GALAPAGOS FUR SEAL

 

Male, Santiago Island

The Galápagos fur seal (Arctocephalus galapagoensis) is one of eight seals in the genus Arctocephalus. It is the smallest of all eared seals. It is endemic to the Galápagos Islands in the eastern Pacific. The total estimated population as of 1970 was said to be about 30,000, although the population has been said to be on the decline since the 1980s due to environmental factors such as pollution, disease, invasive species, and their limited territory. Due to the population having been historically vulnerable to hunting, the Galápagos fur seal has been protected by the Ecuadorian government since 1934.

Distinctive characteristics 

Galápagos fur seals are the smallest otariids. They are born with a black natal coat that they molt to reveal a lighter brown coat before becoming adults. Of the otariids, Galápagos fur seals display the least amount of sexual dimorphism. The males are up to 2x heavier than the females and 1–1.3 times longer. Males grow to be 1.5 m (5 feet) on average and weigh about 64 kg (140 lb.) Females grow to be 1.25 m on average and weigh 27 kg. (60 lb). They also have large eyes which allows them to hunt at night. The Galápagos fur seals look very similar to the Galápagos sea lions so it is important to note some of their differences. Their fur is a light tan on the stomach and around the mouth and ears, with the rest of the fur being a gray-brown. They have longer guard hairs and male fur seals have a mane of slightly longer hairs from the top of the head to their shoulders. Fur seal pups have a blackish-brown coat. The Galapagos fur seal is distinguishable by its short, pointed muzzle and small, button-like nose.  

Dental formula    I 3/2, C 1/1, PC 6/5 But PC 5/5.

Size

Males can be as large as 1.5 m and 64 kg. Females can be up to 1.2 m and 28 kg. New-born’s weigh 3-4.5 kg.

Life Span    Both Male and female live up to 22 years old.

Gestation Period    213 days.

Can be confused with

Galapagos fur seals share their restricted range in the Galapagos Archipelago with the Galapagos sea lion. The fur seal can be readily distinguished from the sea lion by its small and compact stocky body, short pointed muzzle, long pale vibrissae (on adults), thick long fur and shaggy look when wet, long prominent ear pinnae, proportionately large eyes, and equal length toes on the hind flippers. The South American sea lion has also been recorded in the Galapagos from a single stranding. All of the features that separate Galapagos fur seals from Galapagos sea lions can be used to separate them from this even larger sea lion species. Galapagos fur seals are considerably smaller than South American fur seals, and can be separated from them based on overall size, and muzzle length and color.

Distribution

Galapagos fur seals are found primarily on the Galapagos Islands or in the waters of the Pacific Ocean near the Galapagos Islands. During the breeding seasons populations are observed in the northern and western parts of the Galapagos Islands and they are non-migratory. The Galápagos fur seal is endemic to the Galapagos Islands in Ecuador, South America. It is present on nearly all the islands of the Galapagos. They are typically found close to the coastline where there are rock ledges and crevices that they can find shade in, in such a warm climate. It is classified as a non-migrant species. Females that are lactating do not travel long distances and tend to stay within the colony and only have moderately brief outings when they do venture out. However, recent research has documented the presence of Galápagos fur seals in Mexico and Guatemala.

Ecology and behavior

Galapagos fur seals are a polygynous species. They have the longest pupping period of any fur seal (or pinniped). Pups are born between mid-August and mid-November. Pups weigh 3-4.5 kg at birth. Females reach sexual maturity at 3-4 years, males around 7-10 years of age. The preferred breeding habitat is rocky shores with sea caves on the western coasts of the islands. Females give birth 2-3 days after coming ashore. About one week after giving birth, females begin alternating between foraging for food in the water for 1-4 days and nursing for 1 day. The duration of the nursing periods and the feeding trips appear to vary with the phase of the lunar month—mothers have been seen to spend 1.5-75 hours (average 22.5 hours) on shore feeding their pup and 3.5-127 hours (average 33.5 hours) feeding at sea. Observations have shown that the pups spend more time playing and moving around when their mother is away, although they have to take care since females can be quite ferocious towards pups that are not their own. The female mates about 8 days after giving birth. As with other fur seals the males maintain breeding territories, in this case for about 27 days at a time. The Galapagos fur seal has the longest nursing period of any seal, the pups finally being weaned between 1-2 years but sometimes even being nursed at the age of 3 years. Only the walrus has a nursing period close to this. The nursing period of a particular pup tends to be longer if food has been scarce during the time of its nursing, and the long period may therefore be a mechanism that the species has evolved to improve survival rates through such events as El Niños.

Pups begin to swim a little after a few months and start to engage in some independent feeding at 9-12 months. They molt into their grayish-brown adult fur at about 4 months. Galapagos fur seals do not migrate.

Current population size is estimated at about 10,000-15,000. A former estimate of about 40,000 was based on a survey from 1978, and it is thought that the 1982-83 El Niño event significantly reduced the population.

Predation

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. Galapagos fur seals are threatened by feral dogs living on the islands that they inhabit.

Feeding and prey

The Galápagos fur seal feeds primarily on fish, squid and shellfish. 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. 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.

 Exploitation

Thousands of Galapagos fur seals, Arctocephalus galapagoensis, were killed by commercial sealers in the 19th century. They became a protected species under Ecuadorian legislation in the 1930s, however this was not enforced until 1959 when most of the Galápagos Islands were established as a National Park. The waters around the islands are also protected, including a no-fishing zone, to a distance of 40 nautical miles. This species is listed as Endangered (EN A2a) on the IUCN Red List due to: “…its limited distribution, fluctuating (not stable) population size, and marked decline in the last 30 years (in excess of 50%).” 

A taxon is Endangered when the best available evidence indicates that it meets any of the criteria A to E for Endangered, and it is therefore considered to be facing a very high risk of extinction in the wild.

Because of the geographic position of the Galapagos Islands, El Niño events can significantly reduce food supplies causing starvation among the seals, which happened during the 1982-1983 El Niño event. Almost all of young fur seals were lost along with about 30% of adult females and non-territorial males and almost 100% of the large territorial males.

These fur seals have also been at risk of mortality due to entanglement in gill nets, but this problem seems to have been solved. Feral dogs have also attacked and killed Galapagos fur seals, however this problem is now controlled by the Galapagos National Park Service. 

Threats and status

The fur seals’ habitat is naturally restricted which makes them more threatened by environmental changes. Other potential and existing threats are tourism, oil spills, and boat collisions. Oil spills would be particularly damaging to the fur seal as their thick pelage is an important part of their thermoregulation. The waters near the archipelago are trafficked by vessels of ranging sizes that could contain and release moderate amounts of oil.

Isabela Island was documented as having a population of dogs that were known to kill the Galápagos fur seals. Since then all of the feral dog population on Isabela Island has been exterminated and the seals no longer face this threat. Now, the biggest direct threats to Galápagos fur seals involve climate change which includes ocean warming as well as ESNO weather events. Some of the indirect threats for them are marine pollution, pathogen spill overs, and by catch. There is not a lot known about the relation between pathogens and pinnipeds, but there were diseases found carried by dogs and cats on Isabela Island.

 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. Since 1983, no major calamity has occurred to decrease their population significantly.

Factors hypothesized include

The direct and indirect effects of large-scale commercial fisheries on key prey species, long –term ecosystem shifts, and changes in behavior by a primary predator, the killer whale, or a combination of these factors.

IUCN status    Endangered

Female With Pup Galapagos Island Ecuador