Popov and Bukhtiyarov (1975)5. Spotted seals in their first year

of life tend to eat mostly small crustaceans (amphipods, shrimps,

and euphausiids) and commonly eat algae, sticks, and other debris.

These kinds of items were not found in older animals. Animals I to 4

yr old mostly ate fishes, larger shrimps, and occasionally octopus.

Those 5 yr or older fed more on benthic organisms, such as crabs and

octopus. Similar changes in diet with age have been observed in

ringed seals, Phoca hispida, in northern Bering and Chukchi Seas

(Lowry et al. 1980).

Most of the prey species eaten by spotted seals in the Bering Sea

also are eaten by other marine mammals and by seabirds and fishes

(McAlister and Perez 1976)6. Many of the same species also are

'Popov, V. N., and Y. A. Bukhtiyarov. 1975. On age-related changes in feeding

and helminth faunas of spotted seals in the Okhotsk Sea. Abstracts 6th all-union

conf. marine mammals, 2:62-64. Naukova Dumka, Kiev.

'McAlister, W. B., and M. A. Perez. 1976. Ecosystem dynamics: Birds and

marine mammals. Part I. Preliminary estimate of pinniped-finfish relationships in

the Bering Sea. Final report R. U. 77. 29 p. Outer Continental Shelf Environmental

Assessment Program, NOAA Environ. Res. Lab., Boulder, Colo.

59

harvested in commercial fisheries (Lowry et al. 1979). A detailed

understanding of the trophic interrelationships of major marine

consumers in this area is essential for the design of national policies

for marine resource utilization and conservation. Further studies of

the foods of spotted seals and other Bering Sea pinnipeds by both

Soviet and American scientists are needed to supply the information

required for multispecies resource management.

ACKNOWLEDGMENTS

We thank the officers and crews of the ships from which this

research was conducted for their encouragement and support.

American studies were funded in part by the Bureau of Land

Management through interagency agreement with the National

Oceanic and Atmospheric Administration, as part of the Outer

Continental Shelf Environmental Assessment Program and in part

by Federal Aid in Wildlife Restoration Project W-I7-9. Francis H.

Fay, Clifford H. Fiscus, Ole A. Mathisen, Kenneth W. Pitcher, and

Victor B. Scheffer reviewed the manuscript and offered helpful

comments. Kathy Valentine typed and edited the manuscript.

LITERATURE CITED

ASHWELL-ERICKSON. S., R. ELSNER, and D. WARTZOK.

1979. Metabolism and nutrition of Bering Sea harbor and spotted seals.

Proc. Alaska Sci. Conf. 29:651-665.

BAILEY, R. M., J. E. FITCH, E. S. HERALD, E. A. LACHNER, C. C. LINDSEY.

C. R. ROBINS, and W. B. SCOTT.

1970. A list of common and scientific names of fishes from the United States

and Canada. 3rd ed. Am. Fish. Soc. Spec. Publ. 6, 150 p.

BURNS, J. 1.

1970. Remarks on the distribution and natural history of pagophilic pinnipeds

in the Bering and Chukchi Seas. J. Mammal. 51:445-454.

BURNS, J. J., G. C. RAY, F. H. FAY, and P. D. SHAUGHNESSY.

1972. Adoption of a strange pup by the ice-inhabiting harbor seal, Phoca

vilulina /argha. J. Mammal. 53:594-598.

FROST, K. J., and L. F. LOWRY.

1980. Feeding of ribbon seals (Phocafasciala) in the Bering Sea in spring.

Can. J. Zool. 58:1601-1607.

1981. Trophic importance ofsome marine gadids in northern Alaska and their

body-otolith size relationships. Fish. Bull., U.S. 79: 187-192.

GOL'TSEV, V. N.

1971. Feeding of the harbor seal. Ekologiya 2:62-70.

KEYES. M. C.

1968. The nutrition of pinnipeds. In R. J. Harrison. R. C. Hubbard, R. S.

Peterson, C. E. Rice, and R. J.. Schusterman (editors), The behavior and

physiology of pinnipeds, p. 359-395. Appleton-Century-Crofts, N.Y.

LOWRY, L. F., K. J. FROST, and J. J. BURNS.

1979. Potential resource competition in the southeastern Bering Sea: fisheries

and phocid seals. Proc. Alaska Sci. Conf. 29:287-296.

1980. Variability in the diet of ringed seals, Phoca hispida, in Alaska. Can.

J. Fish. Aquat. Sci. 37:2254-2261.

NIKOLAEV, A. M., and V. A. SKALKIN.

1975. On the food of true seals of the eastern coast of Sakhalin. Izv. TINRO

95: 120-125.

SHAUGHNESSY, P. D., and F. H. FAY.

1977. A review of the taxonomy and nomenclature of North Pacific harbour

seals. J. Zool. (Lond.) 182:385-419.

WILKE,F.

1954. Seals of northern Hokkaido. J. Mammal. 35:218-224.

Helminthological Comparison of Subpopulations of

Bering Sea Spotted Seals, Phoca largha Pallas

SEMYON L. DELYAMURE/ MIKHAIL v. YURAKHNO/ VALENTIN N. POPOV/

LARRY M. SHULTS,2 and FRANCIS H. FAy2

ABSTRACT

The population of spotted seals in the Bering Sea appears to consist of three major groups, which

concentrate at the time of giving birth and mating in Karaginskii Gulf, the Navarin-Anadyr region, and in

southeastern Bering Sea from the PribiiofIslands to Bristol Bay, respectively. As part of an investigation ofthe

biological characteristics ofthe seals in each group, their helminth faunas were compared. Samples consisted of

122 seals from the Karaginskii region, 130 from the Navarin-Anadyr region, and 57 from the Pribilof-Bristol

Bay region. Of 22 species of helminths isolated from these seals, only 10 were common to all three regional

samples, and most differed to a significant degree among regions in both prevalence and intensity of infection.

The seals of the Karaginskii and Pribilof regions had fewer species of helminths in common (ll) than either had

with the Anadyr group (13), but were significantly more similar in the prevalences of the respective helminths.

In numbers of helminths per host, the Anadyr and Pribilofseals were much more similar than either was to the

Karaginskii seals. The differences between regional samples appear to be attributable in part to the somewhat

different assemblages of prey available and, perhaps in part, to regional food preferences derived from learned,

traditional, or inherited behaviors.

PE310ME

nonyJUIU.HH JlaprH B liepHHrOBOM Mope ncrBHAHMOMy COCTOUT Hl TPex rJl8BHbiX rpynn, KOTopwe

cOCpejl,OTOlfH03IOTCA 80 BpeMA pOmJl,eHHA H cnapHB3HHA B KaparHHCKOM 3811Hoe, B HaBapHH-AHaAwpcKOM

paHOHe, H B IOrO-BOCTO~HOH Q8CTH J)epHHr003 Mopa OT npH6bUlOBCKHX OCTPOBOB)];O IipHCTOJ1bCKOrO Janusa. B

CBRl" C HCC/leJl,OU3HHeM 6HOJlOrH"IeCKHX oc06eHHocTeii 3THX TlOneHeii B K3>KJl,OH rpynne cpaBHHB3n3Cb HX

rel1hMHIITo<!>aYlla. np06h1 nOl1y..eHhI OT 122 l1apr HJ KaparHHcKoro Jal1HBa, 130 HJ AHaAhlpcKoro JaJlHBa, H57

HJ n pll6hliloBo-IipHCTOJlhCKOrO paiioHa. TOl1hKO 10 HJ 22 BHAOB reJlhMHHTOB aBl1alOTCa 0611\HMH Ma Bcex TPex

paHonoB; O)l,MBKO CTeneHb HHTellCHBHOCTH H )KCTeHCHBHOCTH HHBalM" lHal.fHTeJlbHO UlMeHAeTCR B KaiK~OM Hl

lTHX paHoHoB. KaparHHcKaA H npHOblJlOBCKaR nonYJ1Au.HH HMenu 11 OOI..U,HX BH,LlOB reJlhMHHTOB, HO KaiK~aR 83

JTHX nony"al\HiI HMeJla 13 BHAOB reJlhMHHTOB 061l\Hx c. aHaAhlpcKoH rpynnoil. AHaAhlpCKHe HnpH6hIJJOBCKHe

nOlle"" HaH60JJee CXO,LlHble no HHTeHCHBHOCTH HUBa3HH. Pa3HHI.\a Mem,LlY perHOHaJlbHblMH npo6aMH OT"taCTH

MOiKeT 6bITb o6YCJlOOlleH3 JJOK3J1hllbIM" ocooeHHoCTAMH nHTaHKA, a c J:lpyroii CTOPOHbI - pau.HoHoM,

onpe.ll,eJlReMhlM npHo6peTeHHWM, Tpa.ll,Hu.HOIIHblM "JIM YHaCne.ll,OBaHHbIM nOoe,LleHHeM TlOJleHeH.

INTRODUCTION

Spotted or larga seals, Phoca largha, inhabit the seas bounding

the northern part of the Pacific Ocean, wherever pack ice is a

dominant physical feature in winter (Mohr 1965; Chapskii 1969;

Shaughnessy and Fay 1977). During their breeding season in early

spring, the spotted seals of the Bering Sea are associated with the

southern part of the pack ice, within about 100 km of its edge.

Surveys of their distribution in April to early May, at the time of

parturition and mating, repeatedly have disclosed a consistent pattern of varying abundance in different sectors of the ice (Tikhomirov and Kosygin 1966; Gol'tsev et al. 1975,3 1978; Burns and

I Laboratory of Marine Mammal Parasitology, Frunze State University, Simferopol' 333036, USSR.

'Institute of Marine Science, University of Alaska, Fairbanks, AK 99701, USA.

'Gol'tsev, V. N., V. N. Popov, and M. V. Yurakhno. 1975. On the localization of

stocks of Bering Sea largas. In Marine m'ammals. Materials 6th all-union conf.

1:100-102. [Abstr.] Naukova Dumka, Kiev.

'Burns, J. J., and S. J. Harbo, Jr. 1977. An aerial census of spotted seal, Phoca

vitulina /argha, and walruses, Odobenus rosmarus, in the ice front of Bering Sea. In

Environmental assessment of the Alaskan continental shelf. Quarterly reports of

principal investigators. April-June 1977, Vol. I, p. 58-132. NOAA Environ. Res,

Lab., Boulder. Colo.

61

Harbo 19774 ). The seals tend to concentrate at that time principally

in three regions: 1) In Karaginskii Gulf, 2) south of Cape Navarin to

St. Matthew Island, and 3) in southeastern Bering Sea, from the

Pribilof Islands to outer Bristol Bay (Braham et al. 1984). Later in

the spring, with melting and recession of the pack ice, the

Karaginskii seals apparently disperse to Kamchatkan and Koryak

nearshore waters, the Navarin-St. Matthew seals move, northward

into Anadyr Gulf, while the others continue through the Bering

Strait, into the Chukchi Sea. They summer principally in coastal

and estuarine habitats.

Because the three concentrations appear to be semi-isolated during the breeding season, they may warrant separate consideration in

the formulation of management procedures. In order to assess the

degree of their isolation, series of specimens have been collected

from each group in recent years, for comparison of their craniological and helminthological characteristics. The results of the helminthological investigations are presented in this report.

MATERIALS AND METHODS

Helminthological data from the Karaginskii Gulf breeding concentration were obtained from 122 seals taken there between 6 and
28 May 1972 (examined by Popov). In the Navarin-Anadyr concentration, data were obtained from 116 seals taken in Anadyr Gulf

between 8 April and 16 June 1967 (Yurakhno), and from 14 taken

there between 5 May and II July 1972 (Popov). Data for the

Pribilof-Bristol Bay concentration were obtained from 26 seals

taken in the vicinity of the Pribilof Islands between I7 and 28 April

1976 (Yurakhno), 15 in southern Bristol Bay between 25 March and

25 April 1976 (Shults); 8 about 275 km north of the Pribilof Islands

between 22 Marchand 26 April 1977 (Shults); and 8 about 450 km

north oftbe Pribilofs between 26 May and4 June 1977 (Shults). The

geographic position of each sample is shown in Figure I.

For each seal, the contents of the heart, lungs, gall bladder,

stomach, and both the large and the small intestines were examined

thoroughly. All helminths from them were then washed in fresh- or

seawater and fixed in 10% Formalin.s Later, in the laboratory, they

were examined and identified by conventional methods.

The resultant data were treated statistically, following Beklemishev (1970) and Breev (1976), by Student's t-test for significance of difference between sample means:

where x sample mean, assuming binomial distribution

S = standard deviation about the sample mean.

When the value of twas> 2.0, the differences between regional

samples were considered to be significant at the 0.95 level; when t >

3.03, the difference was accepted as significant at the 0.999 level.

'Reference to trade names does not imply endorsement by the National Marine

FISheries Service, NOAA.

RESULTS

The qualitative and quantitative characteristics of the helminths

from spotted seals in the samples from the three compared concentrations are presented in Tables I to 3 and in Figures 2 and 3.

The results of comparison of the helminth faunas of the

Karaginskii and Anadyr populations already have been published

(Gol'tsevet al. 1978). Therefore, we confine ourselves here principally to comparison of the helminths of the southeastern Bering Sea

seals with those from the Anadyr and Karaginskii regions. Larval

forms of helminths were excluded from the comparison.

From Table I, one can see that the species composition of the

helminths in the seals from each of the three regions was similar;

nevertheless, only 10 of the 22 species were shared. These included

several widely prevalent parasites of marine mammals (Delyamure

et al. 1979): The trematode Phocitrema fusiforme; the cestode

Anophryocephalus Sp.;6 the acanthocephalans Corynosoma

semerme, C. strumosum, C. validum, and C. villosum; and the

nematodes Anasakis simplex. Phocascaris cystophorae, Terranova

sp. (footnote 6), and Dipetalonema spirocauda.

The qualitative similarity of the helminth fauna of the seals from

southeastern Bering Sea to those in the Karaginskii and NavarinAnadyr regions lay almost exclusively within those 10 species. The

only other resemblances were I) to the Karaginskii seals in the

presence of the cestode Diplogonoporus tetrapterus, and 2) to the

Navarin-Anadyr seals in the presence of the trematode Orthosplanchnus arcticus, the cestode Diphyllobothrium sp., and the

nematode Contracaecum osculatum. The remaining species did not

occur in common.

"1lte authors are not in full agreement as to the specific identification of cestodes

of the genus AnophryocephaJus, nematodes of the genus Terranova (=Phocanema),

and acanthocephalans of the genus 801bosoma, hence these are indicated here as

indeterminate species ("sp."), pending further study.

BERING

Figure I.-Locations in which samples ofspotted seals were taken

for helminthologicaJ investigation in the Beripg Sea. Dashed line

marks approximate maximal extent of winter pack ice.

• May 1972

A Apr-Jul 1967,1972

• April 1976

• Mar-April 1976

65°N 0 Mar-A~ri 1 1977

May-June 1977

..

62

1800

SEA

,....... :....". -'."
Table I.-Comparative percentage frequency of occurrence of species of helminths in spotted seals

taken in Karaginskii and Anadyr Gulfs and in the Pribilof·Bristol Bay region of Bering Sea.

2 3

Karaginskii Anadyr Pribilof

(n= 122) (n= 130) (n=57)

Species of helminth x±S ; ±S x±s 11

_ 2 11 - 3 12 _ 3

Orthosplanchnus arcticus 8.5±2.43 1.8± 1.73 2.25

Orthosplanehnus pygmaeus 0.8±0.81

Phoeitrema fusiforme 29.5±4.11 10.8±2.n 1.8±1.73 3.78 6.22 2.81

Microphallus orienta/is 1.8± 1.73

Anophryveepha/us sp.t 24.5±3.76 23.8±3.74 56.1 ±6.56 0.13 4.18 4.28

Diphyllobothrium sp. 2.3± 1.32 7.0±3.38 1.29

Diplogonoporus tetrapterus 1.7± 1.15 8.8±3.78 1.80

Pyramieoeephalus phoearum 1.8± 1.73

Diphyllobothriidae gen. sp. 3.3± 1.61 1.8± 1.73 0.05

Corynosoma semerme 45.8±4.51 54.6±4.36 '88.1 ±4.99 1.40 6.30 5.07

Corynosoma strumosum 87.0±3.05 81 6±3.39 93.0±3.38 1.19 1.32 2.39

Corynosoma validum 8.2±2.48 4.6± 1.18 3.5±2.44 1.31 1.35 0.40

Corynosoma vil/osum 2.5± 1.40 3.0± 1.50 3.5±2.44 0.28 0.37 0.16

Corynosoma wegener; 6.2±2.24 8.5±2.43 0.58

Bolbosoma Spl 5.3 ±2. 96

Anisakis simplex 36.1 ±4.35 2.3± 1.32 7.0±3.38 7.44 5.29 1.31

Contracaecum GSeu/alum 2.3± 1.32 31.6±6.30 4.54

Phocasearis eyslOphorae 54.9±4.50 n.3±3.93 52.6:;:6.60 2.92 0.29 2.57

rerranova Sp.1 65.3±4.31 33.1 ±4.12 50.9±6.61 5.40 1.82 2.29

7e~ranova decipiensI 1.6±1.15 4.6± 1.84 1.37

Anisakidae gen. sp. 0.8±0.77

Otostrongy/us cireumlitus 1.8± 1.73

Parajilaroides krascheninnikovi 2.4± 1.38 0.8±0.77 1.04

Dipeta/onema spirocauda 4.0± 1.77 8.5±2.44 1.8± 1.73 1.47 0.92 3.41

'Species in question; authors disagree on identifications.

'Based on sample size of 42 seals.

Table 2.-Comparative abundance (number per host) of each species of helminth in spotted seals taken

in Karaginskii and Anadyr Gulfs and in the Pribilof region I of Bering Sea.

I 2 3

Karaginskii Anadyr Pribilof

(n= 122) (n=130) (n=26)

Species of helminth x ±S x±S x±S 11 - 2 (1_3 1

2 _ 3

Orthosplanchnus arcticus 1.5± 0.97 0.3± 0.26 1.25

Orthosplanchnus pygmaeus O.O± 0.01

Phocitrema fusiforme p' p p

Microphallus orlentalis p

Anophryoeepha/us skrjabini' 10.2± 3.47 p 1.7± 0.81 2.38

Diphyllobothrium sp. O.O± 0.05 p

Diplogonoporus tetrapterus O.I± 0.06 1.9± 1.84 0.99

Pyramieoeephalus phoearum 0.2± 0.15

Diphyllobothriidae gen. sp. O.I± 0.10 O.I± 0.08 0.08

Corynosoma semerme 2.7± 0.48 14.4± 3.26 8.5± 1.43 2.71 3.85 1.65

Corynosoma strumosum 119.0±87.60 835.0±208.oo 397.0± 103.00 3.18 2.04 1.89

Corynosoma validum 0.2± 0.08 O.I± 0.08 O.I± 0.08 1.10 0.83 0.28

Corynosoma villosum O.I± 0.06 O.O± 0.02 0.2± 0.09 0.67 0.73 1.44

Corynosoma wegener; 0.3± 0.24 0.6± 0.30 0.76

Bolbosoma nipponieum' p

Anisakis simplex 11.9± 1.13 O.I± 0.10 0.4± 0.14 10.4 10.1 1.45

Contracaecum oscula/urn O.I± 0.06 p

Phoeasearis cyslOphorae 7.0± 0.62 16.9± 3.03 7.7± 1.32 3.18 0.47 2.79

Terranova azarasi 3 13.0± 2.31 4.3± 1.10 3.4± 1.02 3.14 3.80 0.56

7i!rranova decipiens 3 0.2± 0.19 0.6± 0.53 0.71

Anisakidae gen. sp. O.O± 0.01

Otostrongylus eireumlitus 03± 0.31

Parajilaroides krascheninnikovi O.I± 0.10 O.O± 0.02 0.99

Dipetalonema spiroeauda 0.8± 0.69 0.8± 0.63 p 0.05

'Includes only the April 1976 (Yurakhno) sample; comparable data not available from others.

'Present but not counted.

'Species in question; authors disagree on identifications.

63
Table 3.-Comparative diversity of species of helminths in spotted seals of different ages, taken in Karaginskii and Anadyr Gulfs and in

the Pribilof regionI of Bering Sea.

I 2 3

Karaginskii Anadyr Pribilof

Age of seals n ~±S C.V' n ~±S C.V. n x±S c.v. '1_2 1 1- 3 '2_3

Newborn 8 7 2

Yearlings 18 1.4±0.27 102.0 18 0.4±0.26 286.0 2.66

1-4 yr 46 4.5±0.23 34.5 45 3.8±0.18 31.6 5 3.8±0.16 9.5 2.28 2.36 0.00

5-12 yr 27 4.4±0.38 23.2 44 4.3±0.20 31.4 12 4.4±0.28 21.5 0.40 0.04 0.44

13 yr and older 23 4.6±0.21 23.6 14 4. I±0.46 41.8 7 4.7±0.28 20.6 0.92 0.27 1.06

Age unknown 2 3.5±0.35 14.3

Total 122 3.7±0.18 52.1 130 3.3±0.17 59.0 26 4.0±0.28 35.9 1.71 0.90 2.19

1Includes only the April 1976 (Yurakhno) sample; comparable data not available from others.

'C. V. = coefficient of variation about the sample mean.

O'--........-....l----'---....

Pups 1-4 5-12 13+

Age (yrs)

OL--=-_..-_..J......_...J....

B 1

(

~,~--~ 0 .....--"'-;;;.-_·- ........_·_.......__......-

Pups [-4 5-12 13+

Age (yrs)

ci

Z

_ 30 l/l

o

I

"-

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.c

C 20

E

Q)

I

'0 10

A

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/

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80

100

'0

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60 c

Pups 1-4 5-12 13+

Age(yrs)

c 40 Q)

Q)

a.. 20

B 2 r-----

I

/

I

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I

I

I

I

I

I

I

.r:-.~

.I / ""-.3

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./

It'

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,

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Pups [-4 5-12 13+

Age (yrs)

E

Q) 10 I

-o

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.c

15

A 3

60

20

40

80

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-c

Figure 2.-Percentage ofseals infected (A) by Corynosoma semerme, and mean

numbers per host (B) in relation to age ofspotted seals taken in the Karaginskii

(1), Anadyr (2), and Pribilof (3) regions of the Bering Sea.

Figure 3.-Percentage of seals infected (A) by Terranova azarasi, and mean

numbers per host (B) in relation to age ofspotted seals taken in the Karaginskii

(I), Anadyr (2), and Pribilof (3) regions of the Bering Sea.

The seals from the southeastern Bering Sea differed from the

others in that they alone had the trematode Microphallus orientalis,

the acanthocephalan Bolbosoma sp. (footnote 6), the cestode

Pyramicocephalus phocarum, and the nematode Otostrongylus circumUtus. Only the Karaginskii seals had the trematode Orthosplanchnus pygmaeus, and only they and the Navarin-Anadyr seals

had the acanthocephalan Corynosoma wegeneri and nematodes

identified as Terranova decipiens and Parafilaroides krascheninnikovi.

Quantitative comparison between regional samples could be

done only with the species ofhelminths which they had in common.

Those, of course, were the ones which most frequently and most

intensively infected these seals. The data obtained indicate substantial differences in frequency ofoccurrence ofthe helminths between

samples (Table I).

The southeastern and southwestern (Karaginskii) samples differed significantly to highly significantly in infection rate by four

species [Phocitremafusiforme, Anophryocephalus sp. (footnote 6),

Corynosoma semerme, and Anasakis simplex]; the mean numbers

per host (Table 2) also differed significantly to highly significantly

for five species [Anophryocephalus skrjabini (footnote 6),

Corynosoma semerme, C. strumosum, Anasakis simplex, and Terranova azarasi (footnote 6)]. Significant differences in infection

rate were not indicated for the cestode Diplogonoporus tetrapterus;

the acanthocephalans Corynosoma strumosum, C. vaUdum, and C.

villosum; or for the nematodes Phocascaris cystophorae, Terranova

sp. (footnote 6), and Dipetalonema spirocauda. Most of those

[excepting C. strumosum and T. azarasi (footnote 6)] also did not

differ significantly in numbers per host.

The helminth fauna of the sample from the southeastern Bering

Sea also differed significantly to highly significantly from that of

the Navarin-Anadyr sample in infection rate by nine species of

helminths [Orthosplanchnus arcticus, Phocitrema fusiforme,

Anophryocephalus sp. (footnote 6), Corynosoma semerme, C.

strumosum, Contracaecum osculatum, Phocascaris cystophorae,

Terranova sp. (footnote 6), and Dipetalonema spirocauda]. For

only P. cystophorae, however, did the numbers per host differ

significantly.

Some differences between regional samples also were apparent in

the species diversity of helminths in seals of different age classes

(Table 3). The clearest tendency toward increased diversity in relation to the age of the hosts was evident in the seals from the

southeastern Bering Sea. In the Anadyr sample, conversely, a tendency toward diminution in number ofspecies was indicated in the

oldest age group of seals. The coefficient of variation of species

diversity also was least overall (35.9%) in the southeastern sample

and lower for each age group than in the other regional samples.

DISCUSSION

The great similarity between the three samples of seals in the

composition of their helminth faunas indicates a high degree of

uniformity in the diets ofthe spotted seals in all regions. The greater

similarity in some respects between the helminths of the southeastern and Karaginskii seals than between those ofthe southeastern and

64
Navarin-Anadyr concentrations is notable and may be attributable

to the greater similarity of habitats occupied by the seals in

Karaginskii Gulf and the Pribilof-Bristol Bay regions, with consequent availability of similar, subarctic prey. The waters of the

Navarin-Anadyr region, conversely, are appreciably deeper and

colder than ,hose of the southeastern and southwestern shelves of

the Bering Sea and support a predominantly arctic assemblage of

organisms (Zenkevitch 1963).

