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February 23, 2006

Northern Elephant Seals: Physical Traits

Young Male Elephant Seal Año Nuevo State Reserve

Northern Elephant Seals are carnivorous mammals. They cannot breathe underwater, but spend most of their time there. They come up onto land only to molt, mate, and birth cute little pups. The large, adult bulls can be up to 18 feet long and weigh 6000 pounds, although the cows are significantly smaller.

The seals have well-developed senses - sight, hearing, smell - but these all work better under the water than on land.

Adult Male Proboscis Año Nuevo State Reserve

The male Elephant Seal has a very unique nose, or proboscis. Only the mature males have this long nose, which can sometimes reach up to two feet in length when fully inflated. The nose is quite delicate, and scientists believe that its main purpose is to magnify his bellow. He pushes his nose down his throat when he makes his call, inviting other males to battle him and take their places in the dominance hierarchy. The sound can be heard up to a mile away.

Strong Back Flippers For Propulsion Año Nuevo State Reserve

Elephant Seals are incredibly agile swimmers. They have four flippers - two in the front and two in the back. The strong back flippers are used to propel the animal, while the front flippers are used for steering and walking on land.

Strong Flippers Año Nuevo State Reserve

Elephant Seals can swim up to 12mph and hold their breath for a long time - the record is 119 minutes. They have specially adapted bodies to help them live in the water. They have much more blood than a land mammal of similar size, and their blood contains more hemoglobin to hold oxygen. They also have more myoglobin in their muscles, allowing them to store oxygen there as well. Finally, they can shut off some of their bodily functions while submerged, and only supply vital ones with oxygen.

Front Flippers For Steering Año Nuevo State Reserve

Elephant Seal flippers have five digits, just like humans. Each digit has a nail-like claw, with the first and fifth being slightly longer than the others.

You'll often see Elephant Seals on land using their front flippers to scratch themselves or flip sand onto their backs in order to protect themselves from the heat of the sun. They do not use their flippers in battle with other bulls, from what I've seen.

Big Black Eyes For Seeing Underwater Año Nuevo State Reserve

Seals are quite famous for their large, black eyes. These eyes help the seal, an underwater hunter, find prey in the dark, deep waters where their favorite foods live. Seals have mirror-like membranes at the back of their eyes that help let in any available light.

Seals can see on land, but not as well as in the water. They can only see sharp images in bright light, otherwise they just see blurs. This allows researchers to sneak up on the animals fairly easily. It also allowed hunters to do so in centuries past.

Because they live primarily under the water, seals do not have tear ducts. On land, the tears used to keep their eyes moist drain right out of their eyes, making it appear that they are crying.

Stiff, Sensitive Whiskers For Finding Food Año Nuevo State Reserve

Visibility at 1500 feet is often non-existent. The Elephant Seal does not just depend on its eyesight to hunt, but its other senses at well. Seals depend on their sense of touch to hunt prey, and they also have long, sensitive whiskers.

Whiskers For Finding Prey Año Nuevo State Reserve

The seals can detect the waves of pressure produced by moving objects like fish. They can hunt down an animal that produced these waves up to two minutes prior, determining the direction they went and then catching them. Elephant Seals can also tell when they are swimming towards large, stationary objects by sensing their own waves bouncing back at them.

30 Teeth For Holding Prey Año Nuevo State Reserve

Elephant Seals have 30 spiky teeth for grabbing and holding their prey. They have four large, sharp canines that the bulls use as weapons when they fight each other. The seals do not have molars for chewing, but tend to swallow prey whole.

They eat deepwater fish like squid and octopus, sharks, skates, and ratfish, as well as halibut, cod, flounder, sole, anchovies, herring, smelt, and salmon. An adult male might eat hundreds of pounds of fish per day. If the seal opens its mouth underwater, its strong throat muscles seal off its lungs from the water pressure.

Cumbersome Land Movement Of Elephant Seals Año Nuevo State Reserve

Although the seals haul out for important activities like mating, they are quite clumsy on land. They flop along by dragging themselves on their bellies, pulling themselves by their front flippers. They leave long trails where they have dragged themselves up and down the sand dunes.

Posted by sorsha at February 23, 2006 1:41 PM