Table of Contents
Overview
Brief Summary
Biology
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Description
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Distribution
Range Description
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Geographic Range
Arctocephalus galapagoensis are found only in the Galapagos Islands, they do not migrate (Gentry & Kooyman, 1986).
Biogeographic Regions: neotropical (Native ); pacific ocean (Native )
Other Geographic Terms: island endemic
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UNESCO-IOC Register of Marine Organisms
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
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Wilson D.E. & Reeder D.A.M. (1993). Mammals species of the world. A taxonomic and geographic reference. Second edition. Smithsonian Institution Press, Washington, 1206 pp.
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Range
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Physical Description
Morphology
Physical Description
Male southern fur seals are 154 cm long, while the females are about 120 cm long. Although there is a 30 cm difference, it is the least sexually dimorphic of otariids in size and in color. Dorsal body surface is gray-brown, the venter is light tan. Arctocephalus galapagoensis is the smallest of the fur seals, possibly an adaptation to the warm ambient and aquatic temperatures of their tropical habitat (Wartzok, 1991).
Range mass: 27 to 64 kg.
Other Physical Features: endothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger
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Ecology
Habitat
Habitat and Ecology
The few adult males measured to date have been 1.5?1.6 m and weighed 60-68 kg. Adult females have curvilinear lengths of 1.1-1.3 m and an average weight of about 27.3 kg, with a maximum of 33 kg. Pups are 3?4 kg at birth and an average of 11.3 kg when they are 12 months old. Galápagos Fur Seals mature at an age of about 5 years, from which time females usually produce one pup a year but usually rear a pup only every other year for most of the rest of their lives.
Males do not become physically mature, and large enough to compete for a territory that will be used by females until they are considerably older than the average age of maturity of females. Males hold territories that average 200 m², which is large compared to the average size of territories held by of other otariid males; this is particularly notable given the Galápagos Fur Seal?s small size.
The behaviour of the Galápagos Fur Seal has been extensively studied. They occasionally occur on nearly all of the islands in the Archipelago, and prefer to haul-out on rocky coasts with large boulders and ledges that provide shade and the opportunity to rest in crevices and spaces between the rocks. Galápagos Fur Seals have a fairly long pupping and breeding season, lasting from mid-August to mid-November. The peak of pupping shifts little from year to year and usually occurs between the last week of September and the first week of October.
Colonies are located close to foraging areas and the average length of female trips is the shortest for a fur seal with a mean trip length of 1.5 days in the cold season (May to November and up to 4 days in the warm season (December to April). Most foraging occurs at night and the mean depth of foraging dives is 26 m with duration of less than 2 minutes. The maximum dive depth recorded is 115 m, and the longest duration is 5 minutes. Pups are visited around 300 times before weaning, with attendance periods lasting 0.5-1.3 days. Weaning occurs at 18-36 months, with most pups being weaned in their third year. Pups born prior to the weaning of an older sibling rarely survive, with most starving to death and a small percentage being killed by the older pup. Females will allow multiple pups to nurse but this rarely lasts long enough for the youngest pup to get strong enough to survive. In exceptional cases offspring were allowed to nurse when they were 4-5 years old.
In the water, particularly near haul-outs, Galápagos fur seals raft in postures typical of many of the southern fur seal species. There is no evidence for migration, and they do not seem to spend prolonged periods of time at sea, except for males immediately before the period of territory tenure.
Galápagos fur seals consume a variety of small squids including Onychoteuthis banksi, and a number of species of omastrephids. A variety of fish species are also taken mostly myctophids and bathylagids. They feed mostly at night, possibly exploiting vertically migrating species when they come closer to the surface.
Predators of Galápagos fur seals include sharks and killer whales. On land feral dogs on Isabela Island decimated colonies on the south-western end of the island, killing pups and adults.
Systems
- Terrestrial
- Marine
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Southern fur seals live only on the Galapagos Islands and in the surrounding waters. Air temperature is fairly constant year round at an average of 23.8 degrees C (Trites, 1990).
Aquatic Biomes: coastal
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Water temperature and chemistry ranges based on 70 samples.
