IUCN Red List Assessment
Red List Category
Red List Criteria
IUCN Evaluation of the Galápagos Sea Lion, Zalophus wollebaeki
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 are not available for the Galápagos Sea Lion population so the generation time cannot be calculated precisely. However, with sexual maturity attained at 5-6 years of age and a maximum longevity of approximately 20 years, the average age of reproducing individuals should be around 10 years. A population reduction of 50% of Galápagos Sea Lions has been estimated over the past 30 years. This meets the criterion for Vulnerable.
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 Galápagos Sea Lions has been estimated in the past 30 years. The population is protected within a National Park and the reasons for the reduction are not clearly understood. This decline hence warrants a classification of Endangered.
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 Galápagos Sea Lions is suspected in the future because of increased anthropogenic influences (particularly fisheries interactions). The likely degree of population reduction attributable to this threat in the future cannot, however, be projected with any confidence.
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 around 50% of Galapagos sea lions has been estimated over 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 Galápagos Sea Lions is approximately > 138 000 km².
B2. Area of occupancy (AOO): CR
The AOO of Galápagos Sea Lions is > 120,000 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 Galapagos sea lions is roughly known and estimated to be about 20,000.
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
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 Galápagos Sea Lions.
Listing recommendation ? Past estimates of Galápagos Sea Lion abundance in 1977-1978 suggested a total population size of about 40,000. Current abundance is estimated around 20,000. The population is protected with a National Park and the cause of the decline is unknown. Thus, Galápagos Sea Lions qualify for listing as Endangered under IUCN criterion A2a.
- 1996Vulnerable(Baillie and Groombridge 1996)