ORDER: |
CARNIVORA |
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Superfamily:
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PINNIPEDIA |
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Family:
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Phocidae |
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Species: |
Mirounga leonina |
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Common
name: |
Southern Elephant Seal
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Natural History
Size, Shape &
Distinctive Characteristics:
South American sea lions show strong
sexual dimorphism. Adult males are
around 3m in length and around 350kg in
weight. Adult females are noticeably
smaller, measuring around 2.2m and
weighing around 140kg.
Overall they are large-bodied and robust
with bulky torsos. Both sexes have
relatively large heads with a short,
blunt, upturned snout. Males have a much
bigger head, with a square muzzle,
pointed nose and a crest across the rear
of the skull. Females have more rounded
heads and muzzles. The pinnae (ears) are
small relative to head size, may be
hidden by the fur, and positioned close
to the eyes. There are 10 pairs of teeth
in the upper jaw and 8 pairs in the
lower jaw. The teeth are not all the
same shape, with definition between the
incisors, canines and molars. Their
necks are telescopic.
The fore-flippers are broad and long and
used to swim, while the hind-flippers
appear short and have no fur. The
hind-flippers are used for walking on
land, due to the ability to rotate the
hips.
Adults have a light-yellow to
orange-brown pelage and males are
generally darker than females.
The whiskers are the same colour
as the coat. Adult males have a
well-defined mane of guard hairs from
the forehead and chin down to the
shoulders, which is lighter than the
rest of the pelage. Dominant, alpha
males are larger than submissive males,
with a more discrete mane.
Female coats appear yellowish and
are more uniform in colour. Pups have a
black or dark brown natal pelage,
allowing them to blend in with the
rocks. They moult this pelage after
about 3 month and then have a shorter
bronze coat that turns into silver at 6
months old, which fades during their
first year to a dark brown for males and
lighter yellowish brown for females.
Geographical Range &
Habitat:
The South American Sea Lion is endemic
to the coastal waters around South
America and is found in disjointed
populations from Zorritos, Peru around
to Bahia, Brazil, including the
Falklands. They may be vagrant further
north up both coasts. The population
around Peru is unstable and populations
may be resident or transient to an area.
They generally breed in the south during
the summer and travel northwards in
winter and spring.
Behaviour:
South American sea lions aggregate into
colonies, with density varying according
to topography and temperature. Colonies
are more dispersed on rocky coasts and
when it is warm and sunny. Rookeries are
segregated by age and sex.
Males have individually variable
vocalisations used to defend territories
and herd females, while females use
vocalisations primarily in pup
recognition.
Females and juveniles moult in the late
summer, early autumn, while in generally
males moult slightly later.
When diving, males poke only the nose
out of the water to breathe.
Pups are vulnerable to killer whale
predation and vampire bats are known to
attack them along the coast of Peru and
Chile.
Life History:
The lifespan of both males and females
it thought to be about 20 years for
males, 25 for females. Their
reproductive behaviour is polygynous,
and males build up harems that are then
defended through vocalisations,
posturing and sometimes, aggressive
physical fights. One male will defend up
to 21 females at a time. He will also
defend the pups of his females and will
fast for the duration of the breeding
season.
Around Peru, the breeding season starts
in late November and lasts up until
early March, with the birthing and
nursing season taking place between late
December and late March. The whole
season is now extending due to climate
change and the exact dates are location
dependent. Seasons are matched to prey
abundance cycles so that pups are born
at times when appropriately sized prey
are plentiful for them to learn to eat
fish.
Reproduction physiology includes a
delayed implantation of the fertilized
egg for 3 months in this species, with
pregnancy lasting 11 months. Sexual
dimorphism is shown at birth too, with
male pups weighing 13-15kg and measuring
79-83cm, and females, 10-14kg and
73-82cm. After birth the mother stays
with her pup for about a week and then
returns to the sea for 3-day foraging
trips, not ranging far from the
colonies, and comes back for 2-day
nursing breaks in-between. Pups are born
with no teeth and suckle with their
tongue rather than their lips. They are
born with a diving reflex but can’t swim
so the first five months are important
learning stages with information
transfer from mother to offspring and
practice. Pups are weaned at between
6-18 months, at the yearling or earliest
juvenile stage, when they can swim and
eat by themselves.
Diet & Foraging
Behaviour:
The diet of South American sea lions is
diverse and includes a wide range of
fish, cephalopods, and sometimes
invertebrates. These otariids (pinnipeds
with ears) forage all day long and may
have large foraging ranges.
Population Status
Abundance:
Populations are variable and unstable
throughout the range. Estimates from the
1970s and early 1980s have a population
of 20,000 along the coast of Peru,
100,000 in Chile, 50,000 in Argentina
and 30,000 in Uruguay. Currently Peru
population ranges around 35,000 animals
year round.
IUCN Status:
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LEAST CONCERN
They are relatively common in other
locations of South America, but in Peru
is locally threatened and classified as
VULNERABLE, meaning that the threats
to the species are consistent enough
that could lead into an endangered
species.
Conservation Issues:
Competition with fisheries is one of the
most severe threats to sea lion
populations. Animals are shot or clubbed
by fishermen as a result. Directed
harvests of them resumed in Chile in
1976. Coastal development also threatens
populations due to loss of habitat.
Climate change, such as an increase in
the occurrence of El Niño,
is also threatening populations due to
changes in prey abundance and increased
disease transmission.
Sources: International Commission for Zoological Nomenclature (ICZN), Society for Marine Mammalogy (SMM), & Organization for Research and Conservation of Aquatic Animals (ORCA).
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