ELEPHANT SEALS, THEIR BEHAVIOR AND AMAZING DIVING ABILITY

ELEPHANT SEALS

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Alpha seals
The Elephant seals is also one the world's most amazing creatures. It can dive to depths of nearly a mile, stay submerged for hours at a time and go for months without sleeping. They are named after the large trunk-like proboscis. Groups of elephant seals are called pods. Females are call cows; males, bulls. [Source: Susan Casey, National Geographic, November 2008; Roger Gentry, National Geographic, April 1987; Kathleen McAuliffe, Smithsonian magazine]

Susan Casey wrote in National Geographic, “When it comes to ocean predators, it is easy to underestimate the southern elephant seal... To judge by appearance, this is one misfit beast...The nose is a preposterous trunk that can grow one-and-a-half feet long, earning the elephant seal its name... Car-size and blimp-shaped on land the southern elephant seal...is usually found lolling around on the beach. But as with other sea creatures, the truth lies below the surface. Sure, its no supermodel, put underneath the blubbery disguise turns out to be a superhero, its life a series of magnificent feats.”

Elephant seals are the largest of all seals. They are larger than walruses. A bull typically weighs two to three tons and measure between 16 and 18 feet. Cows are about half that size. According to the Guinness Book of Records, the largest specimen ever measured was 22½ feet in length and weighed 4 tons. It was killed near South Georgia in 1913.

Northern and Southern Elephant Seals

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Female northern elephant seal with pup
There are two species of elephant seal: the northern and the larger southern elephant seal. The northern elephant seal was hunted to the edge of extinction for its blubber but made a stunning comeback, from fewer than 100 animals---all on Guadalupe Island off Baja California---to over 200,000 today. Today northern elephant seals come ashore at beaches and islands from San Francisco to Baja California. After breeding they return to their offshore feeding grounds.

The southern elephant seal is the largest pinniped. It can reach 4.5meters in length and weigh four tons. They breed on island groups in the South Atlantic and southern Indian oceans and the Peninsula Valdez in Argentina. Male proboscises are smaller than those of their northern cousin. Southern elephant seals are more supple than northerners; they able to bend their bodies almost completely in half.

The number of southern elephant seals around certain Antarctic islands plummeted from 450,000 to 280,000 before stabilizing in the 1980s. Around 400,000 gather at South Georgia Island, about 1,500 kilometers east of the Falkland Island, for the breeding season, which runs from mid September to November. The populations of elephant seals on Peninsula Valdez has been increasing.

Elephant Seal Characteristics and Behavior

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Southern elephant seal range
The largest male elephant seal ever observed was 20 feet long and weighed around 8,500 pounds. Their large body size helps them stay warm in the cold oceans. The males can be quite ugly with their large proboscises, but the females have surprisingly cute faces.

Except for the two or three month summer mating season, elephant seals spend their entire time at sea usually hundreds of miles from the nearest shore.

A beach covered by elephant seals can be a noisey place full of squealing, hissing, grunting, barking, belching and sighing. The loud, strangely metallic, pulsing noise like the pounding of a tin drum, is a “clap threat” made by bulls warning other bulls to keep their distance.

Elephant Seal Mating Behavior

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Elephant seals fighting
Only about a third of males win the chance to breed. Dominant males stake out a stretch of beach and establish huge harems. They may inseminate hundreds of cows during the summer mating season. The majority of males end up as lonely bachelor seals, wandering the seas by themselves and never having sex. Scientists call the dominant males beachmasters. Their harems can range in size from 20 females to more than 300, with the largest have over 1,000 members.

Large males fiercely defend their harems against other males. During the mating season bulls make loud bellowing noises, puff up their noses and ram one another. Occasionally they bite each other, sometimes inflicting terrible wounds. The fights can go on for hours---with the males wacking each other with their chests and pendulous snouts, sending chunks of flesh flying in the air and piecing the wind with the sound of deep thwacks. The elephant seals often have blood all over their faces. Occasionally eyes land on the ground. Most fights end with the weak bull backing down.

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Mating elephant seals
Female elephant seals often try to escape the bull males but the males are faster and often catch the females. The mating process itself often looks quite violent. The bulls are often very rough, seizing the females in their jaws by the scruff of the females’ neck and almost crushing the females with their weight.

A few secondary males gets some action. While the main bulls are engaged in trying to capture and mate with females, junior males see opportunities to stealthily approach other receptive females and mate with them. Females howl and protest when the dominant male tries to mate with the, but howl even louder when lesser males try to mate with them.

Both males and females eat little if anything during the breeding season. Females that escape into the water are approached by males hovering around the waves. For males, defending the beach often means not going back to the sea to eat. A male typically loses 30 percent of its weight during the three-month breeding season and may lose more than half its blubber.

Elephant Seal Females and Young

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Elephant seal colony
Females arrive in the breeding area about a month after the males. First they give birth to their pups, then suckle them and about three weeks after they give birth, mate again. They often join a harem not to have sex with the dominant male but to get his help warding off unwanted advances by other males.

Young pups are born after a ten month incubation period. For their first month or of life they feed entirely on their mother’s fat-enriched milk and gain about five kilograms a day.

Sea elephant pups have been observed standing on their sleeping mothers, at which time she uses her flipper to gentle brush them off. As the females prepare to leave the beach she mates, weans her pup abruptly and leaves, returning to same shores ten months later to give birth to a new pup.

Young pups start going to the sea to fend for themselves when they are two months old. The pups head out into the sea on their own with no training or guidance.

