| Last modified: Thursday September 24th, 1999 |
Other sea lions and fur seals
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Southern sea lion
Otaria byronia (Blainville, 1820)
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Nomenclature
There is some confusion about the correct scientific name of this species.
Although Otaria byronia is now widely accepted, still Otaria
flavescens (Shaw, 1800) is used as an alternative (Vaz-Ferreira, 1982).
Rice (1998) argues, that O. flavescens is the correct name.
Common names that are used instead of Southern Sea Lion include South American
Sea Lion and Patagonian Sea Lion.
Appearance
Males measure on average 260 cm and weigh around 300 kg. Females are usually
about 200 cm and weigh 150 kg.
Pups measure around 80 cm and weigh from 10 to 15 kg. Male pups are usually
bigger. The Southern sea lion has a dark brown dorsal side and a yellowish
brown ventral. Males have lighter coloured manes. Females have no manes,
but have a lighter coloured fur in the head and neck area. Pups are born
with a black coat. After a few months they have a grey coat which at the
age of one year is reddish brown.
Distribution
The Southern sea lion can be found on both the Atlantic and Pacific shores
of South America. On the Atlantic side the range stretches from Rio de
Janeiro at 23S down to the southern tip of the continent at 55S. At the
Pacific side it ranges as far north as Zorritos in Peru (4S). There is
no obvious migration.
Feeding
Otaria is an opportunistic feeder. Its diet includes anchovy, squid, crustaceans
and occasionally penguins.
Population dynamics and life history
The age at maturity is 4 years for females and 5-6 years for males. The
pregnancy rate is unknown. Gestation lasts about one year. Lactation lasts
6-12 months. Longevity is about 20 years. Adult mortality is unknown. Pup
mortality ranges from 2 to 50%, depending on the crowding of the rookery.
Trophic relations
Although the South American fur seal, Arctocephalus australis, lives in
the same area, there seems to be little interaction or competition. Pups
are commonly attacked by the leopard seal, Hydrurga leptonyx, while all
age groups are predated upon by sharks and the killer whale.
Interactions
The Southern sea lion often interferes with long line and gill net fisheries,
although the extend of this interaction is unknown. It seems likely that
incidental killing occurs, but there are no quantitative data available
on this.
Population size
Counts from land, boat and aeroplane have been carried out in the 50's
and 60's. Then the total population was estimated at 273,500. Vaz-Ferreira
(1982) reports a population estimate of 275,000, which does not include
the Chilean population. Included in this estimate are the populations in
Uruguay (30,000), the Falkland Islands (30,000) and Peru (20,000).
Exploitation
The Southern sea lion is protected in Argentina. Currently there is no
harvest in the Falkland Islands. Small number can be harvested with a permit
in Chile. In Uruguay there is an annual harvest of about 3,000 pups.
Threats to the population
probably none.
References
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History), London
and Oxford University Press, Oxford, 240pp.
- Rice, D.W. (1998)
- Marine mammals of the world - Systematics and distribution
Society of Marine Mammalogy Special Publication Number 4, 231 pp.
- Vaz-Ferreira, R. (1979)
- South American Sea Lion. in: Mammals in the Seas, volume II: pinniped species
summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II,
pp. 9-12
- Vaz-Ferreira, R. (1981)
- South American Sea Lion, Otaria flavescens (Shaw, 1800). in: Ridgway,
S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 1: The
walrus, sea lions, fur seals and sea otter, pp. 39-65, Academic Press Inc.,
Ltd, London
- Vaz-Ferreira, R. (1982)
- Otaria flavescens (Shaw), South American Sea Lion. in: Mammals in
the Seas, Volume IV: small cetaceans, seals, sirenians and otters. FAO
Fisheries Series, No. 5, vol. IV, pp. 477-495
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Australian sea lion
Neophoca cinerea (Péron, 1816)
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Appearance
Adult males range in lengh from 300 to 350 cm and their weight is around
400 kg. Females are 250-300 cm long and weigh about 250 kg. Pups are 75
cm long and weigh 6.5 kg. Males have a blackish brown colour with manes
around the shoulders. The head is cream coloured. Females are silver grey
directly after the moult, which slowly fades to brown. Pups are chocolate
brown with a pale crown.
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Distribution
Australian sea lions can be found on sandy beaches and on smooth rock.
They live on the Australian islands from Houtman's Abrolhos (28°S,
112°E) to Kangaroo Island (34°S, 138°E).
Feeding
The diet consists of several fish species, including salmon and whiting,
sharks, penguins and fiddler crabs.
