Galapagos sea lions are found scattered amongst the Galapagos Archipelago, which consists of island clusters positioned directly west of Ecuador. These sea lions reside on all the main islands, rocks, and other diminutive islands of this archipelago. Some are also found ranging along Ecuadorian north coast to Isla Gorgona of Columbia. In 1986, a group arrived at Isla de la Plata near the shores of Ecuador. Some were even spotted 500 km southwest of Costa Rica on Isla del Coco. (Halpin, et al., 2009)
Male Galapagos sea lions can usually be found inland where abundant shade is present, while females occupy different habitats depending on the age of their pups (Wolf et al., 2005). During the day, sea lions can be found on beaches near the water, which they enter throughout the day. At night, they move higher on the beach. Energy costs of locomotion and thermoregulation contribute to habitat use; Galapagos sea lions most frequently occupy areas neighboring the sea that have adequate levels of shade, flat, uncomplicated terrain, and nearby tide pools. Habitat usage also varies with maturity level and sex during the reproductive period, in which sexual separation occurs (Wolf et al., 2005). (Orr, 1967; Wolf, et al., 2005)
Galapagos sea lions differ in color depending on sex and whether their coats are wet or dry. The area surrounding the eyes as well as the muzzle of both males and females are lighter in hue than the rest of the body. After being submerged in water, the bull's coat takes on a dark black hue. When dry, the coat is usually dark brown but can range from different shades of brown to gray. Once a bull reaches full maturity, the coat ceases to get any darker, and its back usually turns a light shade of gray. Mature females, adolescent males, and juveniles vary in shade from light brown to tan. Pups experience their initial molt around five months of age, losing the darker coat they were born with. (Halpin, et al., 2009)
Galapagos sea lions are sexually dimorphic, with males larger than females. Males tend to have a thicker, stouter neck, shoulders and chest than females, and adult canines are substantially larger and stronger in males. As males grow, their sagittal crest develops more rapidly, leaving a pronounced protrusion on their head. After the male reaches full maturity, the crest ceases to grow, and its forehead becomes steeper due to the pronounced ridge that forms at the back of its eyes. Female Galapagos sea lions have a more elongated, sleek neck and a wider upper body relative to their body size. Females, along with immature sea lions, do not have sagittal crests; their forehead is less defined and adolescents foreheads are almost nonexistent, with virtually a flat head. Galapagos sea lions can weigh between 50 and 250 kg and are often 150 to 250 cm in length. ("Galapagos Sea Lion", 2006; Halpin, et al., 2009)
Galapagos sea lions have a long breeding season from May to January, as witnessed by the great size variation of Galapagos sea lions within the Galapagos Archipelago. Gestation lasts 11 months, and single pup is born per female during each breeding interval. Male and female pups weigh about 6 kg when born, and they are weaned at 11 to 12 months of age. Galapagos sea lion pups are partially independent between 12 and 24 months, while still returning to nurse from time to time (Aurioles and Trillmich, 2008; Halpin et al., 2009; Orr, 1967). The age of sexual maturity for both male and female Galapagos sea lions is between 4 and 5 years of age (Aurioles and Trillmich, 2008). (Aurioles and Trillmich, 2008; Halpin, et al., 2009; Orr, 1967)
Mother Galapagos sea lions have a close bond with their pups. Mothers attend to their pups continuously for 6 to 7 days after birth, after which they feed in the sea, returning at night to continue feeding their young. Mother and pups recognize each other by their unique scent and vocal calls (Halpin et al., 2009). Female sea lions nurse only one pup at a time, until they give birth to the next pup. Some females allow both her yearling and pup to nurse simultaneously. If the female does not bare another pup, then the first can nurse for up to three years (Trillmich, 1981). (Halpin, et al., 2009; Trillmich, 1981)
Galapagos sea lions are estimated to live 15 to 24 years in the wild and 20 years on average (Aurioles and Trillmich, 2008)
