Northern Elephant Seal - Range and Ecology

Range and Ecology

The northern elephant seal lives in the eastern Pacific Ocean. Feeding grounds extend from northern Baja California to northern Vancouver Island. Males migrate as far north as Alaska and British Columbia, while females migrate as far west as Hawaii. They come ashore to breed, give birth and molt, mostly on offshore islands. While the pelagic range covers an enormous span, breeding is restricted to only about seven principal areas, four of which are on islands off the coast of California. Recently, increasing numbers have been observed in the Gulf of California. Breeding colonies exist at Channel Islands, Año Nuevo State Reserve, Piedras Blancas Light, Morro Bay State Park and the Farallon Islands in the US, and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico. Some breeding has been observed at Castle Rock in Northern California and Shell Island off Oregon and in January, 2009, the first elephant seal births were recorded in British Columbia at Race Rocks. The California breeding population is now demographically isolated from the population in Baja California.

The northern elephant seals are nocturnal deep feeders famous for the long time intervals they remain underwater. This species dives to great depths while feeding, typically between 300 m (1,000 ft) and 800 m (2,600 ft); moreover, the northern elephant seal will generally not feed in depths of less than 200 m (700 ft). Both sexes eat a variety of prey, including pelagic, deep water squid, Pacific hake, sharks, rays, and ratfish. Octopoteuthis deletron squid are the most common prey item, found in the stomachs of 58% of individuals sampled off the coast of California. Elephant seals do not need to drink, as they get their water from food and metabolism of fats.

While hunting in the dark depths, elephant seals seem to locate their prey at least partly by vision; the bioluminescence of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation in the manner of cetaceans, but their vibrissae, which are sensitive to vibrations, are assumed to play a role in search of food. Males and females differ in diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom, while females have more jagged routes and forage in the open ocean. Males return to the same feeding ground every year, while females have less predictable feeding migrations. Elephant seals are prey for killer whales and white sharks. Both are most likely to hunt pups, and seldom hunt large bull elephant seals, but have taken seals of all ages. The shark, when hunting adults, is most likely to ambush a seal with a damaging bite and wait until it is weakened by blood loss to finish the kill.