Tag Archives: marine wildlife

Steller’s sea cow – a surviving giant of the Pleistocene

The Steller’s sea cow was one of the last survivors of the megafauna of the Pleistocene to die out in our era. The giant marine mammal was discovered in 1741 by Georg Steller – naturalist of the expedition led by Danish explorer Vitus Bering on the commission of the Imperial Russian government to chart the route between Siberia and Kamchatka – when their ship wrecked on an uninhabited island on the way back to Russia. The sea cow population was confined to the waters surrounding two small islands – the newly discovered species was completely extirpated during the following decades by expeditions of the flourishing Pacific maritime fur trade. The demise of the sea cow was so rapid that in fact everything we know about its appearance and habits is based on the detailed accounts of Steller from his posthumous published work: De bestiis marinis – The Beasts of the Sea, and the few dozen skeletons that were found from the mid 1800s until today.

Model of the Steller’s sea cow based on descriptions and skeletons; a reconstruction made for the Skin & Bones project of the Smithsonian’s National Museum of Natural History by
©Copyright Diana Marques

Date of extinction: Johann Friedrich von Brandt, director of the Russian Academy of Sciences concluded based on reports from fur hunters following Vitus Bering’s route to Alaska that the Steller’s sea cow was extinct by 1768, only 27 years after it was discovered by the Bering expedition.
However, there were some reports of alleged sightings dating after the official extinction date, even from the mid 20^th century.

Range: At the time of its discovery, the Steller’s sea cow had only one last population: in the surrounding waters of the Bering and Copper Islands, two members of the Commander Chain between the Aleutians and the Kamchatka Peninsula.
Later discovered evidence of bone fragments proves the existence of another population in the northern Bering Sea at St. Lawrence Island around the 9-10^th centuries; and based on bone fragments and accounts of Aleut people it is probable that another population persisted into the late 18^th century at the Near Islands (western Aleutian Islands).
Fossil finds from the Pleistocene show that before the Ice Age sea cows were probably ubiquitous along the edge of the Pacific from Japan to the Baja Peninsula.

Illustration of the Steller’s sea cow grazing on kelp
©Copyright Encyclopaedia Britannica, Inc

Habitat: The Steller’s sea cow used to inhabit the cold shallow waters along the shores.

Description: Steller’s sea cows (Hydrodamalis gigas) were large sirenians, members of the once-diverse family Dugongidae. Their closest living relatives are the dugong and three manatee species, but instead of the warm tropical seas they adapted to living in frigid Arctic waters. Their huge size – adults grew to be 8-9 m long, weighing up to 10 tons – their thick blubber and outer skin were effective adaptation methods to conserve the heat of their body in the icy sea and to prevent injury from the sharp rocks of the shallow waters.

Manatees are sirenians closely related to the extinct Steller’s sea cow
©Copyright Alex Mustard

They were obligate algivores eating seaweed; but being unable to completely submerge, their food source was reduced to kelp and seagrass species inhabiting the coastal waters, with their canopy not deeper than 1 meter below the tide. They could hold their breath for a few minutes under water and the inside of their flippers was covered with bristles to anchor them down and prevent them from being swept away by strong waves. The flippers and the forked tail fluke were used for swimming and walking in shallow water.

The sea cow’s snout and mouth were perfectly adapted to grazing on kelp: the snout pointed downwards, with large and broad upper lips extending beyond the lower jaw. Instead of teeth they had white bristles on their upper lip, with some of them protruding from the muzzle; and two keratinous plates in their mouth, used for chewing.

Portrait of a dugong, the closest living relative of the Steller’s sea cow
©Copyright Laura Dinraths

Sea cows were highly social animals, probably monogamous. They lived in small family groups, guarded and helped each other and protected their calves against predators. Females had one calf after a more than one year long pregnancy period.

Cause of extinction: The rapid demise of the Steller’s sea cow population of the Commander Islands was apparently the consequence of overhunting for their tasty meat and valuable subcutaneous fat by European and Russian sailors and fur traders. The populations of the Aleut and St. Lawrence Islands were wiped out by native people for the same reasons.

However, recent studies (James A. Estes) based on modern methods of mathematical simulations to model indirect community interactions prove that the extinction of the Steller’s sea cow at the Commander Islands would have been inevitable anyway as a consequence of the ongoing overkill of sea otters by Russian and Aleut hunters after the onset of the Pacific maritime fur trade in the 1740s.

The sea otter is a keystone species in the trophic cascade of the kelp forest
©Copyright Robin Agarwal / CC BY-NC-NC 2.0 

Several observations during the 20^th century in different areas of the Northern Pacific showed evidence that sea otters are key species in the trophic cascades of the kelp forest: they maintain the ecological equilibrium by limiting the number of sea urchins, one of their main food sources. Sea urchins are herbivorous animals thriving in kelp forests: without sea otters their population increases rapidly, creating kelp-free dead zones and leaving other herbivores with nothing to eat. The elimination of sea otters from the Commander Islands ecosystem caused a chain reaction reshaping the whole habitat: with the decline of the kelp forest the environmental carrying capacity for sea cows drastically reduced – the species most probably would have starved to extinction in a few decades.

The example of the Steller’s sea cow has major significance as it supports the long debated hypothesis about the sudden extinction of the New World’s megafauna at the turn of the Pleistocene/Holocene eras that the directly caused extinction of a few keystone species responsible for maintaining the balance of their ecosystem may have resulted in the coextinction of other species. This theory explains the sudden disappearance of several other giant species: for example, the Haast’s Eagle vanished from New Zealand along with its prey, the giant moa, that went extinct about a hundred years after the Maori landed on New Zealand.