Although the availability to the seals of somewhat different

assemblages of prey in each of the three regions may account for

some of the difference between their helminth faunas, other factors

such as prey selection may be of equal or greater importance. That

is, the spotted seals inhabiting each region may exhibit learned,

traditional, or inherited preferences for different kinds or sizes of

prey than those in the other regions, the result of which could be

infection by different kinds and numbers of helminths. That this is a

plausible factor is suggested by the distinct differences in helminth

faunas between the southeastern Bering Sea spotted seals and their

sympatric relatives, the Pacific harbor seals, Phoca vitulina

richardsi, of the Pribilof Islands (Shults 1979,7 1982). The same

kinds of prey were available to both species ofseals at the same time

(April) and some of those were eaten by both species (Lowry and

Frost 1981). Nevertheless, the harbor and spotted seals were infected

in common by only six species of helminths [Anophryocephalus sp.

(footnote 6), Diplogonoporus tetrapterus, Corynosoma semerme,

C. strumosum, Contracaecum osculatum, and Dipetalonema

spirocauda]. The infection rates by each helminth also were markedly different in the two species of seals. Furthermore, the harbor

seals lacked the other 12 species which were present in the spotted

seals and were infected by one (Corynosoma hadweni) which was

absent from the spotted seals. The contrasting results indicate that

these two closely related species of seals, given access to the same

food sources, have somewhat dissimilar dietary preferences as a

consequence of learned or inherited behaviors. We suggest that the

same may be true of the spotted seals in the three areas where

breeding is concentrated. Since each is genetically differentiated to

some degree, as indicated by their craniological variation (Fedoseev

1984), a corollary may be behavioral differentiation.

In our opinion, the helminthological findings reported here lend

some support to the concept of three semidiscrete subpopulations of

spotted seals in the Bering Sea, as has been indicated by the

distributional and craniological data.

'Shults, L. M. 1979. Helminth parasites of the Pacific harbor seal, Phoca vituliM

richardsi, from Alaskan waters. Unpubl. manuscr., 10 p. Institute of Marine Science, University of Alaska, Fairbanks, AK 99701.

ACKNOWLEDGMENTS

We wish to thank Robert L. Rausch, Murray D. Dailey, and Carol

A. Nielsen who read and commented on an earlier draft of this

report. Support for our work was provided in part by the Pacific

Research Institute of Fisheries and Oceanography, U.S.S .R. Ministry of Fisheries, and the Frunze State University (Delyamure,

Yurakhno, Popov), and in part by the U.S. Bureau of Land Management through interagency agreement with the National Oceanic

and Atmospheric Administration, as a part of the Outer Continental

Shelf Environmental Assessment Program (Shults and Fay).

LITERATURE CITED

BEKLEMISHEV, V. N.

1970. Population biology as one of the theoretical bases for mosquito control.

In Biocenological basis of comparative parasitology, p. 202-214. Nauka,

Moscow.

BRAHAM, H. w., J. J. BURNS, G. A. FEDOSEEV, and B. D. KROGMAN.

1984. Habitat partitioning by ice-associated pinnipeds: Distribution and density of seals and walruses in the Bering Sea, April 1976. U.S. Dep.

Commer. , NOAA Tech. Rep. NMFS 12:25-47.

BREEV, A. K.

1976. Applications of mathematical methods in parasitology. Izv. GOSNIORKH 105:109-126.

CHAPS II, K. K.

1969. Taxonomy of seals of the genus Phoca sensu stricto in the light of

contemporary craniological data. In V. A. Arsen'ev, B. A. Zenkovich, and

K. K. Chapskii (editors), Marine mammals, p. 294-304. Nauka, Moscow.

DELYAMURE, S. L., M. V. YURAKHNO, and V. N. POPOV.

1979. Composition of helminths as a population marker in seals. Priroda

1979(5):111-113.

FEDOSEEV, G. A.

1984. Use of nonmetrical characters ofskulls of Bering Sea seals in a study of

the phenotypic structure of their populations. U.S. Dep. Commer. , NOAA

Tech. Rep. NMFS J2:49-54.

GOL'TSEV, V. N., M. V. YURAKHNO, and V. N. POPOv.

1978. On the question of local Karaginskii and Anadyr populations of the

Bering Sea larga. Zool. Zh. 57:280-287.

LOWRY, L. E, and K. J. FROST.

1981. Feeding and trophic relationships of phocid seals and walruses in the

eastern Bering Sea. In D. W. Hood and J. A. Calder (editors), The eastern

Bering Sea shelf: oceanography and resources, Vol. 2, p. 813-824. Univ.

Washington Press, Seattle.

MOHR, E.

1965. Dber Phoca vituliM largha Pallas, 1811 und weissgeoorene Seehunde.

Z. Saugetierkd. 30:273-287.

SHAUGHNESSY, P. D., and E H. FAY.

) 977. A review of the taxonomy and nomenclature of north Pacific harbour

seals. J. Zool. (Lond.) 182:385-419.

SHULTS, L. M.

1982. Helminths of the spotted seal, Phoca largha, from the Bering Sea. J.

Wildl. Dis. 18:59-62.

TIKHOMIROV, E. A., and G. M. KOSYGIN.

1966. Prospects for commercial sealing in the Bering Sea. Rybn. Khoz.

8:25-28.

ZENKEVITCH, L.

1963. Biology ofthe seas ofthe U.S.S.R. Wiley-Inlerscience, N.Y., 955 p.

Abundance and Distribution of the Pacific Walrus,

Odobenus rosmarus divergens: ~esults of the First

Soviet-American Joint Aerial Survey, Autumn 1975

JAMES A. ESTESl and VITALI N. GOL'TSEV2

ABSTRACT

An aerial survey ofthe Pacific walrus, Odobenusrosmarus divergens, coordinated between the Soviet Union

and the United States, was carried out during autumn 1975. Purposes of the survey were to estimate walrus

abundance and distribution, and to evaluate aerial survey methods. Biologists from the United States surveyed

the edge of the pack ice from Pt. Barrow west to long. 174°W. Biologists from the Soviet Union surveyed coastal

areas and the edge of the pack ice east to long. 178°W. Congregations of walruses on shore were counted from

aerial photographs, the distribution and abundance of walruses hauled out on the pack ice were estimated from

random and systematic aerial transects. Walruses were most abundant between about long. 162° and 16SOW in

the U.S. sector. Most of these animals were associated closely with the southern edge of the pack ice. The

number of walruses hauled out and the frequency distribution of group size varied significantly among days.

Abundance estimates in the U.S. sector ranged between about 2,500 and 100,000 animals. In the So"iet sector of

the Bering and Chukchi Seas nearly 100,000 walruses were counted from photographs of coastal aggregations,

and 26,000 were estimated from surveys of the pack ice. The number in the Bering Sea was greater than usual,

possibly due to unusually heavy sea ice in the western Chukchi Sea. Although these and earlier data support the

notion that the Pacific walrus population has increased in size in recent years, their substantial bias and

variation contribute to unacceptably wide confidence limits on estimates of abundance and population trends.

PE310ME

AepoBH3yaJlbHble HaOJlIOAellHR 33 THXOOKealiCKHM MOP*OM, CKOOPAHHHPOB3HHbie MemAY COBeTCKHM

COt010M II ClUA, 6MnH BblnOJ1HeHbl QCeHblO 1975 r. C ttenblO H1YIlfeHHR pacnpeAeJleHHII, OlteHKH 3anaCOB, a TaK>Ke

anpo6HpoB311HR pa3Hblx cnoe0608 alpoYQeT3. AMepHK3HcKHe HccneAOB3TellH oOcne.o,o03JlH paiioH KpOMKH

JlbA3 OT Mhlca liappoy AD 1740 3.,[1,•• CooeTCKHe HccneAo03TenH OCMOTpeJlH npHopeiKHble paiiOHbI" KpOMKy JlbA3

Ha BOCToKe AO 178° 3.A.. nOAC'IeT MoplKeH 113 nelK6HIl\3X npoBoAHnCA no 33P0<!>OTOCIIHMK3M. PacnpeAeneHHe H

KOJlHlLfeCTRQ Mopmeii liS nb):(y onpe,ll,eJlHIlOCb oeCCHCTeMHO, a TaKiKe no cxeMe lIa y'leTHbiX nOilocax. HaH60ill.l11ee

KOnll'leCTBO MOplKe" 33perHCTp"pOB3110 MelKAY 1620 3.A. H 165° 3.A. B 3Mep"K3HcKOM ceKTope. 3TH 3BepH B

OCH08HOM pacnOilorailHcb 86ilH3" tOmHOH KpOMKH naKODoro ilb)).3. KOilHlfeCTBO MopiKeH Ha ilb,uy, 'laCTOTa

BCTpel.1aeMOCTH CTa,n H HX BellH'lHHa 311a'lHTeilbit H)MeItMIIHCb B OT~enbllble ,nIlH. lJHcneHHOCTI. lBepeH B

3Mep"KaIlCKoM ceKTope Kone63noCb OT 2,500 AO 100,000 ronOB. B COBeTcKOM ceKTope IiepHHroB3 H

IfyKoTcKoro MopeH OKono 100,000 rOJlOB nOAC'IHT3Hbl no UP0<!>oTorpa<!>IIAM nelK6HIl\; 26,000 nOAC'IHTaHbI no

a3poBH3yanbHbiM Ha6nlO,neHHAM tla naKODOM J1bJl.Y. KOnH'-tfCT80 MOp>KeH D liepHHr080M Mope 6b1no 6onbwe,

'leM 06b1'lHO, 'lTO BOlMomHO C8HlallO C THmelloH ne;J.oBoH o6cTalloBKoH B 3anallHoH 'laCTH lfyKoTcKoro MOpH.

HecMoTpH Ha TO, l.1TO HaWM ,natlHble Ii 60nee paUHHe HccnellOBaUHH nOllT8epmJl.alOT MHeHMe 0 pocTe

1l0nYIlA~HH THXOOKeaHCKoro Mopma B nOClle~HHe ro.Ql.I, TeM He Meuee HeT 60i1bWOH yBepetiHOCTH B

llOCTOBepHOCTH OI~eHOK 'lHCJ1eHHOCTH H TeH,lleUl.I.HH nonynHl.I.HH BBH)lY WHpOKOH BapHa6HJ1bIlOCTII .n3HllbiX.

INTRODUCTION

The Pacific walrus, Odobenus rosmarus divergens, is conspicuous and unique among ice-inhabiting pinnipeds of the Bering and

Chukchi Seas. Walruses are closely associated with the southern

part of the polar ice cap, and they migrate great distances in

response to seasonal variation in Ihe distribution of pack ice. During late winter, the population occupies the area from Bristol Bay

(Fig. I) northwestward to Anadyr Gulf. Walruses migrate Ihrough

Bering Strait in spring. By late September, when the pack ice has

receded into the Arctic Ocean, walruses are found along the ice edge

from about Point Barrow westward to the mouth of the Kolyma

'u.S. Fish and Wildlife Service. Denver Wildlife Research Center, Center for

Marine Studies, Applied Sciences Building, University of California, Santa Cruz,

CA 95064, USA.

'Magadan Branch, Pacific Research Institute of Fisheries and Oceanography

(MoTINRO), Nagaevskaya 51, Magadan 685013, USSR.

67

River in the East Siberian Sea. At least 6,000 to 8,000 males remain

throughout the summer in Anadyr Gulf at Rudder and Meechken

Spits, and at least 12,000 remain in Bristol Bay at Round Island

(Gol'tsev 1968; Taggart and Zabel 19803 ).

During summers when the weather is warm and the edge of the

pack ice is far north (to lat. 73° or 74°N), walruses abandon the pack

ice and haul oul on Wrangel and Herald Islands and at a number of

locations along the northern coast ofthe Chukchi Peninsula. During

cooler summers, when the ice edge is farther south, they remain

with the ice ralher than coming ashore (Tomilin and Kibal'chich

1975). Formation of new ice begins in Long Slrait during early

OClober and the walruses begin to migrate southeastward toward

Bering Strait. When there is no sea ice along their migration route,

they haul out to rest on the northern coast of the Chukchi Peninsula

'Taggart, S. J., and C. Zabel. 1980. Round Island report, summer 1980. IJnpllbl.

rep., 13 p. Alaska Dep. Fish Game, Dillingham, AK 99576.
1700 E

us S R

..Commander

,",'\ Is,

••

1800

• Herald I,

.. 'l\junya"9a

,,/L

Arakamchechen

~'

• Prlbllol

• Is.

Aleulian Islands

,...• . ...,.:J... " .

Figure I.-The Soviet Far Eastern Coast, showlllI places referred to In this report.

(Nikulin 1947). The peculiarities of this distribution and of the

behavior of walruses in autumn can be used advantageously to

census a substantial portion of the total population directly.

Before about the middle of the 19th century the Pacific walrus

population had been little affected by human exploitation, although

walruses had been harvested for at least 2,500 yr by Eskimos.

During the last half of the 19th century, the walrus population

declined in abundance and range as a consequence of commercial

harvesting by Yankee whalers (Fay 1957). By the beginning of the

20th century, those harvests had decreased to a low level, and

practically ceased during World War I. Commercial harvests of

walruses were taken by the Soviet Union from 1930 to 1957. By the

late 1950's, both the USA and the USSR had forbidden the harvest of

walruses except for subsistence use by local people.

Resear'h on the natural history and population status of the

Pacific walrus began in Alaska and Chukotka in the 1930's (Belopol'skii I 39; Collins 1940) and was intensified in the 1950's

(Brooks 1954; Fay 1955; Fedoseev 1962; Krylov 1962). In 1958 the

State of Alaska and the Soviet Government initiated management

programs based on the harvests of walruses by natives in Alaskan

and Far Eastern waters (Burns 1965;4 Krylov 1968). Aerial surveys

to determine the abundance of walruses were begun by the Soviet

Union in 1958 (P. G. Nikulin in Fedoseev 1962) and by the United

'Bums, J. J. 1%5. The walrus in Alaska, its ecology and management. Alaska

Dep. Fish Game, Juneau, 48 p.

68

States in 1960 (Kenyon 19605). Later, surveys were conducted by

the Soviet Union in 1960, 1964, and 1970, and by the United States

in 1961, 1968, and 1972. The results of those surveys suggested that

walruses were increasing in abundance, though the basis for that

conclusion was weak because some portions ofthe area occupied by

walruses were not surveyed.

This paper reports the results of an internationally coordinated

aerial survey of the Pacific walrus. The accuracy and precision of

the population estimates derived from it are discussed and the utility

of aerial surveys for future studies of walruses is considered.

METHODS

During June 1975, scientists from the United States and Soviet

Union met in Leningrad to discuss procedures whereby the joint

survey of walruses would be carried out. Agreement was reached on

beginning the survey in early September, the exact time depending

on availability of aircraft. The boundary between the American and

Soviet survey areas would be the International Date Line. Because

the problems associated with surveying walruses in the pack ice

differ from those in surveying coastal haul out areas, methods

employed by the United States and the Soviet Union are discussed

separately.

'Kenyon, K. w. 1960. Aerial surveys of marine mammals in the Bering Sea, 23

February to 2 March 1960 and 25-28 April 1960. Unpubl. rep., 39 p. U.S. Bur. Sport

Fish. Wildl., Seattle, WA 98115.
American Survey

The survey was carried out along the ice edge zone of the eastern

Chukchi Sea, between Point Barrow and the International Date

Line. The northern boundary of the survey area was about 50 nmi

(93 km) north of the ice edge; the southern boundary was at lat.

69°30' N and the Alaskan coastl ine. The southern boundary at lat.

69°30'N was about 100 nmi (185 km) south of the ice edge. We

assumed that most walruses in the open water south of the pack ice

would occur within that range.

We allocated 4 d of our survey effort to the pack ice zone and I d to

the expanse of open water south of the ice edge. The survey strips

were selected at random each day from a set of 360 potential

north-south transects, I nmi (I. 85 km) apart. These were located

between long. 156° and 174°W. For surveys over the ice zone, each

survey strip crossed the area between the consolidated pack and the

southern extremity of dispersed drifting ice. The northern and

southern ends of those strips were predetermined each day, on the

basis of ice information provided by the U.S. Navy Fleet Weather

Facility and our observations from the previous day's survey.

The survey aircraft was a Lockheed P2 V6 equipped with a Global

Navigation System and long range fuel capacity. This aircraft was

selected because it afforded excellent air to surface visibility from

the nose bubble. It was flown at a speed of 150 nmi/h (278 km/h)

and at an altitude of 500 ft (152 m), except where the cloud ceiling

required a lower altitude for adequate visibility. Two observers

counted the animals along a strip extending 0.5 nmi to each side of

the flight track. We counted each walrus or group of walruses; the

number of animals per group was counted or estimated. A group

was defined as two or more walruses within about one body length

of each other. Animals within the 0.5 nmi (0.93 km) wide transect

on each side ofthe flight track were classified further as occurring I)

within the inner 0.125 nmi (0.23 km), 2) between 0.125 and 0.25

nmi (0.46 km), or 3) between 0.25 and 0.5 nmi from the flight track.

We determined those distances by sighting along the appropriate

angles marked on protractors mounted at eye level on each side of

the nose bubble. Angles were adjusted for changes in altitude.

Each day, 9 to 14 strips were surveyed. On 9 September, however,

we terminated the survey after 7 strips, because of equipment

failure. The number of strips per day was determined by the maximal range of the aircraft and the location of each transect. By this

means, we obtained random samples of the distribution and abundance of the walruses visible to us within the survey areas.

Soviet Survey

"Reference to trade names does nOI imply endorsement by the National Marine

Fisheries Service, NOAA.

Walruses in the Bering and Chukchi Seas west ofthe International

Date Line were surveyed via an IL-14 aircraft between 15 September

and 16 October. In that area, walruses occur in large numbers both

on the pack ice and on coastal hauling grounds.

•

•

.P..· p•.

..•. /

1800A RCTtC

BERING SEA

""". :~. ""'.. '

OCEA N

••

US S R

Figure 2.-Major features of the Bering-Chukchi region, showing the areas surveyed in this study.

69
The shoreline was surveyed from Ossor Spit and Karaginskii

Island, southwestern Bering Sea, to Cape Schmidt and western

Chukchi Sea (Fig. 2). The larger groups of walruses were photographed from directly overhead (Fig. 3) at an altitude of700 to 1,000

m (depending on ceiling), with a linear overlap between adjacent

frames of 30 to 35%. The areas occupied by walruses on the

photographs were measured with a planimeter, and the density of

animals was determined by sample counts with a binocular magnifier. With these data, the total number of walruses occupying the

hauling ground was estimated. In areas where density varied over

the hauling ground, walruses were counted individually, as were

those nearby in the water. We found that extrapolated estimates

varied from exact counts by less than ± 2.5%.

Reconnaissance flights were flown initially over the pack ice to

determine the distribution of walruses and ice conditions. Systematic transects were flown on subsequent days over the areas in which

walruses had been seen. The distance between adjacent transects

varied from 10 to 20 km. Estimates of abundance were based on the

area sampled and walrus density. We have no reason to believe that

the different methods we employed in surveys over the ice were of

any real consequence to our results.

The aircraft was flown at an average speed of 250 km/h. Width of

the transect was estimated from angles marked on the viewing port.

The plane was equipped with two cameras: An AFA-TE-500, 18 x

18 cm format, with a 500 mm objective lens, and an AFA-42-20, 30

x 30 cm format, with a 200 mm objective lens. From an altitude of

1,000 m, these camera systems provide respective scales of 1/2,000

and 1/5,000. The AFA-42-20 was operated simultaneously only

when there were many walruses in the water that could not be

photographed by the AFA-TE-500.

RESULTS

American Survey

The ice edge east of the International Date Line drifted in a

generally southward direction from I September when the surveys

began, to 12 September when they were completed. This movement

was as great as 139 to 185 km in some areas. The ice edge was

convoluted in the vicinity of the International Date Line, crossing

the Date Line at several locations.

Walruses were most abundant between about long. 1620

and

l65°W (Fig. 4). Large numbers of animals were observed in all ice

concentrations (Estes and Gilbert 1978). Of 3,572 walruses sighted

in the sample strips from the ice edge northward, 3,522 (98.6%)

were situated in the southernmost 6 deciles of the transects (Fig.

SA), compared with an expected 2,143 (60%) ifthe distribution had

been uniform. These data suggest that our survey area over the ice

Figure 3.-Aerial photograph of walruses on hauling ground at

Meechken Island, 18 September 1975.

70
Figure 4.-The number of walruses observed (solid line) within longitudinal

intervals of 30 along the ice edge of the eastern Chukchi Sea. Only data from 5,

8, and 12 September 1975 are included. Numbers were adjusted (dash line) by

multiplying by nln; where =the number ofstrip samples taken from the ith

interval of3° longitude and n = the mean ofthese values (after Estes and Gilbert

1978).

r-----

I

I

I

I

I

I

n= 3572 INDIVIDUALS

n= 190 GROUPS

/END TRANSECT

30 c:j-,--,--r--..,----,-.---.----,-.----r''---------

ICE EDGE 20 40 60 80 100

DECILES

A ICE

30

20

10

>-

U

Z

W

:J 0

0

W

a::

ll..

10

20

156

- Number of wolruses

observed

---Number adjusfed 10

equal sampling effort

in each 3 Dinterval

159

----,,

168 165 162

LONGITUDE

174 171

300

1500

900

0:

w

CD

::! 600 :J

Z

'"w

'" 1200

...J

«

;l:

n =9 GROUPS

END TRANSECT

40 60 80 100

DECILES

OPEN WATER

20

B

30

20

30

i

ICE EDGE

20 n=94 INDIVIDUALS

10

>-

U

Z

W 0 :J

0

W

a::

ll..

10

Distance from ft ight track (km)

sampled most of the walruses which were associated with the pack

ice. The distributional pattern of animals in the open water south of

the ice was more irregular (Fig. 5B). Hence, our survey area there

may have been too small by limiting its southward extent to lat.

69°30' N. This suggestion is partly negated by the fact that the

number of animals seen in the open water survey was very small.

The numbers of walruses counted on ice and in the water in the

three subtransects (i.e., ato 0.23 km, 0.23 to 0.46 km, and 0.46 to

0.93 km) on each side of the flight track are shown in Table I. The

probability of variation from a uniform distribution was tested by

the X2 method. The results suggest that the probability of sighting

walruses on the ice was nearly constant from ato at least 0.93 km (as

was concluded also by Kenyon 19727), whereas the probability of

sighting walruses in the water decreased at distances> 0.23 km.

For a more detailed discussion of this, see Estes and Gilbert

(1978: 1113-1114).

'Kenyon. K. W. 1972. Aerial surveys of marine mammals in the Bering Sea, 6-16

April 1972. Unpubl. rep.• 79 p. u.S. Bur. Sport Fish. Wild\., Seattle. WA 98115.

Table J.-Chi-squared tests of goodness of fit of sighted, as compared with

expected (uniform), distribution of walruses in relation to distance from the

aircraft.'

0-0.23 0.23-0.46 0.46-0.93 X2

Groups on ice

Sighted 31 41 80 I.7

Expected 38 38 76

Individuals on ice

Sighted 442 944 2,323 2372.5

Expected 927 927 1,854

Groups in water

Sighted 26 17 13 218.9

Expected 14 14 28

Individuals in water

Sighted 68 53 39 242.6

Expected 40 40 79

'From American survey only.

2P(xi> 9.2) = 0.01.

Figure 5.-Frequency distributions ofthe numbers of individuals and numbers

ofgroups of walruses sighted within decile segments ofthe survey strips, A) from

the ice edge northward, and B) from the ice edge southward in the Chukchi Sea,

5-12 September 1975 (after Estes and Gilbert 1978).

The total number of groups sighted on 8 September was an

order of magnitude greater than the number sighted on any of the

other 3 d of over-ice surveys (Table 2). Furthermore, in the overice surveys the number of walruses sighted in the water versus on

the ice each day differed highly significantly from the expected

(overall mean) number (X~ = 208.56; P < 0.01). The same

71
'Summarized from ESles and Gilberl (1978).

Table 2.-Summary of counts of walruses from the American surveys in the

eastern Chukchi Sea, 1975.'

Figure 6.-Comparative frequency distributions of group sizes of walruses

sighted on ice in the eastern Chukchi Sea, on 8 (upper) versus 5, 9, and 12

(lower) September 1975. Dash line F(X) shows the cumulative frequency distribution (after Estes and Gilbert 1978).

Table 3.-Estimates of the total abundance Cf) and standard deviation S(1')

of walruses in the eastern Chukchi Sea, based on the American surveys in 1975.

Estimated abundance

Based on number

Based on number of groups and

Dale. location. and of individuals mean group size

method of estimation T S(T> T S(T>

I Sept., over waler

Method I'

All strips 818 684 818 665

N-S strips only 1,581 1,309 1,621 1,348

Method 0'

All strips 1,026 927 1,026 954

N-S strips only 1.716 1,6% 1,760 1,740

5 Sept., over ice

Method I

All slrips 2,475 1,606 2,475 2,170

N-S strips only 4,656 2,846 4,224 4,094

Method II

All strips 5,000 2,737 5,000 2,871

N-S strips only 8,568 4,480 7,773 4,650

8 Sept., over ice

Melhod I

All strips 75,959 30,921 75,959 19,121

N-S strips only 100,568 57,689 85,848 29,222

Method II

All strips 82,620 37,428 82,620 26,020

N-S strips only 90,765 63,561 77,480 33,007

12 Sept., over ice

Melhod I

All strips 7,755 4,551 7,755 5,920

N-S strips only 13,533 7,990 11,587 9,259

Method II

All slrips 9,138 6,130 9,138 6,743

N-S strips only 12,780 9,915 10,942 8,402

Combined, over ice, all days

Method I

All strips 27,000 10,731 27,000 7,097

N-S strips only 36,337 20,616 32,871 11,511

Method II

All strips 36,680 15,127 36,680 10,191

N·S strips only 41,486 24,551 37,528 12,937

'Mean density per survey, extrapolated to total area. "All strip," include lhe

north-south strips. as well as the diagonals belween them.

