Northern Elephant Seal
Encyclopedia
The northern elephant seal (Mirounga angustirostris) is one of two species
of elephant seal
(the other is the southern elephant seal
). It is a member of the family
Phocidae ("true seals"). 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 competition. There is a great sexual dimorphism
in size. The males can grow to 14 ft (4 m) and 5000 lb (2,268 kg), while the females grow to 11 ft (3 m) and 1400 lb (635 kg). Correspondingly, there is a highly polygynous mating system, with a successful male able to impregnate up to 50 females in one season.
The eyes are large, round and black. The width of the eyes and a high concentration of low light pigments suggests that sight plays an important role in the capture of prey. Like all seals, elephant seals have atrophied hind limbs whose underdeveloped ends form the tail and tail fin. Each of the "feet" can deploy 5 long webbed fingers. This agile, dual palm is used to propel water. The pectoral fins are used little while swimming.
While the hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h) in this way for short-distance travel, to return to water, catch up with a female or chase an intruder.
Like other seals, elephant seals have a bloodstream adapted to the cold in which a mixture of small veins surrounds arteries capturing heat from them. This structure is present in extremities such as the hind legs.
. Feeding grounds extend from northern Baja California to northern Vancouver Island. Males migrate as far north as Alaska
and British Columbia
, while females migrate as far west as Hawaii
. They come ashore to breed, give birth and molt, mostly on offshore islands. While the pelagic range covers an enormous span, there are only about seven principal breeding areas, four of which are on islands off the coast of California. Recently increasing numbers have been observed in the Gulf of California
. Breeding colonies exist at Channel Islands
, Año Nuevo State Reserve
, Piedras Blancas Light
, Morro Bay State Park
and the Farallon Islands
in the US and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico. Some breeding has been observed at Castle Rock
in Northern California and Shell Island
off Oregon and in January, 2009 the first elephant seal births were recorded in British Columbia at Race Rocks
. The California breeding population is now demographically isolated from the population in Baja California.
The northern elephant seals are nocturnal deep feeders famous for the long time intervals they remain underwater. This species dives to great depths while feeding, typically between 300 m (984.3 ft) and 800 m (2,624.7 ft); moreover, the Northern elephant seal will generally not feed in depths of less than 200 m (656.2 ft). Both sexes eat a variety of prey including pelagic, deep water squid, Pacific hake
, sharks, rays, and ratfish
. Octopoteuthis deletron
squid are the most common prey item, found in the stomachs of 58% of individuals sampled off the coast of California. Elephant seals don't need to drink as they get their water from food and broken down fats.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; the bioluminescence
of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation
in the manner of cetaceans, but it is assumed that their vibrissae
, which are sensitive to vibrations, play a role in search of food. Males and females differ in both diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom, while females have more jagged routes and forage in the open ocean.
The northern elephant seal (Mirounga angustirostris) is one of two species
of elephant seal
(the other is the southern elephant seal
). It is a member of the family
Phocidae ("true seals"). 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 competition. There is a great sexual dimorphism
in size. The males can grow to 14 ft (4 m) and 5000 lb (2,268 kg), while the females grow to 11 ft (3 m) and 1400 lb (635 kg). Correspondingly, there is a highly polygynous mating system, with a successful male able to impregnate up to 50 females in one season.
The eyes are large, round and black. The width of the eyes and a high concentration of low light pigments suggests that sight plays an important role in the capture of prey. Like all seals, elephant seals have atrophied hind limbs whose underdeveloped ends form the tail and tail fin. Each of the "feet" can deploy 5 long webbed fingers. This agile, dual palm is used to propel water. The pectoral fins are used little while swimming.
While the hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h) in this way for short-distance travel, to return to water, catch up with a female or chase an intruder.
Like other seals, elephant seals have a bloodstream adapted to the cold in which a mixture of small veins surrounds arteries capturing heat from them. This structure is present in extremities such as the hind legs.
