There has been a fair interest at this blog in marine mammals, in particular whales. (If you are a new reader just do a search using the word ‘whale’ or ‘whaling’.)
But I actually think dugongs are more beautiful and probably more vulnerable as a species.
Dugongs are more closely related to elephants than to whales and dolphins.
Their closest living aquatic relatives are the manatees. Manatees live in rivers and also coastal waters of West Africa, the Caribbean, South America and the southern United States.
I was interested to read this morning that the also closely related Stellar’s Sea Cow was the first marine mammal recorded as becoming extinct, in recent times.
According to this website, the sea cow’s grew to 8 m long and weighed more than 6000 kg.
The last populations were found in the Bering Sea in 1741, but previous populations had occurred along the Pacific rim from Mexico to Japan.
Apparently the entire estimated population of 2000 became extinct by 1768 due to intensive hunting by seal hunters, taking them for their meat.
It got me thinking, which is the rarest species of marine mammal in the world today?
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Dugongs are vulnerable throughout their range, but as a species, there are species of whales, dolphin and porpoise that are much more vulnerable.
It is true that when it comes to the main marine mammal groups, the cetaceans (whales, dolphins and porpoises) have not suffered an extinction, as such. The pinnipeds (seals, sea lions, walruses and fur seals) have lost the Carribean monk seal, and species such as the Hawaiian and Mediterranean monk seals, Hooker’s sea lion and even our very own Australian sea lion are in a bad way.
The sirenians (dugong and manatees) have lost the Stellar’s, and all face big pressures throughout their ranges.
The rarest cetacean is a fresh water dolphin called the baiji, and it would be sfe to say if they are not extinct yet, they will be in a few years. The river dolphins are all facing huge pressures, due to their habitat and proximity to human activities. The North Atlantic right whale, North Pacific right whale, western gray whale, vaquita, bowhead whale, and Maui’s and Hector’s dolphin (from New Zealand) are all critically endangered. Many other cetacean species such as true blue whales, South African and South American coastal dolphins, our own Irrawaddy dolphins and others are also nearing the edge.
The British Museum had a great display on Stellar’s sea cow, and put their size in perspective. Let’s face it, the sea cows and whales are not your conventional beauties,unlike a dewy-eyed harp seal pup, and it is a pity that Australians don’t embrace the dugong more, and learn more about their habits and conservation.
The Narwhal or Unicorn Whale is a creature of mythological importance (the Norse called it the “corpse whale”), is it still prevalent?
http://www.eurekalert.org/pub_releases/2005-12/hms-mb121305.php
According to the IUCN Red List the “baiji”, which is a species of freshwater dolphin, is the most endangered cetacean species. Cetecean is a classification that includes whales, dolphins and porpoises.
It lives in the Yangtze River in China and is down to about 13 individuals.
see http://www.arkive.org/species/GES/mammals/Lipotes_vexillifer/more_info.html
I’m sure any paleontologist you meet will assure you that extinction is the norm, not the exception. In spite of this, there is still life on this planet. So apparently, new species emerge. Does anyone have figures on the emergence of new species which could put extinctions in perspective?
On a personal note–my dad worked for the Department of Natural Resources (central USA) for years in their forestry and prairie programs. In one of the managed native prairies, he found a plant he had never seen before. He sent it off to a botanist and the plant was confirmed to be an unknown species. It now bears his name.
Schiller.
Rog,
Narwhals are classified as “Insufficiently Known”. Detailed and recent data on population estimates throughout their range appears to be lacking. They are still hunted by Inuits and have been found with high traces of heavy metals and organochlorines. Cadmium concentrations have been found to be very high in Narwhals. Changes in sea ice conditions caused by global warming (or whatever people here choose to believe in) are also being noted as a threat to certain populations .
The British Museum has a skull from a male narwhal that has two tusks instead of the normal one, and no, I have no ties to the British Museum!
Schiller,
Are you suggesting that extinctions which are caused my over-hunting and other human activities are all part of the natural process and therefore OK?
Schiller compare the rate of extinctions. Can you nominate any period in the historical record where the pace of extinctions has exceeded that of modern times?
Historically the rate of speciation over time has exceeded that of extinction, and climate changes have happened slowly enough for many organisms to adapt and to move their habitat range. Adaptations to a changing environment can lead to new species. But what opportunities are there for most organisms to adapt to the myriad of rapidly increasing pressures (harvesting, development, pollution, habitat fragmentation, exotics, etc and now climate change) now that they’re hemmed in?
It’s true though, extinctions happen. Modern humans behave as though we can manage nature, but human population growth is following a normal distribution curve so far –> exponential growth until resources are depleted, then bust (extinction or bottleneck).
Thinksy,
Humans have never precipitated anything close to the Permian-Triassic extinction event, with about 90 percent of all marine species and 70 percent of terrestrial vertebrate species going extinct. See
http://en.wikipedia.org/wiki/Permian-Triassic_extinction_event
Compare that to the “Cambrian Explosion,” when most of the major groups of animals first appear in the fossil record. See
http://www.ucmp.berkeley.edu/cambrian/camb.html
In my universe, things that are not natural do not occur at all. Things might be different elsewhere, I suppose, but it would be an odd place indeed.
Schiller.
Schiller “humans have never” is past tense, but we’re not done yet.
However, the issue for comparison that I raised was the *rate*, the *pace* of extinctions. You speak of extinctions that took a million years, perhaps several million. At current rates, how long will take us to eradicate the majority of macro species?
But if all processes in your world are natural and therefore needs no correction (?) then don’t ever repair your house or service your car or brush your teeth or bother trying to mitigate the rate of extinctions due to human activities because entropy, death and extinctions are all natural processes.
Schiller,
Is genocide natural??
Humans aren’t done yet, this is true.
We’ve had Chernobyl, Three Mile Island, Hiroshima and Nagasaki, which haven’t hurt biodiversity that anyone has seen. Might even have caused some biodiversity, via radiation mutation.
Perhaps some day in the future we’ll do things like volcanoes–though obviously it would take lots more than there’ve been since we descended from apes. Likely we’ll not be steering any comets or asteroids at ourselves, at least not any time soon.
For the time being, we’re not doing anything *near* what it takes to cause massive extinction. The biosphere has proved itself quite durable, surviving cataclysms far beyond our powers to create.
Sure, there are people who say there should never be any extinction at all, but that’s not terribly realistic. This planet is not completely tamed, so until that happenes, the rule is, adapt or die. Sometimes, that means die out, as we can see from the fossil record.
As to genocide–history says it’s natural. Indeed, what organism did humans first subject to selective breeding? The *very* first? Humans. And we’re still doing that, from selecting a mate to blocking development in Africa to other things.
This is *not* the Garden of Eden, sorry. When it comes to improving what we have, there’s a lot to be done. Preventing extinction is not a terribly realistic goal, so I’d suggest attempting more productive activities.
Schiller.
I’m doing a project 4 school on the steller sea cow, and I really need help.help help…