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STELLER SEA LION
(Eumetopias jubatus)
Status
ESA Endangered - Western Distinct Population Segment
ESA Threatened - Eastern Distinct Population Segment
MMPA Depleted - throughout its range
Fast Fun Facts
Did You Know?
· Steller sea lions' impressive low-frequency vocalizations sound more like a "roar" when
compared to California sea lions, which sound more like a "bark."
· The scientific name, Eumetopias jubatus, comes from the Greek words "eu" and
"metopion" for "typical/well" and "broad forehead," and the Latin word jubatus for "having a
mane."
· Steller sea lions are named for the German surgeon and naturalist George Wilhelm Steller.
In 1742, he observed and described these large pinnipeds.
· Steller sea lions are the fourth largest pinniped in the world, behind the northern elephant
seal, southern elephant seal, and walrus.
Taxonomy
Kingdom: Animalia; Phylum: Chordata; Class: Mammalia; Order: Carnivora; Family: Otariidae; Genus: Eumetopias; Species: jubatus
Species Description
Weight: males: up to 2,500 lbs (1,120 kg) females: up to 770 lbs (350 kg) pups: about 35-50 lbs (16-22.5 kg)
Length: males: about 10-11 ft (3-3.4 m) females: about 7.5-9.5 ft (2.5-3.0 m) pups: about 3.3 ft (1 m)
Appearance: adults: light blonde to reddish brown and slightly darker on the chest and abdomen; pups: dark brown to black. The light colo ration is
still visible when the body is wet, which is different from many pinniped species. Like other pinnipeds, their coat of fur "molts" every year. Both
sexes also have long whitish whiskers, or vibrissae, on their muzzle. The flippers and other hairless parts of the skin are b lack. The fore-flippers
are broader and longer than the hind-flippers and are the primary means of locomotion in water. On land, sea lions, unlike "true " seals, can turn
their hind flippers forward for walking.
Lifespan: 20-30 years
Diet: variety of fishes (capelin, cod, herring, mackerel, pollock, rockfish, salmon, sand lance, etc.), bivalves, squid, octopus, and gastropods
Behavior: use land habitat as haul-out sites for periods of rest, molting, and as rookeries for mating and pupping; colonial breeders, adult males
("bulls") establish and defend territories on rookeries to mate . They are capable of powerful vocalizations that are accompa nied by a vertical head
bobbing motion by males.
Adult males, also known as bulls, establish and defend territories on rookeries to mate with females. Bulls become sexually m ature between 3 and
8 years of age, but typically are not large enough to hold territory successfully until 9 or 10 years old. Mature males may g o without eating for 1-2
months while they are aggressively defending their territory. Females typically reproduce for the first time at 4 to 6 years of age, usually giving birth
to a single pup each year.
Adult females, also known as cows, stay with their pups for a few days after birth before beginning a regular routine of alte rnating foraging trips at
sea with nursing their pups on land. Female Steller sea lions use smell and distinct vocalizations to recognize and create strong social bonds with
their newborn pups.
Pups have a dark brown to black "lanugo" coat until 4 to 6 months old, when they molt to a lighter brown. By the end of their second year, pups are
on the same color as adults. Females usually mate again with males within 2 weeks after giving birth. Males can live to be up to 20 years old,
while females can live to be 30.
-On average, nose-to-tail length of 3 m and weight about 680 kg (1496 lbs). Weighing up to 1000 kg (2200 lbs);
have a thick neck and big chest.
-Males hold territories for an average of two years.
-Males are much larger in appearance and overall size than females.
-Male Steller sea lions have a thick mane to protect themselves when fighting with other males or from the cold
temperatures & from jagged rocks.
-Males have a higher mortality rate than females, by ten years of age there is a 3:1 ratio of females to males.
-Males are 1.3 times as long and 2.5 times as heavy as females.
-Adult males lose weight & grow little during the summer breeding season while fasting.
-Adult males gain weight from autumn through early spring in preparation for the breeding season.
-Length of 2.3 m and weigh about 270 kg (594 lbs).
-Lighter coat than pups.
-Slimmer neck than males.
-Arrive at rookeries shortly after the males and give birth to a single pup each year, within three days of being on land.
-Females usually mate about two weeks after pupping.