. Feeding grounds extend from northern Baja California to northern Vancouver Island. Males migrate as far north as Alaska
and British Columbia
, while females migrate as far west as Hawaii
. They come ashore to breed, give birth and molt, mostly on offshore islands. While the pelagic range covers an enormous span, there are only about seven principal breeding areas, four of which are on islands off the coast of California. Recently increasing numbers have been observed in the Gulf of California
. Breeding colonies exist at Channel Islands
, Año Nuevo State Reserve
, Piedras Blancas Light
, Morro Bay State Park
and the Farallon Islands
in the USU.S. Pacific Marine Mammal Stock Assessments: 2007 (NMFS-SWFSC-414). (PDF) . Retrieved on 2011-09-15. and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico. Some breeding has been observed at Castle Rock
in Northern California and Shell Island
off Oregon and in January, 2009 the first elephant seal births were recorded in British Columbia at Race Rocks
. The California breeding population is now demographically isolated from the population in Baja California.
The northern elephant seals are nocturnal deep feeders famous for the long time intervals they remain underwater. This species dives to great depths while feeding, typically between 300 m (984.3 ft) and 800 m (2,624.7 ft); moreover, the Northern elephant seal will generally not feed in depths of less than 200 m (656.2 ft). Both sexes eat a variety of prey including pelagic, deep water squid, Pacific hake
, sharks, rays, and ratfish
. Octopoteuthis deletron
squid are the most common prey item, found in the stomachs of 58% of individuals sampled off the coast of California. Elephant seals don't need to drink as they get their water from food and broken down fats.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; the bioluminescence
of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation
in the manner of cetaceans, but it is assumed that their vibrissae
, which are sensitive to vibrations, play a role in search of food. Males and females differ in both diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom, while females have more jagged routes and forage in the open ocean.
The northern elephant seal (Mirounga angustirostris) is one of two species
of elephant seal
(the other is the southern elephant seal
). It is a member of the family
Phocidae ("true seals"). 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 competition. There is a great sexual dimorphism
in size. The males can grow to 14 ft (4 m) and 5000 lb (2,268 kg), while the females grow to 11 ft (3 m) and 1400 lb (635 kg). Correspondingly, there is a highly polygynous mating system, with a successful male able to impregnate up to 50 females in one season.
The eyes are large, round and black. The width of the eyes and a high concentration of low light pigments suggests that sight plays an important role in the capture of prey. Like all seals, elephant seals have atrophied hind limbs whose underdeveloped ends form the tail and tail fin. Each of the "feet" can deploy 5 long webbed fingers. This agile, dual palm is used to propel water. The pectoral fins are used little while swimming.
While the hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h) in this way for short-distance travel, to return to water, catch up with a female or chase an intruder.
Like other seals, elephant seals have a bloodstream adapted to the cold in which a mixture of small veins surrounds arteries capturing heat from them. This structure is present in extremities such as the hind legs.
. Feeding grounds extend from northern Baja California to northern Vancouver Island. Males migrate as far north as Alaska
and British Columbia
, while females migrate as far west as Hawaii
. They come ashore to breed, give birth and molt, mostly on offshore islands. While the pelagic range covers an enormous span, there are only about seven principal breeding areas, four of which are on islands off the coast of California. Recently increasing numbers have been observed in the Gulf of California
. Breeding colonies exist at Channel Islands
, Año Nuevo State Reserve
, Piedras Blancas Light
, Morro Bay State Park
and the Farallon Islands
in the USU.S. Pacific Marine Mammal Stock Assessments: 2007 (NMFS-SWFSC-414). (PDF) . Retrieved on 2011-09-15. and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico. Some breeding has been observed at Castle Rock
in Northern California and Shell Island
off Oregon and in January, 2009 the first elephant seal births were recorded in British Columbia at Race Rocks
. The California breeding population is now demographically isolated from the population in Baja California.
The northern elephant seals are nocturnal deep feeders famous for the long time intervals they remain underwater. This species dives to great depths while feeding, typically between 300 m (984.3 ft) and 800 m (2,624.7 ft); moreover, the Northern elephant seal will generally not feed in depths of less than 200 m (656.2 ft). Both sexes eat a variety of prey including pelagic, deep water squid, Pacific hake
, sharks, rays, and ratfish
. Octopoteuthis deletron
squid are the most common prey item, found in the stomachs of 58% of individuals sampled off the coast of California. Elephant seals don't need to drink as they get their water from food and broken down fats.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; the bioluminescence
of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation
in the manner of cetaceans, but it is assumed that their vibrissae
, which are sensitive to vibrations, play a role in search of food. Males and females differ in both diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom, while females have more jagged routes and forage in the open ocean. Males return to the same feeding ground every year while female have less predictable feeding migrations. Elephant seals are preyed on by orca
s and white sharks. Both are most likely to hunt pups and seldom hunt large bull elephant seals but have taken seals of all ages. The shark, when hunting adults, is most likely to ambush a seal with a damaging bite and wait to finish the kill until it is weakened by blood loss.
in December and January, with the bulls arriving first. The bulls haul out on isolated or otherwise protected beaches typically on islands or very remote mainland locations. It is important that these beach areas offer protection from the winter storms and high surf wave action. The bulls engage in fights of supremacy to determine which few bulls will achieve a harem.
