Dog seals
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Seals ( Phoca vitulina ) on the east beach of dune |
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| Phocidae | ||||||||||||
| Gray , 1821 |
The dog seals ( Phocidae) are the largest of the three families of seals (Pinnipedia). The family is most species-rich in the Arctic and Antarctic Oceans; They are also represented several times in the temperate latitudes, while only a few species live in the tropics . Harbor seals and gray seals , the two seal species native to German coasts, are dog seals.
features
height and weight
The dog seals include both the largest and smallest seals. On average, however, they are smaller than the representatives of the ear seals and walruses . The smallest species are baikal seals and ringed seals with lengths between 110 and 140 cm and a weight of just over 50 kg. The size record is held by the southern elephant seal , whose bulls can be six and a half meters long and weigh three and a half tons.
Unlike the ear seals, males and females are usually the same size or the females are slightly larger than the males. Exceptions are the elephant seals and the folding hats, where the bulls are considerably larger.
hide
Dog seals have a sparse coat of hair. While the ear seals are continually renewing their fur, there is a time for dog seals once a year when they shed and replace all of their coat. The blood vessels then supply the skin where the new hair is created, causing heat loss. This is why dog seals spend a lot of time on land and go into the water less often than usual. Due to the change of coat , there are seasonal changes in color in some dog seals; the new coat looks particularly strong and shiny, but fades noticeably over the months.
At the same time as their coat, elephant seals also repel the top layer of their skin, which then loosens in large pieces.
Fins
As described under Locomotion , the front fins of the dog seals are considerably smaller than those of the ear seals. Each toe usually ends in a strong claw - this is only degenerated in some Antarctic species. With the help of these claws, dog seals can anchor themselves in the ground or dig caves in the snow.
In the hind fins, the outermost toe is always the longest. These too often end in claws, which are largely inoperable. Numerous dog seals in the southern hemisphere have no claws at all on their hind fins.
Skeleton and muscles
In the dog seals, unlike the ear seals, the strongest muscle concentration is not in the shoulder area, but in the lumbar region. The musculus longissimus and the musculus iliocostalis are the most strongly developed muscles here.
Dog seals do not seem to have a visible neck, the head attaches directly to the body. However, like almost all mammals, they have seven cervical vertebrae (exceptions: manatees and sloths ). The neck area is riddled with powerful muscles. When swimming, the head is usually pointed downward, but can be stretched in a flash to grab a prey.
Locomotion
Dog seals differ from the other large seal family, the ear seals, primarily in that the drive is shifted to the rear end of the body. While ear seals get their drive in the water like a penguin by powerful blows of the muscular front fins, the much smaller and weaker front fins of the dog seals are placed close to the body when swimming. In contrast, the hind fins form large areas that are created by the wide spread of the toes. Dog seals move in the water with beats of the hind fins.
These characteristics represent a better adaptation to aquatic life than it is given by the eared seals. However, this comes at the expense of locomotion on land, which is awkward for the dog seals. Since the front fins are no longer able to support the body and the rear fins cannot be pushed under the body, dog seals move forward crawling on their stomach. To do this, you bend your back, move your back body forward and then push your chest forward. Because this movement is very tedious, they often try to move by rolling sideways. Less disadvantageous is the way the dog seals move in ice and snow, where even a small amount of drive is sufficient to let the body slide over the smooth surface.
Often one saw the "more primitive" group in the ear seals and the "more advanced" group in the dog seals. The modern system, however, avoids such classifications, and fossil remains of both taxa are about the same age.
Way of life
As a rule, dog seals do not form large colonies like the ear seals. However, the elephant seals have developed very similar behavior with fighting males watching over harems. Most dog seals are solitary or live in small groups.
Most dog seals feed on fish and other marine animals, but there are also food specialists in this group. The crab eater is adapted to the Antarctic krill as a nutritional basis through its way of life and above all through its teeth . The leopard seal, on the other hand, represents a predator that primarily hunts penguins and other seal species and, alongside the killer whale and sharks, is one of the most effective predators of the Southern Ocean.
Systematics
The dog seals are without a doubt monophyletic . They have been known as fossils since the middle Miocene . Since then, its range has steadily expanded.
The dog seals are often divided into a number of subfamilies. A common method is to separate the dog seals of the southern hemisphere as Monachinae from the dog seals of the northern hemisphere (Phocinae). The Monachinae are characterized by a shortened first metacarpal bone of the front fins and stunted claws on the rear fins. The following subdivision is based on Wilson & Reeder 2005, the cladogram shows the current status of the relationship analysis of the dog seals and comes from the first description by Neomonachus from 2014.
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Relationships within the dog seals according to Scheel et al. 2014.
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- Subfamily Monachinae
- Genus Monachus
- Mediterranean monk seal ( Monachus monachus )
- Genus Neomonachus
- Hawaiian monk seal ( Neomonachus schauinslandi )
- Caribbean monk seal ( Neomonachus tropicalis ); extinct.
- Genus elephant seals ( Mirounga )
- Northern elephant seal ( Mirounga angustirostris )
- Southern elephant seal ( Mirounga leonina )
- Genus Ommatophoca
- Ross seal ( Ommatophoca rossii )
- Genus Lobodon
- Crabeater ( Lobodon carcinophaga )
- Genus Hydrurga
- Leopard seal ( Hydrurga leptonyx )
- Genus Leptonychotes
- Weddell seal ( Leptonychotes weddellii )
- Genus Monachus
- Subfamily Phocinae
- Genus Cystophora
- Folding cap ( Cystophora cristata )
- Genus Erignathus
- Bearded seal ( Erignathus barbatus )
- Genus Histriophoca
- Ribbon seal ( Histriophoca fasciata )
- Genus Real Dog Seals ( Phoca )
- Largha seal ( Phoca largha )
- Common seal ( Phoca vitulina )
- Genus Pagophilus
- Harp seal ( Pagophilus groenlandicus )
- Genus Pusa
- Ringed Seal ( Pusa hispida )
- Caspian seal ( Pusa caspica )
- Baikal seal ( Pusa sibirica )
- Genus Halichoerus
- Gray seal ( Halichoerus grypus )
- Genus Cystophora
supporting documents
- ↑ Don E. Wilson & DeeAnn M. Reeder (eds.): Phocidae ( Memento of the original from May 17, 2014 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. in Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed).
- ↑ a b Dirk-Martin Scheel, Graham Slater, Sergios-Orestis Kolokotronis, Charles Potter, David Rotstein, Kyriakos Tsangaras, Alex Greenwood, Kristofer M. Helgen: Biogeography and taxonomy of extinct and endangered monk seals illuminated by ancient DNA and skull morphology. ZooKeys 409 (2014), Pages: 1–33, doi: 10.3897 / zookeys.409.6244
literature
- Ronald M. Nowak: Walker's Mammals of the World . Johns Hopkins University Press, 1999 ISBN 0-8018-5789-9
- Malcolm C. McKenna, Susan K. Bell: Classification of Mammals: Above the Species Level . Columbia University Press, 2000 ISBN 0-231-11013-8
- Nigel Bonner: Seals and Sea Lions of the World . Facts on File, 1994 ISBN 0-8160-2955-5
- Olaf RP Bininda-Emonds & AP Russell: A morphological perspective on the phylogenetic relationships of the extant phocid seals (Mammalia: Carnivora: Phocidae) . In: Bonner Zoologische Monographien 1996, Vol. 41, pp. 1–256
