The foraging ecology of two sympatric fur seal species, Arctocephalus gazella and Arctocephalus tropicalis, at Macquarie Island during the austral summer

2002 ◽  
Vol 53 (7) ◽  
pp. 1071 ◽  
Author(s):  
S. A. Robinson ◽  
S. G. Goldsworthy ◽  
J. van den Hoff ◽  
M. A. Hindell
Keyword(s):  
Foraging Behaviour ◽  
Foraging Ecology ◽  
Austral Summer ◽  
Sympatric Species ◽  
Arctocephalus Gazella ◽  
Macquarie Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Marine Environmental ◽  
Arctocephalus Tropicalis

Antarctic Arctocephalus gazella and subantarctic Arctocephalus tropicalis fur seals breed sympatrically at Macquarie Island. The two species have different lactation strategies, the former rearing its pup in 4 months and the latter taking 10 months. The diet and at-sea foraging behaviour of these sympatric species was compared during the austral summer period when their pup rearing period overlapped. The prey of the two fur seal species was very similar, with fish dominating the diet. The myctophid, Electrona subaspera, was the main prey item (93.9%) in all months of the study. There were no major differences in the diving behaviour between species. Both species foraged north of the island parallel to the Macquarie Ridge. Foraging activity was concentrated at two sites: (i) within 30�km north of the island; and (ii) at 60 km north. Most locations for overnight foraging trips were within 10 km of the colonies. The different lactation strategies of A. gazella and A. tropicalis allowed for flexibility in foraging behaviour. At Macquarie Island, the local marine environmental conditions have resulted in similar foraging behaviour for both species.

The composition of the milk of antarctic (Arctocephalus gazella) and subantarctic (A. tropicalis) fur seals at Macquarie Island

1999 ◽  
Vol 47 (6) ◽  
pp. 593 ◽  
Author(s):  
Simon D. Goldsworthy ◽  
Helen M. Crowley
Keyword(s):  
Water Content ◽  
Energy Content ◽  
Post Partum ◽  
Milk Composition ◽  
Arctocephalus Gazella ◽  
Macquarie Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Gross Energy ◽  
Subantarctic Fur Seals

The composition of milk collected from 36 antarctic (Arctocephalus gazella) and 17 subantarctic fur seals (A. tropicalis) breeding sympatrically at Macquarie Island was examined over the first 100 days of lactation in the 1990/91 season. The mean composition of milk in A. gazella and A. tropicalis was 41.3% and 44.6% water, 39.8% and 38.6% lipid, 18.1% and 16.1% protein, and the estimated gross energy content of milk was 19.9 and 18.9 kJ g–1, respectively. Neither the composition of milk nor its energy density differed significantly between species, despite a difference of 4–6 months in lactation length. Water content of milk could be used to predict lipid (r2 = 0.67) and protein (r2 = 0.57) content, but was most accurate at predicting gross energy content (r2 = 0.97). These relationships were the same for each species. The water content of milk decreased throughout the first 100 days of lactation in both species, while lipid, protein and energy content all increased. The addition of maternal mass into regression analysis with days post-partum increased the significance of models predicting the content of lipid and proteins in the milk, but not those predicting the water or gross energy content. Milk collected on the first day of 2-day attendance bouts had, on average, 9% greater lipid content, and 5% greater protein content than milk collected on the second day. The growth rates of subantarctic fur seal pups were significantly lower than those of antarctic fur seal pups over the first month of growth, suggesting that (despite similar milk composition, attendance patterns and diet of the two species of fur seal) the overall rates of energy transfer from mother to pup in subantarctic fur seals is lower than in antarctic fur seals.

Fur seal skull from sealers' quarters at Sandy Bay, Macquarie Island, Southern Ocean

Polar Record ◽  
1991 ◽  
Vol 27 (162) ◽  
pp. 245-248 ◽  
Author(s):  
K. Townrow ◽  
P. D. Shaughnessy
Keyword(s):  
Southern Ocean ◽  
Arctocephalus Gazella ◽  
Archaeological Excavation ◽  
Antarctic Fur Seal ◽  
Macquarie Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Antarctic Research ◽  
The Antarctic ◽  
Specific Identity

AbstractFur seals were exterminated from Macquarie Island about 20 years after discovery of the island in 1810. Their specific identity is unknown. Few fur seals were reported at the island until it was occupied by the Australian National Antarctic Research Expeditions in 1948. Fur seal numbers are now increasing. An archaeological excavation at a sealers' quarters at Sandy Bay in 1988 revealed the fragmented skull of a young Antarctic fur sealArctocephalus gazella1.1 m below the surface in a layer dated in the 1870s and 1880s. This period coincides with the recovery of fur seal populations in the South Atlantic Ocean following earlier harvesting. Elsewhere it has been argued that the Antarctic fur seal is unlikely to have been the original fur seal at Macquarie Island because few individuals of that species are ashore in winter, which is the season when the island was discovered and fur-seal harvesting began. It is concluded that the Sandy Bay skull is from a vagrant animal.

