The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands
The detailed analysis of a food of the Antarctic species of seals around Argentine islands archipelago, that was spent through out 11 Ukrainian Antarctic expedition (2006-2007), has shown that krill (Euphausia superba) is the main type of food for the major species of seals in region. Krill makes 97...
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Національний антарктичний науковий центр МОН України
2009
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irk-123456789-1285732018-01-12T03:03:04Z The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands Dykyy, I. Біологічні дослідження The detailed analysis of a food of the Antarctic species of seals around Argentine islands archipelago, that was spent through out 11 Ukrainian Antarctic expedition (2006-2007), has shown that krill (Euphausia superba) is the main type of food for the major species of seals in region. Krill makes 97,2 % to a diet of fur seals (Arctocephalus gazella) and 90 % to a diet crabeater seal (Lobodon carcinophagus) during the summer period. It is established rather big dimensional and weight rates to young growth in comparison with literary data àccording to Weddell seal (L. weddelli) newborns monitoring. It testifies to enough qualitative and sufficient forage reserve for pregnant Weddell seal females in archipelago water area in which diet krill prevails also (about 70 %). Considering that from 5 seals species counted within archipelago, the most numerous is the crabeater seal and a southern fur seal - these species can be used as «species indicators» of krill distribution and quantity in the given region. It is established, that the leopard seal's fodder diet is similar, to a diet of a specie around eastern Antarctic, despite an essential latitude difference of specie habitat arrangements. Проведений протягом 11-ї Української антарктичної експедиції (2006-2007 рр.) грунтовний аналіз живлення антарктичних видів тюленів у районі архіпелагу Аргентинські острови показав що у більшості видів тюленів регіону в раціоні переважає криль (Euphausia superba). Протягом літнього періоду криль складає 97,2% раціону морських котиків (Arctocephalus gazella) та 90% раціону крабоїда (Lobodon carcinophagus). Згідно з моніторингом новонароджених тюленя Уеддела (Leptonychotes weddelli) встановлено відносно великі розмірні та вагові показники молодняку в порівнянні з літературними даними, що свідчить про якісну й достатню кормову базу для вагітних самиць Уеддела в акваторії архіпелагу, в раціоні яких теж переважає криль (близько 70%). Враховуючи, що з п'яти видів облікованих у межах архіпелагу тюленів найбільш багаточисельними є тюлень-крабоїд та південний морський котик, ці види можуть бути використані як «види-індикатори» поширення та чисельності крилю при встановленні його запасів у даному регіоні. Встановлено, що кормовий раціон морського леопарда максимально подібний до раціону виду в районі Східної Антарктики, попри суттєву різницю широтного розташування біотопів виду. 2009 Article The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands / I. Dykyy // Український антарктичний журнал. — 2009. — № 8. — С. 311-319. — Бібліогр.: 36 назв. — англ. 1727-7485 http://dspace.nbuv.gov.ua/handle/123456789/128573 574.23 en Український антарктичний журнал Національний антарктичний науковий центр МОН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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Біологічні дослідження Біологічні дослідження |
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Біологічні дослідження Біологічні дослідження Dykyy, I. The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands Український антарктичний журнал |
| description |