Environmental ranges
Depth range (m): 0 - 0
Temperature range (°C): 22.429 - 24.724
Nitrate (umol/L): 2.793 - 6.059
Salinity (PPS): 34.053 - 34.713
Oxygen (ml/l): 4.635 - 4.758
Phosphate (umol/l): 0.523 - 0.797
Silicate (umol/l): 3.577 - 5.767
Graphical representation
Temperature range (°C): 22.429 - 24.724
Nitrate (umol/L): 2.793 - 6.059
Salinity (PPS): 34.053 - 34.713
Oxygen (ml/l): 4.635 - 4.758
Phosphate (umol/l): 0.523 - 0.797
Silicate (umol/l): 3.577 - 5.767
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
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Trophic Strategy
Food Habits
Arctocephalus galapagoensis feeds on fish and cephalopods. (Nowak, 1999; Reidman, 1990)
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Life History and Behavior
Life Expectancy
Lifespan/Longevity
Average lifespan
Sex: female
Status: wild: 22.0 years.
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Lifespan, longevity, and ageing
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Reproduction
Females are able to have offspring by their fifth year (Reidman, 1990, Trillmich, 1984). Pupping takes place in the cool season beginning in August and lasting until November. Gestation is approximately one year, however, the existence of delayed implantation in this species implies that development time may be less than one year (Nowak, 1999; Reidman, 1990). Bowen (1991) states that the unusual birth time in this species is due to "distribution at low latitudes, a more favourable climate throughout the year, and less pronounced seasonal variation in marine productivity than found in temperate and arctic waters. Females go into estrus 8 days after giving birth, and mate during lactation (Nowak, 1999; Reidman, 1990), which lasts from 365-730 days (Bowen, 1991; Reidman). Peak mating time is during the month of October (Reidman, 1990: Trillmich, 1984). If a female gives birth to another pup the next year, it has a 50% chance of survival. The year old pup may kill the new pup or lack of resources may result in their starvation (Nowak, 1999). Female southern fur seals produce a maximium of 5 offspring in their lifetime (Nowak, 1999).
Average birth mass: 3500 g.
Average gestation period: 213 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (female)
Sex: female: 1461 days.
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Contributor/s
Justification
IUCN Evaluation of the Galápagos Fur Seal, Arctocephalus (australis) galapagoensis
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 Fur Seal population so the generation time cannot be calculated precisely. With sexual maturity attained at perhaps 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% has been estimated for Galápagos Fur Seals 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 Fur Seals has occurred during the past 30 years. The reasons for the reduction are not clearly understood, but may lie mostly in population effects of the 1982/83 and 1997/98 El Niño events. This meets the criteria for 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.
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 Galápagos Fur Seals 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 Fur Seals is approximately > 138,000 km².
B2. Area of occupancy (AOO): CR
The AOO of Galápagos Fur Seals 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 Galápagos Fur Seals is roughly known, but is estimated to be about 15,000-20,000.
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 Fur Seals.
Listing recommendation ? Estimates of Galápagos Fur Seal abundance in 1977-1978 suggested a total population size of about 30,000-40,000. Current abundance is estimated to be around 10,000-15,000. The seals are protected within a National Park and the cause of the decline is unclear. Galápagos Fur Seals qualify for listing as Endangered under IUCN criterion A2(a).
History
- 1996Vulnerable(Baillie and Groombridge 1996)
- 1982Out of Danger(Thornback and Jenkins 1982)
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Ecuador provides protection by law for southern fur seals.
By the early 1900s it was said to be extinct due to overhunting for fur, but a population was found in 1932-33. The population had increased to between 30,000 and 40,000 by 1989. Ecuador reports that feral dogs on some of the 15 Galapagos Islands are a threat to current seal populations (Nowak, 1999).
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: endangered
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Status
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Trends
Population
Population Trend
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Threats
Tourism in the Galápagos, which is an Ecuadorian National Park, is heavy but regulated, and fur seals are protected. Episodes of entanglement in local net fisheries have been reported and are thought to be increasing over the last years. Feral dogs on Isabela Island which killed fur seals of all ages have been exterminated. This problem could erupt again if other feral dogs find their way to colony sites. The most serious threat at present is transmission of diseases from dogs to pinnipeds.