'Mean number pcr ;lrip, times the total number of possible strips.

The frequency distribution of group sizes sighted indicated that a

greater proportion of the animals was in large groups on 8 September than on the combined days of 5,9, and 12 September (Fig.

6). On 5. 9, and 12 September, only a single group larger than 50

walruses and only 6 groups larger than 25 walruses were sighted

(Fig. 6). On 8 September, 12 groups larger than 50 walruses and 62

groups larger than 25 walruses were sighted. The mean group size

tended to be about 10 times greater on ice than in water.

We employed two methods to estimate the abundance of walruses

in U.S. waters. Method I was a modified ratio of means estimator

whereby the sample density of walruses was multiplied by the area

surveyed. Method II was independent of area, treating each sample

transect as a random sample of the ice between long. 156° and

174°W. Essentially, Method II transformed the sample space into a

single dimension which was divided into equal sampling intervals,

each 1.85 km in length. Both methods were modified to obtain

estimates based on the product of group density (or number for

Method II) and mean group size. A variance was calculated for each

population estimate (Estes and Gilbert 1978).

Estimates of walrus abundance ranged between 818 and 1,621 in

the open water and between 2,475 and 100,568 in the ice. Coeffi100 150 200

GROUP SIZE

100 150

GROUP SIZE

5. 9. AND 12 SEPTEMBER

50

25 50

• __1------ -r---------------------- Flit)

r----- .------- ._J •__ J ,

,

, __ J

8 SEPTEMBER

• J-------. F(.)

r-.J

, .---

,

J

1.0

04

0.4

0.8

'.0

08

>-

u

z

0.6

o

OJ

0::

"-

>-

u

z

OJ

::> 0.6

o

OJ

0::

"-

Date. location. and umber of groups Number of individuab

no. of strips (n) On ice In water On ice In water

I Sept.. over water ( 10)

TOlal 21 42

Mean/strip 2.1 4.2

5 Sept.. over ice (9)

Total 10 12 106 19

Mean/strip 1.1 1.3 11.8 2.1

8 Sept.. over ice (14)

Total 118 2~ 3.150 63

Mean/strip 8.4 1.6 225.0 4.5

9 Sept.. over icc (7)

Total 18 9 161 38

Mean/strip 2.6 1.3 23 5.4

12 Sept.. over ice (IJ)

Total 6 13 292 3X

Mean/strip 0.5 1.0 22.5 2.9

comparison, tested without the data from 8 September. indicated

no significant difference among days (;X~ = 5.91; P > 0.05).

Thus, there is high probability that, not only was a much larger

number present in the area on 8 September, but a much higher

proportion of them was on the ice.

72
cients of variation [S(hIT, whereT = estimated size of the population and S(h = standard deviation of estimated population size]

ranged between 0.26 and 0.99 (Table 3, mean = 0.62).

Soviet Survey

The coast of Siberia from Ossor Spit and Karaginskii Island,

eastern Kamchatka, to Kolyuchin Island in the Chukchi Sea, and the

ice edge from Cape Billings to Wrangel Island (Fig. 2) were surveyed during reconnaissance flights on 17 and 19 September and 5

October. Coastal hauling grounds were identified in the Bering Sea

on John the Baptist Island, the western extremity of Meechken Spit,

Rudder Spit, Nunyangan Island, Arakamchechen Island, the eastern

end of Big Diomede Island, and near the former village site of

Naukan. In the Chukchi Sea, coastal hauling grounds were located

at Cape Inchoun and Cape Serdtse Kamen.

About 77,000 and 20,000 walruses were counted from photographs taken of coastal hauling grounds in the Bering and Chukchi

Seas, respectively (Table 4). The large numbers of walruses usually

found on or near Wrangel Island in September apparently were

farther south, because of unusually heavy ice in the western Chukchi Sea. The number in the Bering Sea was much larger than usual,

Table 4.-Number of walruses counted and estimated on coastal hauting grounds along the Soviet Coast, SeptemberOctober 1975.

Number of Area occupied

Date Time Weather walruses per walrus (m2 ) Basis

John the Baptist Island

4Ocl. 1313 Overcast, calm 200 4 Individual counl.

Meechken Spit

18 Sepl. 1007 Clear, calm 8,242 1.8 Extrapolated from

density and area.

18 Sepl. 1007 Clear, calm 8,044 1.8 Individual counl.

21 Sepl. 1547 Clear, light wind 500-600 Visual estimate.

Rudder Spit

21 Sepl. 1533 Clear, light wind 445 Individual counl.

Nunyangan Island

18 Sepl. 1153 Overcast, stormy 1,152 Individual counl.

19 Sepl. 0955 Overcast, windy 627 Individual counl.

21 Sept. 1412 Clear, light wind 19.977 1.54 Extrapolated from

density and area.

90cl. 1033 Overcast, windy 1,628 Individual counl.

Arakamchechen Island

18 Sepl. 1215 Overcast, stormy 3,996 1.89 Extrapolated from

density and area.

19 Sepl. 1007 Overcast, windy 1,208 Individual counl.

21 Sept. 1400 Clear, light wind 41,882 1.56 Extrapolated from

density and area, and

individual counl.

90cl. 1050 Overcast, windy Several thousand

sleeping in the water.

Big Diomede Island

21 Sepl. 1132 Clear, light wind 4,228 2.43 Individual counl.

21 Sept. 1146 Clear, light wind 3,516 Individual count.

Naukan

21 Sepl. 1132 Clear, light wind 2,144 1.76 Extrapolated from

density and area, and

individual counl.

5Ocl. 1233 Clear, calm 2,326 Walruses approaching

from the north.

7Ocl. 1146 Clear, light wind 2,417 1.32 Many walruses in the

water.

9Ocl. 1150 Overcast, windy 3,357 1.88 Walruses approaching

from the north.

Inchoun

21 Sepl. 1115 Clear, light wind 5,029 1.70 Extrapolated from

density and area, and

individual counl.

5 Oct. 1246 Clear, calm 7,742 1.67 Extrapolated from

density and area, and

individual counl.

70et. 1132 Clear, windy 3,700 1.30 Extrapolated from

density and area, and

individual counl.

9 Oct. 1202 Light clouds, calm 5,700 Individual counl.

Cape Serdtse Kamen

5Ocl. 1320 Clear, calm 11,972 1.95 Extrapolated from

density and area, and

individual counl.

90e1. 1245 Clear, calm 9,188 2.83 Extrapolated from

density and area, and

individual counl.

73
possibly for the same reason. For example, during September 1970,

only 20,000 walruses were observed on coastal hauling grounds in

the Bering Sea (Gol'tsev 19728 ).

Walrus hauling grounds on John the Baptist and Nunyangan

Islands were recorded for the first time during the autumn of 1975.

Those animals on John the Baptist Island apparently are part of a

small herd that has remained in the vicinity of Petl1r and Anastasia

Bays and in Olyutorskii Gulf, during the past several summers. V.

V. Zimushk09 saw 12 walruses 11 to 15 km offthe coast of Anastasia

Bay, 3 walruses near Cape Vitgenshtein, and 5 walruses about 59

km east of Cape Navarin. These animals probably all belonged to

.the group that summers in the Koryak region. Walruses that hauled

out on Nunyangan Island may have occupied the Akkaniiskii hauling ground during earlier years. Up to 12,000 animals were observed by Gol'tsev at Cape Kriguigan on the Akkaniiskii hauling

ground during autumn of 1972, 1973, and 1974; however, in 1975

this area was not occupied.

Most of the walruses associated with the ice edge during September were concentrated about 15 to 19 km east of Cape Billings

and in a narrow strip of ice which extended from Kolyuchin Island

to the Two Pilots Spit. Smaller numbers of walruses were seen from

Cape Billings southeastward to the edge of the ice.

The ice edge in Long Strait during September 1975 was 140 to 157

km farther east than usual. The ice coverage also was greater than

usual. During most years, ice conditions are less severe, and large

concentrations of walruses occur in the area west and southwest of

Wrangel Island, some 296 to 352 krn north oftheir location in 1975.

Many small polynas were present near Cape Billings. Small

groups of walruses (3 to 5 animals), frequently including females

with calves, were observed moving in a southeasterly direction.

From Cape Billings to long. 178°W, a densityofO. 76 walruses/km2

was observed, from which we estimated an overall abundance of

65,000 animals in that area. The density of walruses between the

mouth ofthe Amguema River to Cape Onman was 16.4/km2

, which

gave an abundance estimate in that area of 23,000 animals. Because

most animals seen were in the water, these estimates probably were

conservatively biased. The area of heavy ice west of Cape Billings

was not surveyed; there was no ice along the coast southeast of

Kolyuchin Bay, and walruses were not sighted in the water in that

area.

The weather turned very cold in mid-September, and we expected

this to speed up ice formation in the Chukchi Sea, forcing the

walruses to migrate southeastward and to occupy shore hauling

grounds earlier than usual. However, a storm passed over the Chukchi Peninsula in late September breaking up the eastern edge of the

pack ice and driving the ice front 93 to 185 km westward. about to

the longitude of Cape Schmidt. On 5 and 6 October, walruses were

observed in the pack ice 9 to 15 km north of Cape Schmidt, but the

general distributional pattern along the northern coast was unchanged from that observed in September. We estimated 26,000

walruses in the ice, about 20,000 of which were concentrated in two

areas totaling 480 km2.

We estimated walrus abundance in the Soviet sector from data

obtained from the Chukchi Sea on 5 and 6 October and from the

Bering Sea on 18 and 21 September, because the highest counts were

obtained on those days. Those data provided an '~stimate of 128,000

to 130,000 walruses west of the International Date Line (Table 5).

8Gol'tsev. V. N. 1972. Distribution and assessment of numbers of the Pacific

walrus in the autumn of 1970. Abstracts 5th all-union conf. stud. marine mammals

1:25-28. Makhachkala.

"V. V. Zimushko, Fisheries Biologist, Pacific Research Institute of Fisheries and

Oceanography, Nagaevskaya 51. Magadan 685013. pers. commun. August 1975.

74

Table 5.-Summary of numbers of walruses on coastal bauling grounds and on

the ice in the Soviet sector, based on aerial surveys in 1975.

Number of

Location Date Time of day walruses

On coastal hauling grounds

John the Baptist Island 4 Oct. 1313 220

Meechken Spit 18 Sept. 1007 8,242

Rudder Spit 21 Sept. 1533 445

Nunyangan Island 21 Sept. 1412 19,977

Arakamchechen Island 21 Sept. 1400 41,882

Big Diomede Island 21 Sept. 1142 4,228

Naukan 21 Sept. 1132 2,144

[nchoun 5 Oct. 1245 7,742

Cape Serdtse Kamen 5 Oct. 1315 11,972

On ice floes

Cape Billings to

Kolyuchin Island 5-6 Oct. 26,600

In water

Mechigmen Bay 21 Sept. 1350 5,500

Cape Dezhnev to

Cape Serdtse Kamen 5 Oct. 1235-1315 1,500

Grand total 130,452

Combined with results obtained in the U.S. sector, a total population of roughly 140,000 to 200,000 walruses was estimated.

DISCUSSION

Pacific walruses have been exploited in rather large numbers in

the past by both the United States and the Soviet Union. There is still

a substantial take in both countries. Furthermore, walrus habitat

may be affected eventually by commercial developments, such as

hydraulic dredging for bivalve mollusks and petroleum extraction

from the continental shelf. Although the effects of those activities

are uncertain, they could act to the detriment of the walrus population. In view of those potential difficulties, a reliable means of

censusing the walrus population is of considerable importance to

both the United States and the Soviet Union.

Aerial surveys provide information on the abundance and distribution ofthe population. The rei iability of estimates of those two

parameters is affected by both precision and bias in the surveys. The

relative importance of precision and bias in estimates of abundance

and distribution is quite different for walruses on coastal hauling

grounds than for walruses in the pack ice.

The difficulties encountered in censusing walruses in the pack ice

have been discussed in detail by Estes and Gilbert (1978); we

present only a su~mary ofthat discussion here. The major problems

in interpreting the survey data are that an unknown fraction of the

population is visible at any given time, and the animals tend to

congregate in several spatial scales. These sources of bias and

imprecision cannot be separated. The number of walruses hauled

out on the pack ice probably changes considerably with time, but we

cannot determine with certainty that this was the cause of the high

variation among days for the population estimates in the ice edge.

Although the population estimate probably is conservative, it must

be based on the pooled data from all days in which the survey was

carried out. Because the coefficient of variation of the estimates

ranged from 0.26 to 0.99, however, the lower bounds of 95%

confidence limits around the estimates were between 0 and about

50% of the mean. The unfortunate result of this situation is that no

estimate ofthe walrus population in the pack ice can be defended on

scientific grounds much beyond the maximum actually counted.

For walruses on shore, censusing is somewhat less problematic

because large numbers of animals can be counted directly. The
primary requirement is to obtain the counts when the greatest

numbers of walruses are hauled out. Since no estimates are made,

sampling variation is not a problem. The major unanswered questions concerning the reliability of these counts are: I) What fraction

of the total number of walruses in the area were on shore at the time

of the survey; 2) to what extent do walruses move between haul out

areas in the time between surveys of separate areas; and 3) how

many walruses were outside the surveyed areas? We doubt that the

answer to the third question would have had any significant influence on our estimates because the walruses sighted were well within

the boundaries of the areas surveyed. Also. the historical records of

distribution of walruses in September-October show similar spatial

distribution. If large numbers of animals ever occurred outside the

areas surveyed, they probably would have been recorded in the

historical data. The extent to which walruses moved between hauling areas, however, is unknown. Animals observed at Meechkin

Spit on 18 September and at Inchoun and Cape Serdtse Kamen on 5

October could have been at one of the other hauling areas counted

on 21 September, in which case they could have been counted twice.

In view of the short distance between Inchoun and Cape Serdtse

Kamen, the possibility that animals moved from one to the other

during the time of the survey cannot be discounted. Also unknown

is the fraction of walruses in a given area that is likely to be on shore

at any particular time. Recent studies of walrus activity and behavior at Round Island in Bristol Bay have shown that the number of

walruses on shore varies over about lO-d intervals by more than an

order of magnitude; greatest numbers usually tend to be on shore for

less than a day (Taggart and Zabel footnote 3). The proportion of

walruses in the area which haul out on Round Island during this peak

period remains unknown, but preliminary data from a small number

of animals instrumented with radio transmitters indicate that it is

less than unity (Taggart and Zabel footnote 3). These observations

suggest that direct counts of walruses on shore are biased low, to an

extent which probably varies from day to day.

In summary, the numbers of walruses sighted, both on the pack

ice and on the shore, underrepresent to an unknown extent the

numbers actually present in those areas. In the pack ice, this is

complicated further by highly imprecise estimates of the numbers in

the areas not surveyed. As a result, the only reliable numbers are of

the animals actually counted; the statistical confidence in larger

estimates of the popuiation is extremely low. The true number of

walruses must be greater than the number seen, but the magnitude of

the difference remains unknown.

Interpretation of recent changes in the range of Pacific walruses

presents similar difficulties, mainly due to year-to-year variation in

the distribution of pack ice and the opportunistic manner in which

most observations are made. In 1975, walruses were observed in

Listvenichnyi Bay, Kamchatka. Small groups were seen also in

Karaginskii Gulf, as well as on Verkhoturov Island, near the Commander Islands, and in the Okhotsk Sea. Also, several hauling

grounds in the Bering Strait region which had not been occupied by

walruses for many years were reoccupied. Although these observations suggest an increasing range of the population, they are complicated by the fact that the pack ice during the summer of 1975

remained unusually far south. In the southeastern Bering Sea,

occasional walruses have been observed recently near coastal areas

and at the mouths of major rivers in eastern Bristol Bay where they

had not been reported previously. These observations might be

interpreted as evidence of an expanding range but also could be

ascribed to increased numbers of observers in those areas.

Despite those uncertainties, most available evidence suggests

that the Pacific walrus population has increased over the past several

75

decades (Table 6). Fay (1957) and Nikulin (in Fedoseev 1962)

estimated that the number of walruses had declined to an all-time

low of about 40,000-50,000 by the mid- to late 1950's. Various

estimates by Fedoseev (1962), Kenyon (footnotes 5, 7), Burns

(footnote 4), and Gol'tsev (footnote 8) suggested that the numbers

increased subsequently. Although not much confidence can be

placed in any of those numbers, the trend of increase probably is

significant. We point out, however, that this conclusion is based

largely on intuition, and we urge that it be used with caution.

Future research must addre~s the question of walrus activity

rhythms and movements, both at the level of the individual and the

population. Such information would be useful for interpreting possible exchange of individuals among groups, and for estimation of

the fraction of walruses that can be seen and counted at any particular time. Until studies ofthis sort are completed, reliable assessment

ofthe actual abundance of the Pacific walrus population will remain

an illusive goal.

Table 6.-Summary of population estimates of Pacific

walruses from surveys during the past two decades.

Population estimate

Year (thousands) Source

1950's 40-50 Fay 1957

1960 50 Fedoseev 1962

1960 78-113 Kenyon 1960'

1965 90 Burns 19652

1970 101 Gol'tsev 1972'

1972 85-162 Kenyon 1972'

1975 140-200 This report

1See text footnote 5.

2See text footnote 4.

'See text footnote 8.

'See text footnote 7.

ACKNOWLEDGMENTS

This work was a collaborative effort carried out under auspices of

the US-USSR Agreement on Cooperation in the Field of Environmental Protection. We thank the many people whose efforts in

developing and implementing the Agreement made this work possible. James R. Gilbert helped with survey design and data analysis,

and participated in the American survey. Various other individuals

from TINRO (Magadan), Alaska Department of Fish and Game,

National Marine Fisheries Service, Office of Aircraft Services

(U.S. Department of the Interior), Naval Arctic Research Laboratory, and the U.S. Navy Fleet Weather Facility assisted us either as

observers or through technical and logistic support. John J. Burns

translated some of the work from Russian to English. Francis H. Fay

reviewed and edited several earlier drafts of the manuscript, and

helped with communication of information between us. Janet M.

Pumphrey helped locate Russian place names. Financial support

was provided by the Magadan Branch of TINRO, and the National

Fish and Wildlife Laboratory, U.S. Fish and Wildlife Service.

LITERATURE CITED

BELOPOL'SKlI, L. O.

1939. On the migrations and ecology of reproduction of the Pacific walrus

(Odobaenus rosmarl/S divergens lIIiger). Zoo!. Zh. 18:762-774.

BROOKS, J. W.

1954. A contribution to the life history and ecology of the Pacinc walrus. M.S. Thesis, University of Alaska, Fairbanks, 103 p.

COLLINS, G.

1940. Habits of the Pacific walrus (Odobenus divergens). J. Mamilla!.

21:138-144.
ESTES, J. A., and J. R. GILBERT.

1978. Evaluation of an aerial survey of Pacific walruses (Odobenus rosmnrus

divergens). J. Fish. Res. Board Can. 35:1130-1140.

FAY, F. H.

1955. The Pacific walrus: spatial ecology, life history, and population. Ph.D. Thesis, Univ. British Columbia, Vancouver, B.C., Canada,

171 p.

1957. History and present status of the Pacific walrus population. Trans.

North Am. WildI. ConL 22:431-443.

FEDOSEEV, G. A.

1962. On the status of stocks and distribution of the Pacific walrus. Zool.

Zh.41:1083-1089.

GOL'TSEV, V. N.

1968. Dynamics of coastal herds of walruses in connection with their dis76

tribution and numbers. III V. A. Arsen'ev and K. I. Panin (editors), Pinnipeds of the northern part of the Pacific Ocean, p. 205-215. Pischevaya

Promyshlennost', Moscow.

KRYLOV, V. I.

1962. Rates of reproduction of the Pacific walrus. Zool. Zh. 41: 116-120.

1968. Present condition of the Pacific walrus stocks and prospects of their

rational exploitation. In V. A. Arsen'ev and K. I. Panin (editors), Pinnipeds

of the northern part of the Pacific Ocean, p. 189-204. Pischevaya Promyshlennos!', Moscow.

NIKULIN. P. G.

1947. Biological characteristics of the shore herds of the walrus on the

Chukchi Peninsula. 1zv. TINRO 25:226-228.

TOMILlN, A. G., and A. A. KIBAL'CHICH.

1975. Walruses of the Wrangell Island region. Zool. Zh. 54:266-272.
An Analysis of a Hypothetical Population of Walruses

DOUGLAS P. DeMASTER1

ABSTRACT

A series of computer simulations of the Pacific walrus population, using a variable Leslie model, were

conducted primarily to test the hypothesis that the population increased from about 70,000 in 1955 to about

200,000 in 1975 and, secondarily, to evaluate the reliability of the data available on adult survival rates.

Published estimates of the population size, the sex ratio of adults, age at sexual maturity, average reproductive

rate, adult mortality, and size and sex/age composition ofthe annual harvests were incorporated into the model.

The results suggested that, either the estimates ofsize of the 1955 population were too low, or that the survival

rates of adults were significantly higher t:tan believed. They suggested further that an increase to 200,000 in 20

yr would have been possible, if the- initial population in 1955 had been made up of about 94,000 to 98,000

animals, the sex ratio of adults was 1 male:3 females, and the adult survival was 0.96, with nonlinear density

dependence. Such an increase would have been impossible with linear density dependent functions, smaller

initial population size, or lower adult survival rates. The maximum sustained yield (MSY) of the hypothetical

.population, assuming continuation of the current harvest composition at3 males:l female, would be between 3

and 5% and should be available when the population is between 59 and 91% of the carrying capacity (K),

assuming environmental stability. The maximum net productivity (MNP) of this hypothetical population was

estimated to be attained at 50 to 84% of K.

PE310ME

Mo,neilHpOB31tHe Ita C'ieTHo-pewalO~eM yCTpOHCTBe 6b1J1o npoHloe,nelio c nOMOLLJ.blO <mepeMeltHOH MO)J.ellH

J1ecnHJ), rn3BHbiM 06pS10M, ~fT06bl npOBepHTb rH"OTely 06 yoeneqeHHH 'IHCneHHOCTH THXOOKeaHCKoro Mopma

npH6JIHJHTeJlbHO c 70,000 B t955 r. 110 200,000 rOJlOB B t975 r., a u"",e Ol\eHHTb Halle"'HOCTb HMelOll\HXCR

,lJ.3HHhlX 0 cnoco6nocTH BbnKHB3HHA BlpOCnb1X 3BepeH. Ony6J1HKOS3Hllble Jl.3HHble no ou.ellKe ReJlH'IH"bl

nonYilALJ."", nOJlOBoMY COQTHOrneHHIO B3pocnblx, B03pacTy nOilOBoro cOlpe03HHJI, CpeJl.HeMy TeMny

BocnpoH3Bo)J,CTB3, cMepTHocTH BJpOCJlItIX, BOlpacTHoMy cacTaRy II e)KerOjl.HOH )J.06b1'tH HCnOnbJOB3JlHCb B

MO,ll,eJlH. Pe3YJlbT3Tbi ,ll,310T OCHOB3HHe npe,ll,n01l3r3Tb, "ITO BellH"IHH3 nonYllR~H" B 1955 r. 6bl1l3 ClIHWKOM

HH3KO" "11" TeMn BbliK"BaHHH B3POClIblX 6bl1l rOpS3,ll,O Bblwe, "IeM 31'0 C"IHT3JlOCb pSHee. KpOMe Toro,

pe3YllbTaTbi 1l03BOJlHIOT npe,ll,1l0JlOraTb, "ITO yBeJlH"IeH"e ,ll,O 200,000 rOJlOB B Te"leHHe 20 neT 6blJlO 6bl

80]MOiKIlItIM, eCll" nonyJlHUHH 8 1955 r. COCT3BJlHJl3 94·98,000 rOJlOO, nOllOBoe COOTHoweHHe B3POCJlItIX 1 caMe~:

3 caM"H HBbl"'HBaHHe BJpOCJlblX • 96% CHeJlHlleiiHOii nJlOTHOCTblO JaBHCHMOCTH. Ta"oe yBeJlH'''HHe 6b\JlO 6b\

HeB03MOIKHbiM C JlHHeHHOH OJlOTHOCTblO laB"CHMOCTM, MeHbweH nepBOHa"laJlbHOH OeJIH"IHOH nonyJlRUMM, MllM

HH]KMM BbliKMB311HeM B3POCJlbIX. MaKCHMallbliaR emerO,ll,HaR ,Il06b1"1a rHnOTeTH"IeCKOH nonYJUI~"", npH

coxpaHeHHH B ,Il06bl"le COOTHOllleHHH 1 caMKa: 3 caMua, 6Y,IleT COCTaBJlATb 3 - 5%. TaKo" ypooeHb ,Il06bl"'H

BOJMO",ell, eCJlH npH Ma"CHMaJlbIlOii nJlOTHOCTH caMoperyJlHpylOll\eiicR nonYJlRI\HH [K = 59 - 9t%1 H

cTa6HJlbHOCTIt lKOCHCTeMbl. C"IHTaeM, "ITO MaKCHMaJlbHOe "'HC1'oe "POH]BO,lJ.CTOO lToro rH"OTC1'H...eCKoro

lIaCeJleHH" lIoCTHraeTCR npH 50 - 84% K.

no oueHKe aOTopa MaKCHMaJlbHaH ...HC1'a9 "POAyKTHBHOCTb .naHHoH rHnoTe1'WlecKoH nonYllH1.\HH MOlKe1'

6blTb lIocTHrHyTa npH K = 50 • 84%.