-Weigh about 20 kg (44 lbs) when born (male pups are usually larger than female pups).
-Brown or chocolate coat.
-Pups are born from late May to early June.
-Juvenile animals may also grow very little during the breeding season and summer, with most of their growth
occurring from autumn to spring.
-Pups generally nurse for a year and may stay with their mother for up to three years (considered immature at this
point). There is considerable uncertainty about when sea lion pups are weaned.
Adult Male has thick mane and robust chest
Very large body size separates it from other
age and sex classes
Sub-adult Males will have slightly less size
and no pronounced mane
Adult Male with Adult Female and newborn Pup
Sub-Adult Males are larger
than adult females but smaller
than adult males
They lack the full “mane” seen
on adult males but possess a
thicker neck than adult
females
Sub-adult male surrounded by California Sea Lions.
Notice no mane but thickened neck.
Adult Females are generally blonde in most of
pelage with obvious color change to dark or
chocolate brown on flippers (good way to
distinguish between California Sea Lions – although
light colored CSL are somewhat common)
Adult Females can also be distinguished by broad
fore flippers and larger “bear-like” head
SSL do not “bark” like CSL but rather let out a long
deep “belching” sound
Branded Adult Female with newborn pup
Immatures are most often confused with adult females because of similar body size
Immatures can sometimes be seen nursing from adult females if she has not yet produced the current
year’s pup
Look for behavior as a way to distinguish immatures from adult females as immatures will tend to be more
playful and wander around when hauled out where as adult females spend most of their time sleeping
when out of water.
Mixed adult females and immatures
Adult Female
Notice slight size difference
in body and head with
immatures being smaller
than adult females
Immature
Pups are obvious and will be seen on SEFI
starting in June and are considered pups until
they reach 1 yr (in which they become
“immatures” by SEFI standards
Adult Female with pup
“Fuzzy” lanugo apparent on pup
Habitat
Steller sea lions prefer the colder temperate to sub-arctic waters of the North Pacific Ocean. Haul outs and rookeries usually consist of
beaches (gravel, rocky or sand), ledges, rocky reefs. In the Bering Sea and Okhotsk Sea, sea lions may also haul out on sea i ce, but
this is considered atypical behavior.
Critical habitat has been defined for Steller sea lions as a 20 nautical mile buffer around all major haul-outs and rookeries, as well as
associated terrestrial, air and aquatic zones, and three large offshore foraging areas (50 CFR 226.202 on Aug. 27, 1993).
Distribution
Steller sea lions are distributed mainly around the coasts to the outer continental shelf along the North Pacific Ocean rim from nort hern
Hokkaiddo, Japan through the Kuril Islands and Okhotsk Sea, Aleutian Islands and central Bering Sea, southern coast of Alaska and
south to California. The population is divided into the Western and the Eastern "distinct population segments" (DPSs) at 144° West
longitude (Cape Suckling, Alaska). The Western DPS includes Steller sea lions that reside in the central and western Gulf of Alaska,
Aleutian Islands, as well as those that inhabit the coastal waters and breed in Asia (e.g., Japan and Russia). The Eastern DP S includes
sea lions living in southeast Alaska, British Columbia, California, and Oregon.
Population Trends
For management purposes, Steller sea lions inhabiting U.S. waters have been divided into two DPSs: the Western U.S. and the Eastern
U.S. The differentiation is based primarily on genetic and physical differences, but also on differing population trends in t he two regions.
There are approximately 39,000-45,000 Steller sea lions in the Western U.S. and 44,500-48,000 in the Eastern U.S.
The Western DPS declined by 75% between 1976 and 1990, and decreased another 40% between 1991 and 2000 (the average annual
decline during this period was 5.4%). Since the 1970s, the most significant drop in numbers occurred in the eastern Aleutian Islands and
the western Gulf of Alaska. The extent of this decline led NMFS to list the Steller's sea lion as threatened range-wide under the
Endangered Species Act (ESA) in April 1990. In the 1990s, the decline continued in the Western portions of the range leading NMFS to
divide the species into two distinct population segments (DPS), Western and Eastern, and list the Western DPS as endangered i n 1997.
