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Adaptations to a Way of Life

Elephant seals have made many adaptations that allow then to dive deeply and go for extended periods of time without eating .

Diving adaptations: All mammals, carry oxygen in their blood (in hemoglobin, the complex molecule in the red blood cells) and in their muscles (in myoglobin, another complex molecule). Elephant seals have twice the blood volume , three times as much hemoglobin, and much more myoglobin than land mammals of the same size. Thus they live off the oxygen stored in the blood and the muscle for the time they are below the surface and, most remarkably, are able to recharge these complex molecules during the few minutes they are at the surface. In addition to a large and rich blood supply, the seals also have a special region in their circulatory system for storing carbon-dioxide laden, oxygen depleted blood.

As part of the dive reflex blood is diverted away from the skin to the core organs, thus saving energy that would otherwise go into re-warming cooled blood. The reason elephant seals come on the beach to molt is to allow the blood to circulate to the skin so new hair and tissue can receive the nourishment required for growth.

Adaptations to their neurological system, that are not clearly understood, allow elephant seals to dive to depths where the pressure is great enough to make most mammals go into involuntary synapse firing or seizures.

Thermoregulation: Elephant seals have a thick layer of blubber between their skin and their vital organs to help keep them warm at sea. Their problem is keeping cool on land. The blubber is not present in two places on the seal; the flippers and the "arm pits" of the front flippers . Indeed, a common method of cooling on the beach is to lift a front fin and let the breeze cool the uninsulated skin in the arm pit. Two other common means of cooling off are

flipping sand to cover their bodies or simply moving down to the waters edge where it's cooler.

The blood vessels in the flippers are grouped together in such a way that the arteries and veins help maintain a steady body temperature. Therefore at sea, in a process referred to as countercurrent heat exchange, the cooler blood returning toward the heart is warmed by the warm blood heading toward the extremities, further reducing heat loss and maximizing energy. Countercurrent heat exchange is also used in the reverse to provide cooling of reproductive organs which must be kept at lower temperature.

Moisture and Energy Conservation: Elephant seals are extremely energy efficient mammals: conserving energy, hence oxygen, at sea and conserving energy, hence food resources in the blubber, and body moisture on land.

Being neutrally buoyant elephant seals are able to swim efficiently by only having to sweep their rear flippers back and forth a few times then gliding down for a distance before more propulsion is needed. On the beach, seals will often go into apnea (sleeping without breathing) for periods of eight to thirty minutes, depending on their age. As a result, they are often taken for dead by visitors. The normal position for elephant seal nostrils is closed so when they snort them open to breathe there is a discharge of white mucous, creating the misimpression that they are ill.

Elephant seals can remain in the rookery for one to three months without food or water. A mother elephant seal comes on the beach, gives birth to a 60-80 pound pup and nurses it for four weeks without consuming either food or water! Males remain at the rookery without eating for three months during the breeding season. Pups live off their blubber for about two and a half months before leaving on their first delete foraging trip. They accomplish this by metabolizing their blubber into nourishment and moisture.

 

Because of these special adaptations to pressure, elephant seals dive to far greater depths than almost all other marine mammals, and all but specially built research submarines.

Click for Dive Chart
small graph of diving depths

 

 

 

A honeycomb shaped structure in the nasal passage condenses much of the moisture in the exhaled air, recycling it for use by the body.
 

 

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