The detailed analysis of a food of the Antarctic species of seals around Argentine islands archipelago, that was spent through out 11 Ukrainian Antarctic expedition (2006-2007), has shown that krill (Euphausia superba) is the main type of food for the major species of seals in region. Krill makes 97,2 % to a diet of fur seals (Arctocephalus gazella) and 90 % to a diet crabeater seal (Lobodon carcinophagus) during the summer period. It is established rather big dimensional and weight rates to young growth in comparison with literary data àccording to Weddell seal (L. weddelli) newborns monitoring. It testifies to enough qualitative and sufficient forage reserve for pregnant Weddell seal females in archipelago water area in which diet krill prevails also (about 70 %). Considering that from 5 seals species counted within archipelago, the most numerous is the crabeater seal and a southern fur seal - these species can be used as «species indicators» of krill distribution and quantity in the given region. It is established, that the leopard seal's fodder diet is similar, to a diet of a specie around eastern Antarctic, despite an essential latitude difference of specie habitat arrangements. |
| format |
Article |
| author |
Dykyy, I. |
| author_facet |
Dykyy, I. |
| author_sort |
Dykyy, I. |
| title |
The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands |
| title_short |
The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands |
| title_full |
The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands |
| title_fullStr |
The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands |
| title_full_unstemmed |
The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands |
| title_sort |
feeding peculiarities of the antarctic seals in the region of the archipelago of argentina islands |
| publisher |
Національний антарктичний науковий центр МОН України |
| publishDate |
2009 |
| topic_facet |
Біологічні дослідження |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/128573 |
| citation_txt |
The Feeding Peculiarities of the Antarctic Seals in the Region of the Archipelago of Argentina Islands / I. Dykyy // Український антарктичний журнал. — 2009. — № 8. — С. 311-319. — Бібліогр.: 36 назв. — англ. |
| series |
Український антарктичний журнал |
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AT dykyyi thefeedingpeculiaritiesoftheantarcticsealsintheregionofthearchipelagoofargentinaislands AT dykyyi feedingpeculiaritiesoftheantarcticsealsintheregionofthearchipelagoofargentinaislands |
| first_indexed |
2025-07-09T09:22:08Z |
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1837160654374436864 |
| fulltext |
311
THE FEEDING PECULIARITIES OF THE ANTARCTIC SEALS IN THE REGION OF
THE ARGENTINA ISLANDS ARCHIPELAGO
Dykyy I.
Ivan Franko National University of Lviv, e-mail: zoomus@franko.lviv.ua
National Antarctic Scientific Center
Summary. The detailed analysis of a food of the Antarctic species of seals around Argentine islands archipelago,
that was spent through out 11 Ukrainian Antarctic expedition (2006-2007), has shown that krill (Euphausia
superba) is the main type of food for the major species of seals in region. Krill makes 97,2 % to a diet of fur seals
(Arctocephalus gazella) and 90 % to a diet crabeater seal (Lobodon carcinophagus) during the summer period. It
is established rather big dimensional and weight rates to young growth in comparison with literary data àccording
to Weddell seal (L. weddelli) newborns monitoring. It testifies to enough qualitative and sufficient forage reserve
for pregnant Weddell seal females in archipelago water area in which diet krill prevails also (about 70 %).
Considering that from 5 seals species counted within archipelago, the most numerous is the crabeater seal and a
southern fur seal - these species can be used as «species indicators» of krill distribution and quantity in the given
region. It is established, that the leopard seal's fodder diet is similar, to a diet of a specie around eastern Antarctic,
despite an essential latitude difference of specie habitat arrangements.
The trophical researches of Weddell seal have allowed to define a new commercial specie of large squid
Psychroteuthis glacialis for the first time in given region. These results have great value not only for a definition
of an actual condition of Antarctic ecosystem and biovariety preservations in planetary scale. But also can be used
for working out of the management project for future rational use of krill sea stocks and squids in the given region
of Antarctic, at the state level.
Key words: feeding, seals, Argentina Islands, Antarctic ecosystem.
Îñîáëèâîñò³ æèâëåííÿ àíòàðêòè÷íèõ âèä³â òþëåí³â ó ðàéîí³ àðõ³ïåëàãó Àðãåíòèíñüê³ îñòðîâè.
Äèêèé ².
