Steller’s Sea Cow – Extinct in 1768

Steller’s sea cow was first seen by Europeans in 18th century around the Commander Islands in the Bering Sea between Alaska and Russia. Fossil records show that its range was more extensive during the Pleistocene epoch (from 2.6 million to 11.7 thousand years ago) and its population numbers had been much larger than those found around the Commander Islands.

Image of Steller's Sea CowSteller’s Sea Cow: This is what it would have looked like

Steller’s sea cow was part of the order of Sirenia and adults would have reached weights of up to nine thousand kilograms and lengths of up to eleven meters. Sirenians are large aquatic plant-eating mammals such as the manatee or the dugong. But while the four surviving species of Sirenians we know of today live in warm tropical waters, Steller’s sea cow had become highly adapted to the cold sub-Arctic waters of the northern Pacific Ocean.

It had a thicker layer of blubber than other Sirenians, a specialisation due to the cold waters of its environment. Its tail was forked, like that of cetaceans. Instead of teeth, it had an array of white bristles on its upper lip and two keratinous plates within its mouth for chewing. The sea cow floated and it would not dive deeper than a meter. It was a herbivore and fed mainly on surface kelp. It appeared to communicate with sighs and snorting sounds. It spent most of the day feeding, only lifting its head every few minutes in order to breathe.

Steller’s sea cow was named after Georg Wilhelm Steller, a naturalist who discovered the species in 1741 while on Vitus Bering’s Great Northern Expedition after the crew became shipwrecked on Bering Island.

Image Steller's Sea Cow habitat mapLast population of Steller’s Sea Cows at Commander Islands

Steller described the sea cow as being highly social. Evidence suggests that these Sea Cows mated for life and lived in small family groups, raising their young. Killer whales and sharks may have preyed on the Steller’s sea cow. The sea cows helped injured members of the herd and apparently created bonds that lasted a lifetime. The young were kept at the front of the herd for protection against predators. Steller reported an instance where, 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 female sea cow had died.

This social behaviour worked against them. Stellar commented that hunting these animals was made easier because the sea cows had “an uncommon love for one another, which even extended so far that, when one of them was hooked, all the others were intent upon saving him,” placing themselves in grave danger of being harpooned.

Mating season occurred in early spring and gestation took a little over a year, with calves delivered in autumn of the following year. They likely had one calf at a time as the female sea cow had one set of mammary glands. The sea cow used its fore limbs for swimming, feeding, walking in shallow water, defending itself, and holding on to its partner during copulation.

image of hunters killing a Steller's Sea CowHunting the Steller’s Sea Cow

Steller’s sea cow was wiped out by fur traders, seal hunters, and others who followed Vitus Bering’s route past its habitat to Alaska. It was slaughtered for its valuable subcutaneous fat and for food. There are records of this animal being hunted in 1754 and 1762. Later expeditions in 1772 found no trace of the sea cows. It was estimated that the population discovered by Steller in 1741 amounted to only 1,500 individuals.

The sea cows were speared from boats and men on shore would haul them into shallow waters to beach them while others repeatedly stabbed them with bayonets. The hunters then waited until the tide receded to butcher them. After this method had been successfully employed once, they were hunted with relative ease. Fur traders would detour to the Commander Islands to stock up on food supplies during North Pacific expeditions. It was reported that a single sea cow could feed 33 men for an entire month.

Richard Sabin, Principal Curator of Mammals at the London Natural history Museum reflected “What fascinates me most about the development of our awareness of extinctions caused directly by human actions, is at what point in our recent history did we realise – from a compassionate perspective and not an economic one – that numbers were decreasing and there were problems on the horizon?” Richard Sabin continues “They (the sea cows) are held up as an example of the first sea mammal in modern times made extinct by human ignorance and greed.”

Image of Steller's Sea Cow family1898 illustration of a Steller’s sea cow family

Reflecting on this loss two centuries later, biologist Victor Scheffer commented, “The sea cow is gone and Earth is a lonelier place…The wisdom, goodness, and greatness of Man will be measured not wholly by technical power over the wild things of Earth but also by his moral strength in letting them be.”

Studies strongly suggest that humans did in fact hunt the sea cows faster than they could reproduce. Moreover the use by hunters of wasteful and primitive hunting methods may have caused them to kill up to seven times more sea cows than they could eat. These causes as well as the fact that Steller’s sea cows had no place where they could hide from humans, drove the species to extinction within three decades. This makes the Steller’s sea cow one of the first truly large mammals known to have been overkilled to extinction in the modern age.

By 1768, within just twenty seven years of Europeans discovering this last surviving population of one thousand five hundred sea cows, this courageous, loving, slow-moving and easily caught mammal species was hunted until every last one was killed for their meat, fat, and hide.