IUCN Red List Assessment
Red List Category
Red List Criteria
IUCN Evaluation of the Weddell Seal, Leptonychotes weddellii
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.
Generation time in Weddell Seals based on the average age of reproducing adults is uncertain but has been estimated at approximately 12 yrs in an isolated population within McMurdo Sound. With sexual maturity attained at 3-6 years of age and a maximum longevity in excess of 30 years a generation time of 12-15 years seems reasonable. A population reduction of Weddell Seals has not been observed, estimated, inferred, or suspected in the past 30 years. However, global population abundance is difficult to estimate and has only been based on extrapolations from ship-based surveys. These extrapolations use seal density in a given area, extrapolated to an estimate based on ice available to be used by the seals.
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 Weddell 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 Weddell Seals is not suspected in the future as there are no compelling threats to Weddell Seals at this time. They are no longer hunted to feed dog teams and there is no other threats beyond potential habitat losses due to climate change via predicted reductions in sea ice habitats due to continued climate warming.
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 Weddell 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
The EOO of Weddell Seals is > 20,000 km².
B2. Area of occupancy (AOO): CR
The AOO of Weddell Seals is > 2,000 km².
AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN (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
The current abundance of Weddell Seals is poorly known, but the total number of individuals was last estimated at a minimum of 500,000.
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 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 AND/OR restricted area of occupancy typically: AOO
The current abundance of Weddell Seals is poorly known, but the number of mature individuals 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 Weddell Seals.
Listing recommendation — Past, extrapolated, estimates of Weddell Seal abundance suggest a total population size of more than 500,000. Current abundance and population trend are unknown but there has been no evidence of significant changes in recent decades. Currently, the greatest threat to Weddell Seals may be the unknown effects of a changing climate. Recent work in McMurdo Sound suggested that sea ice in the area has expanded, but that there has been a local decrease in pup production. However, the overall effects of climate change on the world wide population of Weddell Seals are unknown. Weddell Seals do not appear to have changed in abundance in recent years and there are no known current threats. Thus, Weddell Seals qualify for listing as Least Concern.
- 1996Lower Risk/least concern