New mammals recognised for Australia - Antarctic and Subantarctic Fur Seals Arctocephalus species

1992 ◽  
Vol 15 (1) ◽  
pp. 77
Author(s):  
P.D. Shaughnessy
Keyword(s):  
Arctocephalus Gazella ◽  
Antarctic Fur Seal ◽  
Macquarie Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Heard Island ◽  
Pinniped Species ◽  
The Antarctic ◽  
Subantarctic Fur Seals

Recent authoritative texts on Australian mammals include several pinniped species but most omit the Antarctic Fur Seal Arctocephalus gazella and Subantarctic Fur Seal A. tropicalis. The former species breeds at Heard Island; at Macquarie Island it breeds in territories with A. tropicalis. Information is tabulated on skulls of these two species held in Australian museums. It is argued that they should be included in comprehensive lists of Australian mammals.

Long term population changes of fur seals Arctocephalus gazella and Arctocephalus tropicalis on subantarctic (Crozet) and subtropical (St. Paul and Amsterdam) islands and their possible relationship to El Niño Southern Oscillation

1994 ◽  
Vol 6 (4) ◽  
pp. 473-478 ◽  
Author(s):  
C. Guinet ◽  
P. Jouventin ◽  
J-Y. Georges
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Enso Events ◽  
Fur Seals ◽  
Fur Seal ◽  
Arctocephalus Tropicalis

The population trend over the last decade for subantarctic fur seals (Arctocephalus tropicalis) on Amsterdam and St. Paul islands and on Possession Island (Crozet Archipelago) and Antarctic fur seals (A. gazella) on Possession Island are analysed. At Amsterdam Island, based on pup counts, the subantarctic fur seal population appears to have stabilized after a period of rapid growth. At Possession Island subantarctic fur seal and Antarctic fur seal, with respective annual growth rates of 19.2 and 17.4%, are reaching the maximum growth rate for the genus Arctocephalus. Annual pup censuses at Possession Island since 1978 indicate important variations from year to year with pup production for A. gazella significantly lower the year after an El Niño Southern Oscillation (ENSO) event, but with no such relationship for A. tropicalis. Several other long term demographic studies of seabirds and marine mammals at different breeding locations in the Southern Ocean indicate that the breeding success of several of these predators appears to be widely affected in years which appear to be related to the ENSO events. To clarify this, it is necessary to analyse in more detail the demographic data obtained for the different subantarctic and Antarctic locations where long term monitoring programmes are conducted.

scholarly journals A memory like a female Fur Seal: long-lasting recognition of pup's voice by mothers

2004 ◽  
Vol 76 (2) ◽  
pp. 237-241 ◽  
Author(s):  
Nicolas Mathevon ◽  
Isabelle Charrier ◽  
Thierry Aubin
Keyword(s):  
Field Experiments ◽  
Individual Characteristics ◽  
Lactation Period ◽  
Acoustic Characteristics ◽  
Call Recognition ◽  
Fur Seals ◽  
Fur Seal ◽  
Vocal Recognition ◽  
Modulation Pattern ◽  
Arctocephalus Tropicalis

In colonial mammals like fur seals, mutual vocal recognition between mothers and their pup is of primary importance for breeding success. Females alternate feeding sea-trips with suckling periods on land, and when coming back from the ocean, they have to vocally find their offspring among numerous similar-looking pups. Young fur seals emit a 'mother-attraction call' that presents individual characteristics. In this paper, we review the perceptual process of pup's call recognition by Subantarctic Fur Seal Arctocephalus tropicalis mothers. To identify their progeny, females rely on the frequency modulation pattern and spectral features of this call. As the acoustic characteristics of a pup's call change throughout the lactation period due to the growing process, mothers have thus to refine their memorization of their pup's voice. Field experiments show that female Fur Seals are able to retain all the successive versions of their pup's call.

