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Associations

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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).

Known Predators:

  • Sharks
  • Killer whales Orcinus orca
  • Dogs Canis lupus familiaris
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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Morphology

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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.

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.

Range mass: 50 to 250 kg.

Range length: 150 to 250 mm.

Sexual Dimorphism: male larger; sexes colored or patterned differently; sexes shaped differently

Other Physical Features: endothermic ; bilateral symmetry

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Life Expectancy

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Galapagos sea lions are estimated to live 15 to 24 years in the wild and 20 years on average

Typical lifespan
Status: wild:
15 to 24 years.

Average lifespan
Status: wild:
20 years.

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Habitat

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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).

Range depth: 186 (high) m.

Average depth: 37 m.

Habitat Regions: saltwater or marine

Aquatic Biomes: temporary pools; coastal ; brackish water

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Behavior

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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).

Communication Channels: visual ; tactile ; acoustic ; chemical

Perception Channels: visual ; tactile ; chemical

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Conservation Status

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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).

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: endangered

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Benefits

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

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Benefits

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

Positive Impacts: ecotourism

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Associations

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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.

Ecosystem Impact: creates habitat

Mutualist Species:

  • Lava lizards Microlophus albemarlensis albemarlensis
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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Trophic Strategy

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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.

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore , Molluscivore )

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Distribution

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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.

Biogeographic Regions: pacific ocean (Native )

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Reproduction

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

Mating System: polygynous

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).

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.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual

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).

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)

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Huhtasaari, K. 2011. "Zalophus wollebaeki" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Zalophus_wollebaeki.html
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Kaila Huhtasaari, Northern Michigan University
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Biology

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The Galapagos sea lion is essentially a coastal animal and is rarely found more than 16 kilometres out to sea (2). Individuals are active during the day and hunt in relatively shallow waters (up to about 200 metres deep) where they feed on fish, octopus, and crustaceans. Sea lions and seals are also capable of making extraordinarily deep dives of up to 200 metres for 20 minutes or more, then rapidly surfacing with no ill effects (5). When ashore, the Galapagos sea lions rest on sandy beaches and rocky areas in colonies of about 30 individuals (2). They are extremely gregarious and pack together on the shore even when space is available (2). Each colony is dominated by one bull that aggressively defends his territory from invading bachelor males (5). This territorial activity occurs throughout the year and males hold their territories for only 27 days or so before being displaced by another male (2). Within this territory the bull has dominance over a group of between 5 and 25 cows. The breeding season is not dependant on migration patterns, as seen in other sea lion species, since the Galapagos sea lion remains around the Galapagos Archipelago all year round. In fact the breeding season is thought to vary from year to year in its onset and duration, though it usually lasts 16 to 40 weeks between June and December (2). Births therefore also take place throughout the year, with females coming ashore to give birth to a single pup. Within two to three weeks of giving birth females go into oestrous again and actively solicit a male (2). Gestation lasts around 11 months, though it probably includes a three month period in which implantation of the fertilised egg is delayed while the female nurses her young (2). Like other sea lions this species relies on cooperation within the group. Often, a single adult female will watch over a group of young pups while other mothers are fishing. They are careful to keep the young pups out of deep water where they may be eaten by sharks (6). The bull will also watch out for his "family" by warning them of the presence of a nearby shark with barks, and even occasionally chasing away the intruder (7).
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Conservation

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The Galapagos sea lion occurs in one of the most biologically diverse areas of the world. The Galapagos Islands have long been studied and protected and were influential in the formulation of Darwin's theory of evolution by natural selection. Most recently, in March 1998, a 133,000 square kilometres area was designated as the Galapagos Marine Reserve, making it one of the world's largest protected areas. Detailed conservation and research programmes have been developed, which focus on studying the islands' ecology, the effects of environmental fluctuations on species and the effects of humans on wildlife. These measures have to some extent protected this sea lion, especially from hunting. The Charles Darwin Research Centre has implemented an ecological monitoring project of the Galapagos sea-lion to determine the state and abundance of the sea lions. This project also studies the ongoing threats to this mammal and has developed simple rescue methods for injured or caught sea lions. Elsewhere in the world, sea lions are suffering dramatic population declines for unknown reasons, and so conservation measures like these, which both monitor and protect the sea lion, are invaluable in the future of the Galapagos sea lion (7).
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Description