Ïðîâåäåíèé ïðîòÿãîì 11-¿ Óêðà¿íñüêî¿ àíòàðêòè÷íî¿ åêñïåäèö³¿ (2006-2007 ðð.) ãðóíòîâíèé àíàë³ç
æèâëåííÿ àíòàðêòè÷íèõ âèä³â òþëåí³â ó ðàéîí³ àðõ³ïåëàãó Àðãåíòèíñüê³ îñòðîâè ïîêàçàâ, ùî ó á³ëüøîñò³
âèä³â òþëåí³â ðåã³îíó â ðàö³îí³ ïåðåâàæຠêðèëü (Euphausia superba). Ïðîòÿãîì ë³òíüîãî ïåð³îäó êðèëü
ñêëàäຠ97,2% ðàö³îíó ìîðñüêèõ êîòèê³â (Arctocephalus gazella) òà 90% ðàö³îíó êðàáî¿äà (Lobodon
carcinophagus). Çã³äíî ç ìîí³òîðèíãîì íîâîíàðîäæåíèõ òþëåíÿ Óåääåëà (Leptonychotes weddelli)
âñòàíîâëåíî â³äíîñíî âåëèê³ ðîçì³ðí³ òà âàãîâ³ ïîêàçíèêè ìîëîäíÿêó â ïîð³âíÿíí³ ç ë³òåðàòóðíèìè
äàíèìè, ùî ñâ³ä÷èòü ïðî ÿê³ñíó é äîñòàòíþ êîðìîâó áàçó äëÿ âàã³òíèõ ñàìèöü Óåääåëà â àêâàòîð³¿
àðõ³ïåëàãó, â ðàö³îí³ ÿêèõ òåæ ïåðåâàæຠêðèëü (áëèçüêî 70%). Âðàõîâóþ÷è, ùî ç ï'ÿòè âèä³â îáë³êîâàíèõ
ó ìåæàõ àðõ³ïåëàãó òþëåí³â íàéá³ëüø áàãàòî÷èñåëüíèìè º òþëåíü-êðàáî¿ä òà ï³âäåííèé ìîðñüêèé êîòèê,
ö³ âèäè ìîæóòü áóòè âèêîðèñòàí³ ÿê «âèäè-³íäèêàòîðè» ïîøèðåííÿ òà ÷èñåëüíîñò³ êðèëþ ïðè
âñòàíîâëåíí³ éîãî çàïàñ³â ó äàíîìó ðåã³îí³. Âñòàíîâëåíî, ùî êîðìîâèé ðàö³îí ìîðñüêîãî ëåîïàðäà
ìàêñèìàëüíî ïîä³áíèé äî ðàö³îíó âèäó â ðàéîí³ Ñõ³äíî¿ Àíòàðêòèêè, ïîïðè ñóòòºâó ð³çíèöþ øèðîòíîãî
ðîçòàøóâàííÿ á³îòîï³â âèäó.
Ïðîâåäåí³ âïåðøå äëÿ ðåã³îíó äîñë³äæåííÿ òðîô³êè òþëåíÿ Óåääåëà äîçâîëèëè âñòàíîâèòè íîâèé
ïðîìèñëîâèé âèä êðóïíîãî êàëüìàðà Psychroteuthis glacialis. Ö³ ðåçóëüòàòè ìàþòü âàæëèâå çíà÷åííÿ íå
ëèøå äëÿ âñòàíîâëåííÿ ôàêòè÷íîãî ñòàíó àíòàðêòè÷íî¿ åêîñèñòåìè òà çáåðåæåííÿ á³îð³çíîìàí³òòÿ ó
ïëàíåòàðíîìó ìàñøòàá³, à é ìîæóòü ó ïåðñïåêòèâ³ ñëóãóâàòè îñíîâîþ äëÿ ðîçðîáêè íà äåðæàâíîìó ð³âí³
ìåíåäæìåíò-ïëàíó äëÿ ìàéáóòíüîãî ðàö³îíàëüíîãî âèêîðèñòàííÿ ìîðñüêèõ çàïàñ³â êðèëþ òà êàëüìàð³â ó
äàíîìó ðåã³îí³ Àíòàðêòèêè.
Êëþ÷îâ³ ñëîâà: æèâëåííÿ, òþëåí³, Àðãåíòèíñüê³ îñòðîâè, àíòàðêòè÷íà åêîñèñòåìà.
