Galápagos sea lion
| Galápagos sea lion | ||||||||||||
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Galápagos sea lion |
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| Zalophus wollebaeki | ||||||||||||
| ( Sivertsen , 1953) |
The Galapagos sea lion ( Zalophus wollebaeki ) is a ears seal , which alone on the Galapagos is native -Archipel. The population there now comprises 50,000 animals. For a long time it was controversial whether it was a subspecies of the California sea lion ( Zalophus californianus wollebaeki ).
As early as 1953, the zoologist Erling Sivertsen carried out a new classification, after he had re-examined and classified the skulls and exhibits that had been collected by the Norwegian expedition ship MK Norvegia between 1928 and 1929 in the Oslo Museum .
A molecular genetic study by the Institute for Genetics at the University of Cologne , the Max Planck Institute for Evolutionary Biology , Plön ( Diethard Tautz ) and the Behavioral Research Department at the University of Bielefeld ( Fritz Trillmich ) came to the conclusion more than 50 years later that the SNPs of the Mitochondria and cell nuclei justify separation into several types. According to the molecular clock , the Californian and Galápagos sea lions separated around 2.3 (± 0.5) million years ago, so that an independent species must be assumed, especially since the Galápagos sea lions do not have the classic genetic bottleneck - Effect of population genetics there.
features
The Galápagos sea lion resembles its relative, the California sea lion, at first glance. The differences arise in the body size and the morphology of the skull, in which the snout is more elongated and more pointed than in its Californian relative. The other sea lion species have real bulldog snouts in comparison . The males reach a length of 250 to 270 centimeters and a weight of around 250 kilograms. The females, on the other hand, remain significantly smaller and lighter with 150 to 170 centimeters and a weight of 60 to 100 kilograms. Their fur can be light brown, golden brown or gray-brown in color, with the fur of the female and juvenile animals having more light brown shades. The external sexual characteristics are easy to identify in the females as well as in the males. The best way to distinguish adult males from females is by their size and, above all, by their forehead crest. Furthermore, they show different behavioral patterns, especially during the breeding season.
distribution
The Galápagos sea lions live in the eastern Pacific on the Galapagos Islands around 1000 km west of the South American state of Ecuador as an endemic species. There they can be found on all islands of the group throughout the year. As their name suggests, the Galápagos sea lions essentially remain location-bound. However, colonies outside of the Galápagos have also settled in the last 30 years: 1986 on the Isla de la Plata not far from the coast of Ecuador, wandering solitary animals were spotted from the Ecuadorian coast north of the island of Gorgona in Colombia . There is also a sighting report from Isla del Coco about 500 km southwest of Costa Rica .
Way of life
Galápagos sea lion on San Cristóbal
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In contrast to the California sea lions, they live in the vicinity of the coastlines of lava fields, as there are hardly any sandy beaches on the Galápagos Islands. However, this is where most of the tourist photos are taken, so that the animals can usually be seen in this environment.
nutrition
So far, no satisfactory empirical studies have been carried out on the diet of the Galápagos sea lions. Random examinations of the stomach contents of individual specimens suggest that the animals capture smaller to medium-sized bony fish in the broader sense ( Osteichthyes ) such as herring ( Clupea pallasii ) or lanternfish (Myctophidae) -40 m. Also molluscs ( Mollusca ) probably belong to their diet. It appears that the Galápagos sea lions hunt only during the day.
Social behavior
In contrast to the other sea lion species such as As the Steller sea lions Schern ( Eumetopias jubatus ) which, like the fur seals , find living in a tight social organization, the Galapagos sea lion as their relatives in California comparatively looser associations with no real organization.
Reproduction and rearing
The males, called bulls , watch over the harem of their females in strictly guarded bank and water zones . The actual mating season lasts from May to the following January. The gestation is 342 up to 365 days. Females wean their young at 11 to 12 months, but some nurse their yearlings alongside the newborns. The light brown cubs learn to swim together with other conspecifics at the age of one to two weeks in quieter bays. After the young are two to three weeks old, the female mates again. While the females go hunting during the day, they also come back briefly at feeding intervals during the day to feed their young. They reduce their own metabolism by staying in the cooling water in order to take care of their young at night. The strong relationships between mother and boy last up to three years.
