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Zalophus wollebaekiGalapagos sealion

By Kaila Huhtasaari

Geographic Range

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)

Habitat

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)

  • Range depth
    186 (high) m
    610.24 (high) ft
  • Average depth
    37 m
    121.39 ft

Physical Description

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)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • sexes shaped differently
  • Range mass
    50 to 250 kg
    110.13 to 550.66 lb
  • Range length
    150 to 250 mm
    5.91 to 9.84 in

Reproduction

Sea lions in the family Otariidae, including Galapagos sea lions, practice polygamy. Little is otherwise known regarding the mating systems of this species. (Orr, 1967; Orr, 1967)

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)

  • Breeding interval
    Galapagos sea lions breed once yearly.
  • Breeding season
    Galapagos sea lions breed between May and January.
  • Average number of offspring
    1
  • Average gestation period
    11 months
  • Average weaning age
    11 to 12 months
  • Average time to independence
    12 to 24 months
  • Average age at sexual or reproductive maturity (female)
    4 to 5 years
  • Average age at sexual or reproductive maturity (male)
    4 to 5 years

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)

  • Parental Investment
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Galapagos sea lions are estimated to live 15 to 24 years in the wild and 20 years on average (Aurioles and Trillmich, 2008)

  • Typical lifespan
    Status: wild
    15 to 24 years
  • Average lifespan
    Status: wild
    20 years

Behavior

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)

Home Range

Little information is available regarding the home range of Galapagos sea lions.

Communication and Perception

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)

Food Habits

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)

  • Animal Foods
  • fish
  • mollusks

Predation

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)

Ecosystem Roles

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)

  • Ecosystem Impact
  • creates habitat
Mutualist Species

Economic Importance for Humans: Positive

Galapagos sea lions may draw in tourists as they are endemic to the Galapagos islands (Aurioles and Trillmich, 2008). (Aurioles and Trillmich, 2008)

Economic Importance for Humans: Negative

There are no known adverse effects of Galapagos sea lions on humans.

Conservation Status

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)

Contributors

Kaila Huhtasaari (author), Northern Michigan University, John Bruggink (editor), Northern Michigan University, Gail McCormick (editor), Animal Diversity Web Staff.

Glossary

Pacific Ocean

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.

World Map

acoustic

uses sound to communicate

bilateral symmetry

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.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

ecotourism

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.

endothermic

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.

female parental care

parental care is carried out by females

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

territorial

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

visual

uses sight to communicate

References

2006. "Galapagos Sea Lion" (On-line). The Animal Files. Accessed January 27, 2011 at http://www.theanimalfiles.com/mammals/seals_sea_lions/galapagos_sea_lion.html.

Aurioles, D., F. Trillmich. 2008. "Zalophus wollebaeki." (On-line). IUCN Red List of Threatened Species.. Accessed April 26, 2009 at http://74.125.95.132/search?q=cache:HPbRfWi1D4wJ:www.iucnredlist.org/details/41668+Zalophus+wollebaeki+longevity&cd=1&hl=en&ct=clnk&gl=us.

Barlow, G. 1974. Galapagos Sea Lions are Paternal. Evolution, Vol. 28: 476-478. Accessed February 02, 2009 at http://www.jstor.org/stable/2407169?&Search=yes&term=lion&term=sea&term=Galapagos&list=hide&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3DGalapagos%2Bsea%2Blion%2B%26x%3D11%26y%3D12%26wc%3Don&item=25&ttl=400&returnArticleService=showArticle.

Dellinger, T., F. Trillmich. 1999. Fish prey of the sympatric Galápagos fur seals and sea lions: seasonal variation and niche separation.. Canadian Journal of Zoology, 77: 1204–1216. Accessed February 08, 2009 at http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=eng&journal=cjz&volume=77&year=1999&issue=8&msno=z99-095.

Fariña, J., S. Salazar, K. Wallem, J. Witman, J. Ellis. 2003. Nutrient Exchanges between Marine and Terrestrial Ecosystems: The Case of the Galapagos Sea Lion Zalophus wollebaecki.. Journal of Animal Ecology, Vol 72: 873-887. Accessed February 02, 2009 at http://www.jstor.org/stable/3505369?&Search=yes&term=%22Nutrient+Exchanges+between+Marine+and+Terrestrial+Ecosystems+The+Case+of+the+Galapagos+Sea+Lion+Zalophus+wollebaecki.%22&list=hide&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3D%25E2%2580%259CNutrient%2BExchanges%2Bbetween%2BMarine%2Band%2BTerrestrial%2BEcosystems%253A%2BThe%2BCase%2Bof%2Bthe%2BGalapagos%2BSea%2BLion%2BZalophus%2Bwollebaecki.%25E2%2580%259D%2B%26x%3D0%26y%3D0%26wc%3Don&item=2&ttl=5&returnArticleService=showArticle.

Halpin, A., P. Crowder, B. Best, E. Fujioka. 2009. "Mapping marine mammals, birds and turtles." (On-line). OBIS SEAMAP. Accessed February 08, 2009 at http://seamap.env.duke.edu/species/tsn/622014.

Orr, R. 1967. The Galapagos Sea Lion. Journal of Mammalogy, Vol 48: 62-69. Accessed February 02, 2009 at http://www.jstor.org/stable/1378170?&Search=yes&term=lion&term=sea&term=Galapagos&list=hide&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3DGalapagos%2Bsea%2Blion%2B%26x%3D8%26y%3D15%26wc%3Don&item=6&ttl=400&returnArticleService=showArticle.

Trillmich, F. 1981. Mutual Mother-Pup Recognition in Galápagos Fur Seals and Sea Lions: Cues Used and Functional Significance. Behaviour, 78: 21-42. Accessed February 08, 2009 at http://www.jstor.org/stable/info/4534129?seq=1.

Trillmich, F., D. Limberger. 1985. Drastic effects of El Niño on Galapagos pinnipeds. Oecologia, 67: 19-22. Accessed February 02, 2009 at http://www.springerlink.com/content/p83r389p73017873/.

Wolf, J., G. Kauermann, F. Trillmich. 2005. Males in the Shade: Habitat Use and Sexual Segregation in the Galápagos Sea Lion (Zalophus californianus wollebaeki). Behavioral Ecology and Sociobiology, Vol. 59: 293-302. Accessed February 02, 2009 at http://www.jstor.org/stable/25063702?&Search=yes&term=lion&term=sea&term=Galapagos&list=hide&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3DGalapagos%2Bsea%2Blion%2B%26x%3D0%26y%3D0%26wc%3Don&item=12&ttl=400&returnArticleService=showArticle.

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