Elephant seals are large, oceangoing earless seals in the genus Mirounga. The two species, the northern elephant seal (M. angustirostris) and the southern elephant seal (M. leonina), were both hunted to the brink of extinction by the end of the 19th century, but the numbers have since recovered.
|Male and female northern elephant seals|
The northern elephant seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S., Canada and Mexico. The most northerly breeding location on the Pacific Coast is at Race Rocks, at the southern tip of Vancouver Island in the Strait of Juan de Fuca. The southern elephant seal is found in the Southern Hemisphere on islands such as South Georgia and Macquarie Island, and on the coasts of New Zealand, South Africa, and Argentina in the Peninsula Valdés, which is the fourth-largest elephant seal colony in the world. In southern Chile, there is a small colony of 120 animals at Jackson Bay, Admiralty Sound (Seno Almirantazgo), Tierra del Fuego. The oldest known unambiguous elephant seal fossils are fragmentary fossils of an unnamed member of the tribe Miroungini described from the late Pliocene Petane Formation of New Zealand. Teeth originally identified as representing an unnamed species of Mirounga have been found in South Africa, and dated to the Miocene epoch; however Boessenecker & Churchill (2016) considered these teeth to be almost certainly misidentified odontocete teeth.
Elephant seals breed annually and are seemingly faithful to colonies that have established breeding areas.
Elephant seals take their name from the large proboscis of the adult male (bull), which resembles an elephant's trunk. The bull's proboscis is used in producing extraordinarily loud roaring noises, especially during the mating season. More importantly, however, the nose acts as a sort of rebreather, filled with cavities designed to reabsorb moisture from their exhalations. This is important during the mating season when the seals do not leave the beach to feed, and must conserve body moisture as there is no incoming source of water. They are colossally large in comparison with other pinnipeds, with southern elephant seal bulls typically reaching a length of 5 m (16 ft) and a weight of 3,000 kg (6,600 lb), and are much larger than the adult females (cows), with some exceptionally large males reaching up to 6 m (20 ft) in length and weighing 4,000 kg (8,800 lb); cows typically measure about 3 m (10 ft) and 900 kg (2,000 lb). Northern elephant seal bulls reach a length of 4.3 to 4.8 m (14 to 16 ft) and the heaviest weigh about 2,500 kg (5,500 lb).
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 noncetacean mammal. Elephant seals dive to 1,550 m beneath the ocean's surface (the deepest recorded dive of an elephant seal is 2,388 m (7,835 ft) by a southern elephant seal). The average depth of their dives is about 300 to 600 m (980 to 1,970 ft), typically for around 20 minutes for females and 60 minutes for males, as they search for their favorite foods, which are skates, rays, squid, octopi, eels, small sharks and large fish. Their stomachs also often contain gastroliths. While excellent swimmers, they are also capable of rapid movement on land.
Elephant seals are shielded from extreme cold by their blubber, more so than by fur. Their hair and outer layers of skin molt in large patches. 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". Northern males and young adults haul out during June to July to molt; northern females and immature seals during April to May.
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 concentrations in muscle. In addition, they have a larger proportion of oxygen-carrying red blood cells. These adaptations allow elephant seals to dive to such depths and remain underwater for up to two hours.
Milk produced by elephant seals is remarkably high in milkfat compared to other mammals. After an initially lower state, it rises to over 50% milkfat (human breast milk is about 4% milkfat, and cow milk is about 3.5% milkfat).
The average lifespan of a Northern Elephant Seal is 9 years, while the average lifespan of a Southern Elephant Seal is 20-22 years. Males reach maturity at five to six 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 longest life expectancy of a male northern elephant seal is approximately 14 years.
Females begin breeding at age 3–6 (median=4), and have one pup per breeding attempt. Once they begin breeding, 79% of adult females breed each year. Breeding success is much lower for first-time mothers relative to experienced breeders. Annual survival probability of adult females is 0.83 for experienced breeding females, but only 0.66 for first-time breeders indicating a significant cost of reproduction. More male pups are produced than female pups in years with warmer sea surface temperature in the northeastern Pacific Ocean.
