|Scientific Name:||Ommatophoca rossii|
|Species Authority:||(Gray, 1844)|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Southwell, C. (IUCN SSC Pinniped Specialist Group)|
|Reviewer/s:||Kovacs, K. & Lowry, L. (Pinniped Red List Authority)|
Due to its widespread occurrence and large population size, the Ross Seal should remain classified as Least Concern (LC).
IUCN Evaluation of the Ross Seal, Ommatophoca rossii
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 Ross Seals are limited so the generation time cannot be calculated precisely. With sexual maturity thought to be attained at 2-4 years of age and a maximum longevity at least 20 years, the average age of reproducing individuals should be at least 10 years old. A population reduction of Ross 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 Ross 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 Ross 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 A1.
A population reduction of Ross 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 Ross Seals is > 20,000 km².
B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²
The AOO of Ross 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 Ross 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
(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 Ross 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 Ross Seals.
Listing recommendation — The most recent circumpolar estimate of Ross Seal abundance indicates a total population size of 130,000. 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. Ross 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 the extent of Southern Ocean sea ice habitat. The Ross Seal is a widespread and abundant species that does not qualify for any of the threatened categories in the near future, thus, Ross Seals qualify for listing as Least Concern.
|Range Description:||Ross seals have a circumpolar distribution in the Southern Ocean surrounding Antarctic. They are usually sighted in summer in dense consolidated pack ice where they haulout to breed, moult and rest. Recent satellite tracking suggests that some Ross seals may move north to the open ocean in autumn (Nordøy and Blix 2001). Vagrants have been reported from South Sandwich, Falkland, Scott, South Orkney, Kerguelen, and Heard Islands, and South Australia (Rice 1998, Thomas 2002).|
Vagrant:Australia; Falkland Islands (Malvinas); French Southern Territories; Heard Island and McDonald Islands; South Georgia and the South Sandwich Islands
|FAO Marine Fishing Areas:||
Atlantic – Antarctic; Atlantic – southwest; Indian Ocean – Antarctic; Pacific – Antarctic
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Ross seals typically haulout in dense consolidated pack ice over large geographic areas. Because these areas can usually only be reached by ice-breaking ships or long-range aircraft, it is difficult to estimate population size and trends with high certainty. Published global population estimates range from 20,000-50,000 (Scheffer 1958) up to 220,000 animals (Gilbert and Erickson 1977). 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 Antarctic Continent between 1968 and 1983, provided a point estimate for global Ross seal population size in the pelagic pack ice of the Southern Ocean in the order of 130,000 animals (Erickson and Hanson 1990, Reijnders et al. 1993). No indication of the uncertainty around this estimate was given. A more recent regional survey in the pack-ice off east Antarctica between 64-150ºE indicates that broad-scale estimates are likely to have considerable uncertainty around them. The best estimates for this regional survey were in the order of 50,000, 95% confidence limits ranged from 20 000 to 227 000 (Southwell et al. 2008). Given this uncertainty, only gross changes in Ross seal population size could be confidently detected from repeated surveys.|
|Habitat and Ecology:||
At maturity, Ross seals are the smallest of the four Antarctic phocids. Based on a small sample of measured animals, Ross seal males reach 1.68-2.09 m in length and 129-216 kg and females are slightly larger at 1.96-2.5 m in length and 159-204 kg. It is estimated that pups are about 1 m and 16 kg at birth; eight suckling pups examined in November were109-138 cm in length and 40-75 kg. Age at sexual maturity is thought to be 3-4 years for females and 2-7 years for males (Ray 1981). Adults reach physical maturity at approximately 9 years of age and can live to at least 20 years (Skinner and Klages 1994).
Most pups are born in November, with a peak from early to mid-November (Southwell et al. 2003). Weaning takes place at about one month, although little is known of the relationship between mother and pup. Nursing pups have been seen swimming between ice floes. Mating is thought to occur in the water, but has not been observed. Ross seals are usually found singly on the ice. Moulting is believed to occur in January, at which time many Ross seals appear to fast (Skinner and Klages 1994). During summer Ross seals exhibit a diel haulout pattern with most seals hauled out on the ice at midday (Ray 1981, Bengtson and Stewart 1997, Southwell 2003). Satellite tracking suggests that some Ross seals may move north to the open ocean in autumn (Nordøy and Blix 2001).
Little is known about the activities of Ross seals in the water, although recent work with one female has revealed that when in the water, diving was continuous with dives averaging 110 m in depth and 6.4 minutes in duration, and were to a maximum of 212 m and up to 9.8 minutes. The seal’s dives were deepest at twilight and shallowest at night, and it hauled out during the day (Bengtson and Stewart 1997). The diet of Ross seals consists of 64% cephalopods, 22% fish, and 14% other invertebrates including some krill (Ray 1981). Skinner and Klages (1994) identified only Antarctic silverfish (Pleurogramma antarcticum) in 20 animals examined; no other fish were present. Several species of squid were also recorded, but many stomachs were empty when the animals were collected in January, suggesting fasting during the post-breeding moulting period.
Killer whales and leopard seals are presumed to be predators of the Ross seal.
Ross seals are typically found hauled out singly in dense consolidated pack ice in very low concentrations and can usually only be reached by ice breakers. It has been estimated that as few as 200 sightings of the species were all that were known prior to 1972 (Ray 1981). Small numbers of animals have been collected for commercial purposes, scientific studies and museums, but otherwise interactions with humans have been few. When wandering outside the pack ice zone, Ross seals could come in contact with commercial fishing operations, but there are no reports of interactions to date.
Two of the four species of Antarctic ice seals, Leopard seals and crabeater seals, 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 susceptibility of Ross seals to CDV is unknown, but it is present in the Antarctic, probably having arrived with sled dogs before the advent of vaccines. A mass mortality of crabeater seals occurred in 1955, and many animals displayed viral illness symptoms prior to death (Bengtson and Boveng 1991).
The effects of global climate change on Antarctic seals are unknown. However, Learmonth et al. (2006) suggest that Ross seal numbers may decline with increasing temperatures if Antarctic sea ice is significantly reduced. Loss of sufficient areas of consolidated ice habitat used for pupping, resting, avoidance of predators and access to preferred foraging areas because of changes from warming could lead to population declines of Ross seals. 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.
|Conservation Actions:||Ross seals are protected by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals, and are not listed as threatened or endangered.|
|Citation:||Southwell, C. (IUCN SSC Pinniped Specialist Group) 2008. Ommatophoca rossii. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 07 December 2013.|
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