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Population dynamics and life history
Females are mature at 3 years of age, males at 6 years or more. The pregnancy
rate is unknown. Gestation presumably lasts 12 months but may be as long
as 18 months. It is possible that implantation of the blastocyst is delayed
for as much as 10 months. Their breeding cycle is about 18 months (Robinson
and Dennis, 1988). Longevity and mortality rate are also not known.
Trophic relations
The Australian fur seal, Arctocephalus forsteri, lives in the same
area, but there is apparently no interaction. Sharks are the main predators.
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Interactions
The sea lions are occasionally killed by fishermen. The population at Seal
Bay on Kangaroo Island is a tourist attraction.
Population size
Robinson and Dennis (1988) concluded that it is very difficult to obtain
an accurate estimate of the Australian sea lion population, because the
colonies are scattered over remote islands. They mention the following
estimates for the Southern Australian populations:
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| Location |
1976-77 |
1982 |
| Islands |
1076-2576 |
1845-1879 |
| Seal Bay |
132-487 |
120-390 |
| Pt. Labatt |
15-68 |
17-46 |
| Total |
1223-3181 |
1982-2315 |
The Western Australian population consists probably of about 700 animals.
Exploitation
There is no harvest of this population. Occasionally some animals are captured
for zoos or for research. Since the species is fully protected, this requires
a permit.
Threats to the population
None known.
References
- King, J.B., Marlow, B.J. (1979)
- Australian Sea Lion. in: Mammals in the Seas, volume II: pinniped species
summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II,
pp. 13-15
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History), London
and Oxford University Press, Oxford, 240pp.
- Robinson, A.C. and Dennis, T.E. (1988)
- The status and management of seal populations in South Australia. In: M.L.
Augee (ed.): Marine Mammals of Australasia: Field biology and captive management,
pp: 87-110. Royal Zoological Society of New South Wales.
- Walker, G.E., Ling, B.J. (1981)
- Australian Sea Lion, Neophoca cinerea (Péron, 1816). in:
Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol.
1: The walrus, sea lions, fur seals and sea otter, pp. 99-118, Academic
Press Inc., Ltd, London
Note on the photographs
All the pictures of Australion sea lions on this page were taken in November
1996 at Seal Bay on Kangaroo Island, Australia.
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New Zealand sea lion
Phocarctos hookeri (Gray, 1844)
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Nomenclature
The New Zealand sea lion is also commonly called Hooker's sea lion.
Appearance
Males are 250-300 cm long and weigh 300-400 kg. Females are much smaller
at 200 cm and 250 kg. Pups are about 75 cm. Pup weights have not been recorded.
Adult males are dark blackish brown with clear manes. Females have a silver
grey dorsal side and a pale yellow ventral. Pups are light chocolate brown
with light stripes down the nose to the top of the head and the nape of
the neck.
Distribution
New Zealand sea lions breed and mate on sandy beaches. They reside mainly
on the Auckland Islands (50S, 166E), but also on the Snares (48S, 166E)
and on Campbell Island (52S, 169E). There is no migration.
Feeding
The diets includes cephalopods, prawns, crayfish and crabs and also small
fishes. Occasionally penguins are taken as well.
Population dynamics and life history
Not much is known about the vital parameters of this species. Males become
mature at the age of 6. The age at maturity for females is unknown. Gestation
lasts 12 months. Pregnancy rates, mortality and longevity are unknown.
Trophic relations
Several pinniped species live in the same area, such as the New Zealand
fur seal, Arctocephalus forsteri, the leopard seal, Hydrurga leptonyx,
and the Southern elephant seal, Mirounga leonina, but there seems
to be no interaction. The only possible predator is the killer whale.
Interactions
Since this species lives in very remote areas, there is little or no interaction
with humans.
Population size
There have been censuses of several islands, which resulted in the following
population estimates: Enderby: 1,000; Dundas: 2,000; Snares: 50; Campbell:
100. The total population is estimated to be about 4,000 and stable.
Exploitation
Because of its remoteness there has been no exploitation of this species.
Maybe a few sea lions are killed illegally for use as crab bait. The New
Zealand sea lion's habitat is part of the uninhabited Auckland Fauna Reserve.
Threats to the population
None.
References
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History), London
and Oxford University Press, Oxford, 240pp.
- Marlow, B.J., King, J.B. (1979)
- Hooker's (New Zealand) Sea Lion. in: Mammals in the Seas, volume II: pinniped
species summaries and report on sirenians. FAO Fisheries Series No. 5,
Vol II. pp. 16-18
- Walker, G.E., Ling, J.K. (1981)
- New Zealand Sea Lion. Phocarctos hookeri (Gray, 1844). in: Ridgway,
S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 1: The
walrus, sea lions, fur seals and sea otter, pp. 25-38, Academic Press Inc.,
Ltd, London
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Guadalupe fur seal
Arctocephalus townsendi (Merriam, 1897)
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Nomenclature
Some consider this species to be either a synonym or a subspecies of Arctocephalus
philippii (Peters, 1866).
