Hydrodamalis gigas (Steller's Seacow)

[RSN]

Hydrodamalis gigas
(Steller's sea cow)



By Bret Weinstein and James Patton

Geographic Range
North Pacific Ocean: The range of Hydrodamalis gigas in historic times appears to have been limited to the coastal waters of the Komandorskiye and Blizhnie Islands in the Bering Sea. Accounts of sightings from other islands in the Bering Sea, along the northwest coast of North America and the northeast coast of Asia, in the Arctic Ocean and Greenland are difficult or impossible to confirm and generally discounted. Fossil evidence indicates that the past distribution of genus Hydrodamalis was much wider, including the coasts of Japan and North America. Fossil remains of Hydrodamalis cuestae are known from as far south as the southern coast of California.

Habitat
Hydrodamalis is known to have occurred in cold, shallow, coastal marine waters rich in algae and sea grass. Herds were frequently found near the mouths of streams or rivers. Its range was restricted to islands in the Bering Sea during historic times, but extended to California and Japan during prehistoric times.

Physical Description
Mass:
5400 to 11196 kg; avg. 8000 kg
(11880 to 24631.2 lbs; avg. 17600 lbs)

The few first-hand accounts of Hydrodamalis that are available note several distinctive features. The animal was considerably larger than any other extant sirenian. Steller (1751) gives a length of 296 inches (7.5 meters) for a female specimen that he examined. Larger sizes have been suggested, but after examination of available skeletal material Domning (1978) estimated an upper size limit of about 7.9 meters. However, Domning (1978) also notes that the Bering Sea population appears to have occupied a sub-optimal habitat for the species that may have prevented individuals from reaching their maximum possible size. Published mass estimates range from 5400 to 11,196 kilograms. It has been reported that Hydrodamalis displayed sexual size dimorphism, but Domning (1978) could find no evidence to support this assertion.

Steller (1751) describes the head and neck as being short and weakly delimited from the rest of the body. Pinnae were absent, the nostrils were paired and located near the tip of the snout, and the eyes were relatively small. Many large, vibrissae-like bristles surrounded the mouth. Teeth were absent in adults, but the keratinous rostral pads found in other sirenians were retained in Hydrodamalis. The neck appears to have been more flexible than in other living sirenians and may have helped the animal feed over a wider area with less movement of the large body. The body tapered cranially and caudally, but the belly and sides were rounded and swollen looking. When healthy, the back was slightly convex. Hydrodamalis resembled other dugongids in having a whale-like fluke at the end of its tail. The skin of the animal was unusual in having a black, thickened, bark-like epidermal layer that may have protected it from abrasion against rocks in the shallows where it fed.

The forelimbs of Hydrodamalis are highly derived relative to the flipper-like limbs of most other sirenians. They lack phalanges and show several specializations for a distinctive style of locomotion. Steller (1751) described the forelimbs as being relatively short with a distinct hook-like shape. Several recent artistic reconstructions portray Hydrodamalis as having flipper-like limbs, but drawings made by observers who had seen live individuals support Steller's (1751) account. The epidermal layer was very thick on the limbs, and Steller (1751) describes Hydrodamalis using the limbs to pull itself along while feeding in shallow water.

Domning (1978) examined the skeletal structure of the forelimbs and pectoral girdle of Hydrodamalis. Almost all of the bones show extensive modification and changes in muscle originations and insertions that reflect a greater emphasis on parasagittal movements of the limb. Domning compares these specializations to those of graviportal mammals and tree sloths, animals that also have relatively straight limbs that move in a parasagittal plane. Hydrodamalis appears to have had a narrower, deeper chest in the area of the pectoral girdle than most other sirenians, bringing the limbs closer to the midline of the body and allowing greater fore-aft mobility of the limbs. This reconstruction strongly suggests that Hydrodamalis was specialized to "walk" along in the shallows while feeding, as described by Steller (1751).

