Juan Fernández fur seal
Juan Fernández fur seal is the second smallest of the fur seals,
second only to the Galápagos fur seal. They are found only on the
Pacific Coast of South America, more specifically on the Juan
Fernández Islands and the Desventuradas Islands. There is still much
that is unknown about this species. Scientists still do not know the
average life span of this species, or the diet and behavior of males
apart from the breeding season.
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The Juan Fernandez fur seal is part of the group of eared seals. Fur
seals in general have thick insulating fur that protects the skin from
cold water, they have small ear flaps on the side of their head, and
they hold their weight on their front flippers which are also used for
Fur seals are different from true seals because they
have the external ear flaps, but also true seals use their chest for
support and movement, fur seals walk on their front flippers.
The Juan Fernandez fur seal is the second smallest fur seal, second
only to the Galápagos fur seal. Their bodies are short and robust
with brown pelage. Both the fore flippers and the hind flippers are
relatively short, and the hind flippers have fleshy tips on the
digits. Females are lighter brown and average 100 pounds and 4'6"
long. Males are significantly larger and average 300 pounds and 6'6"
in length. Males have thicker necks than females and have generally
darker brown pelage. Male seals have golden tipped thick guard hairs
on the back of the head, neck, and shoulders. This seal species has
a trait called sexual dimorphism, meaning the males look much
different from the females after reaching sexual maturity.
Juan Fernández fur seal
Juan Fernández fur seal was discovered, and named by Juan
Fernández in the mid 1500s. Once the seal was discovered the
population was decimated by over hunting for the fur trade. It was
believed that the
Juan Fernández fur seal
Juan Fernández fur seal was extinct until a small
group of 200 was found on the Juan Fernández islands in the 1960s.
Now it is estimated that over 12,000 individuals exist today.
This particular seal lives a solitary life. Seals forage out at sea
and haul out on rocky shores to rest. Females seem to be fairly
particular about where she rests during the day and prefer tide pools
and rocky caves. The resting areas that females prefer often become
areas of male competition for breeding rights. Although females will
typically rest in close regions, they are sure to be a few feet away
from each other and never touch one another.
Breeding is a territorial process with the Juan Fernández fur seal,
males will aggressively fight for access to female resting sights.
This seal is polygynous, meaning that one male breeds with multiple
females. Pups are born between November and December and are weaned
off the mother's milk at 10 months of age. Mother's stay with the pups
for about a week and then they leave to mate again and forage. Pups
are born with soft black fur that fades to light brown within the
first few years.
Not much is known about the diet of Juan Fernández fur seals,
scientist have only observed the diet of lactating females that are
caring for pups. What they have observed is that females forage out at
sea sometimes as far as 300 miles off shore and will dive to depths of
30 to 300 feet to find lanternfish and squid. Typically lactating
females will dive and forage at night when prey swims to shallow
waters and become more accessible. Sometimes they will stay out at sea
for up to 25 days, then return to shore and stay with the pups for 5
During the period that the mothers are foraging the pup goes without
milk for several days, sometimes weeks. To combat this, the mother's
milk is high in fat and nutrients that the pup uses for energy while
the mother is away. However, during this time the pups' immune
systems are not as highly functioning as adults and can be prone to
infection from intestinal parasites that leads to fatal infections. In
the early 90s there were 60 pups discovered dead from hookworm
infections, and also the presence of heavy metal ions were found
in their systems. Such loss decimated the population and they are
still recovering now.
^ Aurioles, D. & Trillmich, F. (2008). "
IUCN Red List
IUCN Red List of Threatened Species. Version 2008. International Union
for Conservation of Nature. Retrieved 30 January 2009.
^ a b c d e f Reeves (et. al.), Randal (2002). Guide to Marine Mammals
of the World. Andrew Stewart Publishing. pp. 69–71.
^ Osman, Layla P.; Moreno, Carlos A.; Trites, Andrew W. (2010-10-15).
"Growth rates and differential investment in male and female Juan
Fernández fur seal pups". Journal of Mammalogy. 91 (5): 1188–1196.
doi:10.1644/09-MAMM-A-197.1. ISSN 0022-2372.
^ Francis, John M.; Boness, Daryl J. (1991-11-01). "The Effect of
Thermoregulatory Behaviour on the Mating System of the Juan Fernández
Arctocephalus philippii". Behaviour. 119 (1/2): 104–126.
doi:10.1163/156853991x00391. JSTOR 4534978.
^ Ochoa-Acuña, Hugo; Francis, John M.; Oftedal, Olav T. (1999-08-01).
"Influence of Long Intersuckling Interval on Composition of Milk in
the Juan Fernandez
Arctocephalus philippii". Journal of
Mammalogy. 80 (3): 758–767. doi:10.2307/1383245.
^ Sepúlveda, Maria Soledad (1998-12-01). "Hookworms (Uncinaria sp.)
in Juan Fernandez
Fur Seal Pups (
Arctocephalus philippii) from
Alejandro Selkirk Island, Chile". The Journal of Parasitology. 84 (6):
1305–1307. doi:10.2307/3284700. JSTOR 3284700.
^ Sepúlveda, María S.; Ochoa-Acuña, Hugo; Sundlof, Stephen F.
"Heavy metal concentrations in Juan Fernández fur seals
Arctocephalus philippii)". Marine Pollution Bulletin. 34 (8):
ARKive - images and movies of the Juan Fernández fur seal