ÓÊÐÀ¯ÍÑÜÊÈÉ ÀÍÒÀÐÊÒÈ×ÍÈÉ
ÆÓÐÍÀË
ÓÀÆ ¹ 8, 311-319 (2009)
ÓÄÊ 574.23
312
Introduction
Throughout 11 Ukrainian Antarctic expedition (2006-2007) we have spent professional
teriological researches of the sea mammals on territory of the Argentine islands and adjoining water
areas, for the first time for 10th years of UAS "Academician Vernadsky" existence. Teriological
researches were conducted on Ukrainian Antarctic station “Academician Vernadsky” during
wintering on 29.01.2006-01.03.2007 according to tasks of State researches program of Ukraine in
Antarctica for 2002-2010. The researches were made in two topics: “biological recourses and
oceanology” and “Ecological researches and monitoring of environment”. According to the main
tasks those topics the project “Mammals of the Argentina islands (species list, quantity, habitat
distribution, biology) and their role in the Antarctic ecosystem”.
One aspect of researches included gathering and the analysis excrement of all species of seals
in the given region according to standard techniques. Due to the spent analysis, trophical relations
were defined and feeding competition features of sea mammals at investigated region were found out.
The sea mammals of Argentine islands and adjoining territories practically remained not investigated
till this time. At the same time the analysis of all existing fragmentary data which have been collected
by in addition previous biologists-winterers since 3 to 9 Antarctic expeditions, in the given territory
has been carried out.
Material and technique
The Argentine islands archipelago is placed in Pacific sector of Antarctic in the western part of
Antarctic peninsula between 65°13 '-65°16 ' s. and 64°10 '-64°20 ' w., in 142 km. to the north of a
southern polar circle which passes on 66°33' s. The chain of islands lasts from the southeast to
northwest in 5-7,5 km. from the Graham land of Antarctic peninsula. From peninsula it is separated by
2Penola straight. The archipelago total area occupies all nearby 3,5 êì . The archipelago serves original
refugium for seals, owing to successful placing.
A total of 131 faeces of the 5 species of seals (À. gazella - 66; L. weddellii - 23; L.
carcinophagus - 15; H. leptonyx - 24; M. leonina - 3) were collected from January 2006 to March 2007,
respectively, around groups of juvenile and adult specimens of both sexes resting at beaches
surrounding on archipelago of Argentina islands and Antarctic Peninsula. Given that before the
collection of the samples, the beaches to be surveyed were cleaned from old faeces. Àll the samples
analysed were produced by seals during the study periods. The samples were individually washed
through sieves (minimum mesh 0.54 mm) and the prey remains were sorted to the lowest taxonomic
level possible (Casaux et al. 2005). In order to estimate the approximate number of individuals of the
Antarctic krill Euphausia superba present in each sample, we considered the number of eyes and
telsons or the dry weight of the total of the carapaces present in the sample according to the technique
described by Casaux et al. (1998). The highest of these three estimations was considered as the
minimum number of krill specimens present per sample. The mass of the individuals was estimated by
comparing with entire specimens recovered from the study area. Isopods, amphipods and decapods
were represented by exoskeletons remains and their mass were estimated by comparing with entire
specimens collected in the study area. Cephalopods were identified using reference materials and the
illustrations «FAO species identification sheets for fishery purposes. Southern Ocean (Fishing Areas
48, 58 and 88)» (Fisher, Hureau, 1985a,b), and descriptions in Clarke (1980), Lipinski and
Woyciechowski (1981), and Okutani, Clarke (1985). The number of individuals represented in the
samples was estimated by the number of upper and lower beaks or eye lenses. Almost all the squids
represented in the samples were tentatively identified as Brachioteuthis picta. The nine beaks from
one sample faeces one specimen Leptonychotås weddelli were identified as Psychroteuthis glacialis.