Steller (1751) and other first-hand observers also describe Hydrodamalis as being unable to dive or even completely submerge its body. Sirenians generally have precise control of their buoyancy as a result of specializations of their skeleton, diaphragm and lungs (Domning and de Buffrénil, 1991). Domning (1978) speculated that increased buoyancy may have been indirectly selected for as a consequence of large body size because of corresponding increases in lung volume, intestinal volume and thickness of blubber. There may also have been a direct selective advantage to increased buoyancy because it would have reduced the area accessible to parasites, reduced drag when swimming, reduced heat loss to the water via conduction, and allowed Hydrodamalis to enter shallower waters to feed and escape predators. However, Domning (1978) disputes Steller's (1751) claim that Hydrodamalis could not dive, even if it spent most of its time floating. (Domning and de Buffrénil, 1991; Domning, 1978; Steller, 1899 (orig. 1751))

Reproduction
Few details are known of the mating system of Hydrodamalis. Steller (1751) describes them as monogamous, and mating activities appear to have been concentrated in the early spring. Offspring were observed to be born at anytime of year, but most births took place in early autumn. Females produced only one calf per breeding attempt. Steller (1751) inferred the length of gestation to be over one year. (Steller, 1899 (orig. 1751))

Behavior
Hydrodamalis was gregarious, and herds appear to have included juveniles, males and females. Juveniles were kept toward the middle of the herd, and Steller (1751) describes herd members attempting to come to the aid of captured individuals. As noted above, Hydrodamalis appears to have been monogamous, and Steller's account of the animal's behavior suggests the pair bond was quite strong.

Herds of Hydrodamalis congregated in shallow waters near the shore, sometimes so close that hunters could simply wade out to them. Steller (1751) notes that individuals or herds were often found near the mouths of stream or rivers, which suggests they could not tolerate drinking marine water. Individuals spent the majority of their time feeding or resting, and Steller (1751) notes that the head could be kept submerged for 4-5 minutes at a time. Several first-hand observers comment on the apparent fearlessness of Hydrodamalis. According to Steller (1751), boats could be easily rowed into a herd and humans could wade among individuals near shore with little or no reaction.

Food Habits
First-hand accounts of the feeding habits of Hydrodamalis are often vague and contradictory. Based on Steller's (1751) descriptions of plants he saw Hydrodamalis eating, it appears that brown and red algae were its primary food sources, with sea grass a minor component of the diet (Domning, 1976; 1978; Anderson, 1995). Living sirenians are known to ingest brown algae in times of food shortage, but this does not appear to be a preferred food. Steller (1751) describes Hydrodamalis as feeding on parts of algae and sea grass growing near the surface or on rocks in the shallows. Seasonal food availability may have been a problem for the Bering Sea population, as Steller (1751) describes individuals losing enough weight during the winter months to cause their ribs and vertebrae to be visible under the skin.

Many features of the feeding system of Hydrodamalis indicate that it had adapted to its unusual diet of soft kelps and algae. Perhaps the most obvious modification is the absence of teeth. Hydrodamalis retained the keratinous rostral pads found in other sea cows, and the presence of interlocking ridges and grooves on these pads as well as reinforcement of the rostrum may be evidence that the animal used these pads to masticate its food. There is also skeletal and myological evidence that suggests the cropping and mashing motions of the front of the mouth were emphasized at the expense of more traditional chewing movements in Hydrodamalis. In his account, Steller (1751) also describes the animal as masticating its food with the keratinous plates. Living dugongids finely chew sea grasses, but tend to swallow ingested algae relatively intact. Based on this observation, Domning (1978) hypothesized that Hydrodamalis may have simply ripped off pieces of kelp and swallowed them with little or no processing in the mouth. The great enlargement of the gut reported by Steller (1751) probably reflects the need for more thorough chemical digestion of food due to the lack of thorough mastication. The amount of rostral deflection seen in Hydrodamalis is consistent with an emphasis on surface feeding habits, and the highly mobile lips were used in gathering and cropping food, as in other extant sea cows. The claw-like forelimbs may also have been used to dislodge plant matter from rocks.

Economic Importance for Humans: Negative
Hydrodamalis had no negative economic effects on humans.