After the males have arrived the beach, the females arrive to give birth. Females fast for 5 weeks and nurse their single pup for 4 weeks; in last few days of lactation, females come into estrus and mate. In this polygynous society, a high-ranking bull will typically have a harem
of 30–100 cows depending on the size and strength of the bull. Low ranking males are kept out of the harems but will try to copulate with females on the periphery or in the water with females that are leaving. Dominant bulls will prevent lower ranking bulls from mounting cows and disrupt their copulations. Both a male's freedom to be able to copulate without inference and how often it can interfere with the copulation of others depends how high it is in the dominance hierarchy
. However, dominant males commonly break off a copulation to chase off rivals. While fights are not usually to the death, they are brutal and often with significant bloodshed and injury; however, in many cases of mismatched opponents, the younger, less capable males are simply chased away, often to upland dunes. In a lifetime a successful bull could easily sire over 500 pups. The majority of copulations in a breeding colony are done by only a few males with less than one third of the bulls being able to mate with a female. Pups are sometimes crushed during battles between bulls.
After arrival on shore males fast for three months, and females fast for five weeks during mating and when nursing of their pups. The gestation period is approximately eleven months. Sometimes, a female can become very aggressive after giving birth and will defend her pup from other females. Such aggression is more common in crowded beaches. While most females nurse their own pup and reject nursings from alien pups, some do accept alien pups with their own. An orphaned pup may try to find another female to suckle and are commonly adopted at least on Año Nuevo island. Pups nurse about four weeks and are weaned abruptly approximately two months before being abandoned by their mother. Left alone weaned pups will gather into groups and stay on shore for 12 more weeks. The pups learn how to swim in the surf and eventually swim farther to forage. Thus their first long journey at sea begins.
, and the population may have fallen as low as 20. In 1874 Charles Melville Scammon recorded in "Marine Mammals of the Northwestern Coast of America," that a eighteen feet-long bull caught on Santa Barbara Island
yielded 210 gallons of oil. They were thought to be extinct in 1884 until a remnant population of eight individuals was discovered on Guadalupe Island
in 1892 by a Smithsonian
expedition, who promptly killed seven of the eight for their collections. The elephant seals managed to survive, and were finally protected by the Mexican government in 1922. Since the early 20th century, they have been protected by law in both Mexico and in the United States
. Subsequently the U.S. protection was strengthened after passage of the Marine Mammal Protection Act
, and numbers have now recovered to over 100,000.
Nevertheless, there is a genetic bottleneck in the existing population, which could make it more susceptible to disease and pollution In California, the population is continuing to grow at around 25% per year, and new colonies are being established; they are now probably limited mostly by the availability of haulout
space. However, numbers can be adversely affected by El Niño events and the resultant weather conditions, and the 1997–98 El Niño may have caused the loss of about 80% of that year's pups. Presently the northern elephant seal is protected under the Federal Marine Mammal Act and under California law has a fully protected status.
Populations of rookery sites in California have increased during the past century. At Año Nuevo State Park, for example, there were no individuals observed whatsoever until the 1950s; the first pup born there was observed in the early 1960s. Currently, thousands of pups are born every year at Año Nuevo, on both the island and mainland. The growth of the site near San Simeon has proved even more spectacular; there were no animals there prior to 1990. Currently, the San Simeon site hosts more breeding animals than Año Nuevo State Park during winter season.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of elephant seal
Elephant seal
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...
(the other is 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...
). It is a member of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Phocidae ("true seals"). Elephant seals derive their name from their great size and from the male's 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:...
, which is used in making extraordinarily loud roaring noises, especially during the mating competition. There is a great sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in size. The males can grow to 14 ft (4 m) and 5000 lb (2,268 kg), while the females grow to 11 ft (3 m) and 1400 lb (635 kg). Correspondingly, there is a highly polygynous mating system, with a successful male able to impregnate up to 50 females in one season.
