✍️✍️✍️ Stellar Sea Lion Research Paper

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Stellar Sea Lion Research Paper



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Steller Sea Lions: Citizen Science at Work

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Its ribs were large, with five of 17 pairs making contact with the sternum ; it had no clavicles. The anterior border of the scapula was nearly straight, whereas those of modern sirenians are curved. Like other sirenians, the bones of Steller's sea cow were pachyosteosclerotic , meaning they were both bulky pachyostotic and dense osteosclerotic. The sea cow's heart was 16 kg 35 lb in weight; its stomach measured 1. The full length of its intestinal tract was about m ft , equaling more than 20 times the animal's length. The sea cow had no gallbladder , but did have a wide common bile duct.

Its anus was 10 cm 0. The male's penis was 80 cm 2. Whether Steller's sea cow had any natural predators is unknown. It may have been hunted by killer whales and sharks , though its buoyancy may have made it difficult for killer whales to drown, and the rocky kelp forests in which the sea cow lived may have deterred sharks. According to Steller, the adults guarded the young from predators. Steller described an ectoparasite on the sea cows that was similar to the whale louse Cyamus ovalis , but the parasite remains unidentified due to the host 's extinction and loss of all original specimens collected by Steller. Like other sirenians, Steller's sea cow was an obligate herbivore and spent most of the day feeding, only lifting its head every 4—5 minutes for breathing.

The sea cow likely fed on several species of kelp, which have been identified as Agarum spp. Steller's sea cow only fed directly on the soft parts of the kelp, which caused the tougher stem and holdfast to wash up on the shore in heaps. The sea cow may have also fed on seagrass , but the plant was not common enough to support a viable population and could not have been the sea cow's primary food source. Further, the available seagrasses in the sea cow's range Phyllospadix spp. Since the sea cow floated, it likely fed on canopy kelp, as it is believed to have only had access to food no deeper than 1 m 3. Kelp releases a chemical deterrent to protect it from grazing, but canopy kelp releases a lower concentration of the chemical, allowing the sea cow to graze safely.

Steller described the sea cow as being highly social gregarious. It lived in small family groups and helped injured members, and was also apparently monogamous. Steller's sea cow may have exhibited parental care , and the young were kept at the front of the herd for protection against predators. Steller reported that as a female was being captured, a group of other sea cows attacked the hunting boat by ramming and rocking it, and after the hunt, her mate followed the boat to shore, even after the captured animal had died. Mating season occurred in early spring and gestation took a little over a year, with calves likely delivered in autumn, as Steller observed a greater number of calves in autumn than at any other time of the year.

Since female sea cows had only one set of mammary glands , they likely had one calf at a time. The sea cow used its fore limbs for swimming, feeding, walking in shallow water, defending itself, and holding on to its partner during copulation. They often slept on their backs after feeding. According to Steller, the sea cow was nearly mute and made only heavy breathing sounds, raspy snorting similar to a horse, and sighs.

Despite their large size, as with many other marine megafauna in the region, Steller's sea cows may have been prey for the local transient orcas Orcinus orca ; it is likely that they experienced predation, as Steller observed that foraging sea cows with calves would always keep their calves between themselves and the shore, and orcas would have been the most likely candidate for this behavior. In addition, early indigenous peoples of the North Pacific may have depended on the sea cow for food, and it is possible that this dependency may have extirpated the sea cow from portions of the North Pacific aside from the Commander Islands.

Steller's sea cows may have also had a mutualistic or possibly even parasitic relationship with local seabird species; Steller often observed birds perching on the exposed backs of the sea cows, feeding on the parasitic Cyamus rhytinae ; this unique relationship that disappeared with the sea cows may have been a food source for many birds, and is similar to the recorded interactions between oxpeckers Buphagus and extant African megafauna. Steller's sea cow was a member of the genus Hydrodamalis , a group of large sirenians, whose sister taxon was Dusisiren.

Like those of Steller's sea cow, the ancestors of Dusisiren lived in tropical mangroves before adapting to the cold climates of the North Pacific. Steller's sea cow was a direct descendant of the Cuesta sea cow H. The Cuesta sea cow is thought to have become extinct due to the onset of the Quaternary glaciation and the subsequent cooling of the oceans. Many populations died out, but the lineage of Steller's sea cow was able to adapt to the colder temperatures. This has led some to believe that the Takikawa sea cow is its own species. Steller's sea cow was discovered in by Georg Wilhelm Steller, and was named after him.

Steller researched the wildlife of Bering Island while he was shipwrecked there for about a year; [32] the animals on the island included relict populations of sea cows, sea otters, Steller sea lions , and northern fur seals. Steller's account was included in his posthumous publication De bestiis marinis , or The Beasts of the Sea , which was published in by the Russian Academy of Sciences in Saint Petersburg. Zoologist Eberhard von Zimmermann formally described Steller's sea cow in as Manati gigas. Biologist Anders Jahan Retzius in put the sea cow in the new genus Hydrodamalis , with the specific name of stelleri , in honor of Steller. The name Hydrodamalis gigas , the correct combinatio nova if a separate genus is recognised, was first used in by Theodore Sherman Palmer.

