• Northern elephant seal
  (Mirounga angustirostris)
• Southern elephant seal
  (Mirounga leonina)

Appearance

There is a marked sexual dimorphism in this species. Males can be as large as 450 cm and weigh 1,800-2,700 kg. Females can be 360 cm long and weigh 900 kg. At birth, male pups are 153 cm long and weigh 36 kg and female pups are 147 cm long and weigh 31.5 kg. Males have a pronounced proboscis and rugose, corrugated neck shields. The coat color is the same for males and females: dark grey to brown. Pups are born with black lanugo and become silvery after moult.

Distribution

The elephant seals can be found on offshore islands. The breeding range is from central Baja California to central California. Outside the breeding season they can travel north upto British Columbia. There are 10 known rookeries. The largest ones are: Islas San Benito, Isla de Guadalupe and San Miguel Island. The other rookeries are: Isla Cedros, Los Coronados, San Nicolas Island, Santa Barbara Island, Año Nuevo Island, Southeast Farallon Island and the Point Reyes peninsula.

Feeding

The elephant seal feeds on a wide variety of organisms, including skates, rays, sharks, squid, hake, shrimp, euphasiids, octopus, whiting and crab (Antonelis, Jr., et al, 1987)

Population dynamics and life history

Females reach maturity at the age of 3-5 years and males at 9-10 years. Gestation lasts 11.3 months, including a 3 month delay of implantation. The pregancy rate is 95%. Longevity is 14 years. Pup mortality is highly variable:

• Año Nuevo: 15-26%
• SE Farallon: 0-73%
• Los Coronados: 5-10%.

Trophic relations

There is probably no competition between the elephant seals and other pinnipeds, like the California sea lion, the Northern fur seal or the Pacific harbor seal, because the feed on different species and breed at other times. There is an increased competition for terrestial haul-out sites. There are some records of elephant seals attempting to mount harbor seal pups, killing them in the process (Mortenson and Follis, 1997). Possible predators are sharks and killer whales.

Interactions

Population size

The lowest count of this species was between 1884 and 1892: somewhere between 8 and 20 were left. Since then there has been an almost exponential increase, especially in the northern colonies. In 1957 there were 13,000 elephant seals, in 1976: 48,000. The population is still not at equilibrium (Boveng et al, 1988). In 1991, the total population was estimated at 127,000, with 28,164 pups born that year and there appears to be a 6% annual increase (Stewart et al, 1994)

Exploitation

After the population has been hunted to near extinction in the 19th century, there has been no exploitation of this species. The Northern elephant seal is protected in Mexico and the USA.

Threats to the population

Unknown. A lack of genetic diversity may cause problems in the future. It might make the population vulnerable to environmental changes.

References

Antonelis, Jr., G.A., Lowry, M.S., DeMaster, D.P., Fiscus, C.H. (1987)

Assessing Northern elephant seal feeding habits by stomach lavage. Mar. Mamm. Sci. 3(4): 308-322

Boveng, P., DeMaster, D.P., Stewart, B.S. (1988)

Dynamic response analysis. III. A consistency filter and application to four Northern elephant seal colonies. Mar. Mamm. Sci. 4(3): 210-220

DeMaster, D., Miller, D., Henderson, J.R., Coe, J.M. (1985)

Conflicts between marine mammals and fisheries off the coast of California. in: Beddington, J.R., Beverton, R.J.H. and Lavigne, D.M. (eds.): Marine Mammals and Fisheries, pp. 111-118, George Allen & Unwin (Publishers) Ltd, London

LeBoeuf, B.J. (1979)

Northern Elephant Seal. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 110-114

McGinnis, S.M., Schusterman, R.J. (1981)

Northern Elephant Seal, Mirounga angustirostris, Gill 1866. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 329-349, Academic Press Inc., Ltd, London

Mortenson, J. and Follis, M. (1997)

Northern elephant seal (Mirounga angustrirostris) aggression on harbor seal (Phoca vitulina) pups. Mar. Mamm. Sci. 13(3): 526-530

Stewart, B.S., Yochem, P.K., Huber, H.R., DeLong, R.L., Jameson, R.J., Sydeman, W.J., Allen, S.G. and LeBoeuf, B.J (1994)

History and present status of the northern elephant seal population, in: LeBoeuf, B.J. and Laws, R.M. (eds.): Elephant seals: Population ecology, behavior and physiology, University of California Press, Berkeley, pp.29-48

Nomenclature

Three subspecies have been proposed by Lydekker in 1909: Mirounga leonina falclandicus, Mirounga leonina macquariensis and Mirounga leonina crosetensis, but these are probably not valid and are certainly not commonly used. The Southern elephant seal is also referred to as the Southern sea elephant.

