Elephant seal
Overview
Elephant seals are large, oceangoing seal
Earless seal
The true seals or earless seals are one of the three main groups of mammals within the seal superfamily, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae...

s in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Mirounga. There are two species: the northern elephant seal
Northern Elephant Seal
The northern elephant seal is one of two species of elephant seal . It is a member of the family Phocidae . Elephant seals derive their name from their great size and from the male's large proboscis, which is used in making extraordinarily loud roaring noises, especially during the mating...

 (M. angustirostris) and the southern elephant seal
Southern Elephant Seal
The Southern Elephant Seal is one of the two extant species of elephant seal. It is both the most massive pinniped and member of the order Carnivora living today...

 (M. leonina). Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered. The northern elephant seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

.
Encyclopedia
Elephant seals are large, oceangoing seal
Earless seal
The true seals or earless seals are one of the three main groups of mammals within the seal superfamily, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae...

s in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Mirounga. There are two species: the northern elephant seal
Northern Elephant Seal
The northern elephant seal is one of two species of elephant seal . It is a member of the family Phocidae . Elephant seals derive their name from their great size and from the male's large proboscis, which is used in making extraordinarily loud roaring noises, especially during the mating...

 (M. angustirostris) and the southern elephant seal
Southern Elephant Seal
The Southern Elephant Seal is one of the two extant species of elephant seal. It is both the most massive pinniped and member of the order Carnivora living today...

 (M. leonina). Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered. The northern elephant seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

. The most northerly breeding location on the Pacific Coast is at Race Rocks
Race Rocks Marine Protected Area
Race Rocks is a marine ecological reserve in the eastern entrance of the Strait of Juan de Fuca. The reserve served as a Marine Protected Area pilot project and is now seeking Marine Protected Area designation after the first bid in 2000 was derailed in Ottawa. Started in 1978 as a marine science...

, at the southern tip of Vancouver Island in the Strait of Juan de Fuca
Strait of Juan de Fuca
The Strait of Juan de Fuca is a large body of water about long that is the Salish Sea outlet to the Pacific Ocean...

. The southern elephant seal is found in the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

 on islands such as South Georgia, Macquarie Island
Macquarie Island
Macquarie Island lies in the southwest corner of the Pacific Ocean, about half-way between New Zealand and Antarctica, at 54°30S, 158°57E. Politically, it has formed part of the Australian state of Tasmania since 1900 and became a Tasmanian State Reserve in 1978. In 1997 it became a world heritage...

, and on the coasts of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, and Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 in the Peninsula Valdés, which is the fourth largest elephant seal colony in the world.

Description

Elephant seals take their name from the large proboscis
Proboscis
A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...

 of the adult males (bulls) which resembles an elephant's trunk. The bull's proboscis is used in producing extraordinarily loud roaring noises, especially during the mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

 season. More importantly, however, the nose acts as a sort of rebreather
Rebreather
A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...

, filled with cavities designed to reabsorb moisture from the animals' exhalations. This is important during the mating season when the male seals rarely leave the beach to feed and therefore must conserve body moisture as they have no incoming source of water. Bulls of both the northern and the southern elephant seals reach a length of 16 feet (4.9 m) and a weight of 6600 pounds (2,993.7 kg), and are much larger than the cows, which typically measure about 10 feet (3 m) and 2000 pounds (907.2 kg).

Physiology

Elephant seals spend upwards of 80% of their lives in the ocean. They can hold their breath for more than 100 minutes — longer than any other non-cetacean mammal. Elephant seals dive to 1550 m beneath the ocean's surface (the deepest recorded dive of an elephant seal is 2388 metres (7,834.6 ft) by a southern elephant seal). The average depth of their dives is about 300 to 600 metres (1,968.5 ft), typically for around 20 min for females and 60 min (1 hour) for males, as they search for their favorite foods, which are skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....

s, rays
Rajiformes
Rajiformes is one of the four orders of batoids, flattened cartilaginous fishes related to sharks.Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion...

, squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

, octopuses, eel
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...

s, penguin (southerns only), small shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s, and large fish. Their stomachs also often contain gastrolith
Gastrolith
A gastrolith, also called a stomach stone or gizzard stones, is a rock held inside a gastrointestinal tract. Gastroliths are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. The grain size depends upon the size of the animal and the gastrolith's...

s. While excellent swimmers, they are also capable of rapid movement on land.

Elephant seals are shielded from extreme cold by their blubber
Blubber
Blubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...

, more so than by fur. The animals' hair and outer layers of skin molt periodically. The skin has to be regrown by blood vessels reaching through the blubber. When molting occurs, the seal is susceptible to the cold, and must rest on land, in a safe place called a "haul out
Hauling-out
Hauling-out is the behaviour associated with pinnipeds , of temporarily leaving the water between periods of foraging activity for sites on land or ice...

". While the molt is taking place, the bulls cease fighting with one another, as there are then no breeding harems and females in estrous to protect. Northern males haul out in August, and females in May–June.

Elephant seals have a very large volume of blood, allowing them to hold a large amount of oxygen for use when diving. They have large sinuses in their abdomens to hold blood and can also store oxygen in their muscles with increased myoglobin
Myoglobin
Myoglobin is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is related to hemoglobin, which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells. The only time myoglobin is found in the...

 concentrations in muscle. In addition, they have a larger proportion of oxygen-carrying red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

s. These adaptations allow elephant seals to dive to such depths and remain underwater for up to two hours.

Lifespan

Female elephant seals have an average life expectancy of about 23 years, and can give birth starting at the age of four to five. Males reach maturity at five years, but generally do not achieve alpha status until the age of eight, with the prime breeding years being between ages 9 and 12. The average life expectancy of a male elephant seal is 20 years. Only one in 10 males will become an alpha or beta male.

Gallery

See also

  • Marine Mammal Center
  • Penelope Seal
  • Marine Life

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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