T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Elephant seal (Southern) Mirounga leonine

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Clade: Pinnipedia
Family: Phocidae
Tribe: Miroungini
Genus: Mirounga
Species: Mirounga leonine
Common name: Southern elephant seal

Mirounga leonine is the largest species of seal in the world and are residents of New Zealand’s subantarctic islands. They range throughout the Southern Ocean around the Antarctic continent and on most sub-Antarctic islands. The New Zealand population is concentrated on the Antipodes Islands and on Campbell Island. In winter, they frequently visit the Auckland, Antipodes and Snares Islands, less often the Chatham Islands and in winter occasionally various mainland locations, from Stewart Island to the Bay of Islands.
They take their name from the large, inflatable proboscis of the adult male (bull), which resembles an elephant's trunk. This 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.
Southern elephant seal bulls typically reaching a length of 5 m and a weight of 3,000 kg and are much larger than the adult females (cows), with some exceptionally large males reaching up to 6 m in length and weighing 4,000 kg; cows typically measure about 3 m and 900 kg. 
Satellite tracking revealed the seals spend very little time on the surface, usually a few minutes for breathing. They dive repeatedly, each time for more than 20 minutes, to hunt their prey—squid and fish—at depths of 400 to 1,000 m. They are the deepest diving air-breathing non-cetaceans and have been recorded at a maximum of 2,133 m in depth. They are not particularly agile even in the water but can swim at speeds up to 20-25 km/h. They feed on animals such as squid, cuttlefish and large fish, including sharks.
Dives during the day tend to be much deeper than at night. Their high blood volume and oxygen capacity suggests they are capable of deep diving. Elephant seals are not particularly agile even in the water but can swim at speeds up to 20-25 km/h.
Breeding males arrive at rookeries in August, and pregnant females arrive in September and October. Males do not maintain territories but do establish dominance hierarchies structured primarily by age, secondarily by size, and to some extent, by previous experience. Males threaten each other visually and vocally. Males are sexually mature at 3-6 years, but few breed before they are 10 years old. Only the largest two or three males breed in a given year. Many males will never breed with 90% dying before reaching sexual maturity. Females are sexually mature at 2-4 years old and may then give birth annually for 12 years. Breeding males may mate with 100 females in a season.
Females give birth to a single pup shortly after coming ashore in September or October and will then remain ashore for the next 23 or so days nursing her pup. A few weeks later the females mate and then depart, abruptly weaning their pups. Females then remain at sea feeding for 70 days before coming ashore to moult. Pups remain ashore for a period of 50 days before finally going to sea to feed.
Life expectancy is approximately 23 for females and 20 for males.
Leopard seals occasionally attack and kill pups, and killer whales may prey on pups and older seals, though neither are believed to have any significant affect on the population.
Southern elephant seals were harvested for oil in the early 1800s after Antarctic fur seal numbers dropped. Numbers reduced dramatically and by 1900 sealing was no longer economically profitable. After a short period of recovery sealing was resumed but following management regulations from 1909 to 1964 when it was found to be no longer viable. Approximately 260,000 bull elephant seals were harvested from 1910 - 1965. Today, the main threat to elephant seals in New Zealand is harassment by humans or dogs while ashore. Seals usually haul out on land to rest, moult or breed and at these times they should be left undisturbed. It is also possible that elephant seals are affected by ship-strike and fishing mortality though little information exists on these impacts.

Warning: Southern elephant seals are better viewed from a safe distance; all seals can move surprisingly fast on land, and if annoyed can inflict serious bite wounds which become badly infected.

Southern elephant seal, Macquarie Is, Subantarctic
The two photos below are courtesy of Tamzin Henderson @ https://www.tamzinnz.com/
  

The green shading shows the Southern Elephant Seal (Mirounga leonina) range

Thanks to Wikipedia for text and information http://creativecommons.org/licenses/by-sa/3.0/

 


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