|Scientific Name:||Zalophus wollebaeki|
|Species Authority:||Sivertsen, 1953|
Zalophus californianus subspecies wollebaeki (Sivertsen, 1953)
|Taxonomic Notes:||This species has been considered a subspecies of Z. californianus, (Z. c. wollebaeki) by many authors. Rice (1998), followed here, argued for the retention of Z. californianus, Z. japonicus, and Z. wollebaeki as distinct species. Recent genetic data support the classification as a separate species (Wolf et al. 2007).|
|Red List Category & Criteria:||Endangered A2a ver 3.1|
|Assessor/s:||Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group)|
|Reviewer/s:||Kovacs, K. & Lowry, L. (Pinniped Red List Authority)|
Due to its small-scale occurrence and small, fluctuating population size, and suggested decline of 50% over the last 30 years the Galápagos Sea Lion should be classified as Endangered.
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 < 100 km²; EN < 5,000 km²; VU < 20,000 km²
The EOO of Galápagos Sea Lions is approximately > 138 000 km².
B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²
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 < 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 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 < 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
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.
|Range Description:||Galápagos Sea Lions are found throughout the Galápagos Archipelago on all the major islands and on many smaller islands and rocks. A colony was established in 1986 at Isla de la Plata, just offshore from mainland Ecuador, but this site is not regularly used. Vagrants can be seen from the Ecuadorian coast north to Isla Gorgona in Columbia. There is also a record from Isla del Coco approximately 500 km southwest of Costa Rica, presumably a vagrant.|
Native:Ecuador (Ecuador (mainland), Galápagos)
Vagrant:Colombia; Costa Rica (Cocos I.)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population fluctuates between 20,000 and 40,000 animals. A census in 1978 suggested a population size of about 40,000, but a recent survey in 2001 ? found a 50% decline from this earlier estimate (Alava and Salazar 2006). Methodological differences might exist between counts over this period, but the marked decline suggested is cause for serious concern.|
|Habitat and Ecology:||
Galápagos Sea Lions are similar in appearance to California Sea Lions, but differ in size, behavior, and skull morphology. Galápagos Sea Lions are sexually dimorphic, with males growing larger than females and having a suite of several secondary sexual characteristics. The degree of sexual dimorphism appears to be less than in California Sea Lions, although few weights and measurements are available for adults to confirm this suggestion.
There is little information on the lengths and weights attained by Galápagos Sea Lions, but they are said to be somewhat smaller than California Sea Lions. Adult males are estimated to weigh up to 250 kg, but this has not been confirmed through direct study. Adult females caring for pups weigh between 50 and 100 kg. Pups of both sexes are born at approximately six kilograms and weaned at approximately 25-40 kg. Pups are born with a brownish-black lanugo coat that fades to pale brown by three to five months. Pups go through their first moult at around five months of age and emerge with the pelage of adult females and juveniles.
Age of maturity for both sexes is estimated to be about 4-5 years. Females produce one pup each year after a gestation of about 11 months, but may abort (or not produce a pup) while still caring for an older offspring (Trillmich and Wolf 2008). Longevity is estimated to be around 15-24 years but the higher ages are not confirmed (Reijnders et al. 1993).
Galápagos Sea Lions are polygynous and males hold territories both on land and in shallow water near shore that they vociferously and aggressively defend. Male tenure on territories usually lasts from ten days to three months. Males may repeatedly be on territory during the drawn out reproductive period. Most copulations occur in the water.
Pupping and breeding take place across an extended period from May through January. Because of the protracted breeding season and extended care provided to the pups (up to 3 years) by females, there are dependent pups on the rookeries year-round. Females may wean pups in 11-12 months in productive years, but most continue to suckle yearlings for a second year. Some females care for a yearling along with a newborn pup. Pups are attended continuously for the first 4-7 days after birth, after which the female goes to sea to feed. With the departure, the female begins a cycle of foraging trips that last 0.5-3 days during the cold season but may last much longer in the warm season. Pups will enter the water and begin to develop swimming skills 1-2 weeks after birth. In some colonies, females return at night to nurse their pup, departing again the next morning (Trillmich 1986). Females and pups recognize each other and reunite based on calls and scent (Trillmich 1981). Galápagos Sea Lion females feed during day and night, in contrast to Galápagos Fur Seals, which primarily feed at night.