Like all fur seals, Galápagos Fur Seals are vulnerable to oil spills because of their dependence on their thick pelage for thermoregulation. Although there is limited large vessel traffic in the Galápagos Archipelago, numerous small and medium sized vessels operate in the area that could release moderate quantities of oils, fuels, and lubricants if involved in a marine accident.
Galápagos Fur Seals have experienced declines from El Niño-caused ocean warming and associated reduced marine productivity (Trillmich and Dellinger 1991) estimated of up to 80% (Salazar 2002; Alava and Salazar 2006), but the exact extent of population reduction is not clear. Therefore, although the effects of global climate change on this species and its habitat are uncertain at this time, it is possible that any change related disruption of present day ocean currents, levels of marine productivity, or increased air temperatures at haul out sites would adversely affect this species.
Despite their population size, the Galápagos Fur Seal population will always be vulnerable to a variety of threats because of the species? restricted distribution to a relatively small Archipelago of islands.
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Management
Conservation Actions
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Conservation
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Relevance to Humans and Ecosystems
Benefits
Economic Importance for Humans: Positive
Arctocephalus galapagoensis were previously hunted for their furs.
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Wikipedia
Galápagos fur seal
The Galápagos fur seal (Arctocephalus galapagoensis) breeds on the Galápagos Islands in the eastern Pacific, west of mainland Ecuador.
Contents |
Description [edit]
Galápagos fur seals are the smallest of otariids. They have a grayish brown fur coat. The adult males of the species average 1.5 m (4 ft 11 in) in length and 64 kg (140 lb) in mass. The females average 1.2 m (3 ft 11 in) in length and 28 kg (62 lb) in mass. They spend more time out of the water than almost any other seal. On average, 70% of their time is spent on land. Most seal species spend 50% of their time on land and 50% in the water.
Range and habitat [edit]
The Galápagos fur seal is endemic to the Galápagos Islands, with a single colony in northern Peru, according to the Organisation for Research and Conservation of Aquatic Animals[who?][citation needed]; they live on the rocky shores of the islands which tend to be on the west sides, leaving only to feed.
Reproduction [edit]
Galápagos fur seals live in large colonies on the rocky shores. These colonies are then divided into territories by the female seals during breeding season, which is mid-August to mid-November. Every mother seal claims a territory for herself and breeds her pups there.[2]
Maternal care [edit]
Galápagos fur seals have the lowest reproductive rate reported in seals, and it takes an unusually long time to raise seal pups to independence.[2] Females bear only one pup at a time, and she remains with her newborn for a week before leaving to feed. She then periodically returns to the pup and stays to suckle it for a few days before leaving on another hunting trip. Females recognize their own pups by smell and sound, and pups also learn to identify their mothers by the females’ “Pup Attraction Calls”.[3] Mother-pup recognition is crucial because females exclusively nurse their own pups, often violently rejecting strange pups that approach. Orphaned seal pups usually try to sneak up on sleeping or calling females to suckle, but stealing milk is not enough to sustain the pups, and they usually die within a month.[3]
Interbrood conflict [edit]
Fur seal pups rely on their mother’s milk for the first eighteen months, and weaning may be delayed for up to two or three years if conditions are poor. The result is that every year up to 23% of pups are born when an older sibling is still suckling.[4] Survival of the younger sibling greatly depends on the availability of resources. In years when there is abundant food, the mortality rate of second pups is as low as 5%, which is equivalent to the mortality rate of pups without siblings. In years when food is scarce, 80% of pups with suckling older siblings die within a month.[2] The younger sibling thus serves as an insurance in case the first sibling dies, and also provides extra reproductive value in case conditions prove better than expected. Such a bet-hedging strategy is particularly useful in Galapagos fur seals, since there is a great deal of maternal investment in raising a seal pup to independence in an environment that has great fluctuations in food.