Galapagos sea lions are sexually dimorphic, and tend to live among social groups of approximately 30 individuals (Wolf et al., 2005; "Galapagos Sea Lion," 2006), which consist of mature females, their young, and one dominant male. Dominant bulls are very territorial, and when an intruder is sighted, the bull takes immediate action. He patrols back and forth in the water for most of the day, aggressively barking to declare his territory (Orr, 1967). Males tend to hold their territory from 10 days to 3 months before being displaced by another male. Bulls not dominating a colony gather in bachelor colonies ("Galapagos Sea Lion," 2006). (Orr, 1967; Wolf, et al., 2005)
Galapagos sea lions become active at the first sign of light, when the dominant bull first enters the water to feed followed by the rest of the group. The majority of their time in spent the water looking for food, and they frequently enter the water thrughout the day. They rarely travel beyond 16 km from the shore and, under threat of predators, they will flee from the water as quick as possible and find safety on shore (Barlow, 1974). The rest of the group's time is spent on the beach, where they care for the young and, during the breeding season, copulate. Males also enter the water to swim to a different area in search of new mates. Galapagos sea lions tend to sleep throughout the night on higher beaches. Members of the group, especially the bull, may sleep apart from each other. (Barlow, 1974; Orr, 1967; Wolf, et al., 2005)
Little information is available regarding the home range of Galapagos sea lions.
Dominant male Galapagos sea lions patrol their territory, warding off intruders, often with a bark. Dominant bulls also touch the muzzle of females of interest (Orr, 1967). Mother and pups recognize each other by their unique scent and vocal calls (Halpin et al., 2009). (Halpin, et al., 2009; Orr, 1967)
Galapagos sea lions usually forage at shallow depths for fish, squid, octopus, and crustaceans. They have been observed smashing octopus on the water's surface, allowing for easier consumption. During El Niño of the 1980s, their primary diet consisted of sardines and myctophids, or lanternfish. ("Galapagos Sea Lion", 2006; Dellinger and Trillmich, 1999)
When in danger, Galapagos sea lions flee from the water, seeking safety on on shore (Barlow, 1974). Sea lion pups risk predation from feral, wild dogs, which are capable of transmitting diseases to the sea lion population. Killer whales and sharks prey on sea lions; those sea lions that escape are often left with with scars and other injuries (Halpin et al., 2009). (Barlow, 1974; Halpin, et al., 2009)
Galapagos sea lions are mutualists with lava lizards on Barrington Island. These lizards are attracted to the flies around the sea lions, and the lava lizards are often found resting on or around Galapagos sea lions. Galapagos sea lions also transport nautical nutrients into the terrestrial ecosystem, moving nutrients in high concentrations to shoreline flora at low elevations (Fariña et al., 2003). Additionally, young Galapagos sea lion can catch disease from ferrel dogs, which also prey on young sea lions. (Fariña, et al., 2003; Orr, 1967)
Galapagos sea lions may draw in tourists as they are endemic to the Galapagos islands (Aurioles and Trillmich, 2008). (Aurioles and Trillmich, 2008)
There are no known adverse effects of Galapagos sea lions on humans.
There are an estimated 20,000 to 50,000 individuals of Galapagos sea lions found mainly in the Galapagos Archipelago. The archipelago is part of an Ecuadorian National Park, which is enclosed by a marine resources reserve. Tourism of the park does persist largely, but is carefully monitored to deter any disturbances (Halpin et al., 2009). El Niño of the early 1980’s greatly affected sea lion populations, causing dozens of yearlings to die, and decreasing the pup fecundity for the following year (Trillimich and Limberger, 1985). (Halpin, et al., 2009; Trillmich and Limberger, 1985)
Kaila Huhtasaari (author), Northern Michigan University, John Bruggink (editor), Northern Michigan University, Gail McCormick (editor), Animal Diversity Web Staff.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats fish
having more than one female as a mate at one time
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
uses sight to communicate
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