Galápagos Sea Lions are non-migratory. They are unafraid of humans when ashore. Haul-out sites can be on rugged shoreline types, including steep rocky shorelines, ledges and offshore stacks, but colonies are mostly on gently sloping sandy and rocky beaches. Sea lions will use shade from vegetation, rocks, and cliffs, and wade into tidal and drainage pools or move into the ocean, as needed during the heat of the day to avoid overheating.
Diving has been studied in four females on Fernandina and about 20 in the centre of the archipelago. The maximum depth of dive recorded was 338 m and maximum duration was 9.8 minutes. Average depth of dives varied between 45 and 150 m and lasted for 3-5 minutes (Villegas-Amtmann et al. in press). At sea they will raft at the surface and rest on their sides with one or more flippers held vertically in the air.
Galápagos Sea Lions prey on sardines in the west and on sardines as well as myctophids and bathylagids together with small squid in the central parts of the archipelago. Galápagos Sea Lions have been seen smashing octopus on the surface of the water, presumably to stun or break them up to facilitate swallowing. During El Niño events even in the west prey includes green-eyes and myctophids, suggesting a change in foraging strategy.
Feral and uncontrolled dogs have been reported to kill sea lion pups. Shark predation is evident from animals seen with injuries and scars from attacks, and killer whales are presumed to be another predator on Galápagos Sea Lions. Interestingly, juvenile and adult Galápagos Sea Lions have been observed to mob Galápagos sharks that approach rookeries.
|Major Threat(s):||The population fluctuates widely due to die-offs and cessation of reproduction during El Niño events, when marine productivity collapses. Irruptions of a sea lion epidemic of unknown causation have occurred during El Niño events, adding to the stress on individuals from starvation. Feral dogs which occasionally prey on sea lions could transmit various diseases to the population, but frequent direct contact between sea lions and domestic dogs in the settlements on San Cristobal, Santa Cruz and Isabela present the greatest danger of disease transmission. The population seems to have declined from a 1978 census until today by an estimated 50% or more (Alava and Salazar 2006) and the reasons for this may partly lie in repeated strong El Niño events but are not clearly understood.|
|Conservation Actions:||The Galápagos Sea Lion population lives in the Galápagos Archipelago, which is an Ecuadorian National Park surrounded by a marine resources reserve. Tourism occurs on a large scale but is controlled to protect wildlife from disturbance.|
Alava, J. J. and Salazar, S. 2006. Status and conservation of Otariids in Ecuador and the Galápagos Islands. In: A. W. Trites, S. K. Atkinson, D. P. DeMaster, L. W. Fritz, T. S. Gelatt, L. D. Rea and K. M. Wynne (eds), Sea Lions of the World, pp. 495-520. Fairbanks: Alaska Sea Grant College Program, Alaska, USA.
Antonelis, G. A., Stewart, B. S. and Perryman, W. F. 1990. Foraging characteristics of female northern fur seals (Callorhinus ursinus) and California sea lions (Zalophus californianus). Canadian Journal of Zoology 68: 150-158.
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Aurioles, D. and Sinsel, F. 1988. Mortality of Californian sea lions pups, at Los Islotes, Baja California Sur. Mexico. Journal of Mammalogy 69: 180-183.
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de Anda, H. 1985. Habitos Alimenticios del Lobo Marino de Califomia (Zalophus californianus) en Las Islas Los Coronados B.C., de Noviembre 1983 a Octubre 1984. Tesis de Licenciatura en Ciencias Marinas., Univ. Auton.
Dellinger, T. and Trillmich, F. 1999. Fish prey of the sympatric Galápagos fur seals and sea lions: seasonal variation and niche separation. Canadian Journal of Zoology 77: 1204-1216.
Demaster, D., Miller, D., Henderson, J. R. and Coe, J. M. 1985. Conflicts between marine mammals and fisheries off the coast of California. In: J. R. Beddington, R. J. H. Beverton and D. M. Lavigne (eds), Marine mammals and fisheries, pp. 111-118. George Allen & Unwin.
