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Elephant seal

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Elephant seals are massive marine mammals belonging to the genus Mirounga. They are part of the clade Pinnipedia, a term meaning "fin-footed."

Miroungaskull
Miroungaskull

These animals are categorized within the family Phocidae, which refers to true or earless seals. Unlike eared seals, Phocids lack external ear flaps and possess reduced limbs. This limb reduction creates a streamlined shape for efficient swimming. However, it also makes moving on land quite difficult because they cannot turn their hind flippers forward to walk.

There are two distinct species: the northern elephant seal (Mirounga angustirostris) and the southern elephant seal (Mirounga leonina). The northern species lives along the Pacific coasts of the United States, Canada, and Mexico. One notable breeding site is the Race Rocks Marine Protected Area at the southern tip of Vancouver Island. The southern elephant seal inhabits the Southern Hemisphere. They are found on islands like South Georgia and Macquarie Island, as well as the coasts of New Zealand, Tasmania, South Africa, and Argentina. In Chile, a small colony of 120 animals lives at Jackson Bay in Admiralty Sound.

Elephant seals show extreme sexual dimorphism, meaning males and females look very different. Adult males possess a large, fleshy nose called a proboscis. This organ is a secondary sexual characteristic used to produce loud roaring noises during mating season. The proboscis also functions as a rebreather by using internal cavities to reabsorb moisture from exhalations. This is vital during breeding when seals fast and cannot drink water.

Southern elephant seal bulls are much larger than northern ones. A southern bull can reach 4,000 kilograms in weight and 6 meters in length. Some exceptional males even reach 5,000 kilograms. Northern bulls are smaller, but they often have a larger proboscis and a red-colored chest area compared to southern males.

To survive deep dives, elephant seals have developed incredible physiological adaptations. They spend approximately 90% of their lives underwater. They can hold their breath for over 100 minutes, which is longer than any other non-cetacean mammal. To manage oxygen, they have a very large blood volume and large sinuses in their abdomens to store blood. They also have high concentrations of myoglobin in their muscles to hold oxygen. During deep dives, they exhibit bradycardia, which is the slowing of the heartbeat. They also slow their metabolism to conserve energy while searching for prey like squid, eels, and sharks.

Maintaining body temperature in freezing oceans is another major challenge. Elephant seals rely on thick blubber rather than fur for insulation. This is linked to the inactivation of the UCP1 gene, which favors heat conservation through fat rather than heat production. They also use a countercurrent heat exchanger. In this system, arteries and veins are arranged so that cool blood flowing to the heart is warmed by blood returning from the body's exterior.

Animal warning sign, Onrus Beach (South Africa)
Animal warning sign, Onrus Beach (South Africa)

When they molt, their skin and hair fall off in large patches. During this time, they must stay in a safe resting area on land called a "haul out."

Reproduction involves intense competition and social structures. Males arrive at breeding sites in the spring and fast to prepare for combat. By age eight or nine, males develop a thickened chest shield to protect them. They establish dominance through roaring, posturing, and ramming each other with their chests and teeth.

A dominant male, or alpha, typically controls a harem of up to 50 females. A secondary male, called a beta bull, often assists the alpha by preventing other males from reaching the females. Females nurse their pups with milk that is over 50% milkfat, which is much higher than human or cow milk. This high fat content helps the pups grow quickly during their short nursing period.

History has significantly impacted these populations. In the late 19th century, both species were hunted nearly to extinction to produce lamp oil. Fortunately, conservation efforts have allowed their numbers to recover. The genus name Mirounga was established by John Edward Gray in 1827. The name is a Latinization of "miouroung," a term from an unidentified Australian Aboriginal language. While their history includes periods of great danger, elephant seals remain some of the most impressive divers in the animal kingdom.

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🖼️ Images & Media (4)
File:Miroungaskull.jpg
Miroungaskull.jpg
Northern elephant seals fighting.webm
File:Northern Elephant Seal rookery at San Simeon.jpg
Northern Elephant Seal rookery at San Simeon.jpg
File:Animal warning sign, Onrus Beach (South Africa).jpg
Animal warning sign, Onrus Beach (South...
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