Mass Mortality of Adult Male Subantarctic Fur Seals: Are Alien Mice the Culprits?

Age distribution was estimated for 108 breeding-age female subantarctic fur seals, Arctocephalus tropicalis (Gray, 1872), sampled during the 1999–2000 breeding season on Amsterdam Island, southern Indian Ocean. The growth features were described and demographic parameters assessed from transversal life tables constructed for this female population. The breeding females had a longer mean body length than was observed for other breeding populations of the same species. These females also showed a later start to reproduction (6 years old), a lower overall age-specific reproductive rate (R6–16 = 48.0%), and a lower survival in older age classes (>13 years). Females reproduced up to a maximum age of 16 years, with none older than 19 years observed in the colony, suggesting an apparent senescence in the population. This consequently reduced the theoretical reproductive period of the females, which has led to a lower number of reproductive outputs per individual (i.e., 3.65 weaned pups per female throughout its reproductive life). Although such differences between islands may be related to genotypic traits, these results are consistent with low food availability and suggest that density-dependent regulatory processes operate on the Amsterdam Island population.

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

Australian Journal of Zoology ◽

10.1071/zo98067 ◽

1999 ◽

Vol 47 (6) ◽

pp. 593 ◽

Cited By ~ 10

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.

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MOBBING OF A GREAT WHITE SHARK (CARCHARODON CARCHARIAS) BY ADULT MALE AUSTRALIAN FUR SEALS (ARCTOCEPHALUS PUSILLUS DORIFERUS)

Marine Mammal Science ◽

10.1111/j.1748-7692.2005.tb01234.x ◽

2005 ◽

Vol 21 (2) ◽

pp. 336-339 ◽

Cited By ~ 16

Author(s):

Roger Kirkwood ◽

John Dickie

Keyword(s):

Adult Male ◽

White Shark ◽

Carcharodon Carcharias ◽

Fur Seals ◽

Great White Shark

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Pathology and bacteriology of adult male antarctic fur seals, Arctocephalus gazella, dying at Bird Island, South Georgia

British Veterinary Journal ◽

10.1016/0007-1935(89)90079-1 ◽

1989 ◽

Vol 145 (3) ◽

pp. 263-275 ◽

Cited By ~ 21

Author(s):

J.R. Baker ◽

T.S. McCann

Keyword(s):

Adult Male ◽

Arctocephalus Gazella ◽

South Georgia ◽

Fur Seals ◽

Antarctic Fur Seals

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Records of vagrant fur seals (family Otariidae) in South Australia

Australian Mammalogy ◽

10.1071/am13038 ◽

2014 ◽

Vol 36 (2) ◽

pp. 154 ◽

Cited By ~ 4

Author(s):

Peter D. Shaughnessy ◽

Catherine M. Kemper ◽

David Stemmer ◽

Jane McKenzie

Keyword(s):

New Zealand ◽

South Australia ◽

The South ◽

South Indian Ocean ◽

Fur Seals ◽

South Indian ◽

Fur Seal ◽

New Zealand Fur Seal ◽

The Antarctic ◽

Subantarctic Fur Seals

Two fur seal species breed on the southern coast of Australia: the Australian fur seal (Arctocephalus pusillus doriferus) and the New Zealand fur seal (A. forsteri). Two other species are vagrants: the subantarctic fur seal (A. tropicalis) and the Antarctic fur seal (A. gazella). We document records of vagrant fur seals in South Australia from 1982 to 2012 based primarily on records from the South Australian Museum. There were 86 subantarctic fur seals: 49 specimens and 37 sightings. Most (77%) were recorded from July to October and 83% of all records were juveniles. All but two specimens were collected between July and November. Sightings were prevalent during the same period, but there were also nine sightings during summer (December–February), several of healthy-looking adults. Notable concentrations were near Victor Harbor, on Kangaroo Island and Eyre Peninsula. Likely sources of subantarctic fur seals seen in South Australia are Macquarie and Amsterdam Islands in the South Indian Ocean, ~2700 km south-east and 5200 km west of SA, respectively. There were two sightings of Antarctic fur seals, both of adults, on Kangaroo Island at New Zealand fur seal breeding colonies. Records of this species for continental Australia and nearby islands are infrequent.

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Satellite Tracker Deployments On Adult, Male Australian Fur Seals (Arctophalus Pusillus Doriferus): Methods And Preliminary Results

Australian Mammalogy ◽

10.1071/am02073 ◽

2002 ◽

Vol 24 (1) ◽

pp. 73 ◽

Cited By ~ 8

Author(s):

R Kirkwood ◽

N Gales ◽

M Lynch ◽

P Dann

Keyword(s):

Adult Male ◽

Early Spring ◽

Preliminary Results ◽

Fur Seals ◽

Satellite Transmitters ◽

Rest Sites ◽

Water Depths

In May 1999, four adult male, Australian fur seals (Arctocephalus pusillus doriferus) from the Seal Rocks colony, Victoria, were fitted with satellite transmitters that provided locations for between 2 and 7 months. Foraging trips during winter and early spring averaged 7.4 days (range for all trips 0.9 to 24.6) and between-trip rests lasted 2.8 days (range 0.3 to 5.7). Between-trip rest sites included Seal Rocks, other colonies and other haul-out sites. The seals foraged mostly in western Bass Strait and in water depths < 100 m.

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At-sea movements and habitat use of adult male Australian fur seals (Arctocephalus pusillus doriferus)

Canadian Journal of Zoology ◽

10.1139/z06-164 ◽

2006 ◽

Vol 84 (12) ◽

pp. 1781-1788 ◽

Cited By ~ 31

Author(s):

Roger Kirkwood ◽

Michael Lynch ◽

Nick Gales ◽

Peter Dann ◽

Michael Sumner

Keyword(s):

Habitat Use ◽

Continental Shelf ◽

Adult Male ◽

Maximum Distance ◽

Commercial Fisheries ◽

Southeastern Australia ◽

Foraging Area ◽

Fur Seals ◽

Water Columns ◽

Foraging Ranges

Foraging by adult male otariids, a demographic component that often interacts with commercial fisheries, are poorly known. To assess movement patterns and habitat use, nine adult male Australian fur seals ( Arctocephalus pusillus doriferus Wood Jones, 1925) from Seal Rocks, in northern Bass Strait, southeastern Australia, were tracked for periods ranging from 66 to 223 d during 1999–2001. Mean ± SD at-sea and on-land durations were 6.9 ± 2.1 d (range 2.3–10.3 d, n = 9 seals) and 2.4 ± 0.9 d (range 0.8–4.1 d), respectively. All seals foraged almost exclusively in continental shelf waters and mostly (65%–97% of time at sea) in water columns that were between 40 and 100 m deep. Six of nine seals tracked for >30 d spent 64%–98% of their time-at-sea foraging at distances <200 km from Seal Rocks, although the maximum distance achieved from the colony was 1208 km. The seals’ foraging ranges overlapped with the ranges of operation of virtually all fin-fish fisheries in southeastern Australia, but fisheries overlap was low in the most frequented foraging area of central-western Bass Strait.

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