Economic Importance for Humans: Positive
Hydrodamalis was hunted primarily as a source of food. Steller (1751) describes the meat as being easily prepared and similar to beef in taste and texture. The blubber was useful for cooking and was also a source of lamp oil. The milk of harvested cows was consumed directly or made into butter. The thick, tough hide was used for shoes, belts and to make skin-covered boats.

Conservation Status
IUCN Red List:
Extinct.
It is not known exactly when the last individual of Hydrodamalis died, but it appears likely that the species was extinct by 1768. Yakolev, a first-hand observer of Hydrodamalis, claims that an order was given to the headquarters of the outpost on the Komandorskiye Islands on November 27, 1755, prohibiting hunting of the sea cows (translated in Domning, 1978). However, he also notes that by this time Hydrodamalis was extremely rare.

Much has been written about the extinction of Hydrodamalis at the hands of humans. The hunting practices described in first-hand accounts are extremely wasteful. Often, hunters would simply wade out to an individual, spear it, and then allow the animal to swim off, hoping that it would later die and drift to shore. No sustained yield practices were used, and the low reproductive rate of the population, combined with its probable existence in a sub-optimal environment likely hastened the species' decline. Anderson (1995) has also noted that the intense hunting of sea otters on the Bering Sea islands may have contributed to the final extinction of Hydrodamalis. It is known that sea urchin populations can severely deplete sea grass and algae communities when otters are removed, and as this happened on the Bering Sea islands, the sea cows would have faced a new competitor for food. A similar course of events may have occurred 12,000-14,000 years earlier along the coast of Asia and North America as aboriginal peoples colonized the areas and began hunting otters and sea cows (Anderson, 1995).

Other Comments
A cladistic analysis of the Sirenia (Domning, 1994) has shown that Hydrodamalis falls within the family Dugongidae. The genera Dusisiren and Hydrodamalis form the sub-family Hydrodamalinae. Domning (1976; 1978; 1994) has commented on the relatively good fossil record of the hydrodamalines and its documentation of the transition from a more traditional sirenian ancestor to the highly specialized Hydrodamalis.

Steller (1751) describes parasitic crustaceans that sometimes severely infested the submerged areas of Hydrodamalis. There has been much speculation as to the identity and relationships of these parasites, but the lack of preserved specimens has forced the issue to remain unresolved. In his dissections of captured specimens, Steller (1751) also noted the presence of white, parasitic worms in the gut. It has been suggested that these parasites may have been ascarid nematodes, but the absence of any preserved specimens prevents a definite identification.

Humans are the only known predators of Hydrodamalis, although Domning (1978) suggested that sharks and killer whales were also likely predators.


Weinstein, B. and J. Patton. 2000. "Hydrodamalis gigas" (On-line), Animal Diversity Web. Accessed March 10, 2007 at animaldiversity.ummz.umich.edu/site/accounts/information/Hydrodamalis_gigas.html.

[another specialist]

To the crew of Vitus Bering's ship St. Peter, shipwrecked off the coast of Kamchatka in early November 1741, the huge, easily-hunted sea cow was a godsend that helped most of them to survive and return home. Within 3 decades, though, their countrymen had hunted sea cows to extinction.

Steller's sea cows were the largest, and the only cold-water members of the scientific order Sirenia, to which manatees and dugongs also belong. Although they look rather like whales or sea lions, the order's closest relatives are elephants and hyrax. Feeding on sea grasses (in the case of the Steller's sea cow, primarily kelp), they are the only aquatic herbivorous mammals. Historically, about 1,500 - 2,000 members of the species known taxonomically as Hydrodamalis gigas ("giant sea calf") lived in the shallow waters off the coasts of Alaska and the Russian Far East, centred in the Commander Islands. Although they undoubtedly faced some hunting pressure from the Aleut and Eskimos, both of whom were expert whalers, their population was probably quite stable.

Georg Wilhelm Steller, the naturalist and physician on Bering's expedition, recorded the first, and best, descriptions of the sea cow. They were up to 28 feet long, and weighed as much as 7-8 tons; drifting just below the surface, they were often mistaken for overturned boats. With a heavy bone stucture, they had huge midsections, a disproportionately small head, and a large, flat, twin-lobed tail. The wrinkly black hide was about an inch thick and very tough, covering a fat layer between 4 and 9 inches thick - the combination provided protection from the cold, pounding by surf, and rubbing against ice and rocks. It did not provide sufficient protection from Russian weapons, though - only one out of five sea cows hit by harpoon or rifle fire was retrieved, but the majority escaped only to die at sea from their injuries.