Elephant Seal’s Amazing Diving Ability

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Male elephant seal
A northern elephant seal was recorded diving an astounding depth of 5,017 feet in May 1989 seal off of California. This is further down than any other aquatic mammal including the sperm whale has been recorded descending and deeper than most submarines can go. A dive of 5,017 feet is nearly a mile and is the equivalent of descending past four Empire State Buildings piled on top of one another. Elephant seals can stay submerged for two hours. For deep dives it takes around 60 minutes to descend and about the same amount of time to return to the surface. Other creatures live at 5,000 foot depths but die when taken to the surface.

Elephant seals keep breaking their own diving records. In 2002 one elephant seal was recorded traveling to a depth of 5,141 feet. In the late 1980s the deepest recorded dive was only "only" 2,900 feet. These diving feats are measured with dive recorders that often are crushed like squeezed aluminum cans by pressure of one ton per square inch. Census of Marine Life’s Tagging of Pacific Predators (TOPP) project , completed in 2011, recorded an elephant seal diving to 5,492 feet, deeper than any other tagged animal in a study of 23 species of ocean predators.

Humans that dive more than 150 feet run the risk of falling unconscious from nitrogen narcosis or dying of decompression sickness (the painful frothing of the nitrogen in the blood) associated with the bends when they return to the surface.

Biologist believe that elephant seals developed their extraordinary diving ability to escape potential predators like great white sharks and get at food sources that few other marine creatures can reach. An elephant seal’s large brown eyes can gather the dimmest rays of light, particularly the short blue wavelengths found in the depths.


Breeding colony of Mirounga
The average elephant seal dive is around 40 minutes but some individuals have been observed staying submerged for two hours. Even after a particularly long dive they need only a few minutes on the surface to recover. What is even more amazing is that elephant seals dive like this again and again, 24 hours day, for months at a time, apparently without sleeping or somehow sleeping while they dive. No other mammal ever studied can go without sleeps for such long periods. Wendell seals, in contrast, rest 11 to 13 hours every day. Whales take regular naps between 30 minutes and several hours between dives.

The lungs of Wendell seals collapse at a depth of around 100 feet and stay collapsed when the seal dives further and reinflate when the animal ascends. Scientists believe the same thing happens to elephant seals, who draw oxygen from their blood and muscles, and possibly their spleens, during long dives not from their lungs. They are able to get enough oxygen this way because about 20 percent of their body weight is blood compared to seven percent in humans.

During long dives, elephant seals drop their body temperature by 5 or 6 degrees, shut off circulation to their kidneys, stomachs and other organs to conserve oxygen and slow their heart beat to as slow as two beats per minute (slow enough to regarded as cardiac arrest in humans).

Elephant Seal Food, Hunting and Migration

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Elephant seal pup
Elephant seals feed on squid and fish. They eat about 40 pounds of food a day. Female northern elephant seals migrate to a spot north of Hawaii and feed on scary-looking bioluminescent fish that live between 1,500 and 2,400 feet. Bulls migrate father north near the Aleutians, where the dive to top of sea mounts and feed on a variety of creatures including skates, ratfish, rays and sharks at depths of around 1,500 feet.

How elephant seals can hunt these creatures in complete darkness at crushing pressure when their heart is beating only a few beats a seconds and many of their organs have been shout down has not been adequately explained.

It was long thought that northern elephant seals hunted near their breeding ground on islands off of California. The tagging of these animals however show that migrate far to the North Pacific, mostly alone, and spend nine mother of the year hunting While the out at sea they spend about three minutes on the surface and then dive for 20 minutes’sometimes to a depth of 1700 meters---before returning to the surface and then repeating the pattern over and over.

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During their nine months at sea elephant seals might travel 20,000 kilometers and spend 80 percent of the time underwater. They appear to be skilled at riding currents and finding places where water is rich in nutrients, feeding on the food chain. Census of Marine Life’s Tagging of Pacific Predators (TOPP) project noted, the same female elephant seal tagged in 1995 off the island of Ano Nuevo north of Santa Cruz “took the same exact path 11 years later” when researchers tagged her again.

Sharks and killer whales feed on seals. Great white sharks sometimes even eat elephant seals. A large one found off of California was dissected and large chunks of elephant seal were discovered inside, including a completely severed head. Elephant seals were hunted, like whales, by humans for their oil-making blubber. They were easy targets while on land and their numbers were greatly reduced. Since a hunting ban was initiated in the 1960s they have made a remarkable comeback.

Studying Elephant Seals

In an effort to unveil some of the mysteries of elephant seal behavior, Burney Le Boeuf, a marine biologist at the University of California at Santa Clara, attached a video camera to the back of an elephant seal with epoxy glue. The camera was retrieved when the seal came ashore and molted its skin. The images, some from great depths, where mostly of inky black water with a few blurs.

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Elephant seal fishery in the 19th century
To attract males to a weigh station on the beach, biologists use a decoy of female complete with a waging tail and a speaker blasting out the sounds made by a cow having sex.

By studying elephant seals, biologist are hoping to understand how children can survive long periods submerged in cold water, how doctors might control irregular heartbeats and how children might die from sudden infant death syndrome.

Southern elephant seals tagged with satellite tracking devises are not only providing important data about themselves they are also providing important data about the currents, temperatures and salinity in the depths of the Southern Ocean, which plays a critical role in global ocean current circulation and for which there is little data and collecting it without elephant seals would be very difficult.

Male elephant seals have attacked cars and caused major damage. Brent Stewart who has studied northern elephant seals for more than 30 years and tags a couple of thousand pups every year, told the Los Angeles Times, “They’re quiet and sneaky. When their eyes get all scrunched up, that’s when you want to run. British scientist Mike Fedak, who works with southern elephant seals, told National Geographic, “You really have to watch yourself. They can move with amazing agility for animals with no arms or legs.”

Image Sources: Wikimedia Commons, National Oceanic and Atmospheric Administration (NOAA)

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, Yomiuri Shimbun, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

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© 2008 Jeffrey Hays

Last updated January 2012

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