INTRODUCTION

In the late 1950's, the size of the Pacific walrus, Odobenus

rosmarus divergens, population was considered to have been between 40,000 and 70,000 animals (Fay 1957; Kenyon 1960;2

Fedoseev 1962). Nevertheless, Kenyon (footnote 2) felt that the

actual population size in the late 1950's may have been higher than

70,000. Estes (1976),3 Estes and Gilbert (1978), and Estes and

Gol'tsev (1984) supported Kenyon's judgement with evidence that

'National Fish and Wildlife Laboratories, U.S. Fish and Wildlife Service, Anchorage, Alaska; present address: Southwest Fisheries Center La Jolla Laboratory,

National Marine Fisheries Service, NOAA, La Jolla, CA 92038, USA.

'Kenyon, K. W. 1960. Aerial surveys of marine mammals in the Bering Sea, 23

February to 2 March 1960 and 25-28 April 1960. Unpub!. rep., 39 p. U.S. Bur. Sport

Fish. Wild!., Seatlle, WA 98115.

3Estes, J. A. 1976. The reliability of aerial surveys to estimate population

abundance of marine mammals. Consideration from a survey of Pacific walrus.

Scientific Consultants on Marine Mammals, Bergen, Norway. 3J August-September

1976. [FAOI Advis. Comm. Mar. Resour. Res. ACMRR/80, 13 p.

77

Fay and Fedoseev had underestimated the number of walruses in the

American sector of the Chukchi Sea. More recent estimates of the

Pacific walrus population have placed it at 140,000 to 200,000

(Estes and Gol'tsev 1984) and 168,000 to 250,000 individuals

(Krogman et al. 19784 ). Estes and Gilbert (1978) concluded that

estimates produced from limited aerial surveys should not be considered reliable.

Perhaps the best quantitative information available concerning

the Pacific walrus population is contained in the American and

Soviet harvest data from 1959 to 1975 (Harbo 1961;5 Burns 19656

'Krogman, B. D., H. W. Braham, R. M. Sonntag, and R. G. Punsly. 1978. Early

spring distribution, density, and abundance of the Pacific walrus (Odobenu5 '-05-

maru5) in 1976. Final report R.U. 14,47 p. Outer Continental Shelf Environmental

Assessment Program, NOAA Environ. Res. Lab., Boulder, Colo.

sHarbo, S. J., Jr. 1961. Walrus harvest and utilization. Annual project segment

report, Federal Aid in Wildlife Restoration. Alaska Dep. Fish Game, Juneau, 25 p.

"Burns, J. J. 1965. The walrus in Alaska, its ecology and management. Alaska

Dep. Fish Game, Juneau, 48 p.
and unpubl. data; Krylov 1968; E H. Fay7). These data include the

retrieved kill and estimated losses from wounding and sinking; for

the American harvest, they also include the sex ratio of adults and

the number of calves taken. Studies ofthe reproductive organs from

the harvested animals have produced estimates of age-specific rates

of fecundity (Fay 1960;8 Burns footnote 6; Krylov 1968), but these

estimates generally have not been accepted due to suspected sampling bias in the harvests and in the assumptions of the estimation

process.

To date, then, "relatively~ reliable information exists on the size

and sex/age composition of the Alaskan walrus harvests from 1955

to 1975, and on the age-specific rates ofreproduction. Only the total

harvests are known from the Soviet side. The estimates of population size in 1955 to 1975 are questionable, and the estimated rates of

natural mortality appear to be unreliable. Nevertheless, these were

the best figures available and of sufficient quality for use in a

preliminary computer model of the Pacific walrus population.

The primary purpose of integrating the existing estimates of

population parameters into the format of a computer model was to

test the hypothesis that the Pacific walrus population could have

increased in size from 70,000 to 200,000 animals in the 20 yr from

1955 to 1975. Such a model can be used also to estimate unknown

parameters, when all others are fixed, and to assess the reliability of

any that are in question. In addition, the interrelationships between

the various parameters can be examined, and a better understanding

can be gained ofthe relative importance of each to the population.

METHODS

The population model used in this instance was a modification of

Leslie's (1945) model, as described by DeMaster (1981); similar

models were described by Fowler and Smith (1973) and by Fowler

and Barmore (1977).9 The model assumes that the influence of

density dependence on the life history parameters will be within the

range of the following two types of functions:

Table I.-Parameters used in the population models, where mx is the age specific

reproductive rate, and Px is the age specific

survivorship.

Age mx Px I Age mx Px

0 0 0.94 20 0.22 0.96

I 0 .90 21 .22 .96

2 0 .94 22 .22 .96

3 0 .96 23 .22 .96

4 0 '.96 24 .22 .96

5 0.10 .96 25 .15 .96

6 .12 .96 26 .15 .96

7 .17 .96 27 .15 .96

8 .22 .96 28 .15 .96

9 .22 .96 29 .15 .96

10 .22 .96 30 .15 .96

II .22 .96 31 .15 .96

12 .22 .96 32 .15 .96

13 .22 .96 33 .15 .96

14 .22 .96 34 .15 .96

15 .22 .96 35 .15 .96

16 .22 .96 36 .15 .96

17 .22 .96 37 .15 .96

18 .22 .96 38 .15 .96

19 .22 .96 39 .15 .96

'Survival from age 4 and older assumed to

be density dependent. All other parameters

are assumed constant.

Table 2.-Assumed parameters for estimation

of adult survival necessary for the population

to increase from 70,000 to 200,000 in 20 yr.

Parameter 1955 1975

Female population 52,500 150,000

Total population 70,000 200,000

Sex ratio 10:39 10:39

Female kill 1,675 1,675

Total kill 6,700 6,700

Sex ratio of kill 19:30 19:30

where Pi =. annual survival of the ith age class

A maximum annual survivorship

Nx = number of females 4 yr old and older

k = maximum number of females 4 yr old and older

b = constant associated with the shape of the curve

c = constant associated with the slope of the curve.

'F. H. Fay, Associate Professor, Institute of Marine Science, University of Alaska.

Fairbanks, AK 99701, pers. commun. October 1979.

"Fay, F. H. 1960. Investigations ofthe Pacific walrus. Terminal repon, Project 26.

Arctic Institule of Nr,rth America, Montreal, Canada, n p.

"Fowler, C W., and W. J. Barmore. 1977. A population model of the northern

Yellowstone elk herd. In R. M. Linn (editor), Proceedings First Conference on

Scientific Rcsearch In the National Parks, New Orleans, Louisiana, November'9-12

1976. Vol. I, p. 427-434.

The initial values for the projection matrix (Tables I, 2) were

derived from the American and Soviet data. Only the female segment of the population was incorporated into the model; the seA

ratio was assumed to be constant at 1 ma1e:3 females (Fay 1982).

The initial population vector was calculated by solving the following equation for No, the number of female calves in the initial

population:

Pi = A - cNx

Pi = A (l-exp [-b (k -Nx )])

(linear)

(nonlinear)

78

P = NO + .94NO + (.94)(.90)No

36

+ (.94)2(.90)No + I(.94)2(.90)(.96f

x=l

where P = 52,500, the number offemales in a population of 70,000

walruses. Subsequent age classes were calculated by using the

age-specific survival rates from Table 1.

The number of females 4 yr old and older (k) in the maximal

population of about 200,000 walruses (Fay 1957) was assumed to be

150,000. The constant b was arbitrarily set at 0.002, which represents a relatively rapid change in the shape of the nonlinear function

(Eberhardt and Siniff 1977). The constant c was set at 0.o00ooo7,

which was calculated directly from the nonlinear model as the slope

between the two points described by the survivorship and the population at equilibrium, given an initial survivorship of 0.96 at a

population level of 0 (DeMaster 1981). In this way, the simulations

with linear and with nonlinear density dependence had the same

equilibrium population.

The population model assumed that only animals 4 yr old and

older were harvested. The harvest of a particular age class was

weighted in proportion to the frequency of occurrence of that age

class in the harvest data. Compensatory and additive harvests were

represented by the following equations (DeMaster 1981):
harvest mortality additive:

x (i+I) = L[X (i)-H (i)],

Tabte 3.-Comparative dynamic characters of walrus population modets with

linear and nonlinear density dependence.

Density dependence

harvest mortality compensated for:

where

X (i+ I) = L[X (i)-H (i)],

X (i) = the population vector at time i

L the projection matrix

H (i) = the harvest vector.

Character

Maximum net productivity

(MNP)

MSY (no compensation)

Population at MSYnc

MSY (compensation)

Population at MSYc

Linear

50% of K

2,100 adult females

59% ofK

2,200 adult females

59% ofK

Nonlinear

84')'0 of K

6,800 adult females

86% of K

7,400 adult females

91% of K

Using this model, a series of simulations was computed in which

the maximum annual survivorship (A) was increased in each simulation until the population model produced the desired final size.

The total kill of females was assumed to be constant over the 20-yr

period. The average kill was derived from known harvest data.

RESULTS

The hypothetical population, given a nonlinear density dependent function, increased from 70,000 to 200,000 in 20 yr only when

A, the annual survivorship, was set to equal 0.99. This value of A

was necessary whether or not the harvest mortal ity was compensatory. The simulated population, given a linear density dependent

function, could not increase from 70,000 to 200,000 in 20 yr, even

when A was set at 1.00.

Because the natural rate of adult survival probably could not have

been as high as 0.99 to 1.00, one must assume that some other

component of the model is incorrect. For the reasons gi ven by Estes

and Gilbert (1978), the most questionable component is the initial

size of the population. Given the entries for the projection matrix

from Tables I and 2 (excluding initial population size), nonlinear

density dependence, and a harvest mortality that was additive, the

initial population of females would have had to have been 73,828

(total population 97,828) to have produced the hypothetical final

population of 200,000 in 20 yr. Ifthe harvest mortality was assumed

not to be additive, an initial population of 70,645 females (total

population 94,194) would have been necessary for the increase to

200,000. If the form of the density dependent function was assumed

to be linear, initial populations even of these sizes could not have

reached 200,000 in 20 yr, given an adult female harvest of 1,675/yr.

In the United States, the Marine Mammal Protection Act of 1972

(MMPA) dictates that marine mammals should be managed at the

level of "optimum sustainable population" (OSP). The concept of

OSP is interpreted to mean that the population should remain

between an upper level imposed by environmental constraints

(commonly called K) and a lower level at which the population

would produce the greatest annual increment (maximum net productivity = MNP) if the population were not being harvested. To

estimate this lower level directly from a population that is being

harvested is impossible, but it can be estimated through modeling.

Given the age specific rates of births and deaths in Table I and the

nonlinear density dependent function previously described, the

MNP of the simulated population would occur at 84% of K, the

equilibrium population (Table 3). For simulations with linear density dependence, the MNP would occur at 50% of K. If we assume

that the real MNP is within the range of these two forms of density

dependence, the lowest level of the population that would be acceptable under the MMPA would be between 50 and 84% of K.

Current information on the Pacific walrus population suggests

that it has increased dramatically since 1955. Within the guidelines

79

of the MMPA, the population could conceivably be managed

somewhere between K and the MNP levels. As a starting point, the

maximum sustainable yield (MSY) of a specific segment of the

population can be estimated, but only if various age and sex specific

life history parameters are known. In addition, how these parameters respond to changes in density must be known. Even then, the

estimated MSY is only reliable if the environment is relatively

constant. To estimate the MSY of adult female walruses, a series of

simulations were computed, in which the harvest was continually

increased, until the population no longer could sustain it (DeMaster

1981). Using the life history parameters of Table I and a nonlinear

form of density dependence, the MSY of adult females (females 4 yr

and older) would be 5.1 % of the total population of females, and

would occur at 91 % ofK (Table 3). Ifthe density dependent function

was assumed to be linear, the MSY of adult females would be 2.3%,

and would occur at 59% ofK. Obviously, we do not know the proper

form of the density dependent function, but these results suggest

that an adult female harvest of 2 to 5% could be sustained, and

presumably would result in the population reaching an equilibrium

when it was between 59 and 91 % of K.

DISCUSSION

The exact details of the recovery of the Pacific walrus population

are not known, but at least a partial recovery has taken place (Burns

footnote 6; Fay footnote 8; Estes and Gilbert 1978; Estes and

Gol'tsev 1984). This recovery has occurred in spite of a continual

harvest of adults. The average growth rate necessary for a population to double in 20 yr is 1.035, and to triple in 20 yr is 1.056. Such

rates of growth are common for many species of marine mammals

(Eberhardt and Siniff 1977), but seem somewhat improbable in this

instance. considering the low productivity and ongoing harvest of

Pacific walruses.

The purpose of this paper was to produce a model that would

incorporate the existing data and shed some light on the reliability

of the estimate of population size in 1955 and the estimated rate of

annual mortality. The results from the various simulations suggest

that, either the natural rate of adult mortality is extremely low

relative to other pinnipeds (Eberhardt and Siniff 1977), or that the

population estimate for 1955 was too low.

The model described in this paper was based on numerous assumptions for which substantive data are few and, in some cases,

questionable. In all of the simulations, I assumed that the sex ratio

ofthe adult population remained constant at I male:3 females, based

on Fay's (1982) derivations from shipboard visual and aerial photographic surveys of the Pacific walrus population. Further information on herd composition and how it varies throughout the year is

needed for improvement of the estimate of adult sex ratio. Simulations in which the sex ratio is assumed to be 1:2 and 1:1 also should

be computed. The effect ofthese would be to increase the difference

between the estimated and required population in 1955, given the
life history values of Table 1. Increasing this difference will only

strengthen the argument that either the 1955 population estimate

was too low or that estimates of adult survival were too low. Second,

I have assumed that the environment of the walrus remained relatively constant. Although human perturbation (other than hunting)

probably has been minimal over the past 20 yr, natural perturbations

may have occurred and not been recognized.

In all of the simulations where a harvest took place, I assumed

that the sex ratio of the harvest was 3 males:l female, and that a

constant number was taken each year. Data concerning the sex ratio

of the harvest supports a 1:3 ratio (Burns footnote 6; Fay footnote 8).

but the numbers taken were not constant; rather, they declined from

about 9,000 in 1955 to about 3,000 in 1969, and have been rising

slowly since then to about 7,000. The effects ofthese changes on the

population probably were insignificant, if the initial harvests were

low enough to allow the population to increase (which, apparently,

it did).

Data on the kinds of density dependent factors influencing this

population were not available at this writing. Simulations which

incorporate density dependent reproduction or calfsurvival should

be computed.

Evidence from Weddell seals, Leptonychotes weddelli, suggests

that reproduction may be relatively unaffected by changes in density, because the time of reproduction does not coincide with the

seasonal onset of poor feeding conditions (DeMaster 1981), and this

may be the case for walruses as well. One could assume that all

independent walruses will be affected equally by food shortages,

and that younger individuals will not be more disadvantaged than

the older ones in obtaining food. The advantages usually invoked

for older pinnipeds, such as greater experience with the area, better

diving capabilities, and outright dominance, may not apply under

conditions where all feeding is done in relatively shallow waters,

the distribution ofthe ice dictates which areas can be utilized, and a

major portion of the adult males may not be feeding in the same

areas where the subadults and adult females feed. Obviously more

information is needed on these points.

Throughout this paper, a distinction has been made between

natural mortality and mortality due to harvests. One problem that

arises in estimating mortality rates from age composition of the

harvest is that mortality from both sources is combined. Furthermore, estimates of mortality derived from samples of populations

that are growing will be biased upward (Payne 1977). Burns (footnote 6) suggested that adult male mortality was about 13%/yr, based

on the age fecundity from the harvest. Ifthe Pacific walrus population was growing at about 5%/yr, the estimate of survival from age

composition will be negatively biased (Payne 1977). When corrected as:

S = e(ln .87 + In \.050) = .91

where S = annual survivorship, the better estimate for adult male

mortality would be 9%/yr. Again, this includes both natural and

hunting mortality. If the Pacific walrus is polygynous (Fay et al.

1984), and the harvest of males is greater than that of females, the

rate of natural mortality for adult females should be less than the

total mortality for adult males, rather than greater as indicated by

Burns (footnote 6). Therefore, the male mortality rate of 13% (Burns

footnote 6) should exceed the maximum for adult females, the actual

rate probably being much lower.

All of the simulations in which the population increased as

80

rapidly as hypothesized (3 to 5%/yr) required that natural adult

survivorship be above 95%, given the known level of harvest. The

model suggests that the Pacific walrus population was theoretically

capable of increasing from 70,000 to 200,000 in 20 yr, but to have

done so, the sex ratio ofthe population would have had to have been

strongly weighted to females. Information on the current sexual

composition of the population would, therefore, be extremely useful for better understanding of the population dynamics of this

species.

Finally, the model suggests that the MNP of a population varies

considerably with the type of density dependence that is operative.

This has been demonstrated also for MSY values (DeMaster 1981).

MNP values for marine mammals commonly are assumed to lie

between 50 and 60% of K. More realistic estimates of MNP will

require information on the age at which density related changes take

place in life history parameters, and on the form of the relationship

between life history parameters and density of the population.

ACKNOWLEDGMENTS

The author wishes to thank L. L. Eberhardt and C. W. Fowler for

reading and commenting on an earlier draft of this paper, and J. J.

Burns and F. H. Fay for providing unpublished data on population

parameters and composition of recent walrus harvests.

LITERATURE CITED

DeMASTER, D. P.

1981 . Incorporation of density dependence and harvest into a general population model for seals. In C. W. Fowler and T. D. Smith (editors), Dynamics of

large mammal populations, p. 389-401. Wiley-lnterscience, N.Y.

EBERHARDT, L. L., and D. B. SINIFF.

1977. Population dynamics and marine mammal management policies. J.

Fish. Res. Board Can. 34: 183-190.

ESTES, J. A., and J. R. GILBERT.

1978. Evaluation of an aerial survey of Pacific walruses (Odobenus rosmarus

divergens). J. Fish. Res. Board Can. 35:1130-1140.

ESTES, J. A., and Y. N. GOL·TSEY.

1984. Abundance and distribution of the Pacific walrus, Odobenus rosmarus

divergens: Results of the first Soviet-American joint aerial survey, autumn

1975. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 12:67-76.

FAY, F. H.

1957. History and present status of the Pacific walrus population. Trans.

North Am. Wild\. Nat. Resour. Conf. 22:431-443.

1982. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens 1Iliger. North Am. Fauna 74, 279 p. U.S. Fish Wild\. Serv..

Washington, D.C.

FAY, F. H., G. C. RAY, and A. A. KIBAL'CHICH.

1984. Time and location of mating and associated behavior of the Pacific

walrus, Odobenus rosmarus di vergens III iger. U. S. Dep. Commer. , NOAA

Tech. Rep. NMFS 12:89-99.

FEDOSEEV, G. A.

1962. On the status of the stocks and the distribution of the Pacific walrus. Zoo\. Zh. 41:1083-1089.

FOWLER, C. w., and T. SMITH.

1973. Characterizing stable populations: an application to the African

elephant population. J. Wild\. Manage. 37:513-523.

KRYLOV, V.1.

1968. Present condition of Pacific walrus stocks and prospects of their rational exploitation. In V. A. Arsen'ev and K. I. Panin (editors), Pinnipeds of

the northern part of the Pacific Ocean, p. 189-204. Pischevaya Promyshlennost', Moscow.

LESLIE, P. H.

1945. On the use of matrices in certain population mathematics. Biometrika 33:183-212.

PAYNE, M. R.

1977. Growth of a fur seal population. Philos. Trans. R. Soc. Lond.

279:67-79.
Foods of the Pacific Walrus in Winter and

Spring in the Bering Sea

FRANCIS H. FAY,! YURI A. BUKHTIYAROV,2 SAMUEL W. STOKER,! and

LARRY M. SHULTS·

ABSTRACT

Part of the information required for effective multispecies management of the marine resources of the

Bering Sea is a documentation ofthe feeding habits ofthe pinnipeds residing there. In this report, new data on

the foods of walruses in their wintering areas and along a major spring migration route through Bering Strait

are summarized. These data were acquired during several research cruises and shore-based studiesfrom 1970 to

1976. In general, the findings from those studies indicate a primary reliance ofthe walruses in all areas on a few

genera of bivalve mollusks, namely Serripes, Mya, and Hiatella, with significant but lesser reliance on other

bivalves, priapulids, polychaetes, snails, mOlting brachyuran crabs, and holothureans. In areas where both

male and female walruses were sampled, the adult males tended to eat organisms which were about six times as

large as those taken by the adult females, suggesting that the sexes are selectively partitioning food supplies in

those areas. The need for further quantitative information on the feeding habits ofthe walruses in their primary

wintering areas, and on the benthic faunas of those areas, is emphasized.

PE310ME

)l,J1R ,ljIl!>eKTHBHoro ynpUJleHHR KOMnJ1eKCOM MOpCKHX peCypCOB liepHHroB8 MOpR HYlKHbl i\8HHble 0

nHTaHHH n8CTOHorHX, 06HT81Ol.IJ,HX 8 lTOM perHoue. B ,JJ.OKJl8..o.e HlJlaralOTCR HOBbie ..o.8HHbie 0 nHTSHHK MopmeH

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lIeCKonbKHX Hay"lHblx peHCOB II fieperOBblX HCentAORSH"" C 1970..0.01976 r. B OCHOBHOM, nOJ1YllleHHltle CBe..o.eHHR

yte:83bIBaIOT, "ITO MopmH 80 Bcex paHoHax HCnOJ1blYIOT HeOOJlbWOe "IIIC1I0 pO)J.OB AByCTBOp"'STbIX MOJlJlIOCKOB,

KOHKpeTHO Serr;pes, Mya, Hiatella II 8 MfULlUeR CTeneHH npHsnyJlH)J., MHorOmeTHHKOObiX qepOeH, 6plOXOHorHX

MOJlJ1IOCKOB, JlHHHlOmHX AeCHTHHorHX Kpa6oB, ronoTypHH. B paiiOHax, H3 KOTOpblX nonyqellbl caMu.bl "CaMKH

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BeJlH'tmte, qeM opraHH3Mbl, KOTOpblMH nHTaJlHCb B3pocnble caMKH. 3TOT 4laKT A3eT OCHOB311He npeAnonaraTb,

qTO 06a nOIla CeJleKTHBHO HcnoJlb3YlOT nHmeOble lanaCbI B lTHX paHoHax.

nOAQepKHBaeTcR ne06XOJl,HMOCTb npOJl,OniKeHHR C60pOB no nHT3HHIO MopiKeH B OCHOBHblX paHoH3x

]HMllero o6HTaHHJI H H3yqCIIHR 6eHTocitoit 4layHbi 8 lTHX p3Honax.

INTRODUCTION

To the common knowledge that walruses, Odobenus rosmarus

(L.), feed principally on bivalve mollusks, Chapskii (1936), Nikulin (1941), Vibe (1950), Brooks (1954), Krylov (1971), and Fay et al.

(1977)3 have contributed a substantial amount of specific information on the kinds and quantities of prey that walruses eat. As a

whole, those findings indicated that the quality of the walrus' diet

varies seasonally and geographically, and that it is made up of more

than 60 different kinds of benthic organisms.

The need for further quantitative information on the feeding

habits of walruses and other pinnipeds ofthe Bering Sea has become

increasingly apparent in recent years. In order to facilitate multiple

resource management, detailed knowledge of the interrelationships

and interdependencies among the major components of the system

is required. For a sea of its size, the Bering Sea is one of the richest

in the world, as shown by its highly productive fisheries and large

marine mammal populations.

'Institute of Marine Science, University of Alaska, Fairbanks, AK 99701, USA.

'Magadan Branch. Pacific Research Institute of Fisheries and Oceanography

(MoTINRO), Nagaevskaya 51, Magadan 685013, USSR.

'Fay, F. H., H. M. Feder. and S. W. Stoker. 1977. An estimation of the impact of

the Pacific walrus population on its food resources in the Bering Sea. U.S. Mar.

Mammal Comm., Wash., D.C., 38 p.

81

The information presented in this report is a contribution to the

data base concerning the food web of the Bering Sea. It consists of

new qualitative and quantitative data on the feeding habits of a

major component of that system, the Pacific walrus population.

Walruses are dependent on the benthic resources of the region,

principally during the winter and spring of each year. This information was acquired by American and Soviet biologists during the

course of five scientific expeditions: I) The oceanographic cruise of

the US Coast Guard Cutter (CGC) Northwind in the northern and

eastern Bering Sea in January-February 1970; 2) the marine mammal research cruise of the CGC Glacier in the north-central Bering

Sea in March-April 1971; 3) the oceanographic-marine mammal

cruise of the CGC Burton Island in the north-central Bering Sea in

February-March 1972; 4) the Alaskan walrus harvest monitoring

program in northern Bering Sea-Bering Strait during April-June

1974-76; and 5) the joint Soviet-American marine mammal research

cruise of the ZRS Zagoriany in the southeastern Bering Sea in

March-May 1976. The largest samples were obtained during the last

two of those endeavors.

METHODS

The kinds and quantities of prey eaten by walruses were determined mainly from examination of stomach contents of animals

taken at sea. Some of those specimens were obtained for scientific
. ,..e •. ....".~.,. .' ~I· I

RESULTS

Cruise of the CGC Northwind,

January-February 1970

Four walruses were collected, three of which had food in the

mated at the time of collection, and a ~mall sample of each taxon

was preserved in 10% Formalin4 for subsequ(,nt identification and

reference.

On a few occasions, individual food items were retrieved from the

surface of the ice adjacent to breathing holes used by walruses.

Walruses often bring such items to the surface in their mouth and

occasionally drop them on the ice. We presume that this is unintentional, since the same kinds of items occur commonly in the

stomach contents. On a few occasions, we also collected and analyzed samples of feces found on the ice where walruses had lain.

Since many of the organisms eaten by walruses have indigestible

skeletal parts which are diagnostic of the genus, fecal samples are of

some value in assessing the frequency of occurrence ofthose genera

in the diet.

'Reference to trade names does not imply endorsement by the National Marine

Fisheries Service, NOAA.

SEA

••

BERING

SIBERIA

purposes, during the Northwind and Zagoriany expeditions; the rest

were taken by Alaskan Eskimos during the spring walrus harvests of

1974-76. The localities in which the samples were obtained are

shown in Figure I.