Description
The much larger male northern elephant seal typically weighs 1,500–2,300 kg (3,300–5,100 lbs) and measures 4–5 m (13.2–16.5 ft), although some males can weigh up to 3,700 kg (8,152 lbs). Females can range from 400 to 900 kg (990-2,000 lbs) and measure from 2.5 to 3.6 m (8.2–11.9 ft). Both adult and juvenile elephant seals are bar-skinned and black before molting. After molting they generally have a silver to dark gray coat that fades to brown yellow and tan. Adult males have hairless necks and chests speckled with pink, white and light brown. Pups are mostly black at birth and molt to a silver gray after weaning.The eyes are large, round and black. The width of the eyes and a high concentration of low light pigments suggests that sight plays an important role in the capture of prey. Like all seals, elephant seals have atrophied hind limbs whose underdeveloped ends form the tail and tail fin. Each of the "feet" can deploy 5 long webbed fingers. This agile, dual palm is used to propel water. The pectoral fins are used little while swimming.
While the hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h) in this way for short-distance travel, to return to water, catch up with a female or chase an intruder.
Like other seals, elephant seals have a bloodstream adapted to the cold in which a mixture of small veins surrounds arteries capturing heat from them. This structure is present in extremities such as the hind legs.
Range and ecology
The northern elephant seal lives in the Eastern Pacific OceanPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. Feeding grounds extend from northern Baja California to northern Vancouver Island. Males migrate as far north as Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
and British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, while females migrate as far west as Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
. They come ashore to breed, give birth and molt, mostly on offshore islands. While the pelagic range covers an enormous span, there are only about seven principal breeding areas, four of which are on islands off the coast of California. Recently increasing numbers have been observed in the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
. Breeding colonies exist at Channel Islands
Channel Islands of California
The Channel Islands of California are a chain of eight islands located in the Pacific Ocean off the coast of Southern California along the Santa Barbara Channel in the United States of America...
, Año Nuevo State Reserve
Año Nuevo State Reserve
Año Nuevo State Park is a state park of California, USA, encompassing Año Nuevo Island and Año Nuevo Point, which are known for their pinniped rookeries. Located in San Mateo County, the low, rocky, windswept point juts out into the Pacific Ocean about south of San Francisco and the Golden Gate...
, Piedras Blancas Light
Piedras Blancas Light
Piedras Blancas Light Station is a lighthouse on Point Piedras Blancas, about five and half miles west by NW of San Simeon, California.-History:...
, Morro Bay State Park
Morro Bay State Park
Morro Bay State Park is a state park in Morro Bay, in western San Luis Obispo County, California. On the bay’s northeastern edge, there is a saltwater marsh that supports a thriving bird population. -Recreation:...
and the Farallon Islands
Farallon Islands
The Farallon Islands, or Farallones , are a group of islands and sea stacks in the Gulf of the Farallones, off the coast of San Francisco, California, USA. They lie outside the Golden Gate and south of Point Reyes, and are visible from the mainland on clear days...
in the US and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico. Some breeding has been observed at Castle Rock
Castle Rock National Wildlife Refuge
Castle Rock National Wildlife Refuge is half a mile offshore from Crescent City in northern California. This coastal rock covers approximately , and rises steeply above sea level. The refuge provides an important sanctuary for Aleutian Canada geese and nesting seabirds.It is, in fact, known as the...
in Northern California and Shell Island
Cape Arago State Park
Cape Arago State Park is a state park in the U.S. state of Oregon, administered by the Oregon Parks and Recreation Department....
off Oregon and in January, 2009 the first elephant seal births were recorded in British Columbia 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...
. The California breeding population is now demographically isolated from the population in Baja California.
North Pacific hake
The North Pacific hake, Pacific hake, or Pacific whiting, Merluccius productus, is a merluccid hake of the genus Merluccius, found in the north east Pacific Ocean from northern Vancouver Island to the northern part of the Gulf of California....
, sharks, rays, and ratfish
Chimaera
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish , spookfish , or rabbitfishes...
