The Galápagos sea lion is a species of sea lion that exclusively breeds on the Galápagos Islands. 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. They are the smallest sea lions. 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.
Galápagos sea lions can be found on each of the 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 Gorgona in Colombia. They have also been spotted on Isla del Coco Island, which is about 500 km southwest of Costa Rica. Less than a quarter of them reside on the most tourist drawn area, San Cristobal Island. 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.
Galápagos sea lions are very social and on land, they form colonies in their hauling-out areas. Adult males are the head of the colony. As they grow, they fight to win dominance of a harem of between five and 25 cows, and the surrounding territory. Males in this species are two types: territorial and non-territorial. Territorial males vocalize at higher rates and vocalization is important to them because it plays a key role in the selection of female and helps ward off intruding non-territorial males into their harem. The average dominant bull holds his territory for only a few months until he is challenged by another male. 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”. Because the dominant male cannot feed while defending his colony, he eventually becomes too tired and weak and is overpowered by a well-nourished, fresh bull. Galápagos sea lions become active at sunrise when the dominant bull first enters the water to feed followed by the rest of the group. Most of the time is spent in the water hunting, or just to cool down from the heat. They rarely travel far from the shore and, when threatened will flee from the water as quickly as possible. The rest of the time they spend on the beach. Galápagos sea lions are quite vocal. Adult males often bark. Females and juveniles do not bark, but both sexes of younger pups growl. From birth, a mother sea lion recognizes her pup’s distinct bark and finds her offspring from a crowd of barking sea lions.
Little is known about the mating system in Galápagos sea lions. Breeding usually takes place from May through January. Each female in the harem has a single pup born after the gestation period that lasted 11 months. 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 2-3 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. At this time the pups are weaned from their mother’s milk and become dependent on their own hunting skill. The age of maturity for Galápagos sea lions is reached when they are 4 to 5 years old.
During El Niño events, the population of these animals tends to decrease as ocean temperatures warm and cold-adapted marine life on which the sea lions depend declines, which lead to die-offs. Sharks and killer whales are the main predators of the sea lion, especially little pups are easy targets. As the human population continues to grow it nevertheless presents various risks for accident and disease. 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. They are impacted by humans indirectly as well. Stray dogs introduced by humans form packs and attack sea lions. 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.
According to the IUCN Red List, the total population size of Galápagos sea lions is around 9,200-10,600 mature individuals. Currently, this species is classified as Endangered (EN) on the IUCN Red List and its numbers today are decreasing.