Appearance

There is a striking sexual dimorphism in this species, with respect to size and appearance. There are some size differences for the different populations. In the South Georgia population, the males are 450 cm and weigh 4,000 kg, females are 280 cm and weigh 900 kg and pups are 127 cm and weigh 46 kg. The seals from the Macquarie Islands are smaller: males are 420 cm and weigh 3,000 kg, females are 260 cm and weigh 400 kg and pups are 127 cm and weigh 40 kg. The elephant seal gets its name from the large proboscis of the males. The seals are dark grey with a lighter ventral side. Pups are born with a stiff black lanugo.

Distribution

The Southern elephant seal has a circumpolar distribution and can be found on beaches and in grasslands. There are three breeding stocks:

1. South Georgia (including the Falkland Islands and Continental South America)
2. Kerguelen and Heard
3. Macquarie Islands (including the New Zealand subantarctic islands)

Feeding

The elephant seal feeds on fish and cephalopods. They fast 2-3 months each year. When they feed, they consume about 6% of their body weight.

Population dynamics and life history

The population dynamics parameters differ slightly per stock. For the Macquarie stock, the age at maturity for females is 4-7 years and for males 5-6 years. For the South Georgia stock these values are for females: 2-3 years and for males 4 years. Gestation lasts 50 weeks, including a delay of implantation of 12 weeks. Longevity is at least 20 years, but it could be over 23 years (Hindell and Little, 1988).

The mortality rates for females are:

• age 0-1: 40%
• age 1-2: 20%
• age 2-10: 13%
• increasing with age to 100% at around 20 years.

• age 0-1: 57%
• age 1-2: 30%
• age 2-10: 17%
• increasing to 100% at around 20 years.

Trophic relations

There may be some competition with albatrosses, fish and sperm whales, but this is probably not significant. Leopard seals prey on pups and killer whales on adults.

Interactions

None. There have been suggestions that the decline of some stocks is related to an increase in fisheries, but this seems unlikely, because this increase did not occur in the regular feeding areas.

Population size

Most of the population estimates have been derived from pup counts.

1. South Georgia stock: 300,000 (Laws, 1979); in 1985-1986: 340,000 (Harwood and Croxall, 1988). This stock, in contrast to the other stocks, has been stabile or may even be increasing in size ( Hindell, Slip and Burton, 1994).
2. Kerguelen and Heard stock: 200,000 (Laws, 1979); 264,000 (Pascal, 1985). This stock has been declining at least until the mid 1980s ( Hindell, Slip and Burton, 1994)
3. Macquarie stock: 100,000 (Laws,1979). In 1985, this population was found to be declining at a rate of 2% per annum ( Hindell, Slip and Burton, 1994).
4. Total population: 600,000-700,000

Exploitation

None. The South Georgia stock has been exploited until 1964, but now all stocks are protected.

Threats to the population

None.

References

Bonner, W.N. (1982)

Seals and Man. A study of interactions. University of Washington Press, Seattle, 170pp.

Harwood, J., Croxall, J.P. (1988)

The assessment of competition between seals and commercial fisheries in the North Sea and the Antarctic. Mar. Mamm. Sci. 4(1): 13-33

Hindell, M.A., Little, G.J. (1988)

Longevity, fertility and philopatry of two female Southern elephant seals (Mirounga leonina) at Macquarie Island. Mar. Mamm. Sci. 4(2): 168-171

Hindell, M.A., Slip, D.J. and Burton, H.R. (1994)

Possible causes of the decline of the southern elephant seal populations in the Southern Pacific and Southern Indian Oceans, in: LeBoeuf, B.J. and Laws, R.M. (eds.): Elephant seals: Population ecology, behavior and physiology, University of California Press, Berkeley, pp. 66-84

Laws, R.M. (1979)

Southern Elephant Seal. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 106-109

Ling, J.K., Bryden, M.M. (1981)

Southern Elephant Seal, Mirounga leonina, Linnaeus, 1758. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 297-327, Academic Press Inc., Ltd, London

Pascal, M. (1985)

Numerical changes in the population of elephant seals (Mirounga leonina L.) in the Kerguelen Archipelago during the past 30 years. in: Beddington, J.R., Beverton, R.J.H. and Lavigne, D.M. (eds.): Marine Mammals and Fisheries, pp. 170-186, George Allen & Unwin (Publishers) Ltd, London

Back to the Phocid Seal Page

Back to the Main Page