The number of gastropods and bivalves represented in the scats was estimated considering the number
Dykyy I.: THE FEEDING PECULIARITIES OF THE ANTARCTIC SEALS IN THE REGION OF THE ARGENTINA...
313
of shells present in the samples and the mass was estimated by comparing with entire specimens
recovered from the study area. Bones, otoliths and eye lenses indicated the presence of fish in the scat
samples. The sagittal otoliths were identified to species level, where possible, using our own reference
collection and illustrations and descriptions monography «Fishes of the Southern Ocean» (Gon,
Heemstra, 1990) and publication Hecht (1987), Williams, McEldowney (1990) and Reid (1996). The
otoliths belonging to specimens of each species were sorted into right or left and the most abundant of
these was considered as the number of fish present in each sample. Since the estimates of the number
and mass of prey species represented in scats usually give biased results (Clarke and MacLeod 1982;
da Silva and Neilson 1985; Green and Burton 1987; Murie 1987; Casaux et al. 1997), the estimated
mass of the different alimentary items does not necessarily represent their real contribution to the diet.
However, these values were included because they provide information not reflected by the
frequencies of occurrence.
Results of researches
The researches have shown, that from 6 species of Antarctic seals, within Argentine islands
archipelago the 5 species are extended – the family (Otariidae) is presented by one specie – a Southern
fur seal (Arctocephalus gazella Peters, 1875). Four species of seals belongs to a family (Phocidae)
from which three species belongs to subfamily (Monachinae) – Crabeater seal (Lobodon
carcinophagus Hombron and Jacquinot, 1842), Weddell seal (Leptonychotes weddelli Lesson, 1826)
and a Leopard seal (Hydrurga leptonyx Blainville, 1820). The fourth specie – a Southern elephant seal
(Mirounga leonine Linnaeus, 1758) belongs to subfamily (Cystophorinae). The analysis of faeces is
carried out has allowed to find out feeding features of the Antarctic species of seals around the
Argentine islands archipelago.
Southern fur seal. Antarctic krill E. superba is the basic object of fur seal's diet within
archipelago. In particular, a female after reproduction and in time of lactic period are fed exclusively
by krill. Young individuals and adult males eat krill and fish. Besides molluscs (squids) are in their
diet. It has been worked over fifty excrement of an animal throughout the period of researches.
Seasonal researches of a fur seal excrement have shown, that in its summer diet prevails fish of family
Nototheniidae, unlike autumn period. Krill together with fish are constantly presents at a diet of seals
through all period of their being on archipelago (also makes 97,2 percent) (fig. 1). From 100 to 796
fragments of separate krill pieces were in one sample. On the basis of faeces analysis, it is necessary to
notice, that the remains of cephalopodes in excrement of a seal were not founded. However, the specie
consumes Antarctic limpet Nacella concinna, but not in a considerable quantity. Therefore we
suppose, that seals eat limpet and mollusc shells as stones gastrolites, which animals swallow from an
ocean floor in a considerable quantity. In whole, from 10 to 40 such small stones gastrolites in one
sample were founded.
On literary data fur seals hunt, mainly, in the top water layer (about 50 m), young males can
sometimes kill penguins, but do not eat them (Lea et al. 2002) except above listed diet. However, our
observations and the analysis of an animals excrements has shown, that fur seals from territory of
Galindez island and Black island consumed penguins in meal twice. Similar data results are in annual
report of Manilo L., specifying that in March of 2004 and 2005 the skin and feather fragments of
penguins were repeatedly founded in excrements of seals (Manilo, 2005). Possibly young and
wounded penguins become victims of seals. Hence, penguins P. papua and P. adeliae also presents in a
diet of a southern fur seal on territory of Argentine islands archipelago. Animals are active both in the
afternoon and at night. However, food activity of animals mainly is noted on evening hours.
Dykyy I.: THE FEEDING PECULIARITIES OF THE ANTARCTIC SEALS IN THE REGION OF THE ARGENTINA...
314
Fig. 1. Repeatability percent of forages in excrements A. gazella in Argentine Islands water area.
