After a brief shark-related hiatus last week, Pinnipednesday is back with an adorable vengeance!
The Galapagos Sea Lion (Zalophus wollebaeki) is one of the most populous species of the Galapagos Islands and Isla de Plata. Because of their boisterous, social and curious nature, and the fact that they make a real racket when they're all together, has made them the "welcome party" animals of the Galapagos. They have, in their history, been considered a subspecies of the California Sea Lion, but genetic studies have shown them to be distinct from their Californian cousins.
Adult Galapagos Sea Lions exhibit sexual dimorphism in size and color. Males will measure up to 8 feet (2.5 meters) in body length, weighing about 880 pounds (400 kg) at the top of the scale. They are bulky in the neck and shoulders and usually have dark brown coats. Females are smaller, measuring around 6.5 feet (2 meters) in body length and weighing 250 pounds (110 kg). They have coats that are more tawny in color, and instead of being slender in the lower half of their bodies, they have thick torsos but slender necks and tails. Being a member of the family Otariidae, they can move their hind flippers independent of each other, which helps them make sharp turns underwater. They are quick and agile swimmers.
Galapagos Sea Lions travel wide distances in search of food, sometimes as much as 10 miles (15 km) per day. Like the Galapagos Fur Seals, Galapagos Sea Lions are hugely impacted by the effect El Nino has on available food species. They feed mostly on sardines, but when El Nino decreases the sardine population, Galapagos Sea Lions will eat more lantern fish and green-eyes. Traveling so far to hunt means that they come into contact with their natural predators, orcas and sharks, and many sport the scars of those encounters. They can dive to depths of 650 feet (200 meters) and spend about 20 minutes down there with no ill effects.
Galapagos Sea Lions form colonies on the rocky shores where they haul out, and each colony is headed by a bull male. The big ones will fight for dominance and the right to mate with harems of around 25 or so females. Breeding season is fairly flexible, but generally all takes place from January to May. Like other pinnipeds, the gestation period of a pup is about one year, so females are often suckling a pup when they are ready to breed again. Pups will enter the water with their mothers when they're only a week old, still nursing but learning the vital foraging skills that they will need later in life.
Because the breeding season of the Galapagos Sea Lion is so vague - almost half a year - many expectant mothers do not synchronize their pregnancies. This contributes to a high mortality rate for pups within their first year, which is also impacted by the previously mentioned El Nino effect and sea lion pox, which is spread by mosquitoes and causes paralysis. Paralyzed animals are unable to fend for themselves, and often die of starvation. Juveniles, due to their curious and playful natures, often get themselves mixed up in human business, getting entangled in fishing hooks and nets.