Their external ear openings were only about the size of a pea, but the internal ear bones were very large, so excellent hearing can be assumed, although when they were feeding, they would completely ignore even a boat. Steller sometimes described the sea cow as if they were farm animals:

These animals, like cattle, live in herds at sea, males and females going together and driving the young before them about the shore. They are occupied with nothing else but their food. The back and half the body are always seen out of the water.They eat in the same manner as the land animals, with a slow forward movement. They tear the seaweed from the rocks with the feet and chew it without cessation... During the eating they move the head and neck like an ox, and after the lapse of a few minutes they lift the head out of the water and draw fresh air with a rasping and snorting sound after the manner of horses.

During the ten months that Steller and the other survivors of Bering's crew spent on what would later be named Bering Island, Steller was able to gather considerable information on the habits of the sea cow, as well as an extensive set of measurements of various parts of the sea cow's anatomy, allowing scientists to reconstruct the animal around skeletons that have survived. Hans Rothauscher has posted an excellent site, in both English and German, showing the progression and possible errors in such reconstructions of the sea cow.

The meat of the sea cow, which was most often referred to as being similar to veal, remained fresh for much longer than any other available meat source, making it extremely valuable to the Russian sailors and hunters. The fat was described as tasting like sweet almond-oil. Although Bering's crew only killed their first sea cow six weeks before their escape in August 1742, the meat was crucial in restoring their strength during the final stages of building a new boat from the wreckage of the St. Peter. When they left, they took a supply of meat and fat, and stories of the incredible riches of the islands for fur hunters. Those hunters flocked to the area, and in 1768, explorer Martin Sauer entered in his journal an account of the death of the last known sea cow.

Manatees and dugongs are the focus of worldwide conservation efforts to ensure that they don't share the fate of the Steller's sea cow. There is still a chance, though, that the sea cow isn't extinct. In the years since their generally-accepted extinction in 1768, there have been occasional reports suggesting that small colonies may have survived by moving to areas away from the Russian hunting grounds. In the mid-1800s, such reports were not unusual, and as recently as 1962, the crew of a Russian whaler reported seeing six animals that resembled sea cows, feeding in a bay in the Gulf of Anadyr. In 1977, a fisherman in Kamchatka reported actually touching a drifting animal that matched the description of a sea cow. But for now, those reports are just considered to be rumours, fuel for yet another Northern myth.

References & Further Reading:
# Delphine Haley, editor - Marine Mammals of Eastern North Pacific and Arctic Waters (Seattle: Pacific Search, 1978)

explorenorth.com/library/yafeatures/bl-seacow.htm

[another specialist]

This Sketch of Steller's sea cow is from the journal of Sven Waxell, "Kamchatka Expedition 1741-1742"; source: The American Expedition by Sven Waxell 1952.

Hydrodamalis gigas, formerly classified as Rytina gigas, was first seen by modern humans when Captain Vitus Bering and his comrades discovered an uninhabited island (later named Bering Island) in 1741. Bering and his two ships, St. Peter and St. Paul, were on their way home to Kamchatka following an expedition to map the coast of Alaska for Tsar Peter I the Great of Russia. The ships were separated during a storm and Captain Bering, the St. Peter, and her crew were stranded on the island. Although Bering died on the island during the winter of 1741, Georg Wilhelm Steller (a German-born naturalist), and about half of the ship's crew survived to rebuilt their ship and return home in 1742, thanks to the meat of the sea cow.

In his writings, Steller described the giant sea cow and its habits, but was vague in his accounts of abundance and distribution. He said he found it numerous and in herds, leaving future researchers to guess at exactly how many. Stejneger (1887) estimated the number at less than 1500 and hypothesized that they were the last survivors of a once more numerous and widely distributed species which had been spared because man had not yet reached their last resort. Modern scientists agree that Steller's sea cow, and it's ancestors, H. cuestae, Dusisiren dewana, and D. jordani, were once widely distributed around the Pacific rim from Baja to Japan, where Hydrodamalis thrived until the coming of humans in the Pleistocene (Domning 1987).