For each animal, the date, location, sex, and age were recorded.

Age was determined from counts of cementum layers in thin,

longitudinal sections of the postcanine teeth, as described by Mansfield (1958) and Krylov (1965).

Whenever possible, the entire contents of the stomach were

examined in detail. All intact prey were sorted into taxonomic

groups, each group weighed to the nearest whole gram, and the

number of individuals counted. Since the specific gravity of the

food items was essentially the same as that of water, their weight in

grams was tantamount to volume in milliliters. Unless stated otherwise, composition of stomach contents is expressed as percent by

volume.

The remaining particulate organic matter was separated from the

free fluids by centrifugation and weighed to the nearest gram. Large

inorganic solids (stones and gravel) were removed at the time of

sorting; the finer particles were separated by dilution and decantation. The total inorganic solids were air-dried, weighed, and their

volume determined by water displacement.

In a few field situations, where such procedures were not feasible,

the percentage composition of the ingesta by major taxa was estiFigure I.-Chart of the eastern Bering Sea, showing locations In which samples of.stomach contents (cross-hatched)

and feces (dashes) of walruses were collected. BI = Burton Island expedition, March 1972; G = Glacier expedition,

April 1971; NW = Northwind expedition, January.February 1970; S8 =spring barvest areas, 1974.76; Z =Zagoriany expedition, March-April 1976. Dash lines Indicate approximate limits of wintering areas, as currently known

(after Fay 1982).

82
stomach. The first two were taken about 215 km south of Etolin

Strait in water 45 m deep. One of these, an adult male, contained

10.9 kg of the cockle Serripes groenlandicus; no other kinds of prey

were represented. The other, a subadult male, contained 3.71 kg of

ingesta, made up of about 60% whelks of the genera Neptunea and

Buccinum, 25% S. groenlandicus, 5% whole tunicates (cf. Tethyum

sp.), and 10% stones and gravel. The third specimen with food in its

stomach was an adult female taken about 55 km south of the

southeastern cape of St. Lawrence Island, where the water was 33 m

deep. This animal contained about 2.04 kg of ingesta made up of

53% tunicates of the species Pelonaia corrugata, 25% bavalves

represented about equally by Mya spp. and S. groenlandicus, 10%

whelks and other snails of the genera Buccinum, Natica, and

Polinices, 2% amphipods and crangonid shrimps, 1% Echiurus

echiurus, and 9% stones and gravel.

Cruise of the CGC Burton Island,

February-March 1972

Four specimens were collected during this cruise, all of which

had empty stomachs. We found several items on the ice alongside

breathing holes used by walruses, approximately 260 km southwest

of the western end of St. Lawrence Island over water 82 m deep.

Most of these were remains of the bivalve Macoma calcarea, one of

the most common mollusks in that area (Stoker 1978); one was

Musculus niger. In addition, we analyzed two samples of walrus

feces collected from the ice in that location (samples I, II, Table I).

The dominant remains in each were operculae ofsnails of the genera

Natica and Polinices, and exoskeletons of the brachyuran crab

Chionoecetes sp. Two fecal samples from another locality, 65 km

southwest of the island over waters 60 m deep, were similar in

composition but included also several periostracal sheaths of

siphons, probably from bivalves of the genus Mya, and tests of

Priapulus caudatus (samples III, IV, Table I).

Cruise of the CGC Glacier, March-April 1971

One specimen with empty stomach was collected during this

cruise. However, remains of several food items were found on the

ice near breathing holes used by a large herd of walruses about 165

km south of the western end of St. Lawrence Island over water 60 m

deep. These were as follows: Musculus niger-shells of four individuals from which most of the fleshy parts had been removed;

Neptunea heros-one intact individual; Pagurus trigonochierus-one intact individual in a shell of N. heros; and four

fragments of egg cases from an unidentified gastropod mollusk. A

sample of feces collected from the ice where some of the walruses

had lain contained remains of 47 individual prey (sample V, Table

I). The dominant taxa were the mollusks Nucula tenuis, Neptunea

sp., and Polinices sp.

Cruise of the ZRS Zagoriany, March-April 1976

Of 158 walruses collected during this cruise, 21 had food in their

stomachs. These were all taken in southeastern Bering Sea, within

an area bounded by lat. 56°43' to 57°30'N and long. 165°10' to

166°31' W. The greatest amount in one stomach was 29 kg; the

weight of the ingesta relative to the total body weight of the animals

ranged from 2.1 to 2.7%. Seven taxa were identified in the stomach

contents (Table 2). Brachyuran crabs of the genus Chionoecetes and

whelks of the genera Neptunea and Buccinum occurred more frequently than any other kinds of prey, but were of secondary importance in volume compared with the bivalve mollusks, especially the

cockle S. groenlandicus. Nearly all of the cockle feet were of

uniformly small size (mostly 5 to 6 cm long), but nearly all of the

whelks were unusually large relative to those found in walrus

stomachs in other areas. All of the brachyuran crabs were in the

soft-shelled (molting) stage. Several animals observed immediately

to the southwest of the collection area appeared to be feeding in

Table I.-Comparative numbers of prey (represented by undigested parts) in fecal samples from

walruses at five locations in the north-c:entral Bering Sea, dl!ring late winter to early spring.

Sample no. and location'

I II III IV V

Lat. 61°27'N 61°26'N 62°55'N 62°47' N 61°52' N Overall

Prey type Long. 174°24'W 174°27'W 172°II'W 172"2S'W 171°45' W No. %

Worms

Priaputus IS 2 20 S

Echiurus I 3 I

Bivalves

Mya 10 10 4

Nucula 1 13 15 6

Gastropods

Neptunea I I 2 14 IS 7

Buccinum 5 4 2 3 14 6

Natica 10 16 7 12 45 IS

Polinices 21 12 9 15 12 69 28

Margarites 1 1 If

Crabs

Chionoecetes 8 7 4 21 9

Shrimps

Argis 2 4 7 3

Amphipods

Maera 4 4 2

Anonyx 4 4 2

Thnicates

Pelonaia 2 4 2 8 3

Tethyum I 4 2 7 3

Totals 45 44 43 67 47 246 100

'Samples I to IV from Burton Island expedition, March 1972; sample V from Glacier expedition,

April 1971.

83
Harvest Monitoring Program, April-June 1974-76

Table 2.-Frequency of occurrence and relative abundance of prey in stomachs

of 21 walruses from the Zagorwny expedition, southeastern Bering Sea, MarchApril 1976.

Stomachs containing ingesta were acquired from five localities in

the northern Bering Sea-Bering Strait region (Fig. I). Results of the

analyses of these samples are presented in detail in Tables 3-7.

waters 80 to 90 m in depth; in the collection area itself, depths

ranged from about 65 to 80 m. We observed one adult male for

nearly 2 h while it apparently was feeding in 79 m of water. During

that time, it dove 12 times, each dive ranging in length from 2 min,

10 s to 10 min, 2 s (mean, 7 min, 47 s); it remained at the surface

between dives for 31 s to 2 min, 6 s(mean, I min, 34 s). Feces on the

ice nearby, where several walruses had lain, contained abundant

remains of gastropods of the genera Neptunea, Buccinum, and

Polinices, and of crabs of the genus Chionoecetes. The presence in

the feces of several diphyllobothriid cestodes suggested that some

fishes also had been eaten.

Table 3.-Frequency of occurrence, number of individuals, and volume of prey

in stomach contents of 13 walruses taken near the western end or St. Lawrence

Island, April-May 1975.

Frequency of

Individuals Volume Prey Iype occurrence

(genus) (/13) No. % ml %

Priapulus 10 77 0.7 625 0.8

Nephthys 3 28 0.2 719 1.0

Lumbrinereis 2 44 0.4 22 Ir

Echiurus 7 10 0.1 18 Ir

Golfingia 4 62 0.6 215 0.3

Balanus I I Ir I tr

Anonyx I 6 tr 2 Ir

Ampelisca I 2 Ir I Ir

Hippomedon I 1 tr I tr

Argis I 15 0.1 43 0.1

Sclerocrangon 2 39 0.4 118 0.2

Pagurus 2 2 tr 2 Ir

Hyas 10 245 2.2 2.260 3.0

Neptunea 10 236 2.1 644 0.9

Buccinum 8 38 0.3 118 0.2

Narica 6 13 0.1 15 Ir

Polinices 8 26 0.2 38 Ir

Nudibranchia I 1 Ir I tr

Serripes 7 431 3.9 6.957 9.3

Clinocardium 6 78 0.7 1.048 1.4

Hiarella 3 7.586 68.8 7.375 9.9

Mya' 13 1,992 18.0 33.288 44.6

Octopus I I Ir 7 Ir

Cucumaria 10 92 0.8 1,979 2.7

Animal fragments' 13 17,626 23.6

Inorganic sediments 13 1,525 2.0

Totals 11.026 74,648

'Indudes specimens misidentified as "Spisula" by Fay el af. (texi footnole 3).

'Includes 1.095 ml of molluscan fragments not idenlifiable to genus.

2.881

79

1.360

342

1

%9

7

Maximal number of

individuals per

slomach

33

24

24

62

5

62

5

Frequency in slomachs

Prey Iype (%)

Serri~s groen/andicus

Mya

Bivalve, unidentified

Neptunid snails

Hyas coarcUJtus

Chionoecetes sp.

Tunicates, unidentified

West of St. Lawrence Island.-Stomachs from 10 males and 3

females contained from < 1 to more than 14 kg of ingesta (mean,

5.75 kg), 98% of which, by volume, was organic matter. Nearly

90% ofthe identifiable organic materials were parts ofmollusks, the

majority of which were bivalves of the genera Hiatella and Mya

(Table 3). These two genera made up 87% of the total number of

prey and 54% of the total volume of ingesta.

North of St. Lawrence Island.-Stomachs of 13 males and 1

female contained from 0.3 to more than 22 kg of ingesta (mean,

8.26 kg), 99% of which were organic and the remainder inorganic

solids. Nearly all (97%) of the identifiable materials were parts of

mollusks, of which two genera of bivalves (Serripes and Mya) made

up 87% of the number and at least 80% of the volume of organic

matter in the stomachs (Table 4).

South of Nome.-Stomachs from seven males contained from

0.4 to 7.9 kg each (mean, 3.6 kg), 99.8% of which was organic

matter. Nearly all of the identifiable prey were mollusks, one of

which (Serripes) made up 98% of the number of individuals and

73% of the total volume of ingesta (Table 5). The feet of these

Serripes were very small (5-6 cm long, 1-2 g each), comparable with

those found in the Zagoriany sample from southeastern Bering Sea.

King Island.-Stomach contents were obtained from an adult

female and ajuvenile male. The volume of ingesta was 3.8 kg in the

female and 14.7 kg in the male. Nearly all of this material was

organic matter, in which bivalve mollusks of the genus Mya predominated in both numbers and volume (Table 6).

Table 4.-Frequency 01 occurrence, number of individuals, and volume 01 prey

in stomach contents of 14 walruses taken near the northern coast ofSt. Lawrence

Island, May-June 1974-75.

Frequency of

Individuals Volume Prey type occurrence

(genus) (/14) No. % ml %

Priapulus 8 75 1.4 451 0.4

Nephrhys 5 12 0.2 107 0.1

Lumbrinereis I 1 Ir I Ir

Echiurus 8 41 0.8 254 0.2

Golfingia 3 23 0.4 78 0.1

Argis 2 15 0.3 36 Ir

Pagurus 4 6 0.1 9 tr

Hyas 9 74 1.4 338 0.3

Chionoeceres I 2 tr 4 Ir

Neprunea 10 141 2.6 201 0.2

Buccinum 6 10 0.2 16 lr

Na/ica 2 3 Ir 2 tr

Polinices 8 71 1.3 68 0.1

Margari/es I 6 0.1 I tr

Serripes II 1.862 33.9 33.190 28.7

Clinocardium 3 110 2.0 1,434 1.2

TellinalMacoma 2 31 0.6 68 0.1

Hia/ella I I Ir 1 Ir

Mya' 12 2,944 53.6 58,454 50.6

Cucumar;a 9 52 1.0 810 0.7

Pelonaia I 4 0.1 15 Ir

Tunicate (cf. Tethyum) I I If 9 Ir

Animal fragmenls' 14 19,242 16.6

Inorganic sediments 13 841 0.7

Totals 5,485 115,630

'Includes specimens misidentified as "Spisula" by Fay el a!. (texi footnote 3).

'Includes 1.095 ml of molluscan fragmenls not identifiable to genus.

84
Table 5.-Frequency of occurrence, number of individuals, and volume of prey

in stomach contents of seven walruses taken near Nome, May-June 1975.

Frequency of

Individuals Volume

Prey type occurrence

(genus) (/7) No. % ml %

Priapulus 5 16 0.1 99 0.4

Nephthys I 2 tr 7 tr

Argis I I tr 10 tr

Sclerocrangon I I tr 6 tr

Neptunea 5 71 0.6 46 0.2

Natica 3 49 0.4 50 0.2

Polinices 5 45 0.4 77 0.3

Serripes 6 11,399 97.7 18,134 72.6

Tellina 6 65 0.6 175 0.7

Mya' 2 10 0.1 39 0.2

Animal fragments2 7 6,294 25.2

Inorganic sediments 1 45 0.2

Totals II ,659 24,982

'Includes specimens misidentified as "Spisula" by Fay et a!. (text footnote 3).

21ncludes 10 ml of molluscan fragments not identifiable to genus.

Table 6.-Frequency of occurrence, number of individuals, and volume of prey

in stomach contents of two walruses taken in the vicinity of King Island,

June 1976.

Frequency of

Individuals Volume

Prey type occurrence

(genus) (/2) No. % ml %

Nephthys I I 0.2 5 tr

Echiurus 2 2 0.3 2 tr

Hyas I 2 0.3 3 Ir

Natica I 2 0.3 2 Ir

Serripes I 10 1.6 3\ 0.2

Tellina/Macoma I I 0.2 I tr

Hilltella 1 5 0.8 I tr

Mya' 2 590 94.6 16,223 87.6

Cucumaria 2 II 1.8 143 0.7

Animal fragments 2 2,117 11.4

Inorganic sediments 2 7 tr

Totals 624 18,535

'Includes specimens misidentified as "S/}isula" by Fay et aI. (text footnote 3).

Bering Strait.-Stomach contents were obtained from 56 males

and 15 females in volumes ranging from 0.1 to more than 26.5 kg

(mean, 8.1 kg) per stomach. Most of these materials were parts of

mollusks, predominantly Serripes, Hiatella, and Mya (Table 7).

Unique in this sample was the occurrence in one stomach ofremains

of a bearded seal, Erignathus barbatus, including pieces of skin,

blubber, muscle, liver, heart, and pancreas. One other stomach, not

quantitatively analyzed, contained a high proportion of large actiniarian coelenterates, possibly of the genus Metridium.

General Observations.-Whole shells, even of the smallest

bivalves, were uniformly scarce to absent in the samples ofstomach

contents. Shell fragments, most of which were bits broken from

the rim of the valves, were present in 42% of the stomachs but

comprised only trace amounts « 0.1 % by volume of the total

ingesta). Nearly all of the feet and siphons were entire, showing no

signs of mastication.

For the most part, each of the nonmolluscan invertebrates appeared to have been swallowed whole, without mastication. However, they frequently showed signs of having been subjected to local

compression, perhaps by the lips of the walrus, before they were

swallowed. The exoskeletons of all of the brachyuran crabs were

very soft and flexible, suggesting that these crabs had molted just

before the time of ingestion. That their softness was not the result of

85

Table 7.-Frequency of occurrence, number of individuals, and volume of prey

in stomach contents of 71 walruses taken in Bering Strait, May-June 1975.

Frequency of

Individuals Volume Prey type occurrence

(genus) (m) No. % ml %

Priapulus 26 70 0.1 889 0.2

Nephthys 26 267 0.4 3,499 0.6

Lumbrinereis 4 49 0.1 71 tr

Pectinaria 2 2 tr 2 tr

Echiurus 6 27 tr 268 tr

Golfingia 28 991 1.5 3,215 0.6

Anonyx 7 33 tr 24 tr

Lembos 2 3 tr 2 Ir

Argis 2 4 tr 2 tr

Pagurus 7 18 tr 45 tr

Hyas 13 23 tr 109 tr

Neptunea 47 721 I.l 4,980 0.9

Buccinum 41 303 0.5 759 0.1

Natica 31 156 0.2 200 IT

Polinices 30 542 0.8 695 0.1

Margarites I 2 tr I tr

Serripes 62 2,145 3.3 47,906 8.4

Yoldia 10 919 1.4 339 0.1

Nucula I 2 tr I tr

Tellina/Macoma II 1,269 2.0 1,413 0.2

Hiatella 51 41,371 63.8 57,645 10.1

Astarte 2 2 tr 2 tr

Mya' 66 15,840 24.4 373,721 65.2

Octopus 2 2 Ir 45 tr

Cucumaria 9 63 0.1 1,502 0.3

Psolus 7 22 tr 554 0.1

Erignathus 1 I tr 10,498 1.8

Anim", fragments2 67 53.051 9.3

Inorganic sediments 69 11,308 2.0

Totals 64,847 572,746

'Includes specimens misidentified as "Spisula" by Fay et a!. (text footnote 3).

21ncludes 385 ml of molluscan fragments not identifiable to genus.

digestion was indicated by the hard, calcareous quality of a fragment of lithodid crab shell found in one stomach. Presumably, this

small piece (from the carapace of Paralithodes sp.) had been ingested accidentally, along with the inorganic solids.

Inorganic sediments occurred with the organic ingesta in all but 9

of the 107 stomachs from St. Lawrence Island to Bering Strait.

These ranged in amounts from I to 1,040 ml/stomach and consisted

mainly of sand and gravel, with a few stones up to 3 cm in diameter.

Probably, some of the molluscan shell fragments also were ingested

with the gravel, for broken shells make up a significant part of the

sediments in this region. Two items of human origin (from ocean

dumping) also were recovered from the stomachs: A 3 x 4 cm piece

of bottle glass, and a I x 5 cm fragment of fiber gasket material.

In Bering Strait and west of St. Lawrence Island, where both

males and females were sampled, the females tended to feed on the

smaller kinds of bivalves, especially Hiatella; the males had fed

more on the largest ones, especially Mya (Table 8). The single

female taken at King Island contained approximately the same kinds

of prey as did the subadult male. Where the females had fed on the

same kinds of prey as the males, they tended to take individuals of

smaller size than did the males (Table 9). Thus, the stomachs of

the females tended to contain larger numbers of prey but generally

smaller volumes of ingesta than did those of the males (Fig. 2). The

prey in the stomachs of males tended to be about 6 times larger than

those in the stomachs of females. The largest number of individual

prey in one stomach was 6,401 in an adult female taken in Bering

Strait. Nearly all of those were Hiatella arctica. The smallest

number was three, in the adult male that had fed on one bearded seal

and two bivalves.
Table 8.-ComplU'8tive percentage by weight of bivalve prey in the stomachs of 25 0 0

IIUlIes IIDd females, northern Bering Sea, spring 1974-76. 0'

Locality. sex. and sample size .><:

20 0

W.ofSt. N.ofSt. III 0

Lawrence Lawrence King Island Bering Strait C d'r=0.2042, n=78 (I)

Prey type 0 2 0 2 0 2 0 2 l: 0 0 0 r=0.4175, n=20 0

(genus) n=1O n=3 n=13 n=1 n=1 n=1 n=56 n=15 u 15 0

.t::. 0

Hiatella <0.1 80.8 <0.1 0 0 <0.1 6.9 51.8 <) c9 0 • Mya 69.6 11.3 61.2 0 99.2 97.3 80.0 32.6 E 0

0 0 • Cockles' 17.3 0 36.2 50.0 0 0.1 9.8 7.9 Vi 10 0

Tellinids' 0 0 0.1 0 <0.1 0 <0.1 2.5

Other '0 small - • clams' 0 0 0 0 0 0 <0.1 0.5 .J::.

0' • 0 .0 • • 'Serri{H's and Clinocardium. (I) 0

',"/liM and Mocama. • • 'YaIdiD, N"cuJa, and Astarte. .. 00

.,

2000 4000 6000 8000

Number of Prey

DISCUSSION

The Pacific walrus population inhabits the pack ice of the Bering

Sea in winter, mainly to the south of St. Lawrence Island and in

outer Bristol Bay (Braham et al. 1984). The period of winter residence in the Bering Sea appears to be the mating season for these

walruses (Fay et al. 1984). The availability of an adequate supply of

food in that period may be of critical importance only to the adult

females, who are supporting dependent young and/or carrying a

fetus. The adult males appear to fast during much ofthe winter; they

apparently feed intensively only in spring, summer, and autumn,

when they mostly reside in other areas (Fay 1982).

The information on availability of food in the wintering areas is

meager; as is the complementary information on the walruses'

feeding habits at that time. The only samples of walrus food in the

north-central wintering area, south ofSt. Lawrence Island, are from

the contents ofone stomach, plus five fecal samples from the iee and

a few items dropped on the ice beside breathing holes. Together,

these suggest that the diet there is made up of a wide assortment of

bivalves, gastropods, crustaceans, echiurids, and tunicates in about

equal amounts. Because the bivalves mostly have no indigestible

parts (other than the shells, which are not eaten by the walruses),

Figure 2.-'Thndency for correlation between numbers and volumes of prey in

stomachs ofmale (open circles) and female (solid circles) walruses taken in the

St. Lawrence Island to Bering Strait region, spring 1974-76. Tbe tendency for

difference between sexes is not significant.

they probably are underrepresented in fecal analyses. According to

the work of Stoker (1978), the most abundant bivalves in the

north-central wintering area are Macoma calcarea, Nucula tenuis,

N. radiata, Yoldia hyperborea, and Serripes groenlandicus. The

first four of these made up more than 56% by weight ofthe. biomass

of macrobenthos in Stoker's samples, yet to the best of our present

knowledge, they seldom are eaten by walruses when other, larger

prey are available. Of the apparently preferred, larger bivalves,

such as Serripes and Mya, Stoker's samples indicated occurrence

only in small amounts « 5% of the biomass). Because of known

deficiencies ofthe sampling gear (0.1 m2 Van Vee!) grab), however,

this may not be a reliable indication of abundance. Since it is clear

that this north-central area is occupied by about two-thirds to threefourths of the walrus population during winter and spring (Kenyon

Table 9.-Comparative unit weights (glindividuat) of prey in the stomach contents of male and female walruses, nortbem Bering Sea,

spring 1974-76.'

W. of St. Lawrence N. of St. Lawrence King Island Bering Strait

0 2 0 'i 0 2 0 2

No. Unit No. Unit No. Unit No. Unit No. Unit No. Unit No. Unit No. Unit

Polychaetes 72 10.3 0 13 8.3 0 I (5) 0 214 14.0 104 5.6

Sipunculids 6 1.8 56 3.6 23 3.4 0 0 0 912 3.3 79 2.6

Echiurids 6 1.2 4 2.8 41 6.2 0 I (i) I (I) 19 9.4 8 II.l

Priapulids 47 5.5 30 12.3 75 6.0 0 0 0 58 13.6 12 8.5

Gastropods 283 2.4 30 4.5 192 1.3 39 0.8 0 2 1.0 1,177 4.7 547 2.1

Cockles 509 15.7 0 1,966 17.6 6 5.3 0 10 3.1 1,486 29.5 659 6.2

Mya 1,904 16.9 88 11.7 2,944 19.8 0 400 32.2 190 17.6 14,924 23.9 915 18.5

Hiatella 41 0.4 7,539 1.0 1 (I) 0 0 5 0.2 22,538 1.4 18,833 1.4

1ellinids 0 0 31 2.2 0 I (I) 0 39 2.5 1,230 1.1

Other small

clams 0 0 0 0 0 0 188 0.5 735 0.3

Shrimps 54 3.0 0 15 2.4 0 0 0 0 4 0.5

Crabs 246 9.2 I (I) 82 4.3 0 0 2 1.5 35 3.5 6 5.3

Holothureans 91 21.7 1 (6.0) 52 15.6 0 5 17.6 6 9.2 73 24.3 12 23.7

Overall 3,265 14.2 7,749 1.2 5,435 17.6 45 1.4 408 31.8 216 15.9 41,663 10.7 23,144 2.8

'Sample from Nome area excluded, since only male walruses were taken there.

86
1960,5 1972;6 Braham et a!' 1984), we presume that the benthic

stocks are larger than were indicated by Stoker's samples.

Substantially more information is available from the walruses in

the southeastern Bering Sea in winter, but the sample is nonetheless

very small and is mainly from one small part of that region. In

January, March, and April, the cockle S. groenlandicus and whelks

of the genera Neptunea and Buccinum appear to be most heavily

utilized. A high proportion of molting tanner crabs (Chionoecetes

spp.) also has been found in the stomach contents and feces.

Tikhomirov (1964:283) collected a series of 50 walruses in this

same region in March-April 1962 and reported that they had fed

mainly on "shrimps and crabs, among which were found a few

kamchatki [king crab, Paralithodes camtschatica], and to a lesser

degree, mollusks." He remarked on the contrast between these and

the stomach contents of walruses taken in the Chukchi Sea in

summer, "where the principal food ... is mollusks." According to

Stoker's (1978) data, the dominant (by weight) bivalves in this

southeastern region are Macoma calcarea and Astarte borealis,

which made up more than 32% of the biomass of macrobenthos in

his samples. Serripes groenlandicus comprised about 3.5%.

The feeding habits of walruses farther east in Bristol Bay are

unknown. This is clearly an important breeding and feeding area in

some winters and supports several thousand males throughout the

summer. The possibility of competition there between the walruses

and a potential clam fishery is under investigation. Adequate stocks

for support of a clam fishery appear to be present only in the

southern part of Bristol Bay (Hughes et al. 19777 ), which may be

outside the normal range of most of the walruses. There, in the

nearshore waters, the stocks of the two species of interest to the

fishery, Spisula polynyma and Tellina lutea, are more than 10 times

greater than in the northern parts of the Bay.

