Galápagos Sea Lion
Encyclopedia
The Galápagos sea lion (Zalophus wollebaeki), a species of sea lion
, exclusively breeds on the Galápagos Islands
and – in smaller numbers – on Isla de la Plata
(to Ecuador
). Being fairly social, and one of the most numerous species in the Galápagos archipelago, they are often spotted sun-bathing on sandy shores or rock groups or gliding gracefully through the surf. Their loud bark, playful
nature, and graceful agility in water make them the "welcoming party" of the islands.
, Galápagos sea Lions range from 150 to 250 cm in length and weigh between 50 and 400 kg, with the males averaging larger than females. Adult males also tend to have a thicker, more robust neck, chest, and shoulders in comparison to their slender abdomen. Females are somewhat opposite males, with a longer, more slender neck and thick torso. Once sexually mature, a male’s sagittal crest
enlarges, forming a small, characteristic bump-like projection on their forehead. Galápagos sea lions, compared to California sea lions, have a slightly smaller sagittal crest and a shorter muzzle. Adult females and juveniles lack this physical characteristic altogether with a nearly flat head and little or no forehead.
Both male and female sea lions have a pointy, whiskered nose and somewhat long, narrow muzzle. The young pups are almost dog-like in profile. Another characteristic that defines the sea lion are their external ear-like pinnae flaps which distinguish them from their close relative with which they are often confused, the seal. 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 somewhat clumsy on land with their flippers, sea lions are amazingly agile in water. With their streamlined bodies and flipper-like feet, they easily propel themselves through crashing surf and dangerously sharp coastal rocks. They also have the ability to control their flippers independently and thus change directions with ease, and they have more control over their body on land.
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. Born with a longer, brownish-black lanugo, a pup's coat gradually fades to brown within the first five months of life. At this time, they undergo their first molt, resulting in their adult coat.
in Colombia
. Records have also been made of sightings on Isla del Coco which is about 500 km southwest of Costa Rica
.
s and killer whales. Injuries and scars from attacks are often visible. During el Niño events, however, more green-eyes and myctophids are consumed due to a decrease in sardine population.
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 and the 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.
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 800lb. As males grow larger, they fight to win dominance of a harem
of between five and 25 cows, and 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 average dominant bull holds his territory for only a few months, until he is challenged by another male. On land, these fights start by two bulls stretching out their necks and barking in attempt to test each other’s bravery. If this is not enough to scare the opponent off, they begin pushing each other and biting around the neck area. If males were not equipped with thick, muscular necks, their vital organs would be easily damaged during these fights. Blood is often drawn, however, and many male sea lions have battle scars due to these territorial competitions. Losers are dramatically chased far 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. Because the dominant male of the harem cannot feed while defending his colony, he eventually becomes too tired and weak, and is overpowered by a well-nourished, fresh bull.
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 become dependent on their own hunting skill.
The pups have a strong bond with their mothers. 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.
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
, exclusively breeds on the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
and – in smaller numbers – on Isla de la Plata
Isla de la Plata
Isla de la Plata is a small island off the coast of Manabí, Ecuador, and is part of Parque Nacional Machalilla. It can be reached by boat from the city of Puerto López....
(to Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
). Being fairly social, and one of the most numerous species in the Galápagos archipelago, they are often spotted sun-bathing on sandy shores or rock groups or gliding gracefully through the surf. Their loud bark, playful
Play (activity)
Play is a term employed in ethology and psychology to describe to a range of voluntary, intrinsically motivated activities normally associated with pleasure and enjoyment...
nature, and graceful agility in water make them the "welcoming party" of the islands.
Physical characteristics
Slightly smaller than their Californian relativesCalifornia Sea Lion
The California sea lion is a coastal sea lion of western North America. Their numbers are abundant , and the population continues to expand about 5% annually. They are quite intelligent and can adapt to man-made environments...
