Gray whale
| Gray whale | ||||||||||||
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Gray whale |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Eschrichtiidae | ||||||||||||
| Ellerman & Morrison-Scott , 1951 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Eschrichtius | ||||||||||||
| Gray , 1864 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Eschrichtius robustus | ||||||||||||
| ( Lilljeborg , 1861) |
The gray whale ( Eschrichtius robustus ) is a baleen whale that lives in arctic to warm temperate waters . The gray whale is the only representative of the monotypical genus Eschrichtius and is placed in its own family Eschrichtiidae.
features
Gray whales reach a length of 13 to 15 meters, a weight of 25 to 40 tons and an age of 50 to 70 years. The skin color is slate gray to dark gray, but often appears spotted white from a distance due to the massive colonization of the skin by parasitic crustaceans such as barnacles and wall lice . Barnacle barnacles settle particularly frequently on the head and tail fin of the gray whale.
The head with the strongly arched rostrum (the snout) tapers to a point. The fin is missing, but there are several hump-like protrusions along the back, while the fluke is relatively broad and indented. The throat of the gray whale is usually criss-crossed by two, up to a maximum of seven furrows. There are about 150 whiskers 40 centimeters long on each side of the mouth .
The gray whale has two breathing holes and can expel the blow up to four meters high. The ejected water-air mixture rises vertically and appears as a heart-shaped column of fog.
Features of a right whale
The rather strongly arched rostrum of the gray whale indicates a right whale . Although the pointed head resembles that of the blue whale , which belongs to the furrowed whales , the gray whale has a relatively more arched rostrum than the furrowed whale. The lack of a fin in the gray whale is a characteristic of the right whale, and the broad, notched fluke is typical of members of the right whale family.
distribution
Gray whales only live in the Pacific today , with a distinction being made between a western Pacific and an eastern Pacific population . Their number was estimated at around 26,000 specimens in the North Pacific in the late 1990s. In the North Atlantic, however, the gray whales were exterminated by whaling and became extinct around 1700. These Atlantic gray whales lived off Svalbard , Greenland and Canada, and in winter probably off North Africa. Sightings of individual animals in the Mediterranean (2010) and the South Atlantic (2013) indicate that the increasingly melting ice cap of the Arctic enables the gray whales to return to the Atlantic.
Gray whales permanently live closer to the coast than any other whale species. They spend the summer in polar waters and migrate south in the winter. The East Pacific population overwinters off the coasts of California and Mexico . The animals of the Western Pacific stay off Siberia and around the Kamchatka Peninsula in the summer and spend the winter off Korea and Japan .
Way of life
Gray whales are slow swimmers and reach maximum speeds of eight kilometers per hour. Gray whales usually dive for four to five minutes before reappearing. While the whales are on the surface, they often jump, pushing their heads and upper bodies out of the water and then falling back again. Often the gray whales are only a few kilometers from the coast. For the gray whale, a year is divided into three phases: feeding, migration and reproduction.
Hike
The East Pacific population spends the summer months in the nutrient-rich regions of the Bering Sea . In autumn, the migration takes place south, where the gray whales breed off the California coast. After a few months they return to the more northerly feeding grounds. The West Pacific population spends the summer months in the northern areas of the Okhotsk Sea off Japan . Reproduction occurs in winter after migrating to more southern areas of the Pacific.
Gray whales cover greater distances on their migrations than any other whale species. The East Pacific population moves up to 10,000 kilometers across the Pacific each year. This is the longest known mammal migration. The whales form groups of up to 16 animals on the migration between feeding and breeding areas. However, smaller groups of two or three animals are common. Even so, they are extremely social animals. It was observed how sick or injured conspecifics were brought to the surface of the water to breathe.
nutrition
The gray whale eats almost exclusively during the summer months. The stored fat must then be sufficient for the long migration and the reproductive time. The gray whale's main diet is flea , but copepods and small fish are also present. The gray whale is the only whale to search for food on the seabed. Filtering bottom dwellers from the seabed mud is a unique diet among baleen whales. To do this, it stirs up the deposits on the sea floor. The short and robust whales of the gray whale are adapted to this form of food intake . The gray whales roll to one side and slowly swim in the bottom sediment. With the help of the beards, the food-relevant marine animals are then filtered out of the mud. Usually the whales roll over on their right side, which causes the right whales to wear out more quickly.
Reproduction
The mating of the gray whales takes place in the winter months. Sexually mature females are often accompanied by two or more males, but then choose only one partner. After mating, the animals return to the nutrient-rich northern areas for the summer months. The gestation period is eleven to twelve months. After the mother animals return to the southern winter areas, the calves are born. Each whale cow can only give birth to one calf. This mostly happens in protected lagoons. The calves are about five meters long at birth and weigh half a ton. They accompany their mothers during the remaining time in the winter area and on the following hike into the summer feeding grounds. In late summer, the calves are finally weaned and are from now on independent.
