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Pinnipednesday - Mirounga angustirostris Edition

It's officially blanket-at-all-times-while-at-home season.

The Northern Elephant Seal (Mirounga angustirostris) can be found in the eastern Pacific Ocean, with feeding grounds from Baja California to Vancouver Island. Females will migrate as far west as Hawaii, while males will migrate as far north as Alaska and British Columbia. Northern Elephant Seals get their name from their size and the amazing proboscis that are a characteristic of the males. They look large and ungainly on land but are graceful and agile in the water. They are also incredible divers.


Sexual dimorphism among Northern Elephant Seals is incredibly pronounced. Males are massive, measuring 16.5 feet (5 meters) and can weigh up to 5,100 pounds (2,300 kg). Some of the oldest, largest males have even tipped the scales at 8,152 pounds (3,700 kg)! Females are less than half the size of the average male, growing up to 11.9 feet (3.6 meters) and weighing only 2,000 pounds (900 kg). They have large eyes, and the high concentration of low-light pigments in their eyes and their nocturnal habits lead scientists to believe that sight is one of their primary senses when it comes to hunting.

The deep sea diet of Northern Elephant Seals consists of squid, rays, sharks, ratfish and hake. Northern Elephant Seals rarely feed at depths shallower than 700 feet (200 meters), and will often dive as deep as 2,600 feet (800 meters). They use their whiskers and vision to sense prey, looking for bioluminescence and sensing vibrations with their whiskers. Males tend to hunt along the continental shelf, while females prefer to forage in open water. Northern Elephant Seals get their water from the food that they eat, and do not usually need to drink.


The breeding season of Northern Elephant Seals occurs in December and January, with the males arriving at the breeding grounds first to establish their territories by fighting with each other. Male Northern Elephant Seals have what is called a "chest shield" made of tough, scarred skin around their shoulders and necks. This tough skin helps to protect against the attacks of other males. A dominant male can mate with about 50 females during a season, and these fights can end in death. When the females arrive at the breeding grounds, they will first give birth to the pups conceived during the previous year's season. Females can become very aggressive with each other if the grounds are crowded, but will sometimes allow orphaned pups to nurse along with their own. Pups are nursed for only about four weeks, and are on their own at three months.


Like other pinnipeds, Northern Elephant Seals were heavily hunted during the 1800s. It was touch and go for them for a while, as they were believed to be extinct several times between the 1860s and 1920s. They have made a population recovery since legal protections were enacted in California and Mexico, and now there are over 100,000 in the wild. Pup survival is affected by El Nino, just as other pinniped species in the region are similarly affected. They are hunted by orcas and great white sharks, and it's not uncommon to see Northern Elephant Seals with gaping wounds from shark attacks. The hunting tactic employed by great whites comprises an initial devastating attack that causes the animal to become weakened with blood loss.


Source for all images used in this post.

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