Upon the St. Peter's return to Kamchatka in 1742, word of the excellent sea cow meat spread quickly through the sailing community. New hunting expeditions were formed almost every year. They returned to Bering Island where they spent 8-9 months hunting fur-animals and eating sea cow meat to survive. Indeed, many of the expeditions are reported to have wintered on Bering Island for the express purpose of collecting sea cow meat for the remainder of their 3-4 year journey to the Aleutian Islands and America. The last sea cow was reported killed in 1768, just 27 years after the island had been discovered by modern man.

From Steller's description, these huge herbivores are believed to have numbered around 1500-2000 in the Bering Island and Copper Island areas of the North Pacific (circa 1741). The largest animals were 4-5 fathoms long (1 fathom = 6 feet), 3.5 fathoms thick around, and weighed 200 puds or 80 short hundredweight (up to about 8,000 pounds). They had no teeth, but two flat white bones, the one above fixed to the palate, and the one below on the inside of the lower jaw. Both were furrowed and had raised ridges with which they masticated kelp.

The sea cows were found in herds close to shore. They drifted just below the surface of the water, a single animal resembled an overturned boat. Steller and Waxell both noted large midsections and very small heads. To see a photograph of the skeleton of a Steller's sea cow in the Helsinki Museum, go to Ari Lampinen, University of Jyvaskyla, Finland. The text is in Finnish, but the photo is worth the trip!

The ancestor to Steller's Sea Cow was possibly an extinct Dugongidae sea cow, Dusisiren jordani, previously named Metaxytherium jordani. Dusisiren was common in the shallow coastal waters of late Miocene California 10-12 million years ago. Although Sirenian evolution is not fully understood, there is a very clear and compelling fossil record leading up to Steller's sea cow (Domning 1987).

Scientists believe the Order Sirenian originated near Africa in the middle Eocene, 45-50 MYBP (Perry 1995; also see Domning, D. P., 1978, Sirenian Evolution in the North Pacific Ocean, University of California Press). Click to learn more about the Eocene and Geological Time.

References

* Domning, D. P. 1987. Sea cow family reunion. Natural History April 1987 Vol.96(4):64-71.
* Stejneger, Leonhard. 1887. How the great northern sea-cow (Rytina) became exterminated. The American Naturalist 21(12):1047-1054.
* Steller, Georg Wilhelm. 1988. Journal of a Voyage with Bering 1741-1742. Stanford University Press. Stanford, California. 252 pp.
* Waxell, Sven. 1952. The American Expedition. William Hodge and Company, Limited. London. 236 pp.

www.sirenian.org/stellers.html

[savertim]

What if, in another part of the world, a different Stellers sea cow existed, say in deep ocean depths, or an arctic bay?

[sordes]

Sorry, but that´s a bit ridiculous. Steller´s sea cow was probable even not able to dive at all, and they were feeding on floating algae. Even those sea cows which feed on seaweed don´t dive very deep. As they are dependent from marine plants, they can´t life in the arctic or feed in deep water.

[savertim]

they could have evolve or ( slim chance) mutated to suit this type of enviroment. but I do agree that you are quite right

[another specialist]

I agree with you Sordes

[sordes]

Savertim, it seems that your knowledge about evolution and biology is comparably limited. There is no, really no possibility that animals like sea cows just adapted (within some decades) from floating kelp-grazers to deep-sea-living animals.

[savertim]

they may have evolved, over millions of years, but however that would classyfy them as an entirely different specied. You are quite right sordes

[sordes]

Savertim, a mammal can not adapt to become a deep-sea creature. Even sperm whales and beaked whales, which can dive very deep and very long are normally at the surface. And a plant-eating animal, which is even not able to dive at all, will surely never adapt to a life in the deap, because there is nothig it could eat.

