|Scientific Name:||Mirounga angustirostris|
|Species Authority:||(Gill, 1866)|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Campagna, C. (IUCN SSC Pinniped Specialist Group)|
|Reviewer(s):||Kovacs, K. & Lowry, L. (Pinniped Red List Authority)|
The Northern Elephant Seal has recovered from near extinction and population growth is expected to continue over the coming decades. Due to its large and increasing population, expanding range and lack of foreseeable threats, the northern elephant seal should be classified as Least Concern.
IUCN Evaluation of the Northern Elephant Seal, Mirounga angustirostris
Prepared by the Pinniped Specialist Group
A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
The current population is ~170,000 and growing. The population is renowned for its remarkable growth during the 20th century, following virtual annihilation by sealers in the 19th century. In 2005, 42,589 pups were counted, an increase of 14,699 (53%) over the number observed in 1991. Total population size increased at a rate of 3% from 1991 to 2005.
A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
The total population of this species is probably expanding.
A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under Al.
A population reduction is not suspected, although the species is susceptible to El Niño and climate warming may increase its effects.
A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
A population reduction to negligible numbers was observed in the past due to hunting by sealers. Hunting stopped and the population recovered, thus the criteria do not apply.
B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²
The EOO (distribution of colonies) is > 20,000 km². The EOO at sea of foraging individuals is much larger than that.
B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²
The AOO (distribution of colonies) is > 2,000 km². The AOO at sea of foraging individuals is much larger than that.
AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.
Does not apply for the species.
C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000
Population size is larger than the criteria and is not declining.
AND either C1 or C2:
C1. An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
(a ii) % individuals in one subpopulation: CR = 90–100%; EN = 95–100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.
Does not apply to the species.
D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5
Most populations are larger than the criteria and are widely distributed.
E. Quantitative analysis
Indicating the probability of extinction in the wild to be: Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years
There has been no quantitative analysis of the probability of extinction. Climate change may impact the population to the point that the probability of extinction may be important but the quantitative value is unknown.
Listing recommendation — The Northern Elephant Seal is increasing and currently expanding its range. Despite past population reductions, this species should now be classified as Least Concern.
|Range Description:||Northern elephant seals are found in the eastern and north central North Pacific. Breeding takes place on offshore islands and at a few mainland localities from central Baja California to Northern California. The species breeds at over fifteen discrete locations, of which a dozen are well-known and distributed mostly in islands of southern California (USA) and Baja California (Mexico) (Condit et al. in press). A few pups are born in Oregon, Washington and southern British Columbia. Año Nuevo, in Central California, is a major breeding site.
Northern elephant seals migrate to and from their rookeries twice a year, returning once to breed from December to March and again later for several weeks to molt, at different times depending on sex and age. They also show up at additional coastal sites as far north as southern Oregon for moulting. Their post-breeding and post-moult migrations take most seals north and west to oceanic areas of the North Pacific and Gulf of Alaska twice a year. Adult males tend to travel further north and west than adult females. Wanderers have been found as far away as Japan and the Midway Islands.
Native:Canada; Mexico; United States
|FAO Marine Fishing Areas:||
Pacific – eastern central; Pacific – northeast; Pacific – northwest
|Range Map:||Click here to open the map viewer and explore range.|
The northern elephant seal population continues to expand rapidly (R. Condit et al. in press). In 2005, 42,589 pups were counted, an increase of 14,699 (53%) over the number observed in 1991. Based on pup production, total population size in 2005 was estimated to be 171,000, compared to 113,000 in 1991. This is a mean annual growth rate of 3.0% yr1. In 1977, fewer than 14,000 pups were born (Stewart et al. 1994), so annual growth from 1977 to 1991 was 5.2% yr-1.
Population growth was due primarily to growth at colonies in southern California. Three colonies accounted for 88.2% of the growth in pups produced: increases in pup production of 5,683 for San Nicolas Island, 4,096 for Santa Rosa Island and 3,459 for Piedras Blancas.
|Habitat and Ecology:||
Northern elephant seals are huge and imposing animals. Significant sexual dimorphism exists in size and secondary sexual characteristics. Males are three to four times heavier, and nearly 1.5 times the length of adult females. Adult males reach 4.2 m in length and a maximum weight of 2,500 kg. Mean length for males is 3.85 m and mean weight is 1,844 kg. Maximum weight is seen when the bulls are newly arrived for the breeding season after a summer and fall largely spent feeding.
The mean length of adult females is 2.65 m, and they can reach a length of 2.82 m. Mean mass is 488 kg, with a maximum recorded mass of 710 kg, both values are from shortly after females give birth. Newborn pups are about 1.25 m long and weigh 30-40 kg. Pups are born in a long woolly black lanugo coat that is shed without the epidermis starting at about 4-5 weeks and usually lasting several weeks until after the pup is weaned. After molting, the newly weaned juvenile’s coat is made up of short hairs like those found on adults and they are counter shaded dark gray above and silver gray below.
Body weight of adults fluctuates dramatically due to the demands of fasting during the breeding season. Adult females can lose almost half their mass during lactation, when they take their single pup from birth to weaning in approximately 25 days. The situation is similar for breeding males, which also lose about half their mass while ashore for periods that can exceed three months.