. Octopoteuthis deletron
Octopoteuthis deletron
Octopoteuthis deletron is a species of squid in the genus Octopoteuthis. Found at depths of 400 to 800 m in the Pacific Ocean, they grow to at least 24 cm. Males find it difficult to detect the gender of other individuals they encounter in the dark depths, so they have adopted a strategy of...
squid are the most common prey item, found in the stomachs of 58% of individuals sampled off the coast of California. Elephant seals don't need to drink as they get their water from food and broken down fats.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; the bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
in the manner of cetaceans, but it is assumed that their vibrissae
Vibrissae
Vibrissae , or whiskers, are specialized hairs usually employed for tactile sensation. The term may also refer to the thick hairs found inside human nostrils, but these have no sensorial function and only operate as an airborne particulate barrier...
, which are sensitive to vibrations, play a role in search of food. Males and females differ in both diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom, while females have more jagged routes and forage in the open ocean.
The northern elephant seal (Mirounga angustirostris) is one of two species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of elephant seal
Elephant seal
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...
(the other is 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...
). It is a member of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Phocidae ("true seals"). Elephant seals derive their name from their great size and from the male's 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:...
, which is used in making extraordinarily loud roaring noises, especially during the mating competition. There is a great sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in size. The males can grow to 14 ft (4 m) and 5000 lb (2,268 kg), while the females grow to 11 ft (3 m) and 1400 lb (635 kg). Correspondingly, there is a highly polygynous mating system, with a successful male able to impregnate up to 50 females in one season.
Description
The much larger male northern elephant seal typically weighs 1,500–2,300 kg (3,300–5,100 lbs) and measures 4–5 m (13.2–16.5 ft), although some males can weigh up to 3,700 kg (8,152 lbs). Females can range from 400 to 900 kg (990-2,000 lbs) and measure from 2.5 to 3.6 m (8.2–11.9 ft). Both adult and juvenile elephant seals are bar-skinned and black before molting. After molting they generally have a silver to dark gray coat that fades to brown yellow and tan. Adult males have hairless necks and chests speckled with pink, white and light brown. Pups are mostly black at birth and molt to a silver gray after weaning.The eyes are large, round and black. The width of the eyes and a high concentration of low light pigments suggests that sight plays an important role in the capture of prey. Like all seals, elephant seals have atrophied hind limbs whose underdeveloped ends form the tail and tail fin. Each of the "feet" can deploy 5 long webbed fingers. This agile, dual palm is used to propel water. The pectoral fins are used little while swimming.
While the hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h) in this way for short-distance travel, to return to water, catch up with a female or chase an intruder.
Like other seals, elephant seals have a bloodstream adapted to the cold in which a mixture of small veins surrounds arteries capturing heat from them. This structure is present in extremities such as the hind legs.
Range and ecology
The northern elephant seal lives in the Eastern Pacific OceanPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. Feeding grounds extend from northern Baja California to northern Vancouver Island. Males migrate as far north as Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
and British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, while females migrate as far west as Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
. They come ashore to breed, give birth and molt, mostly on offshore islands. While the pelagic range covers an enormous span, there are only about seven principal breeding areas, four of which are on islands off the coast of California. Recently increasing numbers have been observed in the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
. Breeding colonies exist at Channel Islands
Channel Islands of California
The Channel Islands of California are a chain of eight islands located in the Pacific Ocean off the coast of Southern California along the Santa Barbara Channel in the United States of America...
, Año Nuevo State Reserve
Año Nuevo State Reserve
Año Nuevo State Park is a state park of California, USA, encompassing Año Nuevo Island and Año Nuevo Point, which are known for their pinniped rookeries. Located in San Mateo County, the low, rocky, windswept point juts out into the Pacific Ocean about south of San Francisco and the Golden Gate...
, Piedras Blancas Light
Piedras Blancas Light
Piedras Blancas Light Station is a lighthouse on Point Piedras Blancas, about five and half miles west by NW of San Simeon, California.-History:...
