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Hydrurga leptonyx

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CARNIVORA PHOCIDAE

Scientific Name: Hydrurga leptonyx
Species Authority: (de Blainville, 1820)
Common Name(s):
English Leopard Seal

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Southwell, C. (IUCN SSC Pinniped Specialist Group)
Reviewer(s): Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Justification:
Due to its widespread occurrence and large population size, the Leopard Seal should remain classified as Least Concern.

IUCN Evaluation of the Leopard Seal, Hydrurga leptonyx
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.

Age-structure data for leopard seals are limited so the generation time cannot be calculated precisely. Sexual maturity thought to be attained at 4-5 years of age and a maximum longevity possibly up to 25 years, the average age of reproducing individuals should be at least 10 years. A population reduction of Leopard Seals has not been observed, estimated, inferred, or suspected in the past 30 years. However, population abundance is not precisely known and has not been closely monitored.

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.

A population reduction of Leopard Seals has not been observed, estimated, inferred, or suspected in the past 30 years.

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 A1.

A population reduction of Leopard Seals could occur some time in the future if sea ice habitats decline due to continued climate warming. However, while sea ice extent presently appears to be declining in western Antarctica, it may be increasing in eastern Antarctica, and overall there appears to be no change yet in the extent of Southern Ocean sea ice.

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 Al.

A population reduction of leopard seals has not been observed, estimated, inferred, or suspected in the past 30 years.

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 of Leopard Seals is > 20,000 km².

B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²

The AOO of Leopard Seals is > 2,000 km².

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.

C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000

The current abundance of Leopard Seals is certainly > 10,000.

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
or
(a ii) % individuals in one subpopulation: CR = 90–100%; EN = 95–100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.

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

The current abundance of Leopard Seals is certainly > 1,000. AOO is > 20 km² and the number of locations is > 5.

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 for Leopard Seals.

Listing recommendationThe most recent circumpolar estimate of leopard seal abundance indicates a total population size of 300,000. There is no indication of a declining trend in the population, although broad-scale estimates have considerable uncertainty around them, and consequently trend estimates are also uncertain. Leopard Seals depend on sea ice for reproduction and could be adversely affected by a reduction in sea ice due to continued climate warming at some time in the future. However, presently there appears to be no consistent circumpolar trend in Southern Ocean sea ice habitat. Leopard Seals are a widespread and abundant species that does not qualify for any of the threatened categories in the near future; they should be listed as Least Concern.

Geographic Range [top]

Range Description: Leopard seals are widely-distributed in Antarctic and sub-Antarctic waters of the southern Hemisphere, occurring from the coast of the Antarctic Continent north throughout the pack ice and at most sub-Antarctic islands. There is a seasonal presence of juveniles at Kerguelen and Macquarie Islands with the greater numbers being sighted in September and October (Borsa 1990, Rounseveld and Eberhard 1980). Vagrants regularly reach warm temperate latitudes. They haulout on ice and on land, often preferring ice floes near shore when these are available (Kooyman 1981, Rice 1998, Bengtson 2002).
Countries:
Native:
Antarctica; Australia; French Southern Territories; Heard Island and McDonald Islands; South Georgia and the South Sandwich Islands (South Georgia, South Sandwich Is.)
Vagrant:
Bouvet Island; Brazil; Chile; Cook Islands; Falkland Islands (Malvinas); New Zealand; Saint Helena, Ascension and Tristan da Cunha; South Africa
FAO Marine Fishing Areas:
Native:
Atlantic – Antarctic; Atlantic – southwest; Indian Ocean – Antarctic; Pacific – Antarctic; Pacific – southeast; Pacific – southwest
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This is a widespread species and, similar to the other Antarctic seals that inhabit the pack ice, population assessments are very difficult and expensive to conduct and therefore infrequently undertaken. Published global population estimates range from 100,000-300,000 (Scheffer 1958) up to 220,000-440,000 animals (Laws 1984). However, early estimates were based on very limited sampling and were highly speculative. The most recent global estimate, from analysis of ship and aerial sighting surveys carried out around the continent between 1968 and 1983, provided a point estimate for global leopard seal population size in the pelagic pack ice of the Southern Ocean of 300,000 animals (Erickson and Hanson 1990). This estimate is likely to have considerable uncertainty associated with it, and only very large changes in leopard seal population size could be confidently detected from repeated surveys (Southwell et al. In Press).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Adult males are 2.8 to 3.3 m long and weigh up to 300 kg. Adult females are 2.9 to 3.6 m, with very large animals possibly reaching 3.8 m, and weights of 260 to upwards of 500 kg. Pups are 1 to1.6 m in length and weigh 30 to 35 kg at birth. The age at sexual maturity is probably 4 years for females and 4.5 years for males. Longevity is estimated to be over 26 years (Kooyman 1981, Rogers 2002).