Population and species protection
The population of the animals is subject to fluctuations between 20,000 and 50,000 specimens. Due to an excess of deaths and migrating animals due to the El Niño effect when fish stocks declined, the population continued to decline. The outbreak of a smallpox virus and increased stress when searching for food have also occurred in recent years. The population is now considered recovered. There are reports of feral and stray dogs that are said to have killed young sea lions in the Galápagos. The predators of the sea lions there are the Galapagos shark ( Carcharhinus galapagensis ) and the killer whale , as evidenced by the wounds and scars of the surviving animals and film recordings.
Since 1996, the Galapagos sea lions are considered endangered species on the Red List of the IUCN out and is there as endangered (high risk) classified.
Galápagos sea lions as an object of research and attraction for tourists
They show no fear towards humans, with which they were slaughtered in past centuries, like other species of the islands, to refresh the provisions of passing ships. Today people are less afraid of exploring them. In the mid-1950s, I. Eibl-Eibesfeldt published various essays and documentaries on the Galápagos sea lions. However, especially today, they are also the object of observation for various tourists, who are guided through the islands' nature park in limited quantities in a controlled manner, but can ultimately disturb the population. Even with divers, at least the playful females are trusting, while the male Pashas insist on preserving their territory even underwater and can then be dangerous to the diver.
Individual evidence
- ↑ a b https://apiv3.iucnredlist.org/api/v3/taxonredirect/41668https://www.iucnredlist.org/species/14549/45228341
- ↑ Erling Sivertsen: A survey of the eared seals (family Otariidae) with remarks on the Antarctic seals collected by M / K "Norvegia" in 1928-1929, I kommisjon hos Jacob Dybwad: Oslo 1954; Edvard Bull: Norsk biografisk leksikon. 1881-1932, H. Aschehoug 1983, p. 339; Irenäus Eibl-Eibesfeldt , Alan Houghton Brodrick: Galapagos: The Noah's Ark of the Pacific , Doubleday: London 1961, p. 27.
- ↑ http://www.mpil-ploen.mpg.de/deutsch/abteil.htm
- ↑ a b Archive link ( Memento of the original from April 16, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Jochen Brock Wacain Wolf, Diethard Tautz and Fritz Trillmich: Galapagos and Californian sea lions are separate species: Genetic analysis of the genus Zalophus and its implications for conservation management. Frontiers in Zoology, 4:20, 2007
- ↑ a b http://seamap.env.duke.edu/species/tsn/622014
- ↑ a b http://www.world-of-animals.de/Tierlexikon/Tierart_Seeloewen.html
- ↑ Archive link ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ I. Eibl-Eibesfeldt: Some remarks about the Galápagos sea lions (Zalophus wollebaeki Sivertsen) , in: Mammaliankundl. Mitt., Vol. 3, pp. 101-103 (1955); Observations on the territorial behavior and brood care of the Galápagos sea lions , in: Z. Mammaliankunde, 20, pp. 75–78 (1955)
- ↑ Archived copy ( memento of the original from October 6, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ http://www.bionaut-online.de/sonstiges/Ablebnis_Ozean_2008_c%20David%20Hettich.pdf ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
literature
- CB Heath: California, Galapagos, and Japanese sea lions Zalophus californianus, Z. wollebaeki, and Z. japonicus. in: WF Perrin, B. Wursig, and JGM Thiewissen, eds. Encyclopedia of marine mammals. Academic Press 2002, pp. 180-186.
- Ronald M. Nowak: Walker's Mammals of the World. Johns Hopkins University Press, 1999 ISBN 0-8018-5789-9
- Erling Sivertsen: A survey of the eared seals (family Otariidae) with remarks on the Antarctic seals collected by M / K "Norvegia" in 1928-1929, I kommisjon hos Jacob Dybwad: Oslo 1954
- Don E. Wilson & DeeAnn M. Reeder: Mammal Species of the World, a Taxonomic & Geographic Reference. Johns Hopkins Univ. Press, 3rd ed., 2005 ISBN 0-8018-8221-4
Web links
- Galapagos online
- Zalophus wollebaeki inthe IUCN Red List of Threatened Species 2013.1. Listed by: Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group), 2008. Retrieved October 13, 2013.