Weddell Seal. The analysis of Weddell seal excrement from archipelago territory has shown,
that in a diet of animal the first place occupies krill E. superba (about 70 %), during the winter-spring
period. The greatest percent of krill in investigated samples was noted in females feeding during the
lactation period. Small species of fishes compound only 15-20 % of an animal diet. The seal gives
advantage to Trematomus representatives. In samples prevails Trematomus scotti – 45 %. Also in
winter there are fragments of isopodes – Glyptînotus antarcticus and shells of bivalves (small species)
quite often. The last possibly get to a digestive path of a seal from the fishes stomachs caught by it.
During the summer period in its diet prevails molluscs and fish, with a small amount of seaweed.
Among cephalopodes molluscs two species of squids are in Weddell seals diet. In particular, the
chitinous bills of Brachioteuthis picta, are in its excrement in spring-summer periods. Also bills of
squid large specie (Psychroteuthis glacialis) has been allocated and identified from excrements of
Weddell seal several individuals from Cruls Island, which is on distance of 15 km from Galindez
Island, for the first time by us. This specie reaches to 44 sm of length. Its area covers Antarctic
Peninsula region, and the specie gives advantage to depths from 200 to 700 m. It is a new large squid
commercial specie. Its distribution has been confirmed for Argentine islands water area by analysis of
faceas.
Crabeater seal. Antarctic krill E. superba compound about 90 % of a crabeater seal diet. Krill
amounts the greatest percent in a seals diet in spring and summer periods around archipelago.
However, fish, squids and others invertebrates are also in a diet of the given specie of seal. In
particular, in winter months when the krill quantity decreases around archipelago, the seal consumes
ãîëîâîíîãèõ molluscs of specie B. picta more often. Its maintenance can reach 40 % in samples and
small coastal species of fishes. Also crabeater seal food research around Antarctic Peninsula is
confirmed with literary data. However, specie distribution is closely connected with krill stocks
division in habitats. That's why in the winter, when E. superba meets sporadically around archipelago,
the crabeater seals quantity decreases ten times. The detailed analysis of seasonal crabeater seal
amount dynamics in the Argentine islands archipelago testifies to it.
Dykyy I.: THE FEEDING PECULIARITIES OF THE ANTARCTIC SEALS IN THE REGION OF THE ARGENTINA...
315
Leopard seal. Leopard seal is a predator who eats warm-blooded animal (sea birds and young
seals). The only natural enemy of a leopard seal is killer whale. Own observations have shown, that
during the early spring period the specie gives advantage to sea birds and eats any readily available
species - Larus dominicanus, Catharacta maccormicki, Phalacrocorax atriceps. However, the
penguin Pygoscelis ðapua – 61 % — the main component of a diet around the Argentine islands during
the summer period, krill is on 2nd place (fig. 2). Usually, at this time individuals of specie constantly
keep closer to colonies of penguins P. papua and P. adeliae (Galindez, Petermann, Yalour islads). The
successful hunting of leopard seal on young crabeater seal L. carcinophagus has been noted and fixed
on camera, during researches in October in 2006. Thus a leopard has immobilized an animal, having
had a bite a neck of victim. After that predator has hidden the undereated hulk of killed animal under a
fragment of iceberg. The hunting of separate individuals of a specie for a waterfowl is often enough
observed within Galindez island. It is amount, – 77 % from a diet of a specie around archipelago. Also
the animal consumes large copies of Nototheniidae family fishes.
Fig. 2. Leopard seal (H. leptonyx) diet in Argentine Islands water area.
Southern sea elephant. A feeding of the given specie is poorly investigated. It is known, that
the diet contents of specie depends on distribution region. The coastal species of fishes and
cephalopodes compound a basis of feeding. The youth also eats large amphipodes and isopodes.