Appearance
Very little is known about this species. Males are about 180 cm and weigh
140 kg. Pups probably are 60 cm at birth. The fur is black, becoming light
ventrally and on the chest. They have an elongated snout and elongated
flippers.
Distribution
This species lives on rough rocky shores. Currently they are found only
on Isla Guadalupe, Baja California, at 28N.
Feeding
unknown
Population dynamics and life history
no data available.
Trophic relations
There are Northern elephant seals, Mirounga angustirostris, on the
same island, but they are believed to be completely segregated ecologically.
Interactions
very limited
Population size
Currently there are thought to be about 500 Guadalupe fur seals. After
1928 this species was thought to be extinct, but it was rediscovered in
1954. There has been an increase in population size since then.
Exploitation
None. Its habitat is protected by the Mexican government and guided tours
are not allowed in the area.
Threats to the population
Since the population recovered from apparently a very limited number of
individuals, there may be a lack of genetic diversity.
References
- Bonner, W.N. (1981)
- Southern Fur Seals, Arctocephalus (Geoffroy Saint-Hilaire and Cuvier,
1826), in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine
Mammals, vol. 1: The walrus, sea lions, fur seals and sea otter, pp. 161-208,
Academic Press Inc., Ltd, London
- Hubbs, C.L. (1979)
- Guadalupe Fur Seal. in: Mammals in the Seas, volume II: pinniped species
summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II,
pp. 24-27
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History), London
and Oxford University Press, Oxford, 240pp.
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Galapagos fur seal
Arctocephalus galapagoensis (Heller, 1904)
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Nomenclature
This species was originally described as a subspecies of Arctocephalus
australis, but is now recognized as a seperate species.
Appearance
The Galapagos fur seal is quite small: males are usually no larger than
150 cm and females no larger than 130 cm. There are no records of weight
measurements. There is little sexual dimorphism.
Distribution
This species breeds on rocky shoes with sea caves. It is found only on
the Galapagos Islands. The main colonies are located on Isla Fernandina,
Isla Isabela and James Island. They remain near their breeding colonies
year-round (Trillmich, 1986).
Feeding
The Galapagos fur seal feeds mainly on cephalopods and small schooling
fish. Feeding occurs mainly at night. During feeding they dives to depths
of usually no more than 30 m (Kooyman and Trillmich, 1986). While at sea,
2.8% of the time the seals are resting, 24% of the time is spent diving
(probably feeding) and 73.2% is spent swimming. The mean depth of the dives
is about 26m with a maximum of 115m. Most dives are to 20m or less.
Population dynamics and life history
This species has the longest weaning period among the pinnipeds:1-2 years,
although even 3-year old animals still suckle occassionally (Trillmich,
1986). The birth of a new pup does not cause the weaning of older (upto
2 years) pups. Instead, the new pup either starves or is killed by the
older pup. The reproductive season lasts from mid-August until mid-November.
Trophic relations
There may be some competition for food with the Galapagos sea lion, Zalophus
californianus wollebaeki, although their terrestial habitats are separated.
Interactions
none.
Population size
Censuses have been carried out, but they are very incomplete. From these
censuses, population estimates ranging from 1,000 to 5,000 have been made.
There has been an increase in abundance noted, but the species is no doubt
still endangered.
Exploitation
This species has been severely overexploited in the past, but is currently
not exploited. It is protected by the Ecuadorean Fish and Game Service.
Threats to the population
The Galapagos fur seal is, because of its small population size, still
endangered.
References
- Bonner, W.N. (1981)
- Southern Fur Seals, Arctocephalus (Geoffroy Saint-Hilaire and Cuvier,
1826), in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine
Mammals, vol. 1: The walrus, sea lions, fur seals and sea otter, pp. 161-208,
Academic Press Inc., Ltd, London
- Clark, T.W. (1979)
- Galapagos Fur Seal. in: Mammals in the Seas, volume II: pinniped species
summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II,
pp. 31-33
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History), London
and Oxford University Press, Oxford, 240pp.
- Kooyman, G.L. and Trillmich, F. (1986)
- Diving behavior of Galapagos Fur Seals. In: Gentry, R.L. and Kooyman, G.L.
(eds.): Fur seals - Maternal strategies on land and at sea. pp. 185-195,
Princeton University Press.
- Trillmich, F. (1986)
- Attendance behavior of Galapagos Fur Seals. In: Gentry, R.L. and Kooyman,
G.L. (eds.): Fur seals - Maternal strategies on land and at sea. pp. 168-185,
Princeton University Press.
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