Content uploaded by Simon D Goldsworthy
Author content
All content in this area was uploaded by Simon D Goldsworthy
Content may be subject to copyright.
Edward, South Shetland and Heard
Islands. A further population that
survived at Iles Kerguelen was the source
of the recolonised population at
Macquarie Island.
Antarctic Fur Seals at Macquarie and
Heard Islands were exterminated by 1820
and 1870, respectively. At Macquarie
Island, approximately 200 000 fur seals
(species unknown) were killed. Breeding
Antarctic Fur Seals were first recorded on
Heard Island in 1962–63 and, since then,
annual pup production has increased
rapidly; the breeding population there
now exceeds 5000. The status of fur seals
on the McDonald Islands is largely
unknown, as they have rarely been
visited, and recent volcanic activity may
have eliminated this breeding site. On
Macquarie Island, the first pup seen since
sealing ceased was recorded in 1955, but
it was not until the 1980s that the popu-
lation began to increase more rapidly.
This population also includes the
Subantarctic Fur Seal (Arctocephalus tropi-
calis) and New Zealand Fur Seal (A.
forsteri), both of which hybridise with
Antarctic Fur Seals. When ashore, the Antarctic Fur
Seal utilises a variety of habitats. On Heard Island, it
uses flat grassy meadows adjacent to beaches; on
Macquarie Island, it uses open cobblestone beaches
and steep tussock slopes.
Adult males begin to come ashore and contest
territories in early November. They defend territories
containing 5–15 females and fast during the breeding
season until females have been mated. Females come
ashore about a day prior to giving birth to a single
pup. Soon after parturition they come into oestrus
and are mated about seven days later. Most pups are
born over a three- to four-week period, peaking
around early to mid-December. Adult females remain
ashore with their pups for about seven to ten days
before leaving the colony to feed at sea. They then
alternate between nursing bouts ashore and foraging
trips at sea, until their pups wean at about four
months of age. After the weaning period, adult
females and pups abandon colonies; adult females do
not come ashore until the next breeding season.
At Heard Island, lactating females make foraging
trips of about five days, early in lactation, to about
seven days towards the end of lactation. Overall,
females spend 80 per cent of their time at sea and 20
per cent ashore. The attendance patterns of lactating
females at Macquarie Island differ markedly, with
females spending only about 65 per cent of their time
at sea and foraging trips lasting only about three days.
Differences in these attendance patterns are related to
difference in the distance to foraging grounds, diet
and prey availability.
721
Antarctic Fur Seal
Arctocephalus gazella
(Peters, 1875)
ark´-toh-sef´-ah-lus gah-zel´-ah: ‘(HMS) Gazelle’s
bear-head’
Like other fur seals, this species was indiscriminately
hunted to near extinction but its recovery from over-
exploitation has been spectacular. Breeding colonies
were first discovered in the late 1700s at South
Georgia by Captain Cook and were commercially
exterminated there by the 1820s; by the late 1800s it
was thought to be extinct. It was rediscovered in 1915
at South Georgia and, in 1933, a small group of
breeding animals was found on Bird Island, South
Georgia. Between 1957 and 1972 the annual pup
production increased from 5000 to more than
100 000 (17 per cent per year), and the total popula-
tion there is currently estimated at between 4.5–6.2
million. Smaller populations occur at other islands in
the Scotia Arc and Antarctic Peninsula (South Orkney,
South Sandwich and South Shetland Islands, Cape
Shirreff), Southern Indian Ocean (Bouvetøya, Prince
Edward Island, Iles Crozet, Iles Kerguelen, Heard
Island and the McDonald Islands and Macquarie
Island). Three of these sites (Heard, McDonald and
Macquarie) are Australian territory. Genetic studies
suggest that Antarctic Fur Seals survived at South
Georgia and Bouvetøya, which were probably the
sources for recolonised populations at the Prince
720
Arctocephalus gazella
By the late 1800s the Antarctic Fur Seal was thought to
have been hunted to extinction. In places its populations
now number in the millions.
Female Antarctic Fur Seals spend 80 per cent of their
time at sea. After weaning their pups at four months old
the females do not come ashore until the following
breeding season.