, Morro Bay State Park
Morro Bay State Park
Morro Bay State Park is a state park in Morro Bay, in western San Luis Obispo County, California. On the bay’s northeastern edge, there is a saltwater marsh that supports a thriving bird population. -Recreation:...
and the Farallon Islands
Farallon Islands
The Farallon Islands, or Farallones , are a group of islands and sea stacks in the Gulf of the Farallones, off the coast of San Francisco, California, USA. They lie outside the Golden Gate and south of Point Reyes, and are visible from the mainland on clear days...
in the USU.S. Pacific Marine Mammal Stock Assessments: 2007 (NMFS-SWFSC-414). (PDF) . Retrieved on 2011-09-15. and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico. Some breeding has been observed at Castle Rock
Castle Rock National Wildlife Refuge
Castle Rock National Wildlife Refuge is half a mile offshore from Crescent City in northern California. This coastal rock covers approximately , and rises steeply above sea level. The refuge provides an important sanctuary for Aleutian Canada geese and nesting seabirds.It is, in fact, known as the...
in Northern California and Shell Island
Cape Arago State Park
Cape Arago State Park is a state park in the U.S. state of Oregon, administered by the Oregon Parks and Recreation Department....
off Oregon and in January, 2009 the first elephant seal births were recorded in British Columbia 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...
. The California breeding population is now demographically isolated from the population in Baja California.
North Pacific hake
The North Pacific hake, Pacific hake, or Pacific whiting, Merluccius productus, is a merluccid hake of the genus Merluccius, found in the north east Pacific Ocean from northern Vancouver Island to the northern part of the Gulf of California....
, sharks, rays, and ratfish
Chimaera
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish , spookfish , or rabbitfishes...
. Octopoteuthis deletron
Octopoteuthis deletron
Octopoteuthis deletron is a species of squid in the genus Octopoteuthis. Found at depths of 400 to 800 m in the Pacific Ocean, they grow to at least 24 cm. Males find it difficult to detect the gender of other individuals they encounter in the dark depths, so they have adopted a strategy of...
squid are the most common prey item, found in the stomachs of 58% of individuals sampled off the coast of California. Elephant seals don't need to drink as they get their water from food and broken down fats.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; the bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
in the manner of cetaceans, but it is assumed that their vibrissae
Vibrissae
Vibrissae , or whiskers, are specialized hairs usually employed for tactile sensation. The term may also refer to the thick hairs found inside human nostrils, but these have no sensorial function and only operate as an airborne particulate barrier...
, which are sensitive to vibrations, play a role in search of food. Males and females differ in both diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom, while females have more jagged routes and forage in the open ocean.
The northern elephant seal (Mirounga angustirostris) is one of two species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of elephant seal
Elephant seal
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...
(the other is 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...
). It is a member of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Phocidae ("true seals"). Elephant seals derive their name from their great size and from the male's 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:...
, which is used in making extraordinarily loud roaring noises, especially during the mating competition. There is a great sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in size. The males can grow to 14 ft (4 m) and 5000 lb (2,268 kg), while the females grow to 11 ft (3 m) and 1400 lb (635 kg). Correspondingly, there is a highly polygynous mating system, with a successful male able to impregnate up to 50 females in one season.
Description
The much larger male northern elephant seal typically weighs 1,500–2,300 kg (3,300–5,100 lbs) and measures 4–5 m (13.2–16.5 ft), although some males can weigh up to 3,700 kg (8,152 lbs). Females can range from 400 to 900 kg (990-2,000 lbs) and measure from 2.5 to 3.6 m (8.2–11.9 ft). Both adult and juvenile elephant seals are bar-skinned and black before molting. After molting they generally have a silver to dark gray coat that fades to brown yellow and tan. Adult males have hairless necks and chests speckled with pink, white and light brown. Pups are mostly black at birth and molt to a silver gray after weaning.The eyes are large, round and black. The width of the eyes and a high concentration of low light pigments suggests that sight plays an important role in the capture of prey. Like all seals, elephant seals have atrophied hind limbs whose underdeveloped ends form the tail and tail fin. Each of the "feet" can deploy 5 long webbed fingers. This agile, dual palm is used to propel water. The pectoral fins are used little while swimming.
While the hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h) in this way for short-distance travel, to return to water, catch up with a female or chase an intruder.
Like other seals, elephant seals have a bloodstream adapted to the cold in which a mixture of small veins surrounds arteries capturing heat from them. This structure is present in extremities such as the hind legs.
Range and ecology
The northern elephant seal lives in the Eastern Pacific OceanPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. Feeding grounds extend from northern Baja California to northern Vancouver Island. Males migrate as far north as Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
and British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, while females migrate as far west as Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
. They come ashore to breed, give birth and molt, mostly on offshore islands. While the pelagic range covers an enormous span, there are only about seven principal breeding areas, four of which are on islands off the coast of California. Recently increasing numbers have been observed in the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
. Breeding colonies exist at Channel Islands
Channel Islands of California
The Channel Islands of California are a chain of eight islands located in the Pacific Ocean off the coast of Southern California along the Santa Barbara Channel in the United States of America...