Females reach sexual maturity at the age of 2 years and males at 7-9 years. Gestation lasts 11.3 months, including a delay of implantation. The annual pregnancy rate of mature females is 95 %. Longevity is above 14 years for males and 21 years for females (Reijnders et al 1993).
Northern elephant seals are highly polygynous, but not strictly territorial. Males compete for access to females by ranking themselves in a hierarchy. There is much male-male fighting, vocalizing, and displaying during the breeding season, when bulls may be ashore for months at a time. One of the most impressive displays occurs when a male rears up on his hindquarters, thrusts one half to two-thirds of his body upward and produces a distinctive clap threat vocalization as a challenge to other bulls. The sound is a rolling, resonant, metallic-sounding series of backfire like sounds punctuated with pauses.
Females give birth within a few days of coming ashore, from late December to March. Females have a throaty sputtering growl, made with the mouth wide open, which is used as threat gesture. Females and pups have a warbling scream call that they use to call to each other, and in the case of the pup, to notify its mother when it is disturbed. Mother and pup form a strong bond immediately after birth, and females aggressively bite other pups that approach them, occasionally killing them with bites to the head. However, bulls are a greater source of pup mortality as they regularly crush pups when they charge through aggregations of mothers and pups to chase off or fight encroaching males, or when approaching females for mating. Occasionally, bulls suffocate pups by stopping on top of them and not moving again soon enough.
Northern elephant seals hold the record as the deepest-diving pinniped. Time-depth recording devices have documented dives to an astounding 1580 m by an adult male. They also have extreme breath holding ability and have been recorded to dive for as long as 77 minutes. Rest intervals at the surface are usually short, lasting only several minutes between routine dives that last 20-30 minutes and reach 300 to 800 m in depth. After leaving the rookeries, most of these seals spend 80-90% of their time underwater, helping explain why they are infrequently seen at sea.
During migration, females travel further west, but males travel further north. Most of the males go all the way up to the coast of Alaska and the Aleutians, while females move into the deep waters of the Pacific.
Fifty-three species of prey have been identified in the diet of northern elephant seals. More than half of these species are squid. Other prey includes various fishes, such as Pacific whiting, several species of rock fish, and a variety of small sharks and rays. They have also been reported to feed on pelagic red crabs. Approximately 70% of their prey comes from mid and deep water zones in open ocean habitat far offshore.
Great white sharks and killer whales are predators on northern elephant seals. Recent work at the Farallon Islands off of central California has revealed that large great white sharks aggregate around the islands in the fall when juvenile elephant seals return for their annual moult. Seals that swim at or near the surface as they are approaching or departing the islands are particularly vulnerable to ambush attacks by fast-rising sharks that patrol near the bottom in waters seven to ten meters deep.
The northern elephant seal was hunted to the brink of extinction in a surge of commercial exploitation in the late 1800s. Estimates are that as few as 20 animals survived the period of commercial harvesting. Fortunately, for the species, their pelagic nature and the fact that most seals spend 80% or more of their lives at sea, and that they all do all not return to their rookeries at the same time, ensured that enough seals were at sea to support continuation of the species when sealers undertook wholesale slaughters at rookery sites. Following a slow recovery in the early 1900s, northern elephant seals began to recolonize formerly used sites throughout the 1980s.
Incidental take in a variety of coastal net fisheries does occur, but at low levels. This is assumed to be because northern elephant seals move offshore rapidly after leaving colonies to minimize their risk of shark predation. Most of the prey of the northern elephant seal is either of low commercial value or minimally harvested in fisheries. If the population continues to expand there will likely be new rookeries on mainland beaches, and there will be additional challenges to keep conflicts with humans and domestic and feral animals to a minimum. The risk of transfer of diseases, such as morbillivirus from domestic animals to northern elephant seals, is unknown, but the species is considered to be one of several pinnipeds at high risk of disease outbreaks because of their rapidly expanding population and environmental changes associated with global warming (Lavigne and Schmitz 1990). Tourism at several mainland locations in the United States is extremely popular but highly regulated and is not considered a major threat to the species. Tourist access to nearly all of the islands occupied by elephant seals is controlled by law or otherwise regulated in the United States and Mexico, although a number of Mexican islands are inhabited either year round or most of the year by fishermen and their families.
As the species has now recovered from a very small number of survivors, it has likely lost a considerable amount of diversity from passing through this genetic bottleneck, and may now be at greater risk from disease outbreaks and environmental change.
|Conservation Actions:||Northern elephant seals are fully protected on their Mexican and US rookeries, and when they are within the 200 mile EEZ of the United States and Mexico.|
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Stewart, B. S. and Delong, R. L. 1990. Sexual differences in migrations and foraging behavior of northern elephant seals. American Zoology 30: 44.
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Stewart, B. S., Yochem, P. K., Huber, H. R., Delong, R. L., Jameson, R. J., Sydeman, W. J., Allen, S. G. and Le Boeuf, B. J. 1994. History and present status of the norther elephant seal population. In: B. J. Le Boeuf and R. M. Laws (eds), Elephant seals: Population ecology, behavior, and physiology, pp. 29-48. University of California Press.
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|Citation:||Campagna, C. (IUCN SSC Pinniped Specialist Group) 2008. Mirounga angustirostris. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 28 January 2015.|