According to the literature, animal of the given specie can dive to 1500 m depth, remaining under
water nearly 2 hours (Fisher, Hureau, 1985b). However, usually dive to 200-400 m at a food. The
excrement analysis of two young females from Rasmussen Island has shown, that cephalopodes –
Brachioteuthis picta, small representatives of sort Trematomus fish, Antarctic limpet N. concinna and
about 50 % of diet compounds the seaweed rests in investigated territory.
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316
Discussion
The results of krill A. gazella consumption being received during the summer period around
Argentine Islands archipelago confirming the similar researches spent on the given specie around
southern Shetland Islands. There the female together with the kid for four months of a summer season
(from December on March inclusive) consumes 917 kg of krill. And consumption calculations for this
period of all population in the given region make 3,6 õ 106 kg of euphausiids crude weight (Croll,
Tershy 1998). All the same krill occupies a considerable particle in a feeding of fur seals during the
summer period and amount from 50,2 % to 97 % of a diet, despite on partial geographical variability of
species trophic is described in the literature (Casaux et al. 1998, 2003, Daneri et al. 2005). A. gazella
can play a role of E. superba bioindicator accordingly concentrating during this period in places with
the greatest congestion of second. In spite of the fact that on literary data Casaux et al. (2003), Daneri
et al. (1999, 2005) during the summer-autumnal period the specie also often consumes cephalopodes,
around King-George island from 12 % to 14 %, near Antarctic Peninsula (Cierva Point), the rest
cephalopodes in excrement of a seal have not been noted within Argentine islands archipelago.
However, such squid's species as B. picta and P. glacialis, that are a part of the given specie diet
according to Daneri et al. (1999), extended in water area of archipelago also are in excrement of
Weddell seal. Besides, the consumption of penguins by young males of seals, were noted by us. First it
has been suggested that non-breeding male Antarctic fur seals frequently kill but do not eat penguins
Fischer and Hureau (1985b) or that most of the penguins caught are not ingested (Bonner and Hunter
1982). Conversely, other studies reported that seals frequently kill and eat penguins (Laws 1985;
Hofmeyr and Bester 1993), penguin remains being present in 23% of the samples collected at the
South Orkney Islands (Daneri and Coria 1992). Based on that observation and on the occurrence of
penguin remains in 45% of the scats collected at Harmony Point during the 1995/1996, 1996/1997 and
2001/2002 summer seasons, Casaux et al. (1998, 2004) also indicated that penguins are an important
food item of the Antarctic fur seal.
L. carcinophagus is one more basic krill consumer around Argentine islands archipelago.
According to the literary data, everyonecrabeater sealconsumes 20 kg for day (at 20-25 times more
weights of a body in a year), simple calculations show, that the animal can consume nearby 10 tones of
krill annually (Fisher, Hureau, 1985b). Seal crab-eater is the basic consumer of krill for given time at
Southern ocean. Crabeater seals are well suited for investigations of relationships between seasonal
variation in foraging behavior, habitat use, and environmental conditions. Crabeater seals are
abundant, yeararound residents of the Antarctic pack ice, and they forage primarily on Antarctic krill
(E. superba) (Laws, 1985). Krill is a patchily distributed prey resource that varies in abundance and
energy content due to seasonal shifts in environmental conditions (Siegel, 1988; Lascara et al., 1999).
Therefore, crabeater seal behavioral strategies are likely to change seasonally in response to the same
factors that influence krill populations. Previous research has indicated that crabeater seal populations
are sensitive to environmental fluctuations (Testa et al., 1991) and that individuals are often found in
areas where krill abundance is higher (Nordoy et al., 1995; McMahon et al., 2002). Thus, crabeater
seals, like other aquatic predators appear to be selecting regions of their habitat where prey are locally
concentrated (Wilson et al., 1993). Hence, L. carcinophagus can be used as bioindicator for E. superba
also.