[savertim]

I have read about this land mammal evolve into whales sordes, but I have already lost my argument. The stellers sea cow is dead, and it was killed about 14 years after its discovery. men are savages. earth will be happy when we die out

[another specialist]

Any species to evolve into what you mentioned above would take one hell of a long time to do so and of course this would result in one completely different species that would be distantly related to the species it evolved from.

[sordes]

A skeleton which is exhibited in the Museum of natural history at Vienna:
www.petermaas.nl/extinct/gallery/displayimage.php?album=6&pos=14
www.petermaas.nl/extinct/gallery/displayimage.php?album=6&pos=15

[another specialist]

sordes said:

A skeleton which is exhibited in the Museum of natural history at Vienna:
www.petermaas.nl/extinct/gallery/displayimage.php?album=6&pos=14
www.petermaas.nl/extinct/gallery/displayimage.php?album=6&pos=15

[Melanie]

Rhytina [1]
No teeth, their place being supplied functionally by
the dense, strongly-ridged, horny oral plates. Premaxillary rostrum
about as long as the anterior narial aperture, and moderately
deflected. Vertebrae : C 7, D 19, L and C 34-37. Head very small
in proportion to the body. Tail with two lateral pointed lobes.
Pectoral limbs small and truncated. Skin naked and covered with
a very thick, hard, rugged, bark-like epidermis. Stomach without
caecal appendages to the pyloric cavity. Caecum simple.
Only one species of this genus is known, E. stelleri, the Northern
Sea-cow, by far the largest animal of the order, attaining the length
of 20 to 25 feet. It was formerly an inhabitant of the shores of
two small islands in the North Pacific, Behring and the adjacent
Copper Island, on the former of which it was discovered by the
ill-fated navigator whose name the island bears, when, with his
accomplished companion, the German naturalist Steller, he was
wrecked upon it in 1741. Twenty-seven years afterwards (1768),
as is commonly supposed, the last of the race was killed [2] and its very existence would have been unknown to science but for the
interesting account of its anatomy and habits left by Steller, and
the few more or less imperfect skeletons which have recently rewarded
the researches carried on in the frozen soil of the islands
around which it dwelt. There is no evidence at present of its
having inhabited any other coasts than those of the islands just
named, although it can hardly be supposed that its range was
always so restricted. When first discovered it was extremely
numerous in the shallow bays round Behring Island, finding
abundant nutriment in the large laminarise growing in the sea.
Its extirpation is entirely due to the Russian hunters and traders
who followed upon the track of the explorers, and, upon Steller's
suggestion, lived upon the flesh of the great Sea-cows. Its
restricted distribution, large size, inactive habits, fearlessness of
man, and even its affectionate disposition towards its own kind
when wounded or in distress, all contributed to accelerate its final
extinction.
According to Steller's account, the Rhytina had a skin of a dark
brown colour, sometimes spotted or streaked with white. The fore
limb was covered with short brush-like hairs.

Source: An Introduction to the Study of Mammals - Living and Extinct by William Henry Flower & Richard Lydekker 1891

[1] Illiger. Prodromits Syst. Mamm. et Avium, p. 141 (1811). Amended from
Rytina.
[2] Nordensköld, during his voyage in the Vega, obtained some information
from the natives of Behring Island which led him to believe that a few individuals
may have survived to a much later date, even to 1854 ; but this conclusion
is disputed by later writers.

[another specialist]

Link to page if anyone else wants to download this pdf where above info come from.

www.archive.org/details/introductiontost00flowuoft

[another specialist]

Mammalia, recent and extinct; an elementary treatise for the use of the public schools of New South Wales (1873)

www.archive.org/details/mammaliarecentex00scotiala

[another specialist]

Mammal Species of the World: A Taxonomic and Geographic Reference
By Don E. Wilson, DeeAnn M. Reeder

books.google.co.uk/books?id=JgAMbNSt8ikC&pg=PA221&dq=Nesophontes&sig=DEnD1lzF8OOFdgEqp5yQt-poHcw#PPA92,M1

[another specialist]

www.britannica.com/eb/art-57537/The-Stellers-sea-cow-extinct-since-the-18th-century-fed

[sordes]

Sorry, but this pictures shows recent manatis and not Hyrdodamalis gigas.