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The Galapagos sea lion is found in the Galapagos Archipelago where it is one of the most conspicuous and numerous marine mammals. Well adapted to its semi-aquatic lifestyle, it has a streamlined body and powerful fins, and as a member of the eared seals (Otariidae family), which includes fur seals and sea lions; this aquatic mammal is able to control its hind flippers independently (2). This adaptation allows it more agility on land than seals, which cannot move their hind limbs independently. Furthermore, unlike the true seals (family Phocidae), the Galapagos sea lion swims using its strong and well developed fore flippers. Adult males are much larger than females and are brown in colour while females are a lighter tan. Adult males are also distinguished by their raised foreheads, and the hair on the crest may be a lighter colour (2). Juvenile Galapagos sea lions are chestnut brown in colour and measure around 75 centimetres at birth (2) (3).
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Habitat

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On land this sea lion prefers sandy or rocky flat beaches where there is vegetation for shade, tide pools to keep cool and good access to calm waters. It also spends much of its time in the cool, fish-rich waters that surround the Galapagos Islands (2) (4).
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Range

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This sea lion is found on islands in the Galapagos Archipelago and off the coast of Ecuador where a population has been introduced (3).
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Status

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Classified as Endangered (EN) on the IUCN Red List (1).
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Threats

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The Galapagos sea lion faces various threats. In the 19th century, sea-lions worldwide were hunted for their meat, skin and oil. The hunting of some sea-lions, including the Galapagos species, has now been banned and populations have recovered (2). Galapagos sea lions are still vulnerable to human activity as their inquisitive and social nature means they are more likely to approach areas inhabited by humans. This brings them into contact with fishing nets, hooks and human waste, all of which can be fatal (6). There are also problems resulting from the increase in numbers of deep-water tuna and billfish fisheries as these sea-lions become victims of bycatch (7). Research indicates that the majority of these incidents (67 percent) involve juveniles, probably due to their more curious and playful nature (7). These marine mammals are also negatively affected by the phenomenon El Niño. During El Niño 1997 and 1998, Galapagos sea lion populations of the main colonies declined by 48 percent. Many sea lions migrated and, amongst those that stayed in the Galapagos Archipelago, there was high mortality due to starvation (7). A viral disease, known as sea lion pox, is another threat to this marine mammal (5). The illness is spread by mosquitoes and causes paralysis, which in turn prevents the sea lion from feeding and may result in death.
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Galápagos sea lion

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Female with pup
A Galápagos sea lion underwater off the coast of San Cristóbal.

The Galápagos sea lion (Zalophus wollebaeki) is a species of sea lion that lives and breeds on the Galápagos Islands and, in smaller numbers, on Isla de la Plata (Ecuador). Being fairly social, they are often spotted sun-bathing on sandy shores or rock groups, or gliding through the surf. They are the smallest sea lion species.

Taxonomy

This species was first described by E. Sivertsen in 1953. It has been considered a subspecies of Zalophus californianus (called Z. c. wollebaeki) by many authors. But recent genetic data supports Z. wollebaeki as a separate species.[1] The species belongs to the family Otariidae and genus Zalophus.

Physical characteristics

Head and ear detail
Mother and baby at North Seymour Island.
Standing on Land at Rábida Island
Galápagos sea lion in Punta Pitt, San Cristóbal Island.
Galápagos sea lion (Zalophus wollebaeki), Puerto Ayora

Slightly smaller than their Californian relatives, Galápagos sea lions range from 1.5 to 2.5 m (4.9 to 8.2 ft) in length and weigh between 50 and 400 kg (110 and 880 lb), with the males averaging larger than females.[1][2][3] Adult males also tend to have a thicker, more robust neck, chest, and shoulders in comparison to their slender abdomen. Females, by contrast, have a longer, more slender neck and thick torso. The male's sagittal crest enlarges when he reaches sexual maturity, forming a small, characteristic bump-like projection on his forehead. Adult females and juveniles lack this trait and have a nearly flat head and little or no forehead. Galápagos sea lions, compared to California sea lions, have a slightly smaller sagittal crest and a shorter muzzle.[4]

Both male and female sea lions have a pointy, whiskered nose and long, narrow muzzle. Young pups are almost dog-like in profile. Another characteristic that defines the sea lion is the pinnae of the external ears, which distinguish them from seals. The foreflippers have a short fur extending from the wrist to the middle of the dorsal fin surface, but other than that, the flippers are covered in black, leathery skin. Curving posteriorly, the first digit of the flipper is the largest, giving it a swept-back look. At the end of each digit is a claw, usually reduced to a vestigial nodule that rarely emerges above the skin. Although clumsy on land, sea lions are agile in water. With their streamlined bodies and flipper-like feet, they easily propel themselves through crashing surf and sharp coastal rocks. They also have the ability to control their flippers independently and thus change directions with ease.