Population surveys suggest that the Eastern U.S. DPS is stable or increasing in the northern part of its range (Southeast Ala skan and
British Columbia), while the remainder of the Eastern DPS and all the Western DPS is declining.
Steller Sea Lion Distribution
Steller sea lions range from southern California, around the Pacific rim to northern Japan, but most of the world's Steller population
breeds between the central Gulf of Alaska and the western Aleutians.
Steller Sea Lion Diet
Steller sea lions eat a wide range of fish, but also consume cephalopods, crustaceans, birds and occasionally other pinnipeds . Analysis of sea
lion feces has indicated that the major prey species during the 1990s were walleye pollock, Atka mackerel, salmon, Pacific cod, herring,
arrowtooth flounder, cephalopods, rockfish and sandlance. Diet appears to vary between regions and has also changed through t ime (see
changes in diet). The causes and consequences of these changes are still under debate (see ecosystem change and over-fishing).
Feeding Patterns
Sea lions often feed in groups and tend to feed at
night between 9 PM and 6 AM. Feeding in groups
may help to control the movement of large schools
of fish and make them easier to exploit. Sea lions
may feed close to shore or may travel 100 or more
miles (>150 km) out to sea. Stomach samples and
feces (scat) samples indicate sea lions prey upon a
wide selection of fishes including capelin,
sandlance, pollock, herring, cod, salmon, flatfishes,
sculpins, squid, octopus and occasionally seal pups.
Most fish are swallowed whole. Large prey are torn
apart and consumed at the surface. Food
requirements of adult sea lions are believed to be
between 5-6% of their body weight per day.
Steller sea lions forage near shore and pelagic
waters.
They are also capable of traveling long distances in
a season and can dive to approximately 1300 ft
(400 m) in depth.
At sea, they are seen alone or in small groups, but
may gather in large "rafts" at the surface near
rookeries and haul outs.
Threats
Threats to Steller sea lions include:
boat/ ship strikes
contaminants/ pollutants
habitat degradation
illegal hunting/ shooting
offshore oil and gas exploration
interactions (direct and indirect) with fisheries
Direct fishing impacts are largely due to fishing gear (drift and set gillnets, longlines, trawls, etc.) that has the potential to entangle, hook, injure, or
kill sea lions. They have been seen entangled in fishing equipment with what are considered "serious injuries."
Indirect fisheries impacts include having to compete for food resources and possible modifications to critical habitat by fis hing activities
Historically, threats included:
hunting for their meat, fur hides, oil, and various other products (in the 1800s)
killing and placing bounties on this species, which fishermen blamed for stealing fish from them (in the early 1900s)
killing to limit their predation on fish in aquaculture facilities (fish farms), but intentional killing of Steller sea lions has not been permitted since they
were protected under the Marine Mammal Protection Act (MMPA) and listed under the ESA (not since 1972)
Conservation Efforts
Protective zones, catch/harvest limits, various procedures and other measures have been implemented around major haul -outs and rookeries in
order to safeguard their critical habitat. The IUCN Red List of Threatened Species considers this species to be "Endangered."
Subsistence harvests by natives in Alaska and Canada (150-300 taken a year) also occur.
Regulatory Overview
The Steller sea lion was listed under the ESA as threatened throughout its range on December 4, 1990. This listing included animals from Alaska,
California, Oregon and Washington in the U.S., as well as Canada, Japan, and Russia.
On June 4, 1997, the population west of 144° W longitude was listed as an endangered DPS (the Western DPS) under the ESA; the population
east of 144° W remained listed as threatened as the Eastern DPS.
Under the MMPA, all Steller sea lions are classified as "strategic stocks" and are considered "depleted".
Critical habitat has been designated (50 CFR 226.202 on Aug. 27, 1993) for Steller sea lions as a 20 nautical mile buffer around all major haul-outs
and rookeries, as well as associated terrestrial, air, and aquatic zones, and three large offshore foraging areas. NMFS has a lso designated no-entry
zones around rookeries (50 CFR 223.202). NMFS has implemented a complex suite of fishery management measures designed to mini mize
competition between fishing and the endangered population of Steller sea lions in critical habitat areas.
A recovery plan was developed for Steller sea lions in 1992. A revised recovery plan, which discusses separate recovery actions for the threatened
and endangered populations, was issued in 2008.