Evolution and systematics
Tribal history
So far there is no fossil evidence of the ancestry of the gray whale, since early fossil finds differ only insignificantly from today's forms. The oldest known fossil of a whale skeleton classified into the Eschrichtiidae due to skull features comes from the late Pliocene (about 3 million years ago) from the Yuchi formation near Teshio on Hokkaidō , Japan.
Systematics
When it was first described in 1861, Wilhelm Lillebjorg named the gray whale after specimens off the coast of Norway as Balaenoptera robusta . The classification of the gray whale in its own genus Eschrichtius was made by John Gray in 1864, who named him after Daniel Eschricht. In 1869 Edward Drinker Cope described the Pacific species Rhachianectes glaucus , which, after comparing the skeletal morphology , was united with Eschrichtius robustus and is now only considered as a separate population .
The gray whale family consists of only one genus with only one species, the Eschrichtius robustus . The American oceanographer Michael Hall used the term Eschrichtius gibbosus , but could not gain acceptance. The gray whale is placed among the baleen whales on the basis of morphological characteristics . It combines characteristics of the family furrow whale and right whale . In 1951 it was decided to introduce a separate systematic family for the gray whale.
By molecular biology a close relationship between gray whales, the studies was Buckelwal ( Megaptera novaeangliae ) and the blue whale ( Balaenoptera musculus ) is determined which is to be thus more closely related to these two types as with all the other species of the genus Balaenoptera.
Whaling and Protection
As a species living near the coast, the gray whale was hunted by humans from an early age. Whether this is the reason for the very early extinction of the European population (around 500 AD) can no longer be traced. The West Atlantic gray whales became extinct around 1700. Since then, the gray whale has only lived in the Pacific . The West Pacific populations were heavily hunted by Japanese whalers in the 18th and 19th centuries . It is even unclear today whether the gray whales of the western Pacific still exist. Occasional sightings off the Korean coasts can also include stray individual animals from the East Pacific. Whale researchers assume a population of at most 200 animals.
The wintering places of the East Pacific gray whales were discovered in 1846. After that, whaling stations were set up on the local coasts and thousands of whales were killed within a few years. It was not until 1946 that the species was placed under protection and thus saved from extinction. Since then, the stocks have grown again, so that there are around 22,000 gray whales today. But even for this low number compared to the past, the food supplies are apparently no longer sufficient, as is assumed based on the sighting of lean and apparently starving animals. For some years now, around 110 gray whales have been hunted annually by the indigenous population of Russia .
In the 19th century, whalers nicknamed the gray whale devil fish . This was caused by furious attacks by whale cows who wanted to protect their calves.
On the North American coast, gray whales are a very popular destination for modern whale tourism because of their proximity to the coast. Tourists can be brought up to a few meters to the gray whales by boats.
literature
- M. Carwardine: whales and dolphins . Delius Klasing, 2008, ISBN 978-3768824736 (high quality guide)
- Ralf Kiefner: whales and dolphins worldwide . Year Top Special Verlag, 2002 (guide to the magazine "tauchen", very detailed)
- RR Reeves, BS Stewart, PJ Clapham, JA Powell: Sea Mammals of the World. A Complete Guide to Whales, Dolphins, Seals, Sea Lions and Sea Cows. Black, London 2002, ISBN 0-7136-6334-0 (guide with numerous pictures).
- DDP report in the Bremer Nachrichten of September 14, 2007 with reference to Elizabeth Alter in "Proceedings of the National Academy of Sciences"
Web links
- Entry at wale.info
- Eschrichtius robustus in the endangered Red List species the IUCN 2006. Posted by: Cetacean Specialist Group, 1996. Retrieved on 11 May, 2006.
Individual evidence
- ↑ a b Age and number of publications by the Government of Canada on the reintroduction of gray whales in the North Atlantic: Recovery Strategy for the Gray Whale, Atlantic Population, in Canada (2007), accessed June 15, 2019.
- ↑ Characteristics of the gray whale ( Memento of the original from March 3, 2007 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.
- ↑ Gray whales return to the Atlantic Article in the Berliner Zeitung March 9, 2015, accessed on June 15, 2019.
- ↑ Melting of the polar ice caps in ZEIT ONLINE from June 13, 2018, accessed on July 18, 2019
- ↑ Detlef Singer: Fascination Animal & Nature, Group 1 - Mammals , Munich without a year
- ↑ WCDS Whale Protection ( 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.
- ↑ Cetaceen.de: Systematics of the whales ( Memento of the original from June 28, 2007 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.
- ↑ Hiroto Ichishima, Eri Sato, Tsumoru Sagayama, Masaichi Kimura: The oldest record of Eschrichtiidae (Cetacea: Mysticeti) from the late pliocene, Hokkaido, Japan. Journal of Paleontology 80, 2006; Pages 367–379 ( abstract )
- ↑ Lt. DDP report in the Bremer Nachrichten of September 14, 2007, reference to Elizabeth Alter in "Proceedings of the National Academy of Sciences".
- ↑ Table of the annual hunting figures
- ↑ Information on the gray whale