The largest volume of data on the feeding relationships of walruses in the Bering Sea is from the northernmost sector, between St.

Lawrence Island and Bering Strait. In the past, this region was

utilized by walruses mainly during their northward migration in

spring and southward migration in autumn. Since 1971, however, it

also has become an important summering area for a significant part

of the population. Previous information from this region, provided

by Nikulin (1941) and Brooks (1954), indicated that bivalves (especially Mya) were the principal foods there in spring and early

summer. Our data from 1975 tend to confirm that: The stomach

contents of walruses taken in the western and northern parts of this

region contained mainly Mya and Hiatella; in the eastern part

Serripes was dominant. Stoker's (1978) bottom samples from this

region confirmed the abundance of Serripes in the standing stocks

of the eastern sector, but they did not reflect an abundance of either

Mya or Hiatella in the west or north. Presumably, this again was a

deficiency of the sampling gear, which did not function well in the

predominantly rocky to gravelly substrates.

With the prospect of increasing human impact on the environment of the walrus population through expanded fisheries (including clam and snail fisheries) and development of mineral and petroleum resources on the continental shelf of the Bering Sea, the

'Kenyon, K. w. 1960. Aerial surveys of marine mammals in the Bering Sea, 23

February to 2 March 1960 and 25-28 April 1960. Unpubl. rep., 39 p. U.S. Bur. Sport

Fish Wildl., Sealtle, WA 98115.

"Kenyon, K. W. 1972. Aerial surveys of marine mammals in the Bering Sea, 6- 16

April 1972. Unpubl. rep., 79 p. U.S. Bur. Sport Fish. Wildl., Seattle, WA 98115.

'Hughes, S. E., R. W Nelson, and R. Nelson. 1977. Initial assessments of the

distribution, abundance, and quality of subtidal clams in the S.E. Bering Sea.

Processed rep., 43 p. Northwest and Alaska Fisheries Center, National Marine

Fi'heric; Service, NOAA, Sealtle, WA 98112.

87

need for greater knowledge of the animals themselves and of their

environment also will increase. For management of our mutually

important walrus resource, we shall need to know a great deal more

about the feeding relationships of this animal and the benthic stocks

on which it relies. One might ask, for example, how dependent is

the walrus population on the bivalves that make up the bulk of its

diet right now? If those are depleted by commercial development or

pollution, can the walrus population persist in a producti ve mode by

switching to other benthic resources not presently utilized? If so,

what effects would this have on other marine vertebrates (e.g.,

fishes, seals) that may already utilize those same resources? Future

research in support of an effecti ve multispecies management policy

for the Bering Sea will need to examine such relationships in detail.

ACKNOWLEDGMENTS

For assistance in acquisition of several of the samples reported,

we are grateful to the following personnel of the Alaska Department

of Fish and Game: John J. Burns, Kathryn J. Frost, Karl Grauvogel,

Lloyd F. Lowry, and Edward Muktoyuk. We thank also the U.S.

Coast Guard for logistic support during the Arctic Winter West

cruises of the CGC Northwind in 1970, the CGC Glacier in 1971,

and the CGC Burton Island in 1972, and the Sakhalin Fishing Fleet

(SAKHRYBFLOT) for support during the Soviet-American research cruise of the ZRS Zagoriany in 1976. The American studies

were supported in part by funds from the University of Alaska Sea

Grant Program, NOAA Office of Sea Grant, Department of Commerce, under grants GH-83, 1-36109, and 04-3-158-41, and in part

by contracts MM4AC-006 and MM5AC-024 between the U.S,

Marine Mammal Commission and the Institute of Marine Science,

University of Alaska. The Soviet studies were supported by the

Magadan Section of the Pacific Research Institute of Fisheries and

Oceanography (MoTINRO).

LITERATURE CITED

BRAHAM, H. W, J. J. BURNS, G. A. FEDOSEEV, and B. D. KROGMAN.

1984. Habitat partitioning by ice-associated pinnipeds: Distribution and density of seals and walruses in the Bering Sea, April 1976. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 12:25-47.

BROOKS, J. W

1954. A contribution to the life history and ecology of the Pacific walrus. M.S. Thesis, University of Alaska, Fairbanks, 103 p.

CHAPSKlJ, K. K.

1936. The walrus of the Kara Sea. Tr. Svesoyuz. Arkt. Inst. 67: 1-124.

FAY,F. H.

1982. Ecology and biology of the Pacific walrus, Odobenlls rosmarllS divergens JIIiger. North Am. Fauna 74, 279 p. U.S. Fish Wildl. Serv.,

WaShington, D.C.

FAY, F. H., G. C. RAY, and A. A. KIBAL'CHICH.

1984. Time and location of mating and associated behavior of the Pacific

walrus, Odobenlls rosmarllS divergens III iger. U.S. Dep. Commer. , NOAA

Tech. Rep. NMFS 12:89-99.

KRYLOV, y. I.

1965. Determination of age, rate of growth, and analysis of the age structure

of the harvest of Pacific walruses. In E. N. Pavlovskii, B. A. Zenkovich, S.

E. Kleinenberg, and K. K. Chapskii (editors), Marine mammals, p. 201-

2 I I. Nauka, Moscow.

1971. On the food of the Pacific walrus (Odobenlls rosmarllsdivergens 111.). In

E. S. Mil'chenko, T. M. Andreeva, and G. P. Bllrov (editors), Studies of

marine mammals. Tr. AtlantNIRO 39:110-116.

MANSFIELD, A. W

1958. The biology of the Atlantic walrus, Odobenlls rosmarllS I'Osmarus

(Linnaells), in the eastern Canadian Arctic. Ph.D. Thesis, McGill University, Montreal, PQ, Canada, 146 p.

NIKULlN, P. G.

1941. The Chukchi walrus. Izv. TNIRO 20:21-59.
STOKER, S. W.

1978. Benthic invertebrate macrofauna of the eastern continental shelf of the

Bering and Chukchi seas. Ph.D. Thesis, Univ. Alaska, Fairbanks, 259 p.

TlKHOMlROV, E. A.

1964. On the distribution and biology ofpinnipeds afthe Bering Sea. In P. A.

Moiseev, A. G. Kaganovskii, and I. V. Kisevetler (editors), Soviet fisheries

88

investigations in the northea'tern parl of the Pacific Ocean, PI. 3, p. 277·

285. Pischevaya Promyshlennost', Moscow.

VIBE, C.

1950. The marine mammals and the marine fauna in the Thule District

(Northwest Greenland) with observations on ice conditions in 1939·

41. Medd. Grllnl. 150(6): 1-115.
Time and Location of Mating and Associated Behavior

of the Pacific Walrus,

Odobenus rosmarus divergens Illiger

FRANCIS H. FAY,! G. CARLETON RAY,2 and ARKADII A. KIBAL'CHICH3

ABSTRACT

Management ofthe Pacific walrus population by the Soviet Union and the United States has been based up

to now on several untenable assumptions concerning the time and place of mating, the social system during the

mating season, and the sex and age composition of the population. The condition of reproductive organs of

males and females taken throughout the late autumn, winter, and spring indicates that the principal period of

mating is January-February, rather than April-June as has been assumed. During late winter, virtually all of

tbe adult females and most of the adult males are situated in the north-central and southeastern pack ice of tbe

Bering Sea. The sex ratio of adults in those areas is about 1male:l0 females. Most of the subadult males are in

peripheral and intervening areas·. Adult females and young within the two concentration areas in March

associate in tightly knit herds, which move about apparently in search of food and in response to movements of

the pack ice. One or more adult males associates with each such herd. These bulls engage in ritualized visual and

acoustical displays in the water, especially when the females are at rest on ice. While displaying, they maintain a

distance of about 5 to 10 m from each other; closer intrusion is met by threat, followed by fighting. Individual

females enter the water and engage in facial and bodily contact with the displaying males, after which,

presumably, copulation takes place underwater. The social organization appears to be unique among otarioid

pinnipeds, more closely resembling a lek than a "harem" system.

PE310ME

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nOBe)l,eHHA H nonOHoro COCTaa8 nonYJUI~HH B )THX pa"OH3x. COeJl,eHHA nOIlYlJeHllble 80 opeMA OCMOTpa

nOJlOBblX opranOB caMOK H caM~08, B)ATI.IX nOl)l,HeH OCeIlLI(), lHMOH " oeeHOH, YK3JblB3tOT 'ITO OCHOBHOH

nepHo)), cnapHU3HHA npOTeKae'r B Alloape • 4JeBpane, a He B anpeJle - HlOlle, KaK lTO C'JHT8J10Cb pallee. nOlAHe"

lHMOH nO'tTH Bce BlpOCJlbie caMKH H caMQbI OOHTalOT Ha ceoepcrQeHTpaJlbHOM H IOrO-BocTO'tHOM naKOBOM JlbJl,y

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TeJlOM K caMu,aM KoonYlll1pYlOT C H"M" 1l0Jl, 8o.l'oii. lionee MOJlOJl,ble caM"bl, KOTopble nOlme npHXO,llAT 8 Te'tKY,

...eM Blpocnble CaMl(bI, BepORTHO onJlOJ~OTOOpAIOT Tex caMOK, KOTopble ooynHpyloT nocne OKOIIl.l3HHR nHKa

cnapHBanHA.

INTRODUCTION

The formulation of a management plan for any species requires a

thorough knowledge of its natural history, reproductive biology, and

population structure. Management of the Pacific walrus, Odobenus

rosmarus divergens, by both the United States and the Soviet Union

has been founded on several basic but inadequately tested

assumptions.

1) Walruses are polygynous. Walrus are gregarious and sexually

dimorphic, characters typical of polygynous mammals (Nutting

1891; Bertram 1940; Bartholomew 1970; Trivers 1972; Stirling 1975;

I Institute of Marine Science, University of Alaska, Fairbanks, AK 99701, USA.

'Department of Environmental Scicnces, University of Virginia, Charlottesville,

VA 22903. USA.

'All-Union Institute of Fisheries and Oceanography (VNIRO), Laboratory for

Marine Mammal Investigations, Moscow 107140, USSR.

89

Ralls 1977). Their closest relati ves, the fur seals and sea Iions

(Otariidae) have these characters and are polygynous. However, the

otariids congregate on land to mate and bear young, whereas the

walrus accomplishes these functions on or near sea ice. The possibility that walruses are monogamous has been proposed by some

investigators (Allen 1880; Krylov 1968), apparently on the basis of

frequent sightings of small "family groups" during and after the

calving period. This proposal has been widely accepted in the

Soviet Union but not in the United States. However, the only support

for either view has been by inference.

2) The sex ratio of adults is about 1:1. Substantial data on the sex

ratio of newborn walruses indicate that there are about as many

males as females at birth (Nikulin 1941; Brooks 1954; Burns 19654 ).

Representative samples of adults have not been available, however,

'Burns. J. J. 1965. The walrus in Alaska, its ecology and management. Alaska

Dep. Fish Game, Juneau. 48 p.
since the sexes tend to segregate during most ofthe year. Because of

differential availability and vulnerability of the sexes to hunting,

and because of various preferences among hunters, harvest samples

tend to be strongly biased and cannot be assumed to be representative of the population as a whole (Burns footnote 4; Krylov 1965;

Gol'tsev 1968). Thus, the sex ratio of the breeding adults is

unknown.

3) Mating takes place in April to June. All other pinnipeds, as far

as is known, mate within a few days or weeks after giving birth. It

has been assumed that walruses are not different. Calves are born

mainly in the month of May (Krylov 19665), and by extrapolation

from the size of fetuses obtained in summer and autumn, implantation of the blastocyst has been estimated to occur mainly in June

(Chapskii 1936; Mansfield 1958). The findings of Brooks (1954),

Burns (footnote 4), and Krylov (1969) have confirmed this and have

shown that some females have large Graffian follicles at that time.

Thus, it has been presumed that mating takes place about the same

time as birth, that pregnancy lasts about II or 12 mo, and that, unlike

the other pinnipeds, there is no delay in implantation (Harrison

1969).

4) There is a "surplus" ofmales. Given that the sexratio at birth is

about 1:1, and that there is a high probability of polygyny, there may

be a large "surplus" of males that could be harvested without

adversely affecting recruitment of males into the breeding population. This is the basis of management of other polygynous species,

especially the northern fur seal, Callorhinus ursinus (Roppel and

Davey 1965), and it has been at the foundation of management also

of the Pacific walrus population in both the United States and the

Soviet Union.

The principal weakness in these assumptions lies in their inconsistency with each other and with other relevant findings. For

example, while the sex ratio at birth in most species of mammals is

about 1:1, the ratio in the adults usually is unequal (Glucksmann

1974). In marine mammals that are strongly polygynous, adult

females greatly outnumber adult males (Carrick et al. 1962; Chapman 1964; Ralls et al. 1980). If walruses are monogamous, their

adult sex ratio should be near parity; if they are polygynous, then

adult females should be considerably more numerous than adult

males.

It is now clear that female walruses usually breed at 2- to 3-yr

intervals, and that less than half of them bear young in any given

year (Freiman 1941; Brooks 1954; Mansfield 1958; Loughrey 1959;6

Krylov 1962, footnote 5; Burns footnote 4). This suggests that the

period ofgestation is longer than I yr and points to the possibility of

an earlier (than April-June) mating season. The latter was implied

also by Mansfield's (1958) finding of fertile adult males in late

November and March, and by Fay's (1955) observations that the

testes of adult males in April-June were mainly in retrogressive

stages.

Because less than half of the females breed in a given year. there

could be a large "surplus" of males, if the adult sex ratio is I: 1.

Conversely, if walruses are polygynous, differentially high mortality of males from natural causes is probable (Ralls et al. 1980),

which could result in a more balanced sex ratio of breeders or in a

'Krylov, V. L 1966. Time of calving and mating of the Pacific walrus. [AbstrJ

Third all-union conf. stud. marine mammals, p. 28-29. VNIRO, Vladivostok.

·Loughrey, A. G. 1959. Preliminary investigation of the Atlantic walrus,

Odobenus rosmarus rosmarus (Linnaeus). Can. Wildl. Serv., wildI. Manage. Bull.

(Ser. I) No. 14, 123 p. Queen's Printer, Ottawa.

90

"surplus" of females. Only 3 to 14% of male elephant seals,

Mirounga angustirostris, survive to sexual maturity (Le Boeuf ~'

1974); in northern fur seals, Calorhinus ursinus, the natural mortality rate of males is more than three times that of females (Chapman

1964; Johnson 1968). The concept of "surplus" deserves careful

examination.

In our work, both jointly and separately, over the past several

years, we have gathered new data pertaining to the time and place of

mating, composition of the breeding adult segment of the population, and social behavior of the mating groups. We present that

information here as a contribution to clarification of these matters,

which are of vital importance for managing the Pacific walrus

population on an international basis.

METHODS

We obtained information on the time and place of mating and

associated behavior, first, by examination ofreproductive organs of

walruses taken throughout the winter, spring, and summer; second,

by visual and photographic methods during aerial surveys; third, by

observation of animals via icebreaking ships; and fourth, byacoustical methods.

Fay obtained testes and epididymides from 111 juvenile, subadult, and adult males at St. Lawrence Island in November to June

and at Barrow in July and August 1952 to 1963. Testes were

weighed, and tissue samples were fixed in 10% Formalin 7 or AFA,

embedded in paraffin, sectioned on a rotary microtome at 7 to 10 IL,

stained with hematoxylin-eosin, and mounted on glass slides.

These were examined microscopically to determine seasonal stages

of development ofthe seminiferous epithelium and the period when

spermatozoa were present in the epididymal tubules. Kibal'chich

obtained testes from 115 juvenile, subadult, and adult males in the

southeastern Bering Sea during March-April 1976 via the joint

Soviet-American research cruise ofthe ZRS Zagoriany. These were

weighed to the nearest gram, and the presence or absence of spermatozoa was determined microscopically by the impression smear

method at the time of collection.

Fay obtained reproductive tracts from 218 adult females taken in

the north-central Bering Sea from November to June 1952 to 1972.

The ovaries from these were fixed and stored whole in 10% Formalin for I to 3 mo, then sliced into I to 2 mm thick serial sections.

They were examined without magnification, to determine the

number and size of vesicular follicles and the size and state of

development of corpora lutea. Gol'tsev (1978)8 obtained reproductive tracts from 34 adult females, during the ZRS Zagoriany cruise,

and treated them in essentially the same way. In all instances, age of

the animals was determined from counts of cementum layers in thin

sections of the cheek teeth, as described by Mansfield (1958) and

Krylov (1965).

Information on the geographical location of the animals during

and just after the mating season was obtained mainly from unpublished aerovisual survey data made available by K. W. Kenyon, G.

A. Fedoseev, J. J. Burns, and H. W. Braham. These surveys were

made during February to April of 1960 to 1972. Additional aerial

survey data were obtained by Ray, during flights over the Bering Sea

ice in April 1975 and 1976 via National Aeronautics and Space

Administration remote-sensing aircraft. These were supplemented

'Reference to trade names does not imply endorsement by the National Marine

Fisheries Service, NOAA.

8Gol'lsev, V. N. 1978. Materials on reproduction of the Pacific walrus. Abstracts

7th all-union conf. marine mammal" p. 89. Ministerstro Rybncgo Khozyaistva

SSSR, Moscow.
A

o

o

o

o o

00 0 0

-1-------- 0 0 0

-- --.......

00 """," 0 ......~, 8 0"/ oB a 0 8 ............. , 0

0..... / 0 Q ..........Q...

-11 0 0 8 0 --- o 00

o 0 0

600

700

100

E

~fSOO ..

~400 '..300

..

... 200

by surface observations via iceworthy ships in March-April 1971

(CGC Glacier), February-March 1972 (CGC Burton Island), and

March-April 1976 (ZRS Zagoriany).

Direct observations ofsocial behavior were made by Fay and Ray

during March 1972 and April 1971 via the CGC Burton Island and

CGC Glacier, respectively, in the north-central Bering Sea, and in

April to June 1952 to 1966 via small boats in the vicinity of the

western end of St. Lawrence Island. Kibal'chich and Fay observed

social behavior of walruses in the southeastern Bering Sea via the

ZRS Zagoriany in March-April 1976.

RESULTS OLA-u-e-,--SE=-P-'--O"""CT:-'-N-O-V-'-O=-E=-C-'-J-A--N-'-F--E--B..........-A--R........A--P:":R.........."':'"A::-y........J-u-N..L-J-U....J L

O,l---L_........_L..---L_-'-----'_-'-_-'-----'-_-'-_.l...-......J

AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL

B

00

o

o

o

o o

o

o O--'"tJ---_ o .,// 0 ..... - ...... o~a...

all, a 0 -~.....

o ~o 'b o ...............

_.-"'0000 8 0.

0 --0..

o oo(]) 8 0 00 0

CO

Time of Mating

Data from the reproductive organs of males taken in the northern

Bering and Chukchi Seas in November to August 1952 to 1963

(Table I) indicate that 1) the mature adults, 17 to 37 yr old, were most

often fertile, principally in the period November to February, 2) the

younger adults, 12 to 16 yr old, were fertile less often and over a

longer period, and 3) the subadults, 5 to II yr old, were least often

fertile, and their highest fertility occurred about 2 mo later than for

the mature males. The cycle of testis weights suggests a peak in

development in December or January for the older males and in

February or March for the younger individuals (Fig. 1). None of the

Table I.-Number of male walruses examined (n) and percentage in which seminiferous tubules contained spermatozoa in

bi-monthly samples from the northern Bering and Chukchi

Seas, 1952-63.

Figure 1.-Weight in grams of one testis from each of 109 male walruses taken

in the northern Bering and Chukchi Seas, in relation to date of collection. A)

Males 14 to 37 yr old; B) males 5 to 13 yr old. Each symbol represents one

specimen. Curves are visually estimated means.

Age November- January- March- May- Julyclass December February April June August

(yr) n % 11 % n % 11 % n%

5-11 14 14 3 67 540 944 3 0

12-16 18 72 3 67 450 1450 5 0

17-37 6 100 3 100 825 10 10 6 0

Table 2.-Results of examination of ovaries from female walruses that were not

carrying a large fetus and had not recenlly given birth (northern Bering Sea

1952-63; southeastern Bering Sea 1976).

Findings in ovaries

luteum of pregnancy. All but two of the corpora lutea of these

animals taken in February to June already were fully luteinized; one

from a specimen taken in early April and one in mid-February were

incompletely formed, indicating that fertilization had taken place

about 2 wk earlier.

The remaining 164 females that we examined in November to

June were either carrying a large fetus (November-April) or had

recently given birth (April-June). Only one of these, taken in June,

had a follicle larger than IO mm in its ovaries, and none had any new

corpora lutea of pregnancy like those in the foregoing group.

Thus, our data from both the males and the females indicate that

the period of mating in the Pacific walrus population is principally

in mid-winter, probably beginning no earlier than December and

ending no later than March.

Follicles

> 10mmdiam,

animals younger than 10 yr old had spermatozoa in the

epididymides; spermatozoa were present in a few of the IO to 13 yr

olds from December to May and in most of the fertile mature males

from November to May. By analogy with other pinnipeds and with

other carnivores in general, in which the principal mating period is

just after the peak of the testis cycle of the mature males (Asdell

1964; Harrison 1969), these findings suggest that the mating of

walruses takes place in mid-winter, rather than in spring_

Data obtained from males collected in the southeastern Bering

Sea between 20 March and II April, during the Soviet-American

cruise of the ZRS Zagoriany, confirmed this in part (Gol'tsev

footnote 8). Spermatozoa were most often present in the testes of

animals II to 19 yr old (71 % fertile), whereas the testes of most of

the other mature males, 17 to 32 yr old, were flaccid and in a

retrogressive state. Those of the subadults, 8 to IO yr old, were

mainly in the beginning stages of spermatogenesis,

The data from 88 sexually mature females that were not carrying

a large fetus and had not given birth recently (i.e., within 2 mo) are

shown in Table 2, Again, the samples per month are small, but the

trends seem clear. Their implication is that I) ovulation may begin

as early as December or take place as late as May in some individuals, as indicated by the presence in the ovaries of vesicular follicles

larger than IO mm in diameter, and 2) that fertilization is essentially

completed by March, as indicated by the presence of a new corpus

Month

November

December

January

February

March

April

May

June

Number

examined

I

13

2

2

12

15

33

10

Follicles

< 10mmdiam.

n % n

I 100 0

12 92 I

2 100 0

I 50 0

3 25 0

4 27 0

5 15 4

1 10 0

%

8

12

New corpus

luteum

11 %

o

o

o

I 50,

9 75

II 73

24 73

9 90

91
Location of Mating

Five aerial surveys of the Pacific walrus population in its wi ntering area in the Bering Sea were conducted jointly by the U.S. Fish

and Wildlife Service and the Alaska Department of Fish and Game

between 1960 and 1972.9 The principal objective of those surveys

was to estimate the number of animals in the population, but they

provided, at the same time, an overview ofthe animals' distribution

in the pack ice. The greater part ofthe population was situated in the

north-central Bering Sea, mainly to the south and southwest of St.

Lawrence Island; most of the remainder was in the southeast, from

the vicinity of Nunivak Island and Kuskokwim Bay to inner Bristol

Bay (Fig. 2). In the intervening and peripheral areas, the animals

occurred in low densities. Subsequent surveys in April 1975 and

March-April 1976 by Wartzok and Ray (1980)10 and by Braham et

al. (1984), in general, confirmed those findings. The pattern as

shown in Figure 2 is described only in the most general way, since

the variations in ice conditions from year to year have a strong

influence on it (Burns et al. 198011 ).

From interpretation of aerial photographs taken during one of

those surveys (1972) and from direct observations from ships, we

have repeatedly determined that the two generalized areas of high

density contain mostly females and young during March and April,

whereas the intervening and peripheral areas contain mostly males

OK. W. Kenyon, Biologist, U.S. Fish Wildl. Serv., Bur. Sport Fish. Wildl.,

Seattle, WA 98115, pers. commun. 1960-72.

l°Wartzok, D., and G. C. Ray. 1980. The hauling-out behavior of the Pacific

walrus. PB 80-192 578, 46 p. Natl. Tech. Inf. Serv., Springfield, VA 22161.

"Bums, J. J., L. H. Shapiro, and F. H. Fay. 1980. The relationships of marine

'mammal distributions, densities, and activities to sea ice conditions. Final report,

R.U. 248/249, 172 p. OUlerContinental ShelfEnvironmental Assessment Program,

NOAA Environ. Res. Lab., Boulder, Colo.

55

..

Figure 2.-Chart ofthe Bering Sea, showing the approximate average pattern

of walrus distribution in mid- to late winter (hatched) and the two areas in

which most of the females and adult males were found in mid-February to

mid-April, 1960 to 1972 (cross-hatched).

92

(Table 3). The ratios of adult males to adult females in the northcentral and southeastern areas of high density were about 1:10 and

1:8, respectively. In the low density areas, the ratio of males to

females was about 27:1, and most of those males were subadults.

Thus, it is apparent that, during late winter to early spring, the

Pacific walrus breeding population is essentially split into two

groups, one of which is located in the north-central Bering Sea and

the other is in the southeastern Bering Sea-Bristol Bay region.

Further, there are strong indications that the sex ratio of the adult,

breeding population contains many more females than males.

Table 3.-Composition of visually and photographically surveyed walruses in

Bering Sea during March-April 1971-76.