Fish in the diet of Antarctic fur seals (Arctocephalus gazella) at South Georgia during winter and spring

1996 ◽  
Vol 8 (2) ◽  
pp. 155-160 ◽  
Author(s):  
A.W. North
Keyword(s):  
Arctocephalus Gazella ◽  
South Georgia ◽  
Fur Seals ◽  
Fur Seal ◽  
Total Fish ◽  
Fish Remains ◽  
Gobionotothen Gibberifrons ◽  
Lepidonotothen Larseni ◽  
The Antarctic ◽  
Fish Otoliths

The occurrence of fish in the diet of the Antarctic fur seal (Arctocephalus gazella) at Bird Island, South Georgia was investigated by analysis of fish otoliths in scats (faeces) collected during late May to early November 1983. Of the 55 scats examined, 49 contained fish remains, and 45 contained fish otoliths. Ten fish species were represented by 415 otoliths, and 33 otoliths were too digested to be identified unequivocally. Fish size was estimated from otolith size based on published allometric equations. Four coastal notothenioid fishes dominated the fish component of the diet: Champsocephalus gunnari and Gobionotothen gibberifrons each comprised about 40% of the total fish mass; Chaenocephalus aceratus was ranked third by mass and the smaller Lepidonotothen larseni occurred in one quarter of the scats but was of lower importance in terms of mass. The length-frequency distribution of C. gunnari landed by the commercial fishery in October 1982 to June 1983 is similar to that which comprised the bulk of the diet in the present study. Compared with recent studies on the fish component of the diet in the literature, the dominance of C. gunnari is generally similar, however, there was a greater proportion of G. gibberifrons during the 1983 winter and spring than reported for recent winters.

scholarly journals Fish prey of the sympatric Galápagos fur seals and sea lions: seasonal variation and niche separation

1999 ◽  
Vol 77 (8) ◽  
pp. 1204-1216 ◽  
Author(s):  
Thomas Dellinger ◽  
Fritz Trillmich
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Season ◽  
Niche Overlap ◽  
Sympatric Species ◽  
Niche Separation ◽  
Fish Prey ◽  
Sea Lions ◽  
Fur Seals ◽  
Fur Seal

Analysis of fish otoliths in scats and vomits of Galápagos fur seals (Arctocephalus galapagoensis) and Galápagos sea lions (Zalophus californianus wollebaeki) was used to determine the numerical composition of the diets for the post-El Niño year 1983, the cold seasons in 1984 and 1985, and the warm season in 1986. Between 84 and 99% of all otoliths in fur seal scats were from myctophids and bathylagids. The fur seals' diet included 26 species. Only 3 species contributed more than 1% of otoliths. No seasonal differences in diet were found. Sea lion samples contained a mean of 14 otoliths. Sardines (Sardinops sagax) contributed 75-85% of otoliths. Sea lions preyed on 24 species, but only 3 surpassed 1% abundance. Seasonality was not reflected in the sea lions' diet. After the 1982-1983 El Niño, the diets of both species deviated from those in all other years of the study. Food-niche overlap between the two sympatric species was almost non-existent. This is hard to understand, based on our knowledge of the diving capabilities of the two species, but reflects the fact that Galápagos fur seals are nighttime foragers and sea lions are daytime foragers.

Attendance behaviour of Antarctic and subantarctic fur seal females at Marion Island

1990 ◽  
Vol 2 (4) ◽  
pp. 309-312 ◽  
Author(s):  
Marthán N. Bester ◽  
Peter A. Bartlett
Keyword(s):  
Arctocephalus Gazella ◽  
Marion Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Lactating Females ◽  
The Mean ◽  
Temperate Environment ◽  
The Difference ◽  
Antarctic Fur Seals ◽  
Subantarctic Fur Seals

The female attendance behaviour of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (A.tropicalis), which breed sympatrically on subantarctic Marion Island, was investigated. Over the same period after the breeding season, the mean duration of feeding trips to sea, and percentage of time spent at sea, did not differ significantly between lactating females of the two species. The difference in mean duration of shore visits was significant and the longer onshore attendance of A. tropicalis probably related to the lower demand by their pups which grow at a slower rate. The subpolar maternal adaptations of A. gazella were unchanged under the more temperate environment at Marion Island, and it remains to be established unequivocally whether conditions there are limiting to the species.

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