For decades after its discovery, no skeletal remains of a Steller's sea cow were known. The first partial sea cow skull was discovered in by Ilya Voznesensky while on the Commander Islands, and the first skeleton was discovered in on northern Bering Island. These specimens were sent to Saint Petersburg in , and another nearly complete skeleton arrived in Moscow around Until recently, all the full skeletons were found during the 19th century, being the most productive period in terms of unearthed skeletal remains, from to During this time, 12 of the 22 skeletons having known dates of collection were discovered. Some authors did not believe possible the recovery of further significant skeletal material from the Commander Islands after this period, but a skeleton was found in , and two zoologists collected about 90 bones in As of , 27 nearly complete skeletons and 62 complete skulls have been found, but most of them are assemblages of bones from two to 16 different individuals.

In , the nuclear genome was sequenced. The Pallas Picture is the only known drawing of Steller's sea cow believed to be from a complete specimen. Pallas did not specify a source; Stejneger suggested it may have been one of the original illustrations produced by Friedrich Plenisner, a member of Vitus Bering 's crew as a painter and surveyor who drew a figure of a female sea cow on Steller's request. Most of Plenisner's depictions were lost during transit from Siberia to Saint Petersburg. The picture may have also been based upon a specimen, and was published in by Pekarski. The map depicted Vitus Bering's route during the Great Northern Expedition , and featured illustrations of Steller's sea cow and Steller's sea lion in the upper-left corner.

The drawing contains some inaccurate features such as the inclusion of eyelids and fingers, leading to doubt that it was drawn from a specimen. Johann Friedrich von Brandt , director of the Russian Academy of Sciences, had the "Ideal Image" drawn in based upon the Pallas Picture, and then the "Ideal Picture" in based upon collected skeletons.

Two other possible drawings of Steller's sea cow were found in in Waxell's manuscript diary. There was a map depicting a sea cow, as well as a Steller sea lion and a northern fur seal. The sea cow was depicted with large eyes, a large head, claw-like hands, exaggerated folds on the body, and a tail fluke in perspective lying horizontally rather than vertically.

The drawing may have been a distorted depiction of a juvenile, as the figure bears a resemblance to a manatee calf. Another similar image was found by Alexander von Middendorff in in the library of the Russian Academy of Sciences, and is probably a copy of the Tsarskoye Selo Picture. The Pallas Picture: the only surviving drawing of Steller's sea cow by Friedrich Plenisner , and possibly the only one drawn from a complete specimen The Tsarskoye Selo Picture: a map of the Commander Islands , including illustrations of Steller's sea cow, the Steller sea lion , and the northern fur seal , by Sven Waxell ; the tail is lying flat on the ground in perspective.

The range of Steller's sea cow at the time of its discovery was apparently restricted to the shallow seas around the Commander Islands , which include Bering and Copper Islands. The first fossils discovered outside the Commander Islands were found in interglacial Pleistocene deposits in Amchitka , [12] and further fossils dating to the late Pleistocene were found in Monterey Bay , California, and Honshu , Japan. This suggests that the sea cow had a far more extensive range in prehistoric times.

It cannot be excluded that these fossils belong to other Hydrodamalis species. According to Steller, the sea cow often resided in the shallow, sandy shorelines and in the mouths of freshwater rivers. Bone fragments and accounts by native Aleut people suggest that sea cows also historically inhabited the Near Islands , [42] potentially with viable populations that were in contact with humans in the western Aleutian Islands prior to Steller's discovery in A sea cow rib discovered in on Kiska Island was dated to around 1, years old, and is now in the possession of the Burke Museum in Seattle.

The dating may be skewed due to the marine reservoir effect which causes radiocarbon-dated marine specimens to appear several hundred years older than they are. Marine reservoir effect is caused by the large reserves of C 14 in the ocean, and it is more likely that the animal died between and Lawrence Island , and the specimen is thought to have lived between and CE. Genetic evidence suggests the last Steller's sea cow around the Commander Islands were the last of a much more ubiquitous population dispersed across the North Pacific coastal zones.

They had the same genetic diversity as the last and rather inbred population of woolly mammoths on Wrangel Island. During glacial periods and reduction in sea levels and temperatures, suitable habitat substantially regressed, fragmenting the population. By the time sea levels stabilized around 5, years ago, the population had already plummeted. Together, these indicate that even without human influence, the Steller's sea cow would have still been a dead clade walking , with the vast majority of the population having already gone extinct from natural climatic and sea level shifts, with the tiny remaining population at major risk from a genetic extinction vortex.

The presence of Steller's sea cows in the Aleutian Islands may have caused the Aleut people to migrate westward to hunt them. This possibly led to the sea cow's extirpation in that area, assuming it had not already happened yet, but the archaeological evidence is inconclusive. Lawrence Island, was the Siberian Yupik people who have inhabited St. Lawrence island for 2, years.

They may have hunted the sea cows into extinction, as the natives have a dietary culture heavily dependent upon marine mammals. The onset of the Medieval Warm Period , which reduced the availability of kelp, may have also been the cause for their local extinction in that area. With the otter population reduced, the sea urchin population would have increased, in turn reducing the stock of kelp, its principal food. In any event, the range of the sea cow was limited to coastal areas off uninhabited islands by the time Bering arrived, and the animal was already endangered.

When Europeans discovered them, there may have been only 2, individuals left. The animal was hunted and used by Ivan Krassilnikov in and Ivan Korovin , but Dimitri Bragin, in , and others later, did not see it. Brandt thus concluded that by , twenty-seven years after it had been discovered by Europeans, the species was extinct. It is then checked by our plagiarism-detection software. There is no gap where plagiarism could squeeze in. Your money is safe. Even if we fail to satisfy your expectations, you can always request a refund and get your money back. What happens on our website stays on our website.

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