No. of Immature Subadults and adults

Area Month animals (both sexes) Males Females

North-central Mar. 907 251 90 566

North-central early Apr. 332 113\ 13 '188

North-central mid-Apr. 1,171 '459 40 '672

East-central mid-Apr. 255 4 '240 8

East-central Mar.-Apr. 73 II '54 8

Southeastern mid-Apr. 621 '237 38 '346

'In original field data, adult females and immature males and females were not

recorded separately. Numbers shown here were extrapolated from the totals, based

on a sample of 857 animals in which 509 (59.4%) were identified as adult females

and 348 (40.6%) as immature animals of both sexes.

'More than 75% of these were subadult males; at least 90% of all others listed

were mature males.

Associated Behavior

Most of our data on herd structure and social and acoustical

behavior are from the north-central high density area during March

1972 and April 1971. We obtained some additional behavioral information in the western perimeter of the southeastern area in

March-April 1976. The following are resumes, presented in seasonal chronological order, of 13 instances in which we observed

social behavior relevant to mating in mixed herds.

4 March 1972, 0700 to 0800 h, at Lat. 62°S3'N, Long.

172°06'W.-We encountered about 330 animals in a large open

water lead. About 295 of these were hauled out and most were

sleeping in three groups of20, 75, and 200 on three large floes in the

center of the occupied area (Fig. 3a). Evidently, these groups had

been lying in the same position for several hours, as many of the

animals had deposits of frost on their exposed surfaces. About 80%

of these animals were subadult and adult females; the rest were

immature young, I to 4 or 5 yr old. Another group of about 15

females was in the water and apparently feeding, 0.3 kmaway in the

same lead. We saw no adult bulls within any ofthe groups offemales

and young; however, there were 19 bulls in the vicinity, within a 0.5

km radius, and these were distributed as follows: 12 sleeping on the

ice in groups of 6,2,1,1, I, and 1; one sleeping in the water with its

pharyngeal pouches inflated; six active in the water, alongside the

floes on which the central groups of females lay. The group of six

inactive males was made up of one adult and five subadult animals,

two of which had much blood on the body and on the snow around

them. The six active bulls were spaced 7 to 10 m apart, and in a

35-min period of observation, we saw them dive and surface again

many times in the same place.

6 March 1972, 0900 to 1900 h, at Lat. 63°04'N, Long.

172°23'W.-By helicopter we located several large herds totalling
a

Figure 3.-Charts of the spatial arrangement of mixed herds of Pacific walruses observed in the north-central Bering Sea in March. The number of adult

females and young is shown within each herd. Circles represent bulls that were

active in the water (open) and those that were inactive or sleeping (solid): a) 4

March 1972, b) 8 March 1972, c) 9 March 1972, d) 10 March 1972, e) preliminary

(tusk display) interactions of bulls A and B of9 March. Open water and thin ice

areas are shaded (see text for further description).

about 1,000 animals, most of which were adult females and young.

A few adult bulls were present, some of them bloody about the head

and leaving blood on the ice wherever they went. When the ship was

moved to this position, we had four herds totalling about 500

animals within a 3 km radius. Nearly all were in the water, alternately diving and surfacing in remarkable synchrony and apparently

feeding. Only one animal, an adult bull, was on the ice, sleeping,

and he remained there throughout the daylight hours. One group of

about 50 animals slept in the water near the ship for more than 2 h in

the afternoon, before moving on. These were mainly females and

young, but with them was one adult bull that was active the whole

time, alternately diving and surfacing at 2- to 3-min intervals, in the

midst of and about the periphery of the group.

7 March 1972, 0655 to 1900 h, at Lat. 63°00'N, Long.

17r04'W.-At daybreak, we sighted steam rising from three

herds about 7 km from the ship and moved to that area for observation. All herds were in the water, evidently feeding, and these

appeared to be entirely adult females and their young. Several single

bulls were sleeping on the ice nearby. Between 0820 and 0920 h,

nine other bulls hauled out nearby, two of them with blood streaming from superficial wounds. Except for two groups of two each,

these were all single males which lay separately, about 50 to 100 m

93

apart. Nearly all of these bulls remained in place throughout the

daylight hours, whereas the herds of females were continuously

moving. In late afternoon, one group of about 250 females and

young hauled out to rest on a large floe about 1.5 km from the ship,

in an area where we had seen one or two bulls sleeping previously.

This group was still there at nightfall.

8 March 1972, 0700 to 1900 h, at Lat. 63°00'N, Long.

172°12'W.-The ship drifted slowly westward with the ice overnight and, at daybreak, was in the same position relative to the floe

on which the herd had hauled out the previous afternoon. The

resting herd of females and young was still in the same place, but

most of the single bulls that we had seen the previous day were no

longer on the ice. We left the ship on foot and took a position a few

meters downwind from the resting herd. We found it to be made up

of three partly separated groups of about 50, 150, and 50 adult

females and young, each of which had in its midst one adult male

(Fig. 3b). Those bulls slept soundly during our observations, except

for occasional jostling of their closest neighbors for resting space.

That is, we detected no activity that was even slightly suggestive of

mating behavior, and certainly not indicative of a "beach master"

role, as applied to otariids or elephant seals. We noted several times

an emphatic "knock" sound, like that made by striking knuckles on

wood, which seemed to come from the seaward edge of the groups.

An occasional, short, loud whistle also came from the same location. We moved to the edge of the floe, a few meters from the

perimeter of the largest group, where we observed three adult males

in the water alongside the herd. These bulls were diving and surfacing at short intervals (1-3 min), each in a fixed location several

meters from each other as in the foregoing observations. The dives,

because of their brevity, did not appear to be feeding dives, which in

our experience tend to be 5 to 10 min long at such depths (about 55

m). We observed these bulls for over an hour, in which their

continuous activity contrasted greatly with that ofthe inactive males

on the ice. The females seemed to pay little heed to the diving bulls.

except when the latter surfaced with a burst of spray, wetting those

nearest the edge ofthe floe. However, this only caused some jostling

in the seaward edge of the herd.

By means of hydrophone and amplifier, we detected several

underwater sounds, presumably made by the diving bulls. These

sounds consisted of a series of "knocks" and "bell-like sounds"

(see Schevill et al. 1966), but their significance and that of the other

sounds made at the surface was not apparent to us at the time.

9 March 1972, 1600 to 1900 h, at Lat. 62°44'N, Long.

17r02'W.- We located a group of approximately 95 animals in

the water and 20 that were just in the process of hauling out onto the

ice. By 1800 h, there were about 70 adult females and immature

animals on the ice in three groups of 8, 10, and about 50; two other

groups (15 and 22) of females and young remained in the water,

apparently feeding. Eight bulls also were in the water, "stationed"

about 7 to 10 m apart along the edge ofthe ice where the females and

young lay (Fig. 3c). On one occasion, male A surfaced close

alongside male B, and the two animals faced each other. They held

their tusks horizontally, first obliquely to one another, then parallel,

then directly (Fig. 3e). Immediately thereafter, male B (who was the

larger animal and had the larger tusks) rose chest-high out of the

water and rapidly struck A three or four times on the head and neck

with powerful downward thrusts of his tusks. Both animals dove in

unison, with much splashing and churning of the water, then surfaced again, whereupon B rose once more and struck A two or three

more times. Swiftly, they both dove again, surfaced briefly in a
shower of spray. then down again. then up and rolling together

violently at the surface. then down again ami n:mained beneath the

,;urface for about 2 min. After this. each surfaced at his own stativn.

Earlier. we had noticed a similar encounter between males C and D

near C's station, and this also ended with each withdrawing to his

usual station. It was not clear from our viewpoint on the ship exactly

what these bulls were doing when not engaged in such tights, except

that each was remaining in virtually the same place and repeatedly

diving and surfacing there, as we had seen in the previous instances.

On one occasion, a subadult or young adult female approached

bull A and engaged in some facial contact. She then mounted the

male's back in what appeared to be a "copulatory" position, with

the male and female roles reversed. The two then dove in unison,

arching high out of the water. They remained underwater for about 1

min, then surfaced (the male first) and engaged in further facial

contacts; then the female mounted the male again. They dove in

unison once more. rolled together for a minute or more at a shallow

depth, then surfaced slightly separated. The female swam away and

hauled out again with a nearby group. Another female engaged male

A in the same kind of activity about 30 min later.

Once again, underwater listening revealed "knocks" and the

"bell-like" sounds. The ship remained overnight in the same position relative to the herd. drifting slowly southeastward with the ice.

10 March 1972, 0700 to 1430 h, at Lat. 6r36'N, Long.

172°08'W.-At daybreak, about half of the herd observed the

previous evening was still present. The central group of 10 females

and 5 youngsters was still on the ice; about 50 others were in the

water evidently engaged in feeding. One adult male was in the water

near the group of 10 females on the ice (Fig. 3d); no other males were

in sight. We left the ship at 0830 h and approached on foot to within

30 m ofthe animals. We remained there about 5 h. During that time,

Figure 4.-Upper: 10 March 1972, group of 10 females and young resting on ice

(center), attended by one displaying bull (arrow) who has just surfaced from a

dive. Other females and young engaged in feeding are in the water at left (G. C.

Ray photo). Lower: 21March 1972, bull A (center) in mating display adjacent to

group of 20 females and young, in which were two sleeping bulls (F. H. Fay

photo).

94

the animals did not vary their distribution or their activities notably.

The adult females and immature animals in the water were continuously engaged in feeding dives, with 1.5- to 2-min ventilation rests

at the surface between dives; we did not determine diving times

because individuals were difficult to distinguish from each other.

Those on the ice mostly slept the whole time, except for a "creche"

of 5 filst- and second-year youngsters that were engaged in mutual

play. The bull repeatedly dove and surfaced in virtually the same

place alongside the 10 females for the entire 5 h. pausing for 7 to 32 s

at the surface between dives (Fig. 4 upper). His average time spent

underwater was 2 min 2 s; his average time at the surface between

dives was 23 s (Ray and Watkins 1975). As the bull surfaced

following each dive, he released a large volume of air just beneath

the surface and emerged nearly to shoulder height in a massive

eruption of air and water. Raising his tusks nearly to the horizontal

he made a "knock" which was audible to us for a distance of at least

200 m. At the time of emitting the "knock," he opened and closed

his mouth very swiftly, seemingly making the sound by percussion

of the cheek teeth. He inhaled deeply, then lowered his head so that

only his crown showed above the surface. and lay floating for a few

seconds with one pharyngeal air sac inflated and his back exposed.

He then raised his head high enough to exhale and inhale noisily

through his mouth, followed by another "knock" as he lowered his

head again below the surface. He raised his head thus from one to

four limes during each surface interval, and on the last of these he

"knvcked," emitted a short whistle through pursed lips (Fig. 5

Figure 5.-10 March 1972, displaying bull. Upper: making terminal "whistle,"

jusl prior to dive. Lower: diving after surface display sequence. Note height to

which hind flippers are raised out of the water (G. C. Ray photos).
upper), then immediately dove, arching his back and rear flippers

high out of the water (Fig. 5 lower).

During each dive, we heard the same stereotyped series of underwater pulses and bell-sounds12 as we had heard on 8 and 9

March, including a distinctive 7-pulse coda (Ray and Watkins

1975). This whole sequence of sounds (Fig. 6) was audible to us in

air from our position on the ice and was monitored and recorded by

hydrophone, as well. Comparable sequences of underwater pulses

and bell-sounds of lesser intensity, apparently made by other bulls

some distance away and not within our field of vision, were heard

via the hydrophone. At 1400 h, we intentionally disturbed the

animals by exposing ourselves to their view and moving to their

windward side, whereupon all of the females and youngsters departed. However, the bull continued his displays at his station for

about 10 min longer, before departing in the direction of the

females. Two other bulls, not seen previously, drew close to the area,

then headed in the same direction.

17 March 1972, 1000 to 1300 h, at Lat. 62°47'N, Long.

172028' W. - We encountered a group of 49 animals in an area of

heavy, continuous ice with very few holes or leads. On the ice were

45 adult females and young, arranged in three groups of 6, 15, and

24; four adult males were situated as shown in Figure 7a. Bull A was

sleeping on the ice; bull B was sleeping in the water in a round hole

about the same diameter as his body. The other two bulls were

displaying in the water, as in the previous incidents. Each had one of

12ln air. walruses sometimes chatter their teeth, like a rodent. We have observed

that "knocks" also can be produced when the jaw is moved rapidly as in percussion

of the teeth. Nevertheless, we suspect that the knocking sound is produced by some

other means. Fay and Kibal'chich watched an adult male "knocking" at close range

(3 m) on 21 March 1976 but did not detect any jaw motion; rather, the sounds seemed

to come from deeper in the throat. KibaJ'chich has observed that the bell-sound made

by walruses in air occurs at the time of inflation of one of the pharyngeal air sacs, but

this has not been the case in hundreds of Fay and Ray's observations, in which

animals floating at the surface, head down, were making the sounds without apparently varying the volume of air in their inflated sac(s).

1.5-

Time

Figure 7.-Charts ofthe spatial arrangement ofmixed herds of Pacific walruses

observed in the north-central and southeastern Bering Sea during March and

April. Symbols and scale are as in Figure 3: a) 17 March 1972, b) 21 March 1972,

c) 21 March 1976, d) 3 April 1971, e) 5 April 1971, f) 10 April 1976 (see text for

further description).

Figure 6.-Diagrammatic representation of a typical acoustical sequence during one display by an adult male. Insets are actual sonograms of parts of the underwater

display (after Ray and Watkins 1975).

95
his pharyngeal pouches inflated while he was at the water's surface.

We approached on foot and shot a female from each of the larger

groups. This immediately frightened away all of the others except

the displaying males, who continued their displays for a few minutes before moving in the direction of the departing females.

20 March 1976, about 1200 h, at Lat. 57°15/N, Long.

166°05'W.-We observed a group of four adults (2 males, 2

females) which lay in pairs, side by side on the ice, very close

together but head-to-taiL A third male which swam to, and attempted to haul out on, the same floe was met with raised tusks but no

overt aggression. He hauled out about 2 to 3 m apart from the group,

whereupon they all laid down and were quiet.

21 March 1972, 0830 to 1300 h, at Lat. 61°27/N, Long.

174°24'W.-We encountered six herds on the ice and approached

them on foot at 0830 h. There were about 250 animals in all,

including mostly females and young on the ice and more than 10

adult males in the water. We concentrated our attention on two

groups of 20 and 30 that were attended by 8 bulls (Fig. 7b). The

group of 20 on the ice consisted of more than 10 adult and subadult

females, about 8 juveniles (1 to 6 yr old), and 2 adult males. Nearly

all of these animals had a coating of frost on their exposed body

surfaces, indicating that they had been sleeping in the same position

for several hours. The males in this group continued to sleep

throughout the 4.5-h period of observation, as did most of the

females and young. Only a few of the subadult and immature

females were active, entering and leaving the water several times

during the day. In the water near the ice edge was an adult bull (A)

that was engaged in the same kind of dives and acoustical displays

as the bulls observed earlier, though he did not stay as consistently

in one place as the others had (Fig. 4 lower). The subadult and

immature females that entered the water from this group often

engaged in nose-to-nose and other facial contacts with this bull and

occasionally dove with him, but we saw no copulation. A second

bull (B), which at first stayed some 50 m away, later moved toward

Ns station. However, he did not come closer to A than about 10 m,

nor did he engage in the display routine or elicit any evident

response from bull A or from the young females. Subsequently, bull

B returned to his former place, where he remained at the surface,

making "bell" sounds with head submerged for about I h before

moving out of view. At 1200, a third bull (C) appeared about 50 m

away from A, but did not approach any closer. This animal did not

engage in the same display sequence as the others, though he did

dive occasionally and could have been making underwater sounds.

The larger group of about 30 animals also was frost-covered and

consisted of adult and subadult females and immature animals of

both sexes. There were no adult males in this group. However, three

very large bulls, spaced about 5 m apart in the water along the edge

of the floe, were continuously engaged in display routines all day;

two other, smaller bulls in the water at one end of the group,

displayed irregularly. The one most distant from the females was

least active and, for an hour, simply floated at the surface emitting

"bell" sounds, like bull B. A few of the youngest adult or subadult

females in the resting group went into the water and actively

engaged the bulls in nose-to-nose and other facial contacts. On

several occasions, a female "mounted" a bull, and they participated

together in cO!lsiderable surface and subsurface rolling and splashing. We felt that copulation could have been taking place during

these encounters, but we could not identify any copulations with

certainty from our position.

96

21 March 1976, 0800 to 1300 h, at Lat. 56°45/N, Long.

166°00/ W. _. We observed a group of 5 adult females and young

resting on ice and a group of 9 bulls and I juvenile male also on the

ice about 8 m away from the first group (Fig. 7c). One bull was in

the water about 0.5 km away but apparently was feeding, not

displaying, since his dives were long (9-10 min) and he made no

surface or underwater sounds. The group of females and young,

after about 2 h of our observation, moved along the ice and joined

the males, but other than some jostling for position, there was no

interaction between the groups. We heard a few knocks and an

occasional bell sound made by one or more of the bulls on the ice.

We heard no underwater sounds by hydrophone.

3 April 1971, 1200 to 1800 h, at Lat. 61°52'N, Long.

171°45' W. - We encountered a congregation ofsome 300 animals,

nearly all of which were asleep on the ice. Approaching on foot, we

found them to be in several groups, the largest containing about 275

females and young and one centrally located, sleeping bull (Fig.

7d). Nearby was a smaller group of about 10' females and 2 adult

bulls, also sleeping. Farther away were two groups of 7 and 8

pregnant (near-term) females, and scattered in groups of I, 1,2, and

3 within I km of the large central group were 7 adult and subadult

bulls, also sleeping on the ice. A few animals were in the water near

the largest group, and at least one ofthose was a displaying bulL No

other bulls were sighted in the water.

5 April 1971, 1700 h, at Lat. 61°20'N, Long. 173°55'W.-We

saw another group of 6 females and young on ice, attended by a large

bull who was displaying alongside in the water (Fig. 7e).

10 April 1976, 1200 h, at Lat. 57°30/ N, Long.

165°40'W.-We sighted three groups of 6,8, and 15 females and

young on adjacent floes. One bull (A) was displaying in the water

between the two smaller groups; another bull (B) was on the ice

about 10 m away (Fig. 7f). Bull B entered the water and approached

A, displaying; he was promptly attacked by A, whereupon he

withdrew and hauled out again in the same place. Underwater

sounds, evidently from bull A, were like those made by the displaying bulls observed earlier.

DISCUSSION

All previous studies of reproduction in the Pacific walrus have

been conducted entirely in late spring, summer, and autumn. Those

studies have demonstrated clearly that implantation of the blastocyst takes place mainly in June and that the calf is born about II mo

later, usually in May (Belopol'skii 1939; Freiman 1941; Nikulin

1941; Brooks 1954; Krylov footnote 5). However, the time and place

of mating and the nature of breeding behavior have remained

uncertain, for lack of specimens and observations during late autumn, winter, and early spring. Our specimens and behavioral

observations have now provided enough information to indicate 1)

that mating occurs mainly in winter rather than in spring, 2) that the

population of females usually is split into two discrete groups

(north-central and southeastern) during that period, and 3) that the

so"ial organization and behaviors of adults at that time are distinctively different from those in late spring, summer, and autumn.

Presuming that the mating season was in May and June, Belopol'skii (1939), Freiman (1941), Nikulin (1941), and Brooks

(1954) speculated that small, loosely organized "harems" may be

formed on the ice. They did not observe any such groups, however,

and could only reiterate earlier analogies ofsexual dimorphism and
gregariousness to support their views of an otariid-Iike system of

polygyny. Neither have we ~een any groups suggestive of an otariidlike "harem" structure during observations of hundreds of mixed

herds in the Bering and Chukchi Seas in late April to early September. That is, in no case did any bull appear to be dominating a

group of females or defending a territory; rather, the bulls usually

were sleeping or jostling for resting space on the ice. or simply

swimming or feeding in the water. In that period, the majority of

males stay in all-male groups, some of which are very large (hundreds or even thousands). Many of these remain in the Bering Sea

throughout the summer, while virtually all ofthe females and young

migrate northward into the Chukchi Sea. We often have seen and

heard subadult males in such all-male groups "displaying" to each

other, as well as to mature males (Miller 1975:595-597). In those

cases, the young animals' displays were "incomplete" and

nonstereotyped; that is, they used only fragments of the full,

stereotyped array of sounds and actions that characterize the displays of mature bulls in winter.

Conversely, we have observed that, in winter, most of the mature

bulls occur singly and that they tend to follow and closely attend the

herds offemales. When the females are resting either in the water or

on the ice, these bulls engage in ritualized visual and acoustical

displays in the water near them. We believe that those displays

function both as advertisement of the male's sexual readiness and as

reinforcement of a dominance hierarchy among competitive males.

Our observations indicate that, when bulls are engaged in this

activity, they maintain an individual distance of no less than 5 to 10

m; any closer intrusion is met by threat, followed by fighting. We

have never seen aggression of such intensity nor the association of

displaying bulls with herds of females in any other season of the

year.

For the most part, the subadult and juvenile males seem to remain

outside the areas where the females and adult males congregate in

winter. These younger males associate in small groups (2 to 20).

some of which also include one adult male. They tend to become

sexually active later in the season than do the older males, which

would seem to be advantageous as protection from direct competition with their elders. We often have seen subadult males associated

with females later in the spring and summer, after the adult males

are no longer in rut and have formed all-male herds. Ifthese younger

bulls playa significant role in reproduction, it may be to fertilize

cows that come into estrus after the main mating season.

In March, adult female/male interactions suggestive of precopulatory play occasionally took place when a female entered the

water and swam to a displaying male. These interactions were brief

(up to 3 min), and most of the activity took place underwater.

Presumably copulation ordinarily occurs there (Scheffer and Kenyon 1963). About 80% of copulations by walruses in captivity take

place in the water. 13

Apart from these observations, we feel that the evidence for

polygyny is compelling on several counts. First, we have observed

that females outnumber males by about 10 to 1 in the wintering

groups, and that the number of bulls attending a herd of cows seems

to vary with its size, suggesting that there is some "optimal" sex

ratio. There seemed always to be a few "extra" bulls, however, not

far from each herd of females. At times, all ofthe bulls seemed to be

resting on the ice, while the females and young were feeding.

Because the older bulls tend to come into rut earliest, we suppose

l3E. D. Asper, Curator of Mammals and Birds, Marineland, Orlando, FL 32809,

pers. commun. August 1974.

97

that there is a succession of progressively younger bulls in the

mating areas as the seasons advance from winter to spring.

Second, Ralls (1977) ha~ pointed out the high predictability in

mammals between polygyny and sexual size dimorphism. Adult

male Pacific walruses are about 20% longer and 50% heavier than

adult females; further, they have larger tusks, much thicker, lumpy

skin on the neck and shoulders, and are appreciably paler in color

than the females (Fay 1982). Body and tusk size of males seem to be

the principal determinants of social dominance (Miller 1975). Immature males tend to resemble the females in size, coloration, and

smooth skin. The degree of sexual dimorphism is appreciably less

than it is in most other polygynous pinnipeds, which suggests that

the walrus's social organization is not as rigid, and that the feedback

mechanism favoring dimorphism is not as strong as it is, for example, in the otariids (Bartholomew 1970).

Third, the maturing of the sexes at widely different ages generally is a corollary of polygyny, provided that all individuals of the

sex which matures early are to breed (Wiley 1978). In all pinnipeds,

the females apparently become capable of breeding a year to two

earlier than the males (Harrison 1969), but by no means are all of

them polygynous. The few that are known to be polygynous show an

additional, distinctive feature of development that is a more conclusive corollary: Secondary acceleration of growth in the males (Laws

1959). While the males of polygynous species become physiologically capable of breeding not long after the females, they are unable

to secure positions in the breeding structure until they have undergone this secondary, postpubertal growth and have reached a competitively large size, several years later. Male walruses, like the

otariids and Mirounga, also undergo secondary growth, reaching

their full adult size about 15 yr of age, some 5 to 6 yr after they

become fertile and 7 to 8 yr after the females begin to breed (Fay

1982).

Each of these observations strongly indicates polygynous social

organization, with inter-male competition for access to estrous

females, but not necessarily the same kind of organization as that of

the other polygynous pinnipeds. It clearly differs from the latter in

four major respects: First, there is no discernable Iimit to the amount

of breeding space available. The winter pack ice of the Bering Sea

approaches I million km2 in most years, and at least a third of it is

inhabitable by walruses (Burns et al. footnote II). Second, the

winter pack ice is continually moving (mainly from north to south),

and there is no fixed location within it to which the breeding adults

can return each year, other than in very broad, general terms. They

do seem to congregate with reasonable regularity within the two

large areas shown in Figure 2, but the variations from year to year in

extent and quality of the ice preclude site tenacity on a finer scale

and, occasionally, preclude even the use of one or both of those

areas. Third, the females do not congregate for calving just prior to

the mating season. Birth ofthe calves takes place some months later,

during the northward migration. Fourth, males on the ice with the

females do not engage the females or other males in any behaviors

that seem related to mating or defense of breeding territory. For the

most part, they simply sleep, paying no heed to either the females

around them or the displaying males in the water. Only the bulls in

the water are aggressive toward each other and attentive to the

presence and actions of the females.

Thus, the circumstances under which walruses mate are quite

different from those of other polygynous pinnipeds, and this has

been the strongest basis for argument in the past against polygyny in

walruses. For example, Bartholomew (1970) dismissed the possibility of a polygynous system being maintained by a species that

copulates in the water, since the greater mobility of pinnipeds there
than on land excludes the establishment of stable territories. Stirling (1975) felt that pack ice was unsuitable for organized polygyny

because of I) unlimited space for haulouts and 2) the instability of

the ice itself, which is continually in motion. We suggest that the

walrus is'M exception. In this case, the "territory" seems to be

more a matter of a 3-dimensional "individual space" around the

male, in which acoustic displays reinforce the dominance established by body and tusk size and by fighting. The inherent gregariousness of the females, evidently irrespective of any influence by

the males, assures unity ofthe breeding group, even in a habitat that

is in motion and constantly changing.