When wet, sea lions are a shade of dark brown, but once dry, their color varies greatly. The females tend to be a lighter shade than the males and the pups a chestnut brown. Pups are born with a longer, brownish-black lanugo that gradually fades to brown within the first five months of life. At this time, they undergo their first molt, resulting in their adult coat. The age of maturity for Galápagos sea lions is about 4–5 years.[1] The life span is estimated to be 15–24 years.[5]

Distribution

Galápagos sea lions can be found on all of the islands of the Galápagos archipelago. Less than a quarter of them reside on San Cristobal Island. They have also colonized Isla de la Plata, just offshore mainland Ecuador, and can be spotted from the Ecuadorian coast north to Isla Gorgona in Colombia. Records have also been made of sightings on Isla del Coco, which is about 500 km southwest of Costa Rica. The population on Isla del Coco is considered vagrant.[1][6]

Diet and feeding patterns

Galápagos sea lion on bench in Puerto Ayora

Feeding mostly on sardines, Galápagos sea lions sometimes travel 10 to 15 kilometers from the coast over a span of days to hunt. This is when they come into contact with their main predators: sharks and killer whales. Injuries and scars from attacks are often visible. During El Niño events, occurring when the water temperature pattern changes in the Pacific,[7] sardine populations either die or migrate, and sea lions dive deeper to feed on lantern fish.[8] The reduction in food availability during El Niño leads to sea lion population declines.[7]

Successful pack hunting of yellowfin tuna, in which the fish were herded into a rocky inlet and occasionally onto land, was recorded in the BBC series Blue Planet II.[9]

Behavior and male competition

Adult sea lion resting on a park bench in Puerto Baquerizo Moreno.

Galápagos sea lions are especially vulnerable to human activity. Their inquisitive and social nature makes them more likely to approach areas inhabited by humans, and thus come into contact with human waste, fishing nets, and hooks. They occupy many different shoreline types, from steep, rocky cliff sides to low-lying sandy beaches. To avoid overheating during the day, sea lions will take refuge from the sun under vegetation, rocks, and cliffs.

Not only are sea lions social, they are also quite vocal. Adult males often bark in long, loud and distinctive repeated sequences. Females and juveniles do not produce this repetitive bark, but both sexes of younger pups will growl. From birth, a mother sea lion recognizes her pup's distinct bark and can pinpoint it from a crowd of 30 or more barking sea lions.

There are clear cut differences in behavior between territorial and non-territorial males, the first being the territorial males vocalized at higher rates than non-territorial males and the onset of vocalization tends to be higher. Vocalization plays a key role in sexual selection and helps ward off intruding non-territorial males from a male's harem. Most vocalizations made by territorial males are long range and not directed to anything specific.

On land, sea lions form colonies at their hauling-out areas. Adult males, bulls, are the head of the colony, growing up to 7 ft (2 m) long and weighing up to 800 pounds (360 kg). As males grow larger, they fight to win dominance of a harem of between five and 25 cows, along with the surrounding territory. Swimming from border to border of his colony, the dominant bull jealously defends his coastline against all other adult males. While patrolling his area, he frequently rears his head out of the water and barks, as an indication of his territorial ownership. The neighboring territorial males tend to display a "dear enemy effect", whereby territorial males decrease vocalization and aggression. Through repetitive encounters with other territorial bulls, males also store key information about a neighbor's strength as an adversary.

The average dominant bull holds his territory for only a few months. Because the dominant male of the harem cannot feed while defending his colony, he eventually becomes weakened and is overpowered by a well-nourished, fresh bull. On land, these fights start with two bulls stretching out their necks and barking to test each other's bravery. If this is not enough to scare the opponent off, they begin pushing each other and biting the opponent's neck. Males are equipped with thick, muscular necks that generally prevent lethal damage during these fights. Blood is often drawn, however, and many male sea lions bear battle scars from these territorial competitions. Losers are chased from their territory by the new dominant bull with much splashing.

Because there is only one male in each harem, there is always a surplus of bachelor male sea lions. They usually congregate fairly peaceably on less favorable areas of the coastline in bachelor colonies. One of the most commonly known is atop the cliffs of the South Plaza Island of the Galápagos chain. Territorial males that lose their territory but decide to stay on the island tend to vocalize less.