, Galápagos sea Lions range from 150 to 250 cm in length and weigh between 50 and 400 kg, with the males averaging larger than females. Adult males also tend to have a thicker, more robust neck, chest, and shoulders in comparison to their slender abdomen. Females are somewhat opposite males, with a longer, more slender neck and thick torso. Once sexually mature, a male’s sagittal crest
Sagittal crest
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull of many mammalian and reptilian skulls, among others....
enlarges, forming a small, characteristic bump-like projection on their forehead. Galápagos sea lions, compared to California sea lions, have a slightly smaller sagittal crest and a shorter muzzle. Adult females and juveniles lack this physical characteristic altogether with a nearly flat head and little or no forehead.
Both male and female sea lions have a pointy, whiskered nose and somewhat long, narrow muzzle. The young pups are almost dog-like in profile. Another characteristic that defines the sea lion are their external ear-like pinnae flaps which distinguish them from their close relative with which they are often confused, the seal. 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 somewhat clumsy on land with their flippers, sea lions are amazingly agile in water. With their streamlined bodies and flipper-like feet, they easily propel themselves through crashing surf and dangerously sharp coastal rocks. They also have the ability to control their flippers independently and thus change directions with ease, and they have more control over their body on land.
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. Born with a longer, brownish-black lanugo, a pup's coat gradually fades to brown within the first five months of life. At this time, they undergo their first molt, resulting in their adult coat.
Distribution
Galápagos sea lions can be found on each of the different islands of the Galápagos archipelago. They have also colonized just offshore the mainland Ecuador at Isla de la Plata, and can be spotted from the Ecuadorian coast north to Isla GorgonaGorgona, Colombia
Gorgona is a Colombian island in the Pacific Ocean situated about 50 km off the Colombian Pacific coast and part of the municipality of Guapi in the Department of Cauca. The island is about 9 km long and 2.5 km wide, with a maximum height of 338 m ; with an area of 10 square miles...
in Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
. Records have also been made of sightings on Isla del Coco which is about 500 km southwest of Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
.
Diet and feeding patterns
Feeding mostly on sardines, Galápagos sea lions sometimes travel 10 to 15 kilometers from the coast over the span of days to hunt for their prey. This is when they come into contact with their biggest predators: sharkShark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s and killer whales. Injuries and scars from attacks are often visible. During el Niño events, however, more green-eyes and myctophids are consumed due to a decrease in sardine population.
Behavior and male competition
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, and wade into.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 and the 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.
On land, sea lions form colonies at their hauling-out
Hauling-out
Hauling-out is the behaviour associated with pinnipeds , of temporarily leaving the water between periods of foraging activity for sites on land or ice...
areas. Adult males, bulls, are the head of the colony, growing up to 7 ft (2;m) long and weighing up to 800lb. As males grow larger, they fight to win dominance of a harem
Harem
Harem refers to the sphere of women in what is usually a polygynous household and their enclosed quarters which are forbidden to men...
of between five and 25 cows, and 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 average dominant bull holds his territory for only a few months, until he is challenged by another male. On land, these fights start by two bulls stretching out their necks and barking in attempt to test each other’s bravery. If this is not enough to scare the opponent off, they begin pushing each other and biting around the neck area. If males were not equipped with thick, muscular necks, their vital organs would be easily damaged during these fights. Blood is often drawn, however, and many male sea lions have battle scars due to these territorial competitions. Losers are dramatically chased far 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
South Plaza Island
South Plaza is a small island off the east coast of Santa Cruz in the Galapagos Islands. It has an area of 0.13 km˛ and a maximum altitude of 23 meters....
of the Galápagos chain. Because the dominant male of the harem cannot feed while defending his colony, he eventually becomes too tired and weak, and is overpowered by a well-nourished, fresh bull.
Breeding
The pups have a strong bond with their mothers. 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
Rookery
A rookery is a colony of breeding animals, generally birds. A rook is a Northern European and Central Asian member of the crow family, which nest in prominent colonies at the tops of trees. The term is applied to the nesting place of birds, such as crows and rooks, the source of the term...
. 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.