The IUCN lists both species of elephant seal as being of least concern, although they are still threatened by entanglement in marine debris, fishery interactions, and boat collisions. Though a complete population count of elephant seals is not possible because all age classes are not ashore at the same time, the most recent estimate of the California breeding stock was approximately 124,000 individuals. In the United States, the elephant seal, like all marine mammals, is protected under the Marine Mammal Protection Act (MMPA), passed in 1972, which outlaws hunting, killing, capture, and harassment of the animal.
Elephant seals (Mirounga angustirostris) on Piedras Blancas beach, near San Simeon, California
Northern elephant seals during molting season at Piedras Blancas beach, near San Simeon, California
Elephant seal snout
Beachmasters, the dominant bulls fighting at Macquarie Island
Elephant seals at Piedras Blancas, California
- "WCS Chile > Especies > Elefantes marinos". programs.wcs.org. Retrieved 2016-05-27.
- Boessenecker, RW; Churchill, M (2016). "The origin of elephant seals: implications of a fragmentary late Pliocene seal (Phocidae: Miroungini) from New Zealand". New Zealand Journal of Geology and Geophysics. 59 (4): 544–550. doi:10.1080/00288306.2016.1199437.
- Pickford, Martin; Senut, Brigitte (1997). "Cainozoic mammals from coastal Namaqualand, South Africa". Palaeontologia Africana. 34: 199–217.
- Berta, A.; Churchill, M. (2012). "Pinniped Taxonomy: evidence for species and subspecies". Mammal Review. 42 (3): 207–234. doi:10.1111/j.1365-2907.2011.00193.x.
- De Bruyn, Mark; Hall, Brenda L.; Chauke, Lucas F.; Baroni, Carlo; Koch, Paul L.; Hoelzel, A. Rus (2009). "Rapid Response of a Marine Mammal Species to Holocene Climate and Habitat Change". PLoS Genetics. 5 (7): e1000554. PMID 19593366. doi:10.1371/journal.pgen.1000554.
- Mirounga. "Elephant Seal, Elephant Seal Profile, Facts, Information, Photos, Pictures, Sounds, Habitats, Reports, News – National Geographic". Animals.nationalgeographic.com. Retrieved 2009-01-08.
- Huntley, A. C.; Costa, D. P.; Rubin, R. D. (1984). "The contribution of nasal countercurrent heat exchange to water balance in the northern elephant seal, Mirounga angustirostris". Journal of experimental biology. 113: 447–454.
- "Elephant Seals". Parks.ca.gov. 2007-05-23. Retrieved 2009-01-08.
- "Elephant Seal – MSN Encarta". Encarta.msn.com. Archived from the original on 2009-10-31. Retrieved 2009-12-29.
- Amos, Jonathan. "Elephant seals dive for science". 2006. BBC News. Retrieved 23 April 2013.
- "Southern Elephant Seals of Sea Lion Island – A Long-term Research Project" (PDF). www.eleseal.org. Retrieved 2010-05-21.
- "Census of Marine Life – From the Edge of Darkness to the Black Abyss" (PDF). Coml.org. Retrieved 2009-12-15.
- "5.4 Seals". Classroom Antarctica.
- "Northern Elephant Seal Fact Sheet" (PDF). Coastside State Parks Association. Archived from the original (PDF) on 13 May 2013. Retrieved 26 March 2013.
- Huber, Harriet R. (1987-06-01). "Natality and weaning success in relation to age of first reproduction in northern elephant seals". Canadian Journal of Zoology. 65 (6): 1311–1316. ISSN 0008-4301. doi:10.1139/z87-207.
- Lee, Derek E. (2011-06-09). "Effects of environmental variability and breeding experience on northern elephant seal demography". Journal of Mammalogy. 92 (3): 517–526. ISSN 0022-2372. doi:10.1644/10-MAMM-A-042.1.
- Lee, Derek E.; Sydeman, William J. (2009). "North Pacific Climate Mediates Offspring Sex Ratio in Northern Elephant Seals". Journal of Mammalogy. 90 (1). ISSN 0022-2372. doi:10.1644/08-MAMM-A-130.1.
- "NOAA's National Marine Fisheries Service – Northern Elephant Seal (Mirounga angustirostris)".
|Wikimedia Commons has media related to Mirounga.|