Breeding

Female suckling a newborn, Santa Fe Island.
Galapagos sea lion with pup on sand. Calves are weaned anywhere from 5-12 months of age.

Breeding takes place from May through January. Because of this prolonged breeding season and the extensive care required by the pups from their mother, there are dependent pups in the colonies year round. Each cow in the harem has a single pup born a year after conception. After about a week of continuous attention from birth, the female returns to the ocean and begins to forage, and just a week after that, the pup will follow her and begin to develop its swimming skills. When the pup is two to three weeks old, the cow will mate again. The mothers will take the young pups with them into the water while nursing until around the 11th month, when the pups are weaned from their mother's milk and begin developing their own hunting skills.

The lasting interaction of mother–offspring pairs is a central social unit in these sea lions.[10] The cow will nurture a pup for up to three years. In that time, the cow and the pup will recognize each other's bark from the rest of the colony. Within the colony, sea lion pups live together in a rookery. Pups can be seen together napping, playing, and feeding. It is not uncommon to see one cow 'baby-sitting' a group of pups while the other cows go off to feed.

Many mammals synchronize their pregnancies to ensure a greater infant survival rate, but not Z. wollebaeki.[11] Plausible reasons for this low synchrony could be the absence of strong photoperiodic change throughout the year, which is thought to regulate embryonic diapause, and/or adaptation to an environment with variable productivity and prey availability.[11]

Galápagos sea lion displaying "jug handle" behavior to reduce heat loss.[12]

Threats and status

The majority of the Galápagos population is protected, as the islands are a part of an Ecuadorian national park surrounded by a marine resources reserve. Although the Galápagos Islands are a popular tourist destination, strict rules exist to protect all wildlife from disturbance. Fluctuating between 20,000 and 50,000 sea lions, the population does have a few threats. During el Niño events, the population tends to decrease as ocean temperatures warm and cold-adapted marine life on which the sea lions depend declines, which lead to die-offs or cessation of reproduction. Sharks and killer whales are the main predators of the sea lion. Although adult sea lions have less to worry about, pups are easy targets. Regulations governing human behavior help mitigate risks to sea lions due to human contact, but as the human population continues to grow it nevertheless presents risks of accident and disease.[6] The sea lions have learned that being near the fisheries they have a better chance at capturing fish with little to no work, but as a result they are in more danger from boats and net entanglement.[6] They are impacted by humans indirectly as well. Stray dogs introduced by humans form packs and attack sea lions.[6] The pesticide DDT, still in targeted use to prevent malaria in tropical countries, accumulates through the food chain and is found at near-toxic concentrations in sea lion pups.[13] From 2008 through 2012, death by disease increased.[6] Galapagos Sea lions are known to be susceptible to canine distemper virus, however this disease is not believed to be endemic among the population.[14]