, Año Nuevo State Reserve
Año Nuevo State Reserve
Año Nuevo State Park is a state park of California, USA, encompassing Año Nuevo Island and Año Nuevo Point, which are known for their pinniped rookeries. Located in San Mateo County, the low, rocky, windswept point juts out into the Pacific Ocean about south of San Francisco and the Golden Gate...
, Piedras Blancas Light
Piedras Blancas Light
Piedras Blancas Light Station is a lighthouse on Point Piedras Blancas, about five and half miles west by NW of San Simeon, California.-History:...
, Morro Bay State Park
Morro Bay State Park
Morro Bay State Park is a state park in Morro Bay, in western San Luis Obispo County, California. On the bay’s northeastern edge, there is a saltwater marsh that supports a thriving bird population. -Recreation:...
and the Farallon Islands
Farallon Islands
The Farallon Islands, or Farallones , are a group of islands and sea stacks in the Gulf of the Farallones, off the coast of San Francisco, California, USA. They lie outside the Golden Gate and south of Point Reyes, and are visible from the mainland on clear days...
in the USU.S. Pacific Marine Mammal Stock Assessments: 2007 (NMFS-SWFSC-414). (PDF) . Retrieved on 2011-09-15. and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico. Some breeding has been observed at Castle Rock
Castle Rock National Wildlife Refuge
Castle Rock National Wildlife Refuge is half a mile offshore from Crescent City in northern California. This coastal rock covers approximately , and rises steeply above sea level. The refuge provides an important sanctuary for Aleutian Canada geese and nesting seabirds.It is, in fact, known as the...
in Northern California and Shell Island
Cape Arago State Park
Cape Arago State Park is a state park in the U.S. state of Oregon, administered by the Oregon Parks and Recreation Department....
off Oregon and in January, 2009 the first elephant seal births were recorded in British Columbia 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...
. The California breeding population is now demographically isolated from the population in Baja California.
North Pacific hake
The North Pacific hake, Pacific hake, or Pacific whiting, Merluccius productus, is a merluccid hake of the genus Merluccius, found in the north east Pacific Ocean from northern Vancouver Island to the northern part of the Gulf of California....
, sharks, rays, and ratfish
Chimaera
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish , spookfish , or rabbitfishes...
. Octopoteuthis deletron
Octopoteuthis deletron
Octopoteuthis deletron is a species of squid in the genus Octopoteuthis. Found at depths of 400 to 800 m in the Pacific Ocean, they grow to at least 24 cm. Males find it difficult to detect the gender of other individuals they encounter in the dark depths, so they have adopted a strategy of...
squid are the most common prey item, found in the stomachs of 58% of individuals sampled off the coast of California. Elephant seals don't need to drink as they get their water from food and broken down fats.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; the bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
in the manner of cetaceans, but it is assumed that their vibrissae
Vibrissae
Vibrissae , or whiskers, are specialized hairs usually employed for tactile sensation. The term may also refer to the thick hairs found inside human nostrils, but these have no sensorial function and only operate as an airborne particulate barrier...
, which are sensitive to vibrations, play a role in search of food. Males and females differ in both diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom, while females have more jagged routes and forage in the open ocean. Males return to the same feeding ground every year while female have less predictable feeding migrations. Elephant seals are preyed on by orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
s and white sharks. Both are most likely to hunt pups and seldom hunt large bull elephant seals but have taken seals of all ages. The shark, when hunting adults, is most likely to ambush a seal with a damaging bite and wait to finish the kill until it is weakened by blood loss.
Social behavior and reproduction
The Northern elephant seal returns to its terrestrial breeding groundHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
in December and January, with the bulls arriving first. The bulls haul out on isolated or otherwise protected beaches typically on islands or very remote mainland locations. It is important that these beach areas offer protection from the winter storms and high surf wave action. The bulls engage in fights of supremacy to determine which few bulls will achieve a harem.