On literary data, the basic objects of L. weddelli feeding is coastal species of fishes
Nototheniidae, Myctophidae and Channichthyidae (about 80 %), cephalopodes (P. glacialis and
Pareledone charcoti) and crustacea (Burns et al., 1998; Casaux et al., 1997, 2004). Last publications
testify about geographical variability of specie trophic (Lake et al., 2003). The research carrying out
by us confirm, that in a diet of an animal around archipelago prevails E. superba, instead of fish,
especially at females during the bringing up period of youth. The newborn Weddell seals monitoring
carried out by us has allowed to establish rather big dimensional (135–144 sm) and weight (25–28,5
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317
kg) indicators to young growth at a birth in comparison with literary data, where the length of
newborns makes 120 sm, weight – 25 kg (Fisher, Hureau, 1985b). Also it is established, the daily gain
of newborns is amount 3,5 kg average. It testifies to enough qualitative and sufficient forage reserve
for pregnant Weddell seals females in the archipelago water area which basis is krill.
Also on literary data the big enough percent (about 50 %) in H. leptonyx food occupies krill
(Fisher, Hureau, 1985b). However, the excrement analysis within archipelago has not confirmed these
data. The forage structure of the given specie during the summer period is similar to a population diet
of leopard seals from the Southern Shetland islands area where their basis is made by penguins
Pygoscelis àntarctica and from the end of December to the beginning of February — youth of fur seals
A. gazella (Hiruki et al., 1999). However, a food by a crabeater seal, noted by us within archipelago, is
described only from area of east Antarctic (gulf Prydz) (Hall-Aspland and Rogers, 2004). Similarly
with region of Argentine islands archipelago, the krill consumption in region of east Antarctic during
the period since 1999 to 2002 according to Hall-Aspland and Rogers (2004) does not exceed 15,8 %,
and a basis of a specie forage reserve are sea birds, in this case penguins Adelie (to 92,1 %).
It is impossible to carry out the detailed comparative analysis of M. leonina diet forage reserve,
because of objective reason. The specie meets seldom in the Argentina islands territory. Mainly specie
finds are dated for Galindez, Black, Rasmussen and Pleneau islands. First meetings of specie often
happens in the summer-autumn period. Exclusively young individuals among whom females prevail
are counted around archipelago in all cases. Only 12 animals have been considered during researches,
and it was possible to select 3 samples of excrements. Diet of sea elephants adult individuals consists
of 75 % cephalopodes and 25 % of fish, the youth prefer only amphipodes, according to Fisher, Hureau
(1985b). In our case almost half of diet was made by vegetative meal (seaweed) together with squids
and fish. However, it is difficult to give an objective estimation of specie trophic, because of worked
samples small quantity.
Conclusions
The faeces analysis of Antarctic seals species food around Argentine Islands archipelago, has
shown that krill E. superba prevails in a diet of the majority seals species of region. Throughout the
summer period krill amount 97,2 % to a diet of fur seals (A. gazella) and 90 % to a diet crabeater seal
(L. carcinophagus). It is established rather big dimensional and weight rates to young growth in
comparison with literary data àccording to Weddell seal (L. weddelli) newborns monitoring. It testifies
to enough qualitative and sufficient forage reserve for pregnant Weddell seal females in archipelago
water area in which diet krill prevails also (about 70 %). Considering that from 5 seals species counted
within archipelago, the most numerous is the crabeater seal and a southern fur seal - these species can
be used as «species indicators» of krill distribution and quantity in the given region. It is established,
that the leopard seal's fodder diet is similar, to a diet of a specie around eastern Antarctic, despite an
essential latitude difference of specie habitat arrangements.
The trophical researches of Weddell seal have allowed to define a new commercial specie of
large squid Psychroteuthis glacialis for the first time in given region. These results have great value
not only for a definition of an actual condition of Antarctic ecosystem and biovariety preservations in
planetary scale. But also can be used for working out of the management project for future rational use
of krill sea stocks and squids in the given region of Antarctic, at the state level.
Acknowledgements. We are particularly grateful to P. Malov and I. Neverovsky for the
help at gathering of materials.
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318
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