References

Notes

  1. ^ a b c d e Trillmich, F. (2015). "Zalophus wollebaeki". IUCN Red List of Threatened Species. 2015: e.T41668A45230540. doi:10.2305/IUCN.UK.2015-2.RLTS.T41668A45230540.en. Retrieved 12 November 2021.
  2. ^ Galapagos sea lion - Galapagos Conservation Trust
  3. ^ Galapagos Sea Lion Facts | Galapagos Wildlife Guide
  4. ^ Wolf, J. B. W.; Tautz, D.; Trillmich, F. (2007). "Galapagos and Californian sea lions are separate species: genetic analysis of the genus Zalophus and its implications for conservation management". Frontiers in Zoology. 4: 20. doi:10.1186/1742-9994-4-20. PMC 2072946. PMID 17868473.
  5. ^ Reijnders et al. 1993
  6. ^ a b c d e Denkinger, Judith; Gordillo, Luis; Montero-Serra, Ignasi; Murrilo, Juan Carlos; Guevara, Nataly; Hirschfield, Maximillian; Fietz, Katharina; Rubianes, Francisco; Dan, Michael (November 2015). "Urban life of Galapagos Sea Lions (Zalophus wollebaeki) on San Cristobal Island, Ecuador:colony trend and threats". Journal of Sea Research. 105: 10–14. Bibcode:2015JSR...105...10D. doi:10.1016/j.seares.2015.07.004.
  7. ^ a b Páez-Rosas, Diego; Aurioles-Gamboa, David (2010). "Alimentary Niche Partitioning In The Galapagos Sea Lion, Zalophus Wollebaeki". Marine Biology. 157 (12): 2769–2781. doi:10.1007/s00227-010-1535-0. S2CID 84197080.
  8. ^ Jeglinski, Jana W.E.; Wolf, Jochen; Werner, Christiane; Costa, Daniel P.; Trillmich, Fritz (December 2015). "Differences in Foraging Ecology align with Genetically Divergent Ecotypes of a Highly mobile marine top Predator". Oceologica. 179 (4): 1041–1052. Bibcode:2015Oecol.179.1041J. doi:10.1007/s00442-015-3424-1. PMID 26307593. S2CID 18977436.
  9. ^ "Blue Planet II - Filming Galapagos sea lions hunting tuna - BBC One". BBC.
  10. ^ Wolf, Jochen B. W.; Trillmich, Fritz (2007). "Beyond Habitat Requirements: Individual Fine-Scale Site Fidelity In A Colony Of The Galapagos Sea Lion (Zalophus Wollebaeki) Creates Conditions For Social Structuring". Oecologia. 152 (3): 553–567. Bibcode:2007Oecol.152..553W. doi:10.1007/s00442-007-0665-7. PMID 17505851. S2CID 23862471.
  11. ^ a b Villegas-Amtmann, S.; Atkinson, S. (2009). "Low Synchrony In The Breeding Cycle Of Galapagos Sea Lions Revealed By Seasonal Progesterone Concentrations". Journal of Mammalogy. 90 (5): 1232–1237. doi:10.1644/08-mamm-a-319.1.
  12. ^ Campagna, Claudio; Le Boeuf, Burney J. (1988). "Thermoregulatory Behavior of Southern Sea Lions And its Effects on Mating Strategies". Behaviour. 107 (1–2): 72–89. doi:10.1163/156853988X00205. S2CID 44050418.
  13. ^ Alava, Juan Jose; Salazar, Sandie; Cruz, Marilyn; Jimenez-Uzcategui, Gustavo; Villegas-Amtmann, Stella; Paez-Rosas, Diego; Costa, Daniel P.; Ross, Peter S.; Ikonomou, Michael G. (18 February 2011). "DDT Strikes Back: Galapagos Sea Lions Facing Increasing Health Risks". Royal Swedish Academy of Sciences: 1–3 – via AMBIO.
  14. ^ Denkinger, Judith; Guevara, Nataly; Ayala, Sofia; Murillo, Juan Carlos; Hirschfeld, Maximilian; Montero-Serra, Ignasi; Fietz, Katharina; Goldstein, Tracey; Ackermann, Mark; Barragan, Veronica; Cabrera, Francisco; Chavez, Cristina; Dubovi, Edward J.; Martinez, Jael; Trueba, Gabriel (1 July 2017). "PUP MORTALITY AND EVIDENCE FOR PATHOGEN EXPOSURE IN GALAPAGOS SEA LIONS (ZALOPHUS WOLLEBAEKI) ON SAN CRISTOBAL ISLAND, GALAPAGOS, ECUADOR". Journal of Wildlife Diseases: 491–498 – via Journal of Wildlife Diseases.

Further reading

  • Kunc, Hansjoerg P.; Wolf, Jochen B. W. (2008). "Seasonal Changes Of Vocal Rates And Their Relation To Territorial Status In Male Galápagos Sea Lions ( Zalophus Wollebaeki)". Ethology. 114 (4): 381–388. doi:10.1111/j.1439-0310.2008.01484.x.
  • Meise, Kristine; Kruger, Oliver; Piedrahita, Paolo; Trillmich, Fritz (2013). "Site Fidelity of Male Galapagos Sea Lions: A Lifetime Perspective". Behavioral Ecology and Sociobiology. 67 (6): 1001–1011. doi:10.1007/s00265-013-1526-5. S2CID 16971697.
  • Wolf, Jochen B.; et al. (2005). "Males in the Shade: Habitat use and Sexual Segregation in the Galápagos Sea Lion (Zalophus Californianus Wollebaeki)". Behavioral Ecology and Sociobiology. 59 (2): 293–302. doi:10.1007/s00265-005-0042-7. S2CID 25257905.

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Galápagos sea lion: Brief Summary

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Female with pup A Galápagos sea lion underwater off the coast of San Cristóbal.

The Galápagos sea lion (Zalophus wollebaeki) is a species of sea lion that lives and breeds on the Galápagos Islands and, in smaller numbers, on Isla de la Plata (Ecuador). Being fairly social, they are often spotted sun-bathing on sandy shores or rock groups, or gliding through the surf. They are the smallest sea lion species.

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