July 1962 a Soviet whaling ship was exploring the Bearing Sea in Northeast Siberia when they spotted a group of large weird looking animals about 80 to 100 m away the animals swam very slowly diving for short periods of time their skin was dark the head was small and the upper lip overhung the lower one the animal's tail shocked the Whalers because it was bordered by a strange filamentous Fringe the crew unanimously agreed that the animals did not belong to any Marine Mammal they had ever seen before the Academy of Sciences of the Soviet Union claimed
this was Stellar's sea cow a large marine mammal that was hunted to Extinction 200 years earlier did this Soviet whaling ship really come across a herd of sea cows that somehow survived Extinction to unravel this mystery we'll need to take a look at Clues left behind all the way from the Ice Age woolly mammoths up to the surprising connection of the world's smallest Marine Mammal and the role they played in The Disappearance of the Stellar sea cow I'm KP a marine biologist who specializes in marine mammals Stellar sea cows were fully aquatic herbivores related to
Duong and manatees but unlike Duong and manatees who live in warm Tropics Stellar seaal was highly adapted to the cold North Pacific one of these adaptations was the Seal's immense size around 10 m in length and weighing 11 tons which is bigger than an adult male killer whale like yeah that's all I have to say about that another adaptation to the cold was an extremely dense layer of blubber and very thick skin because their skin and blubber was so substantial cows were positively buoyant meaning they were unable to dive or fully submerge like manatees and
dugong can instead they bobbed around grazing on the surface canopy of kelp forests it's believed that they couldn't reach food that was more than a meter or around 3 ft deep supposedly they even floated on their backs when they slept just like sea otters now that's what I want to see this is the first clue that the Russian Whalers didn't see Stellar seal because the report clearly states that the animals periodically dived for a short time diving was physically impossible for Stellar seal another clue is where the mysterious animals were spotted near Cape nain fossil
records show this was once part of Stellar seal historic range but by 1741 their range had severely contracted to the shallow seas around the commander Islands 800 km or 500 M south of cape naon and their numbers had shrunk to a fraction of their once large population with some estimates putting them at a maximum of 2,000 individuals to understand what happened we need to go back to the end of the last ice age and what's known as the late Pline extinctions this massive Extinction event saw 65% of the world's megap disappear animals like the Siberian
rhinoceros saber-toothed cats short-faced bears and woolly mammoths all went extinct because of a combination of climate change and the spread of early humans I really love the megap and I miss them the woolly mammoth is of particular interest because their decline mirrors that of Stellar's seaal as global temperatures Rose at the end of the Ice Age major ice sheets retreated causing a reduction in cold dry open habitats suitable for mammoths as as a result populations contracted until only a few were left on Wrangle island in the Bearing Sea this small herd of mammoths managed to
survive until about 4,000 years ago when early humans found them and put the final nail in the coffin a similar thing happened to the Stell sea Cal shifting ice caps and melting glaciers of the late Pline resulted in rising sea levels which decreased the number of shallow kelp forests and suitable feeding grounds for the sea cows this fragmented and decreased sea cow populations until only a small number remained on the commander Islands scientists extracted DNA from bone material and sequenced the seow genome they found the genetic diversity of sea cows was extremely low and nearly
identical to the last wooling mammoths on Wrangle Island this suggests that like mammoths Stellar sea cow had already largely disappeared and the small Relic population that remained was spoiler alert extremely vulnerable to human Hunters as marine biologist colum Roberts put it Stellar's seap out was an Extinction waiting to happen quick note on the late Pine extinctions because I know climate change deniers will flood the comments with climate has always changed it's out of our control nothing we can do about it that's how you sound it's ridiculous yes global temperatures Rose at the end of the
last ice age by about 3° over around 5,000 years today the world has warmed 2° over the last 100 years so it's not that the climate doesn't change the rate at which it changes that's the problem the rate is getting faster that's that's bad I don't know if you can edit out snark or if it stays in snark sarks snark there stays in great that's a great spot for snark we also know why the Earth warmed during the end of the last ice age and it was because of a rise in atmospheric greenhouse gases anyway
now almost everything we know about the physiology and behavior of the sea cows comes from the journals of naturalist George wilhem Stellar who was part of the largest exploration Enterprise in history Russia's Great Northern Expedition setting sail from the Katka Peninsula this Expedition mapped most of the Arctic coast of Siberia and parts of North American Coastline in November 1741 Stellar's ship was battered by storms and wrecked on the commander Islands most of his crewmates died the rest were stranded and forced to Winter on islands that were home to several animals previously unknown to Europeans including
the spectacled corant Stellar seal and this is where sea otters come in from November 1741 until the summer of 1742 stellar and the survivors ate spectacled corant eggs they trapped sea otters and gambled with their pelts and they harpooned sea cows for their meat and blubber sea cows were easy targets for the starving crew because they were large slow-moving animals who were unable to dive there was literally nowh they could hide almost a year after being Shipwrecked the weather finally improved 46 survivors built a boat from the wreckage and sailed back to Siberia in August