The mating system implied by our observations is somewhat

suggestive of a lek in that I) the dominant males display before the

females in a traditional location (albeit a very large and general

one), 2) the subdominant males take peripheral positions, outside

the "arena," and 3) the female appears to take the active role in

consorting with the male of her choice within the arena (Wiley

1978). However, it does not seem to conform to the lek criterion of a

place where males congregate to attract and court females, who

come there just for mating (Wilson 1975). Rather, the females seem

to congregate in the two large areas in winter more because of

suitable ice conditions than for mating per se, and the males simply

go there to engage them. Because the displaying males appear to

control access to the females by defending their individual spaces

alongside them, the social arrangement could be construed as a form

of "female defense polygyny" in which the gregariousness of the

females makes possible the monopolization of each herd by one or a

few males (Bradbury in Kolata 1975; Emlen and Dring 1977). The

fact that males continued to display after the females had left

suggests that a male's "control" over a given herd is very temporary,

perhaps lasting only for the period (24-48 h) when the females are

resting between feeding bouts.

From what we know of it now, the mating system of the walrus

seems most similar among pinnipeds to that ofthe northern elephant

seal, as described by Le Boeufand Peterson (1969), though it differs

in some essential points, presumably because of its occurrence in

the moving pack ice, rather than onshore.

ACKNOWLEDGMENTS

OUf work was made possible by support from several sources

over a period of many years. Fay's participation was sponsored in

part by the Arctic Institute of North America, with approval and

financial support of the Office of Naval Research under contract

Nonr 1138 (01) subcontracts ONR-77 and 91; in part by the Alaska

Sea Grant Program, supported by NOAA Office of Sea Grant,

Department of Commerce, under grants GH-83, 1-36109, and 04-

3-158-41; and in conjunction with studies supported by the Bureau

of Land Management through interagency agreement with the National Oceanic and Atmospheric Administration, under which a

multiyear program responding to the needs of petroleum development of the Alaskan continental shelf managed by the Outer Continental Shelf Environmental Assessment Program (OCSEAP)

Office. Some support and facilities were provided also by the U. S.

Dep1l11ment of Health and Welfare, Public Health Service, in connection with its Arctic Health Research Program, and by the Institute of Marine Science, University of Alaska-Fairbanks. Ray's

participation was sponsored by contracts to The Johns Hopkins

University from the Office of Naval Research (Oceanic Biology),

under contract NOOOI4-75-C-0701, the National Aeronautics and

Space Administration, under contract NAS2-9300, and the National

98

Geographic Society. Kibal'chich's work was supported by the

Soviet Ministry of Fisheries.

Logistical support was provided us additionally by the U.S.

Department of the Interior, Fish and Wildlife Service, during two

aerial surveys; by the U.S. Department of Transportation, Coast

Guard, during the Arctic Winter West operations in 1971 and 1972

and Arctic Summer West of 1977, and by the Soviet Ministry of

Fisheries, under agreement between the USA and USSR for Cooperation in the Field of Environmental Protection.

We gratefully acknowledge also the assistance of several colleagues who provided unpublished materials and aided us in gathering our data, namely John J. Burns ofthe Alaska Department ofFish

and Game, Karl W. Kenyon and James A. Estes of the U.S. Fish and

Wildlife Service, William A. Watkins of Woods Hole Oceanographic Institution, Donald H. Borchert of the Institute of Arctic

Biology, University of Alaska, and our former students Howard M.

Ferren, Edward H. Miller, Peter D. Shaughnessy, and Steven D.

SuIt. We have benefited also from the comments of Charles A.

Repenning, Douglas Wartzok, Edward H. Miller, Burney J. Le

Boeuf, and Ian Stirling on earlier drafts of the manuscript.

LITERATURE CITED

ALLEN, J. A.

1880. History of North American pinnipeds, a monograph of the walruses,

sea-lions, sea-bears and seals of North America. U.S. Geo!. Geog. Surv.

Terr., Misc. Pub!. 12,785 p.

ASDELL, S. A.

1964. PaUerns of mammalian reproduction. 2d ed. Comstock, Ithaca, N.Y.,

670 p.

BARTHOLOMEW, G. A.

1970. A model for the evolution of pinniped polygyny. Evolution 24:546-

559.

BELOPOL'SKll, L. O.

1939. On the migrations and ecology of reproduction of the Pacific walrus

(Odobaenus rosmarus divergens IlIiger). Zoo!' Zh. 18:762-774.

BERTRAM, G. C. L.

1940. The biology of the Weddell and crabeater seals: With a study of the

comparative behaviour of the Pinnipedia. Br. Graham Land Exped. Rep.

1:1-139.

BRAHAM, H. w., J. J. BURNS, G. A. FEDOSEEV, and B. D. KROGMAN.

1984. Habitat partitioning by ice-associated pinnipeds: Distribution and density of seals and walruses in the Bering Sea, April 1976. U.S. Dep.

Commer., NOAA Tech. Rep. NMFS 12:25-47.

BROOKS, J. W.

1954. A contribution to the life history and ecology of the Pacific walrus. M.S. Thesis, University of Alaska, Fairbanks, 103 p.

CARRICK, R., S. E. SCORDAS, and S. E. INGHAM.

1962. Studies on the southern elephant seal, Mirounga leonina (L.). IV.

Breeding and development. C.S.!.R.O. Wildl. Res. 7:161-197.

CHAPMAN. D. G.

1964. A critical study ofPribiloffur seal population estimates. U.S. Fish

Wildl. Serv., Fish. Bull. 63:657-669.

CHAPSKll, K. K.

1936. The walrus of the Kara Sea. Tr. Svesoyuz. Arkt. lnst. 67: 1·124.

EMLEN, S. T., and L. W. ORING.

1977. Ecology, sexual selection, and the evolution of mating systems. Science (Wash., D.C.) 197:215-223.

FAY, F H.

1955. The Pacific walrus: Spatial ecology, life history, and population. Ph.D. Thesis, Univ. British Columbia, Vancouver, B.C., Canada,

171 p.

1982. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens llIiger. North Am. Fauna 74, 279 p. U.S. Fish Wildl. Serv.,

Washington, D.C.

FltEIMAN, S. J.

1941. Materials on the biology ofthe Chukchi walrus. Izv. TlNR020:3-20.

GLUCKSMANN, A.

1974. Sexual dimorphism in mammals. BioI. Rev. Camb. Philos. Soc.

49:423-475.
GOL'TSEV, V. N.

1968. Dynamics of coastal herds of walruses in connection with their distribution and numbers. In V. A. Arsen'ev and K. I. Panin (editors), Pin·

nipeds of the northern part of the Pacific Ocean, p. 205-215. Pischevaya

Promyshlennost', Moscow.

HARRISON, R. J.

1969. Reproduction and reproductive organs. In H. T. Andersen (editor), The

biology of marine mammals, p. 253-348. Acad. Press, N.Y.

JOHNSON, A. M.

1968. Annual mortality of territorial male fur seals and its management

significance. J. Wildl. Manage. 32:94-99.

KOLATA, G. B.

1975. Sociobiology (II): The evolution of social systems. Science (Wash.,

D.C.) 187:156-157.

KRYLOV, V. I.

1962. Rates of reproduction of the Pacific walrus. Zool. Zh. 41: 116-120.

1965. Determination of age, rate of growth, and analysis of the age structure

of the harvest of Pacific walruses. In E. N. Pavlovskii, B. A. Zenkovich, S.

E. Kleinenberg, and K. K. Chapskii (editors), Marine mammals, p. 201-

211. Nauka, Moscow.

1968. Present condition of Pacific walrus stocks and prospects of their rational exploitation. In V. A. Arsen'ev and K. I. Panin (editors), Pinnipeds of

the northern part of the Pacific Ocean, p. 189-204. Pischevaya Promyshlennost" Moscow.

1969. The period of mating and calving of the Pacific walrus. In V. A.

Arsen'ev, B. A. Zenkovich, and K. K. Chapskii (editors), Marine mammals,

p. 275-285. Nauka, Moscow.

LAWS, R. M.

1959. Accelerated growth in seals, with special reference to the Phocidae. Nor. Hvalfangst-Tidende 48:425-452.

Le BOEUF, B. J.

1974. Male-male competition and reproductive success in elephant seals.

Am. Zool. 14:163-176.

Le BOEUF, B. J., and R. S. PETERSON.

1969. Social status and mating activity in elephant seals. Science (Wash.,

D.C.) 163:91-93.

MANSFIELD, A. W.

1958. The biology of the Atlantic walrus, Odobenus rosmarus rosmarus

(Linnaeus), in the eastern Canadian Arctic. Ph.D. Thesis, McGill University, Montreal, PQ, Canada, 146 p.

MILLER, E. H.

1975. Walrus ethology. I. The social role of tusks and applications of multidimensional scaling. Can. J. Zool. 53:590-613.

99

NIKULlN, P. G.

1941. The Chukchi walrus. Izv. TINRO 20:21-59.

NUTTING, C. C.

1891. Some of the causes and results of polygamy among the Pinnipedia.

Am. Nat. 25:103-112.

RALLS, K.

1977. Sexual dimorphism in mammals; Avian models and unanswered questions. Am. Nat. 111:917-938.

RALLS, K., R. L. BROWNELL, Jr., and J. BALLOU.

1980. Differential mortality by sex and age in mammals, with specific reference to the sperm whale. Rep. Int. Whaling Comm. (Spec. issue 2)

1980:233-243.

RAY, G. C., and W. A. WATKINS.

1975. Social function of underwatersounds in the walrus Odobenusrosmarus.

In K. Ronald and A. W. Mansfield (editors), Biology of the seal. Proceedings

of a symposium held in Guelph 14-17 August 1972. Rapp. P.-V. Reun.

Cons. Int. Explor. Mer 169:524-526.

ROPPEL, A. Y., and S. P. DAVEY.

1965. Evolution of fur seal management on the Pribilof Islands. J. Wildl.

Manage. 29:448-463.

SCHEFFER, V. B., and K. W. KENYON.

1963. Baculum size in pinnipeds. Z. Simgetierkd. 28:38·41.

SCHEVILL, W. E., W. A. WATKINS, and G. C. RAY.

1966. Analysis of underwater Odobenus calls with remarks on the development and function of the pharyngeal pouches. Zoologica (N.Y.) 51:103-

III.

STIRLING, I.

1975. Factors affecting the evolution of social behaviour in the Pinnipedia.

In K. Ronald and A. W. Mansfield (editors), Biology ofthe seal. Proceedings

of a symposium held in Guelph 14-17 August 1972. Rapp. P.- V. Reun.

Cons. Int. Explor. Mer 169:205-212.

TRIVERS, R. L.

1972. Parental investment and sexual selection. In B. Campbell (editor),

Sexual selection and descent of man, p. 136-179. Harvard Univ. Press,

Cambridge, Mass.

WILEY, R. H., Jr.

1978. The lek mating system ofthe sage grouse. Sci. Am. 238(5): 114-125.

WILSON, E. O.

1975. Sociobiology: The new synthesis. Harvard Univ. Press, Cambridge,

Mass., 695 p.

A List of American and Soviet Institutions

Possessing Collections of Osteological

Specimens from Pinnipeds and Sea Otters

LARRY J. HANSEN,! WILLIAM F. PERRIN,l ANATOLI S. SOKOLOV,2 and

JAMES G. MEAD3

ABSTRACT

Because different populations of the same species of pinnipeds and sea olters often have different popula.

tional parameters and histories of exploitation, modern conservation policy calls for identification of such

management units below the specific level. 10 do so often requires analysis oflarge numbers ofspecimens from a

morphological aspect, particularly by study of skeletal materials. By mutual agreement, to assist Soviet and

American researchers in locating major sources of osteological specimens, we have compiled a list of the

collections in the USA and USSR. Some 13,000 specimens ofpinnipeds and 1,200 ofsea olters, in 70 institutions,

are recorded.

PE310ME

PalHltle llony.nSl~"H O)),Horo BH,lJ,8 JlaCTOHorHX, a T3KiKe Kan3Ha &laCTO HMelOT pa3Ubie napaMeTp'" JanaCOB H

HCTOpHiO "pOMblena. no ')THM npH"IHH8M c nOlHl.l.HH cOBpeMeHHoH CTpaTerHH oxpaHhI Heo6xo)),HMO

H,QeHTH4JHUHpoB3Tb T3KHe nonYJlAll.HH BHyTP" BH)),3.

B CBA)" C )THM JaqacTyw Tpe6yeTcA aHaJl") 60J1bWOrO K0J1Hl.IeCT03 MopcfwJlorH'fecKoro MaTepH3J13,

oco6eHilO no OCTeOJlorHH. no B13HMilOMY corn3weHHIO B ueJlAX OICOlaH"R nOMOll\H 3MepHK3HcKHM It

cooeTCKHM Hccne)],OB3TeJUIM B onpe,lJ.eJleHHH MeCTOH3XO)K)leHHA OCTeOJlOrWleCKoro M3TepH3Jl3 COCT3BneH

lIacToAU\H" CnHCOl< I<Ollllel<IIH" BClUA HCCCP. 3acjJHI<CHpOBallo 01<0110 13000 )I<leMnIlApoB no lIaCTOHO'HM H

1200 no I<allaHaM B70 Y'lpell(i\eHHRX 06eHx CTpBH.

INTRODUCTION

A major emphasis in modern conservation of marine mammals is

on management by population or stock, because different populations of the same species quite often have different histories of

exploitation and different levels of natural mortality and reproduction. A sound management policy for one population is not necessarily applicable to another population of the same species. For that

reason, the International Whaling Commission and other management bodies, national as well as international, have increasingly

moved to management on a stock-by-stock basis.

For many, if not most, marine mammals, populational variation

and subdivision within the species are very poorly known or understood. The reasons for this are that I) the decision for or against

subdivision below the species level is based on morphology (osteology, coloration, body size and shape, etc.), and 2) morphological

differences at that level are not absolute and require rigorous analysis of large numbers of specimens. Thus, modern management

relies on the availability of large numbers of specimens. Unfortunately, marine mammal specimens are difficult and expensive to

collect, process, and store. Consequently, most museums and other

repositories possess only synoptic collections, or at best, a few

dozen specimens of one or two species. For that reason, one usually

'SOl,thwest Fisheries Center La Jolla Laboratory, National Marine Fisheries

Service, NGAA, La Jolla, CA 92038, USA.

'Academy of Sciences of USSR, Zoological Institute, Leningrad, USSR.

'Division of Mammals, ationa] Museum of Natural History, Washington. DC

20560, USA.

101

must examine the specimens in many collections before reaching a

conclusion on whether a particular subdivision of a species is

justified. Before a collection can be used, of course, one must know

what is in it; it must be cataloged and documented in a readily

accessible publication or report.

Because of growing Soviet-American collaboration in research

and management programs for marine mammals of mutual interest,

the US-USSR Marine Mammal Project meetings in La Jolla, USA,

in 1977 and in Ulan Ude, USSR, in 1978 endorsed the concept of

cataloging world collections of marine mammal osteological

specimens and agreed to assist and expand an existing cataloging

effort by the U.S. National Museum of Natural History. This program has been underway for several years, with many major collections in the United States and Europe already documented. Collections in the Soviet Union have been included very recently and on a

small scale. As the first step in a comprehensive cataloging program, specialists in the United States and the Soviet Union agreed to

compile and exchange lists of collections which contain marine

mammal specimens. The present list was compiled from that

exchange.

METHODS

A total of 151 institutions. including univerSIties, colleges,

museums, government agencies, and oceanaria were surveyed. A

list of institutions with marine mammal specimens compiled by

Mead in 1973 served as a starting point for this survey. Other

collections were located by reviewing catalogs of museums and

educational institutions and published lists (Anderson et al. 1963:
Katz and Katz 1965; Choate and Genoways 1975; Podolsky 1975;

Wolman 19784). Each institution was contacted first by telephone.

If the institution had marine mammal osteological specimens (a

speciman may be anything from a single bone to a complete skeleton) an estimate of the number of specimens was obtained and a

checklist questionnaire was mailed to the institution in order to

obtain a more detailed inventory of the collection. Eighty-five

percent of the questionnaires were returned.

RESULTS

Of the institutions surveyed, 70 reported pinniped osteological

specimens (Table 1), and 81 did not. Six institutions reported only

total numbers of marine mammal specimens.

Ofthe approximately 17,300marine mammal specimens located,

about 75% were pinnipeds and 7% were sea otters; the rest were

cetaceans and sirenians. As an early form of the questionnaire

'Wolman, A. A. 1978. International marine mammal scientists directory-1918.

Processed rep., 81 p. National Marine Mammal Laboratory, National Marine

Fisheries Service, NOAA. 1600 Sand Point Way NE.• Seattle. WA 98115.

included only cetaceans, pinnipeds. and sirenians.5 the numbers

indicated for sea otters probably are low. The U.S. National

Museum of Natural History has the largest collection of pinnipeds,

totaling about 2,500 specimens; the largest collection (about 1,400

specimens) in the USSR is in the Zoological Institute of the

Academy of Sciences in Leningrad.

LITERATURE CITED

ANDERSON, S., J. K. DOUIT. and J. S. FINDLEY.

1963. Collections of mammals in North America. J. Mammal. 44:471-500.

CHOATE, J. R., and H. H. GENOWAYS.

1915. Collections of recent mammals in North America. J. Mammal.

56:452-502.

KATZ, H., and M. KATZ.

1965. Museums, U.S.A.; a history and guide. Doubleday, Garden City,

NY., 395 p.

PODOLSKY, A.

1915. Education directory, higher education. U.S. Gov. Print. Off., Wash.,

D.C., 515 p.

•A list of cetacean and sirenian specimens in American and Soviet collections will

be presented in Volume 2 of this publication series.

-''IiIbIe 1. hMM...kee+ .. VM ... VSSR ..--.. .............. alter Carnegie Museum 463 .Curator of Marn-

• It!' i "',.. ••flIJ-,197', b-.I lID suney• 4400 Forbes Avenue mals

No. of specimens Pittsburgh, W. 15213

Sea OwIestoo Museum -4 A. Sanders

Name of institution Pinnipeds otters Contact 121 Rudedge Avenue Curator of NatCharleston, SC 29401 ural Sciences

Alaska Dep. FISh It Game 730 D. McKnight

Subport Bldg. Game Research Cornell University 53 R. G. Bauer

Juneau. AK 99lI01 Chief Bird It Mammal Museum. Bldg. 3 Curatorial AssoAmerican Museum «Natural History -750 S. Anderson Ithaca, NY 14850 ciale

Qntral Parll: W. al19tb St. Curator of Mam- Denver Museum of Natural History' 27 H. C. Wicbers New York. NY 10024 mals City Parle: Curator of Mam

Bernice P. Bishop Museum 15 A. C. Ziegler Denver, CO 80205 mals

P.O. Box 6031 Vert. Zoologist

Honolulu, HI 96818 Field Museum of Natural History 189 S. Walchuk

Roosevelt Rd. at Lake Shore Dr. Division of

Calif. Academy of Sciences 400 16 L. C. Binford Chicago. IL 60605 Mammals

Dep. Birds & Mammals Chairman

Golden Gale Parll: Florida State Museum 14 S. Humphrey

San Francisco. CA 94118 University of Aorida

Gainesville, FL 32611

Calif. Polytechnic State Univ. 43 119 A. 1. Roest

Biological Sciences Dep. Harvard University 566 E. Rutzmoser

San Luis Obispo, CA 93409 Museum of Comparative Zoology Curatorial Asst.

Calif. State University 9 H. Cogswell Cambridge, MA 02138 of Mammals

Dep. Biology Curator Humboldt State University 81 R. Sullivan

Hayward, CA 94542 Dep. Zoology Vert. Zoology

Calif. State University 11 3 Dr. Huckaby Arcata, CA 95521 Museum

Dep. Biology Los Angeles County Museum of 333 5 D. R. Patten 6101 East1th Street Natural History Long Beach, CA 90804 900 Exposition Blvd.

Calif. State University 6 Los Angeles. CA 90001

Dep. Biology

5151 State University Dr. Louisiana State University J. P. O'Neal

Los Angeles. CA 90032 Museum of Zoology

Baton Rouge, LA 10803

Calif. State University 18 J. Tilley

Dep. Biological Sciences Museum Curator Marineland of Florida R Jenkins

6000 J Street Route I. Box 122

Sacramento, CA 95819 St. Augustine, FL 32084

102
Michigan State University 24 J. Matson Southern Illinois University 4 2 E. C. GaJlbreath

The Museum Zoology Department

East Lansing, MI 48823 Carbondale, IL 6290 I

Monkshire Museum of Science 3 R. Chaffee University of Alaska Museum 487 8 S. MacDonald

Hanover, NH 03755 University of Alaska

National Marine Fisheries Service 2 W. F. Perrin,

Fairbanks, AK 99701

La Jolla Laboratory L. J. Hansen University of California 262 28 W. Z. Lidicker,

PO. Box 271 Museum of Vertebrate Zoology Jr.

La Jolla, CA 92038 2593 Life Sciences Bldg. Curator of MamNational Marine Fisheries Service 271 3 C. Fiscus Berkeley, CA 94720 mals

Marine Mammal Division University of California 17 M. Hildebrand

7600 Sand Point Way, Bldg. 32 Dep. Zoology

Seattle, WA 98115 Davis, CA 95616

National Museum of Natural History -2,500 500 J. G. Mead University of California 10 L. M. Julian

Division of Mammals Curator of Mar- School of Veterinary Medicine

Smithsonian Institution ineMammals Davis, CA 95616

Washington, DC 20560 University of California 28 J. Miller

New England Aquarium 15 L. Garibaldi Biology Dep., Dickey Collections Curator

Central Wharf Curator Los Angeles, CA 90024

Boston, MA 02110 University of Cal ifornia -10 T. Dohl

New York State Museum P Connor Santa Cruz, CA 95060

Washington Avenue

Albany, NY 12224 University of Colorado Museum 14 S. K. Wu

Boulder, CO 80302 Curator of ZoolNorth Carolina State Museum 3 D. Lee ogy

P.O. Box 2281 Curator of Man University of Connecticut 10 R. Dubos Raleigh, NC 27611 mals Dep. Biological Sciences

North Carolina State University 7 Dr. Barkaloo Storrs, cr 06268

Dep. Zoology Univer.;ity of Kansas -12 -1 R. S. Hoffman Raleigh, NC 27607 Museum of Natural History Curator of MamOhio Historical Society' 3 C. W. Albrecht Lawrence, KS 66044 mals

Natural History Division Curator of Nat- University of Miami 4 J. Reynolds Ohio Historical Center ural History School of Marine Sciences Columbus, OH 43211 4600 Rickenbacker Causeway

Oklahoma State University 10 2 B. Glass Miami, F.L 33149

Museum of Natural History University of Michigan 2 Dr. Smith Stillwater, OK 74074 Museum of Paleontology

Oregon Institute of Marine Biology 2 2 J. Hanna Ann Arbor, MI 48104

Charleston, OR 97420 University of Michigan 24 P Myer.;

Museum of Zoology

Oregon State University 17 B. Mate Ann Arbor, MI 48104

Marine Science Center

Newport, OR 97365 University of Missouri 60 Dr. Elder

Peabody Museum of Natural History 66 J. Ostrom Museum of Zoology

Yale University Columbia, MO 65201

New Haven, cr 06520 University of Montana 19

Peabody Museum of Salem 2 S. Pidugalls Dep. Zoology

Salem, MA 01970 Missoula, MT 59801

Philadelphia Academy of Science 137 F. B.Gill University of New Mexico 10 J. Finley

19th St. and Parkway Dep. Biology

Philadelphia, PA 19103 Albuquerque, NM 87106

Princeton University I) D. Baird University of Notre Dame

Dep. Biology Museum of Natural History Geology Dep. Notre Dame, IN 46556 Princeton, NJ 08540

San Diego Natural History Museum 130 R. M. Chandler University of Oregon 17 2 E. Gustafson

P.O. Box 1390 Curator of Birds Museum of Natural History

San Diego, CA 92112 & Mammals Eugene, OR 97403

Univer.;ity of Puget Sound 374 34 E. Kritzman

San Jose State University 103 J. Vollenweider Puget Sound Museum of Natural

125 South Seventh Street Museum ofBirds History

San Jose, CA 95162 & Mammals Tacoma, WA 98416

Santa Barbara Museum of Natural 85 48 C. Woodhouse University of Texas, Austin -6 R. Martin

History Head, Marine Texas Memorial Museum

2559 Puesta del Sol Road Mammal Pro- 2400 Trinity

Santa Barbara, CA 93105 gram Austin, TX 78705

103
University of Washington 53 J. Rozdilsky Academy of Sciences of USSR 1.426 261 I. M. Gromov

Burke Museum Zoology Div. Zoological Institute

Seattle, WA 98195 Leningrad, USSR

Virginia Polytechnic Institute 6 J. Crawford Atlantic Research Institute 372 0 V. A. Zheglov

and State University of Fisheries and Oceanography G. V. Rezvov

Dep. Biology Kaliningrad, USSR 1. E. Filatov

Blacksburg, VA 24061 Pacific Researeh Institute 3~9 195 G. M. Kosygin

Waikiki Aquarium L. Taylor

of Fisheries and Oceanography

2777 Kalakaua Avenue

Vladivostok, USSR

Honolulu, HI 96815 Magadan Section 1,247 0 G. A. Fedoseev

Pacific Research Institute

Washington State University 30 R. E. Johnson of Fisheries and Oceanography

Dep. Zoology Magadan 685013, USSR

Conner Zoology Museum Petropavlovsk Section 16 0

Pullman, WA 99164 Pacific Research Institute of

Moscow State University 1,124 0 O. L. Ross·Jlimo Fisheries and Oceanography

Zoological Museum 1. R. Pavlinov Petropavlovsk-Kamchatka, USSR

Moscow, USSR I Status of collection as of 1973.

104