Pups are born on the ice from early November to late December and the period may be as long as early October to early January (Southwell et al. 2003). Births at South Georgia occur from late August to the middle of September. Pups are probably weaned at four weeks old, and female estrous occurs at or shortly after weaning. Unlike crabeater seals, male leopard seals do not haulout with female-pup pairs. Mating is believed to occur in the water.

At sea and on the ice, leopard seals tend to be solitary. They are well known for their habits of preying upon penguins. However, their diet is in reality highly varied and changes with seasonal and local abundance of prey. Leopard seals will consume krill, fish, squid, penguins, a variety of other types of seabirds, and juvenile seals including crabeater, southern elephant, and fur seals. They also occasionally scavenge from carcasses of whales. Most prey is caught in the water. Penguins are regularly held in the teeth by one end and slung in an arc with a rapid snap of the head and neck and smashed on the surface of the water and torn open. Smaller pieces are then swallowed. Young, newly fledged naïve penguins are most vulnerable, but adult birds are taken as well. Leopard seals patrol and regularly station themselves just off penguin rookeries and wait to ambush and chase penguins transiting to and from the colonies.
Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): There are currently no threats from human activity throughout the species’ normal range. Small numbers of leopard seals have been taken for research purposes and some were previously killed for dog food, but otherwise there is no current or past significant catch of leopard seals (Reijnders et al 1993).

The effects of global climate change on Antarctic seals are unknown. Learmonth et al. (2006) list the effects of global climate change as unknown on leopard seal. However, loss of sufficient areas of pack ice habitat used for pupping, resting, avoidance of predators, availability of preferred prey such as penguins, other ice seals, krill, and fish that could all possibly decline, could all effect leopard seals directly or indirectly to an unknown degree. The effects of loss of large amounts of ice on the Antarctic continent, general climate warming, or sea level rises on Antarctic ocean circulation and productivity, and on Antarctic marine resources such as seals are unknown.

Two of the four species of Antarctic ice seal, leopard and crabeater, tested positive for antibodies to canine distemper virus (CDV). Weddell seals were tested and did not have any antibodies, and Ross seals were not tested. The effects of an outbreak of this or other diseases on leopard seals either as a disease within this species or repeatedly transmitted to it from an outbreak in a prey species such as the crabeater seal are unknown. Leopard seals are generally solitary except when with a pup or mating, so transmission of disease within the species would likely be slow or only seasonally significant. CDV is believed to have arrived in the Antarctic with sled dogs before the advent of vaccines. A mass mortality of crabeater seals occurred in 1955, with many animals displaying viral illness symptoms prior to death, however, the exact cause of death is unknown (Bengtson and Boveng 1991).

Seasonal tourism in the Antarctic and sub-Antarctic has increased steadily in the last 30 plus years, and is currently at all-time high levels. The effects of increased vessel noise, disturbance from vessels passage and close approach by people in small boats and on land on leopard seal behaviour, distribution, and foraging are unknown. There is also a risk of injury to a small number of animals from collision with boats or crushing from large vessels passing through ice fields.

There are no reports of significant fisheries interactions. Commercial harvest of krill may pose direct or indirect threats to leopard seals, if conducted on a large scale.

Conservation Actions [top]

Conservation Actions: The leopard seal is not listed as endangered or threatened. Leopard seals are protected by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals, and any future commercial harvest would be regulated by these international agreements (Reijnders et al. 1993).

Citation: Southwell, C. (IUCN SSC Pinniped Specialist Group) 2008. Hydrurga leptonyx. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 25 October 2014.
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