Demaster, D. P., Miller, D. J., Goodman, D., Delong, R. L. and Stewart, B. S. 1982. Assessment of California sea lion fishery interactions. Transactions of the North American Wildlife and Natural. Resources Conference 47: 253-264.
Heath, C. B. 2002. California, Galapagos, and Japanese sea lions Zalophus californianus, Z. wollebaeki, and Z. japonicus. In: W. F. Perrin, B. Wursig and J. G. M. Thewissen (eds), Encyclopedia of Marine Mammals, pp. 180-186. Academic Press, San Diego, USA.
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Le Boeuf, B. J., Aurioles, D., Condit, R., Fox, C., Gisiner, R., Romero, R. and Sinsel, F. 1983. Size and distribution of the California sea lion population in Mexico. Proceedings of the California Academy of Sciences 43: 77-85.
Lowry, M. S., Oliver, C. W., Macky, C. and Wexler, J. B. 1990. Food habits of Californian sea lions, Zalophus californianus, at San Clemente Island, California, 1981- 1986. Fishery Bulletin 88: 509-521.
Lowry, M. S., Stewart, B. S., Heath, C. B., Yochem, P. K. and Francis, J. M. 1991. Seasonal and annual variability in the diet of California sea lions Zalophus californianus at San Nicholas Island, California, 1981-86. Fishery Bulletin 89: 331-336.
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Odell, D. K. 1981. California sea lion Zalophus californianus (Lesson, 1828). In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, Volume 1: The walrus, sea lions, fur seals, and sea otter, pp. 67-97. Academic Press.
Orr, R. T. 1967. The Galapago sea lion. Journal of Mammalogy 48: 62-69.
Orta, D. F. 1988. Habitos alimenticions del lobo marino de California en El Racito, Golfo de California, Septiembre 1986-Octubre 1987. Tesis de Licenciatura en Ciencias Marinas, Univ. auton. de Baja California. Mexico.
Rice, D.W. 1998. Marine Mammals of the World: Systematics and Distribution. Society for Marine Mammalogy, Lawrence, Kansas.
Stewart, B. S. and Yochem, P. K. 1987. Entanglement of pinnipeds in synthetic debris and fishing net and line fragments at San Nicolas and San Miguel island, California, 1978-1986. Marine Pollution Bulletin 18: 336-339.
Trillmich, F. 1979. Noticias de Galapagos. Noticias de Galapagos 29: 8-14.
Trillmich, F. 1986. Attendance behavior of Galapagos sea lions. In: R. L. Gentry and G. L. Kooyman (eds), Fur seals: Maternal strategies on land and at sea, pp. 196-208. Princeton University Press, Princeton, NJ, USA.
Trillmich, F. 1990. The behavioral ecology of maternal effort in fur seals and sea lions. Behaviour 114: 1-20.
Trillmich, F. and Dellinger, T. 1991. The effects of El Niño on Galápagos pinnipeds. In: F. Trillmich and K. A. Ono (eds), Pinnipeds and El Niño: Responses to environmental stress, pp. 66-74. Springer-Verlag, Berlin, Germany.
Trillmich, F. and Limberger, D. 1985. Drastic effects of El Niño on Galápagos pinnipeds. Oecologia 67: 19-22.
Trillmich, F. and Trillmich, K. G. K. 1984. The mating systems of pinnipeds and marine iguanas: convergent evolution of polygyny. Biological Journal of the Linnean Society 21: 209-216.
Villegas-Amtmann, S., Costa, D. P., Tremblay, Y., Salazar, S. and Aurioles-Gamboa, D. 2008. Multiple foraging strategies in a marine apex predator, the Galapagos Sea Lion Zalophus wollebaeki. Marine Ecology Progress Series 363: 299-309.
Wolf, J. B. W., Tautz, D. and Trillmich, F. 2007. Galapagos and Californian sea lions are separate species: genetic analysis of the genus Zalophus and its implications for conservation management. Frontiers Zoology 4: doi:10.1186/1742-9994-4-20.
|Citation:||Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group) 2008. Zalophus wollebaeki. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 09 March 2014.|
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