1742 they brought with them over 1,000 seaotter pelts seots had the thickest fur in the animal kingdom their pelts were immediately considered the finest in the world and were so valuable they were nicknamed soft gold this set off the great hunt also known as the fur trade Maritime fur Traders looking for sea otter pelts would detour to the commander Islands just to hunt Stellar sea cows and restock Their Food Supplies sea cows were massively and wastefully overexploited being hunted at over seven times the sustainable limit just 27 years after George wilham Stellar first laid eyes
on the seaal they were gone but it isn't that simple a recent study found the seow would have still gone extinct even if not a single sea cow had been killed directly by humans and it's because sea cows depended on sea otters SE otters are a keystone species which are animals that play a vital role in maintaining the structure of their ecosystems just like a keystone in an arch while the Keystone is under the least pressure the entire Arch will collapse without it which is exactly what happened to the kelp force of the commander Islands
this graph shows kelp density before the decline of the sea otters and after this is because sea otter prey on sea urchins who are the dominant Marine herbivore without sea otters to keep them in check a herd of sea urchins will eat kelp until there's nothing left turning vibrant ecosystems into underwater deserts know known as urchin Barons between 1743 and 1753 a reported 8,226 sea otters were harvested from the commander Islands alone this led to an explosion of sea urchins and urchin Barons eliminating the kelp forests that were the sea cow's only source of food
without sea otters the sea cows began to starve using our knowledge of sea otter kelp forest interactions in the nearby Western uan islands and data on the behavioral responses of dongs to food reduction we show that sea cows around bearing Island would have reached near or complete Extinction without any loss of sea cows to human hunting human hunting clearly occurred and may have been largely responsible for the sea cow decline at bearing Island however our analysis suggests that the Sea House Extinction was a nearly inevitable consequence of the loss of sea otters and Kel forests
and this is another big clue as to why the animal encountered by Soviet Whalers in 1962 was not Stellar SE seal because there were no sea otters the fur trade began in 1741 and lasted until 1903 by the end there were only 1 to 2,000 sea otters in pockets of their former range and seots would have gone extinct if not for the treaty for the preservation and protection of fur seals signed in 1911 now translocation and recovery programs began in the 1950s and were wildly successful but that's still 200 years without healthy kelp forest capable
of sustaining a stellar sea Cal there's also something called the minimum viable population or MVP oh minimum viable population is the smallest possible size at which a species can survive without going extinct from natural disasters environmental changes or just chance this population needs to be breeding in the same geographic area historically biologists use the 50x 500 rule that says a minimum population of 50 is necessary to combat inbreeding while 500 are needed to reduce genetic drift so in order for a single Stellar seow to be alive today there would need to be hundreds of adult
seals breeding year after year for the last 250 years in areas that lost sea otter and kelp forests because they were heavily exploited during the maritime fur trade and those waters are still exploited by commercial fishing to this day but if it wasn't Stellar seal what did the Soviets encounter in 1962 these men worked in the whaling industry and agreed that the animal didn't look like any marine mammal that they' ever la laid eyes on but it also clearly didn't look like Stellar seal the report notes that the taals were bordered by a filamentous fringe
in reality a seow fluke was shaped like whales and dolphins and dongs and we also know SE cows couldn't dive like the report describes the head was small the upper lip appeared to be split and overhang the lower one and among existing marine mammals of the Northern Pacific Ocean no animal is known that has these characteristics yeah but that's not true there is one the northern elephant seal their heads are small compared to their massive bodies males have a famous Probus that overhangs over the lower jaw and check out the hind flippers of Neil the
seal they look filamentous don't they worth noting Neil the seal is a southern elephant seal I know there's no difference the Soviet crew had probably never seen an elephant seal before because Cape navarin is outside their normal range but elephant seals are highly migratory some have been recorded TR traveling over 13,000 m in a single year that's 20,000 km for my metric friends elephant seals have been spotted as far east as the Sea of Japan and a few recently established hul out sites on the commander Island I think it's highly likely that most of the
reported sightings of Stellar sea were misidentified elephant seals there is little doubt that Stellar sea is extinct so is another animal that George Stellar discovered on the commander Islands during Russia's Great Northern Expedition the spectacled corant and Stellar sea lion Stellar's Ider Stellar Sea Eagle are all threatened and vulnerable as for sea otters their recovery is considered one of the greatest success stories in marine conservation sea otters have regained much of their historic range and Kel Forest recovered along with them but they are still listed as an endangered species by the iucn and Recovery efforts
continue to this day if you want to get involved or learn more about SE otter recovery programs I've linked a bunch of resources down in the descriptions [Music]