Pleistocene giants from New Zealand: the Haast’s eagle preying on a giant moa
©Copyright Nick Keller

The Steller’s sea cow poster at the top of this post is available in my store on Redbubble, with design variations more suitable for apparel and other products. My whole profit goes to the Sea Shepherd to support their fight to protect our oceans and marine wildlife. 

The great auk – the eponym of the penguins

Nowadays when we mention penguins everybody thinks of the flightless aquatic birds of the Antarctic proudly wearing their tuxedos. Few people now that the original penguin – the eponym of these popular birds – was the great auk (Pinguinus impennis): an already extinct species that once used to be fairly well-known by the people of Europe and North America. Actually, taxonomically the great auk and penguins are only distantly related; but when exploring the seas of the Southern Hemisphere European sailors named the newly discovered species due to their physical resemblance to the great auk. The two taxa are widely considered as an example of convergent evolution and ecological corollary.

Date of extinction:  The nesting colonies of the great auk had been nearly eliminated by humans by the 16^th century along the European side of the Atlantic and by the end of the 18^th century along the American coast. One last nesting colony remained on a remote, inaccessible islet near Iceland – in 1830, the Great Auk Rock was destroyed by a volcanic eruption. The birds moved to the nearby Eldey Rock, where the colony quickly diminished – the adult specimens and their eggs were collected for museums for preservation and display. The last pair incubating an egg was killed on 3 June 1844. The last confirmed sighting of a living great auk dates from 1852, from the shores of Newfoundland.

The last stand – oil painting of Errol Fuller, writer and painter, expert on extinct birds
©Copyright Errol Fuller

Range: Once great auks were fairly common in the coastal area on both sides of the North Atlantic, the estimated maximum population was in the millions. They inhabited mainly the colder coastal waters from Greenland and Norway to Canada and Great Britain, occasionally reaching even the warmer seas of the Iberian Peninsula and Florida.

Habitat: Great auks spent most of their lives in the sea, foraging on smaller fish – they only left the water for land when breeding. They nested in very dense colonies on remote rocky islands with rich feeding areas around them, where the sloping shorelines provided easy access to the sea. It is believed that the great auk never had more than 20 breeding colonies – some of the known localities were Funk Island near Newfundland, St. Kilda off Scotland, Geirfuglasker near Iceland, The Gulf of St. Lawrence and Eldey Island.

Great auk specimen of the Glasgow Museums Collection
©Copyright Glasgow Museums

Description:  Great auks were large, flightless seabirds in the family Alcidae; standing about 75 to 85 cm tall and weighing up to 5 kg. In overall appearance they looked similar to their smaller living relatives, the razorbills. Male and female were similar in plumage, with probably a small difference in size. They appeared chubby due to a thick layer of fat necessary for keeping their bodies warm in the cold water. The adult birds had black plumage dorsally, with white breasts, bellies, and undertail-coverts, with some seasonal and ontogenic differences. Their wings had a white trailing edge and in breeding plumage there was a large white patch in front of each eye, which was replaced in the non-breeding period by a broad, white band and a grey row of feathers extending from the eye to the ear. Their bills were robust and ridged and curved downward at the top. The reduced wings were only about 15 cm in length and were used to propel themselves underwater during dives.

Between late May and early June female auks used to lay one egg each year. The egg had a characteristic, elongated shape with a marbling pattern of varying black, brown or grayish spots and lines on a yellowish base. The size of the egg averaged around 12-13 cm length and 7-8 cm across at the widest.

The characteristic egg of the great auk: an old photograph from 1844 from The Auk, the quarterly journal of the American Ornithologists’ Union on the left
and a colored lithograph by F. W. Frohawk from 1888 on the right ©Copyright Wellcome Collection / CC BY 4.0

Great auk chicks had grey down, the black neck of the juveniles was mottled white. They had white rings around the eyes but instead of the white patch of the adults they had a grey eye line extending to below the ears.

Great auks were excellent swimmers, able to evade capture by people in boats. They were able to dive to great depths (even around 100 meters) and could hold their breath for 15 minutes – that is longer than what a seal is capable of. When on land, they walked slowly and awkwardly with short steps.

Turnaround video of a stuffed great auk and its closest living relative, a razorbill
©Copyright Naturalis Biodiversity Center

Cause of extinction: The story of the extinction of the great auk is one of those stories about the endless stupidity, greed and selfishness of humanity that leave you with incomprehension and seething with anger. In comparison to other bird species that went extinct around the same time, the steps leading to the total disappearance of the great auk are quite well documented – especially the last, brutally cruel acts of the 19^th century. If you are interested in the details I recommend you reading Errol Fuller’s excellent book: The Great Auk: The Extinction of the Original Penguin.

To summarize: after being intensively hunted by humans at least from the 8^th century – mainly for food and fishing bait – this species was eliminated eventually to make pillows from its down, and to provide stuffed specimens and eggs as collectibles for rich Europeans and museums.

A few years ago, an international team of scientists began a discussion about the possibilities of reintroducing the great auk into its former natural habitat by recreating the species using DNA extracted form fossils or preserved organs (edited into the cells of the closest living relative, the razorbill) and implanting fertilized embryos into a bird big enough to be capable to lay a great auk egg.

Life-sized great auk statue by artist Todd McGrain on the Reykjanes headland (Iceland), one of the last known locations of the bird
©Copyright Chuck Reback

 

The great auk poster at the top of this post is available in my store on Redbubble, with design variations more suitable for apparel and other products. My whole profit goes to the Sea Shepherd to support their fight to protect our oceans and marine wildlife.