Elephant Seal Facts (Genus Mirounga)

The Elephant Seal Is Faster Than You

A northern bull (male) elephant seal makes his way ashore in Point Reyes National Seashore, California.
A northern bull (male) elephant seal makes his way ashore in Point Reyes National Seashore, California. Chase Dekker Wild-Life Images, Getty Images

The elephant seal (genus Mirounga) is the world's largest seal. There are two species of elephant seals, named according to the hemisphere in which they are found. Northern elephant seals (M. angustirostris) are found in coastal waters around Canada and Mexico, while southern elephant seals (M. leonina) are found off the coast of New Zealand, South Africa, and Argentina.

Description

A bull elephant seal is much larger than a cow.
A bull elephant seal is much larger than a cow. David Merron Photography, Getty Images

The oldest confirmed elephant seal fossils date back to the Pliocene Petane Formation of New Zealand. Only the adult male (bull) "elephant of the sea" has the large proboscis that resembles an elephant's trunk. The bull uses the proboscis to roar during the mating season. The large nose acts as a rebreather, allowing the seal to reabsorb moisture when it exhales. During the mating season, seals don't leave the beach, so they must conserve water.

Southern elephant seals are a bit larger than northern elephant seals. Males of both species are much larger than females. An average adult southern male may weigh 3,000 kg (6,600 lb) and reach a length of 5 m (16 ft), while the adult female (cow) weighs about 900 kg (2,000 lb) and it measures about 3 m (10 ft) long.

Seal color depends on gender, age, and season. Elephant seals may be rust, light or dark brown, or gray.

The seal has a large body, short front flippers with nails, and webbed hind flippers. There is a thick blubber layer beneath the skin to insulate the animals in cold water. Each year, elephant seals molt the skin and fur above the blubber. The molting process occurs on land, during which time the seal is susceptible to cold.

The average lifespan of a southern elephant seal is 20 to 22 years, while the lifespan of a northern elephant seal is about 9 years.

Reproduction

Even the elephant seal pups molt their skin.
Even the elephant seal pups molt their skin. Brent Stephenson / naturepl.com, Getty Images

At sea, elephant seals range solo. They return to established breeding colonies each winter. Females become mature around 3 to 6 years of age, while males mature at 5 to 6 years.

However, males need to achieve alpha status to mate, which is normally between the ages of 9 and 12. Males battle each other using body weight and teeth. While deaths are rare, scarring is common. An alpha male's harem ranges from 30 to 100 females. Other males wait on the edges of the colony, sometimes mating with females before the alpha male chases them away. Males remain on land over the winter to defend territory, meaning they don't leave to hunt.

About 79 percent of adult females mate, but a little over half of first-time breeders fail to produce a pup. A cow has one pup per year, following an 11 month gestation period. So, females arrive to the breeding grounds already pregnant from the previous year. Elephant seal milk is extremely high in milk fat, rising to over 50 percent fat (compared to 4 percent fat in human milk). Cows don't eat during the one month needed to nurse a pup. Mating occurs during the last few days of nursing.

Diet and Behavior

Elephant seals hunt in the water.
Elephant seals hunt in the water. Richard Herrmann, Getty Images

Elephant seals are carnivores. Their diet includes squid, octopuses, eels, rays, skates, crustaceans, fish, krill, and occasionally penguins. Males hunt on the ocean floor, while females hunt in the open ocean. Seals use eyesight and vibrations of their whiskers (vibrissae) to find food. Seals are preyed upon by sharks, killer whales, and humans.

Elephant seals spend about 20 percent of their lives on land and about 80 percent of their time in the ocean. Although they are aquatic animals, seals on sand can outrun humans. In the sea, they can swim at a speed of 5 to 10 km/hr.

Elephant seals dive to great depths. Males spend more time underwater than females. An adult may spend two hours underwater and dive to 7,834 feet.

Blubber is not the only adaptation that allows seals to dive so deeply. The seals have large abdominal sinuses to hold oxygenated blood. They also have more oxygen-carrying red blood cells than other animals and can store oxygen in muscles with myoglobin. Seals exhale before diving to avoid getting the bends.

Conservation Status

Once hunted to the brink of extinction, elephant seal numbers have recovered.
Once hunted to the brink of extinction, elephant seal numbers have recovered. Danita Delimont, Getty Images

Elephant seals have been hunted for their meat, fur, and blubber. Both northern and southern elephant seals were hunted to the brink of extinction. By 1892, most people believed the northern seals to be extinct. But in 1910, a single breeding colony was found around Guadalupe Island off Mexico's Baja California coast. At the end of the 19th century, new marine conservation legislation was put in place to protect the seals. Today, elephant seals are no longer endangered, although they are at risk of entanglement in debris and fishing nets and from injury due to boat collisions. The IUCN lists the threat level as being of "least concern."

Interesting Elephant Seal Trivia

The rear flipper is surprisingly efficient at helping an elephant seal move on land.
The rear flipper is surprisingly efficient at helping an elephant seal move on land. Bob Evans, Getty Images

Some other facts about elephant seals are interesting and entertaining:

  • Scientists have determined more male pups are born than female pups when the sea surface temperature is warmer.
  • The screech of orcs in the Mines of Moria in The Lord of the Rings: The Fellowship of the Ring was the sound of elephant seal pups.
  • In 2000, an elephant seal bull named Homer terrorized the New Zealand town of Gisborne. Homer attacked cars, boat trailers, a trash bin, a tree, and even a power transformer

References and Further Reading

  • Boessenecker, RW; Churchill, M (2016). "The origin of elephant seals: implications of a fragmentary late Pliocene seal (Phocidae: Miroungini) from New Zealand". New Zealand Journal of Geology and Geophysics59 (4): 544–550.
  • Lee, Derek E.; Sydeman, William J. (2009). "North Pacific Climate Mediates Offspring Sex Ratio in Northern Elephant Seals". Journal of Mammalogy. 90 (1).

 

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Helmenstine, Anne Marie, Ph.D. "Elephant Seal Facts (Genus Mirounga)." ThoughtCo, Dec. 4, 2017, thoughtco.com/elephant-seal-facts-4154853. Helmenstine, Anne Marie, Ph.D. (2017, December 4). Elephant Seal Facts (Genus Mirounga). Retrieved from https://www.thoughtco.com/elephant-seal-facts-4154853 Helmenstine, Anne Marie, Ph.D. "Elephant Seal Facts (Genus Mirounga)." ThoughtCo. https://www.thoughtco.com/elephant-seal-facts-4154853 (accessed December 13, 2017).