After the males have arrived the beach, the females arrive to give birth. Females fast for 5 weeks and nurse their single pup for 4 weeks; in last few days of lactation, females come into estrus and mate. In this polygynous society, a high-ranking bull will typically have a harem
Harem
Harem refers to the sphere of women in what is usually a polygynous household and their enclosed quarters which are forbidden to men...
of 30–100 cows depending on the size and strength of the bull. Low ranking males are kept out of the harems but will try to copulate with females on the periphery or in the water with females that are leaving. Dominant bulls will prevent lower ranking bulls from mounting cows and disrupt their copulations. Both a male's freedom to be able to copulate without inference and how often it can interfere with the copulation of others depends how high it is in the dominance hierarchy
Dominance hierarchy
A dominance hierarchy is the organization of individuals in a group that occurs when competition for resources leads to aggression...
. However, dominant males commonly break off a copulation to chase off rivals. While fights are not usually to the death, they are brutal and often with significant bloodshed and injury; however, in many cases of mismatched opponents, the younger, less capable males are simply chased away, often to upland dunes. In a lifetime a successful bull could easily sire over 500 pups. The majority of copulations in a breeding colony are done by only a few males with less than one third of the bulls being able to mate with a female. Pups are sometimes crushed during battles between bulls.
After arrival on shore males fast for three months, and females fast for five weeks during mating and when nursing of their pups. The gestation period is approximately eleven months. Sometimes, a female can become very aggressive after giving birth and will defend her pup from other females. Such aggression is more common in crowded beaches. While most females nurse their own pup and reject nursings from alien pups, some do accept alien pups with their own. An orphaned pup may try to find another female to suckle and are commonly adopted at least on Año Nuevo island. Pups nurse about four weeks and are weaned abruptly approximately two months before being abandoned by their mother. Left alone weaned pups will gather into groups and stay on shore for 12 more weeks. The pups learn how to swim in the surf and eventually swim farther to forage. Thus their first long journey at sea begins.
History and status
Beginning in the 18th century northern elephant seals were hunted extensively almost to extinction by the end of the 19th century, being prized for oil that could be made from their blubberBlubber
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...
, and the population may have fallen as low as 20. In 1874 Charles Melville Scammon recorded in "Marine Mammals of the Northwestern Coast of America," that a eighteen feet-long bull caught on Santa Barbara Island
Santa Barbara Island
Santa Barbara Island is a small island of the Channel Islands archipelago in California. It is located about off the Southern California coast from the Palos Verdes Peninsula, near Los Angeles in Ventura County, California....
yielded 210 gallons of oil. They were thought to be extinct in 1884 until a remnant population of eight individuals was discovered on Guadalupe Island
Guadalupe Island
Guadalupe Island, or Isla Guadalupe is a volcanic island located 241 kilometers off the west coast of Mexico's Baja California peninsula and some 400 kilometers southwest of the city of Ensenada in Baja California state, in the Pacific Ocean...
in 1892 by a Smithsonian
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...
expedition, who promptly killed seven of the eight for their collections. The elephant seals managed to survive, and were finally protected by the Mexican government in 1922. Since the early 20th century, they have been protected by law in both Mexico and in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Subsequently the U.S. protection was strengthened after passage of the Marine Mammal Protection Act
Marine Mammal Protection Act
The Marine Mammal Protection Act of 1972 was the first article of legislation to call specifically for an ecosystem approach to natural resource management and conservation. MMPA prohibits the taking of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal,...
, and numbers have now recovered to over 100,000.
Nevertheless, there is a genetic bottleneck in the existing population, which could make it more susceptible to disease and pollution In California, the population is continuing to grow at around 25% per year, and new colonies are being established; they are now probably limited mostly by the availability of haulout
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...
space. However, numbers can be adversely affected by El Niño events and the resultant weather conditions, and the 1997–98 El Niño may have caused the loss of about 80% of that year's pups. Presently the northern elephant seal is protected under the Federal Marine Mammal Act and under California law has a fully protected status.
Populations of rookery sites in California have increased during the past century. At Año Nuevo State Park, for example, there were no individuals observed whatsoever until the 1950s; the first pup born there was observed in the early 1960s. Currently, thousands of pups are born every year at Año Nuevo, on both the island and mainland. The growth of the site near San Simeon has proved even more spectacular; there were no animals there prior to 1990. Currently, the San Simeon site hosts more breeding animals than Año Nuevo State Park during winter season.