AUSTRALIAN ANTARCTIC DIVISION
ORDER CARNIVORA FAMILY OTARIIDAE
S.D. GOLDSWORTHY
714-869 809-NHP-MAM-Part4_Final_SH 4/10/07 11:30 AM Page 720
Australian Fur Seal
Arctocephalus pusillus
(Schreber, 1775)
ark´-toh-sef´-ah-lus pue-sil´-us: ‘little bear-head’
Australian Fur Seals are endemic to south-eastern
Australian waters where they breed at 10 colonies, all
within Bass Strait, and may haul out to rest at a
further 40 sites. The Australian taxon (Arctocephalus
pusillus doriferus) is morphologically and genetically
almost identical to the Cape Fur Seal (A. p. pusillus)
but the two subspecies are geographically separated
723
Antarctic Fur Seals at Macquarie Island feed
predominantly on myctophids (Lantern Fish), while
those at Heard Island feed on a mixture of Mackerel
Ice-fish and myctophids. This is in marked contrast to
populations at South Georgia, which feed mostly on
Antarctic krill. At Macquarie Island, seals forage at
night, usually within 70 kilometres of the island and
at shallow depths (10–20 metres), with maximum
depths of around 100 metres at dusk and dawn. This
coincides with movements of myctophid fish, which
make daily vertical migrations from deeper water
during the day, to near the surface at night. At Heard
Island, the seals forage deeper (at around 30 metres)
and further offshore (around 150 kilometres).
Since no adult females are on islands during
winter, it is assumed that they migrate to unknown
locations. Males appear to remain near breeding
colonies throughout winter. At Heard Island, large
numbers of non-breeding males (15 000–30 000)
come ashore to moult after the breeding season. As
this number is much greater than expected from the
size of the breeding population (about 5000 animals),
these itinerants may have travelled from large concen-
trations at South Georgia (approximately 6600
kilometres from Heard Island), or possibly from a
large, undiscovered population on the north-west
coast of Iles Kerguelen. The species is occasionally
sighted on the Antarctic mainland and reasonable
numbers are seen on the Antarctic pack-ice during
winter. Despite an ability to travel great distances,
there have been few reports from mainland Australia.
S.D. GOLDSWORTHY
722
Size
Nose to tail length
160–190 cm (males)
105–135 cm (females)
60–70 cm (pups at birth)
Weight
90–150 kg (males)
25–40 kg (females)
4–6 kg (pups at birth)
Identification Adult males: uniform silver-grey to
brown coat; belly fur dark brown. Well-developed
mane, powerful chest and shoulders. Adult females:
variably coloured silver-grey to brown dorsally, paler
cream to white fur ventrally; dark brown abdomen.
Pups: ash-grey natal coat with grizzled fur around
head and neck; muzzle and belly pale cream colour.
External ears and long, white vibrissae.
Recent synonyms Arctocephalus gazella tropicalis.
Other common names Kerguelen Fur Seal.
Abundance Common.
Conservation status Listed as a Marine Species
(EPBC Act 1999).
Subspecies None.
References
Goldsworthy, S.D. (1995). Differential expenditure of
maternal resources in Antarctic fur seals,
Arctocephalus gazella, at Heard Island, southern
Indian Ocean. Behav. Ecol. 6: 218–228.
Goldsworthy, S.D. (1999). Maternal attendance
behaviour in sympatrically breeding fur seals,
Arctocephalus spp., at Macquarie Island. Polar
Biology 21: 316–325.
Goldsworthy, S.D., M.A. Hindell and H.M. Crowley
(1997). Diet and diving behaviour of sympatric fur
seals, Arctocephalus gazella and A. tropicalis, at
Macquarie Island (in) M.A. Hindell and C. Kemper
(eds) Marine Mammal Research in Australia and
New Zealand. Surrey Beatty & Sons, Sydney.
pp. 151–163.
Page, B., A. Welling, M. Chambellant, S.D.
Goldsworthy, T. Dorr and R. van Veen (2003).
Population status and breeding season chronology
of Heard Island fur seals. Polar Biology 26:
219–224.
Robinson, S., S.D. Goldsworthy, J. van den Hoff and
M.A. Hindell (2002). The foraging ecology of two
sympatric fur seal species, Arctocphalus gazella and
A. tropicalis at Macquarie Island during the austral
summer. Mar. Freshw. Res. 53: 1071–1082.
Arctocephalus gazella
Arctocephalus pusillus doriferus
Australian Fur Seals congregate ashore to breed over a
period of six weeks. R. KIRKWOOD
ORDER CARNIVORA
714-869 809-NHP-MAM-Part4_Final_SH 4/10/07 11:30 AM Page 722
