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:
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
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.
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
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
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
There are no known adverse effects of Galapagos sea lions on humans.
Galapagos sea lions may draw in tourists as they are endemic to the Galapagos islands (Aurioles and Trillmich, 2008).
Positive Impacts: ecotourism
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:
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 )
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 )
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)
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.
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.
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]
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]
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]
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 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]
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]
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.