The high level of resource uncertainty, late weaning, and potential overlap time of suckling young all lead to violent sibling rivalry and provide a good environment for studying parent-offspring conflict. From an offspring’s point of view, it would be most beneficial to continue suckling and receive more than its fair share of milk, but to the mother seal, it would pay to wean the older, more independent offspring in order to invest in the next pup.[4] Thus, studies show that 75% of mothers intervened, often aggressively, when the older sibling harassed the newborn pups. Mothers would bite or lift the older offspring roughly by its skin, which sometimes caused open wounds. Maternal aggression towards the older sibling diminishes with time after the second sibling’s birth. Even without direct aggression, older siblings may still indirectly harm their younger siblings by outcompeting them for milk. The older offspring usually suckles first and allows their younger sibling access to the mother only after it is satiated, resulting in very little milk left over for the younger pup. Thus, the younger siblings often die from starvation.[5]
During periods when there is very little prey, interbrood conflict increases. Galapagos fur seal population is drastically affected by El Nino, a period accompanied by high water temperatures and a deepening thermocline.[6] Food becomes scarce during El Nino, and thus older seals exhibit an intense aversion to weaning, causing the mother seal to neglect the younger sibling.
Feeding and predation [edit]
The Galápagos fur seal feeds primarily on fish and cephalopods. They feed relatively close to shore and near the surface, but have been seen at depths of 169 m (554 ft). They primarily feed at night because their prey is much easier to catch then.[7] During normal years, food is relatively plentiful. However, during an El Niño year, there can be fierce competition for food, and many young pups die during these years. The adult seals feed themselves before their young and during particularly rough El Niño years, most of the young seal populations will die.
The Galápagos fur seal has virtually no constant predators. Occasionally, sharks and orcas have been seen feeding on the seals, but this is very rare. Sharks and orcas are the main predator of most other seal species, but their migration paths do not usually pass the Galápagos.
Conservation [edit]
Galápagos fur seals have had a declining population since the 19th century. Thousands of these seals were killed for their fur in the 1800s by poachers. Starting in 1959, Ecuador established strict laws to protect these animals. The government of Ecuador declared the Galápagos Islands a national park, and since then no major poaching has occurred. Despite the laws, another tragic blow to their population occurred during the 1982–1983 El Niño weather event. Almost all of the seal pups died, and about 30% of the adult population was wiped out.
The population is relatively stable now and is on the rise. Since 1983 no major calamity has occurred to decrease their population significantly.[citation needed]
References [edit]
- ^ Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group) 2008. Arctocephalus galapagoensis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2.
- ^ a b c Horning, M. and Trillmich, F. (1997). "Ontogeny of diving behaviour in the Galapagos fur seal". Behaviour 134 (15): 1211–1257. doi:10.1163/156853997X00133.
- ^ a b Trillmich, Fritz (1981). "Mutual Mother-Pup Recognition in Galápagos Fur Seals and Sea Lions: Cues Used and Functional Significance". Behaviour 78 (1/2): 21–42. doi:10.1163/156853981X00248.
- ^ a b Davies, N. and Krebs, J. and West, S. (2012). An Introduction to Behavioural Ecology (Fourth ed.). Wiley-Blackwell. ISBN 978-1-4443-3949-9.
- ^ Trillmitch, Fritz. and Wolf, Jochen (2008). "Parent–offspring and Sibling Conflict in Galápagos Fur Seals and Sea Lions". Behavioral Ecology and Sociobiology 62 (3): 363–375. doi:10.1007/s00265-007-0423-1.
- ^ Aurioles-Gamboa, D. and Schramm, Y. and Mesnick, S. (2004). "Galapagos Fur Seals, Arctocephalus Galapagoensis, in Mexico". Latin American Journal of Aquatic Mammals 3 (1): 77–80. doi:10.5597/lajam00051.
- ^ Horning, M. and Trillmich, F. (1999). "Lunar Cycles in Diel Prey Migrations Exert a Stronger Effect on the Diving of Juveniles Than Adult Galapagos Fur Seals". Proceedings of the Royal Society London B 266 (1424): 1127–1132. doi:10.1098/rspb.1999.0753.
Further reading [edit]
- MarineBio.(1999). Retrieved September 22, 2008, from http://marinebio.org/species.asp?id=293
- Randall R. Reeves, Brent S. Stewart, Phillip J. Clapham and James A. Powell (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf, Inc. ISBN 0375411410.
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