Galapagos Sea Lion(Zalophus wollebaeki)
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. They can hold their breath for 20 minutes.
Habitat
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.
Diet
Feeding mostly on sardines, Galápagos sea lions sometimes travel 10-15 km 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, sardine populations either die or migrate, and sea lions dive deeper to feed on lantern fish. The reduction in food availability during El Niño leads to sea lion population declines. 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. They have been observed smashing octopus on the water's surface, allowing for easier consumption.
Breeding
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.
Population
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. They were last assessed on 26th October 2014. In 1978 their was around 40,000 in the wild and the number of mature individuals was likely about 26,400 in 1978 and 9,200-10,600 in 2001, which indicates a substantial reduction of about 60-65% in population size of the Galápagos Sea Lion. No further estimates of total population size have been made since 2001.
Threats
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. Plastic refuse drifting at sea and on shore is becoming an increasing problem, frequently entangling Sea Lions. Cargo ships running aground may lead to oil spills that could gravely affect pups onshore (in particular close to the harbours of San Cristobal and Puerto Ayora) and foraging adults.
Conservation
The Galápagos Sea Lion population lives in the Galápagos Archipelago, which is an Ecuadorian National Park surrounded by a marine resources reserve. Tourism occurs on a large scale, but is largely controlled to protect wildlife from disturbance. Local fishing is controlled by the National Park authorities. Unfortunately, despite a quarantine system introduction of domestic animals from the mainland is still occurring occasionally.