Last chance for China's dolphin (BBC) {world's most endangered mammal?}

[eppur_se_muova]

By Richard Black
Environment correspondent, BBC News website

Zoologists have developed a plan to save the Yangtze River dolphin, probably the world's most endangered mammal, from extinction.

They hope to take some dolphins from the Yangtze and rear them in a nearby lake, protected from fishermen.

The species is threatened by overfishing which removes its food, industrialisation, boat collisions, and through being caught in fishing nets.

The most recent surveys found only 17 living individuals.

Also known as the baiji and Chinese lake dolphin, Lipotes vexillifer is listed as Critically Endangered on the internationally recognised Red List of Threatened Species, which describes it as "probably the most endangered cetacean in the world".
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more: http://news.bbc.co.uk/2/hi/science/nature/5122074.stm

[theoldman]

1. With only 17 left it is probably doomed.

I think it takes about 100 or more to repopulate a species. You need a certain amount of genetic variation to avoid inbreeding.

[eppur_se_muova]

2. Whooping cranes were down to 21 wild birds ...

but they reproduce more quickly, or at least I would think so. The dophins may very well be goners.

[NNadir]

3. California Condors were down to zero wild birds.

They were all captured and captively bred.

http://www.bigsurcalifornia.org/condors.html

Although the condor recovery effort has increased the number of birds tenfold in the past two decades, there have been other significant setbacks as well. About 40 percent of released condors have died from lead poisoning, hitting power lines and attacks by golden eagles.

The mortality rate in Big Sur, however, has been much lower -- raising hopes that birds born there will live to ripe old ages. Only nine of 41 condors released there have died. Sorenson theorizes it's because there are fewer power lines, fewer hunters (whose lead bullets kill condors when they munch on carcasses) and more dead marine mammals for the vultures to feast on.

[eppur_se_muova]

5. Good point, and hopeful in a way. But these appear to be all there are.

Apparently, an earlier attempt to capture baiji for breeding was unsuccessful because of their extreme scarcity and their agility in their natural habitat. There are none in captivity, unless this program has since caught some.

http://www.irn.org/programs/threeg/991103.baiji.html A discouraging read.

One article I came across said 12% of humanity lives along the Yangtze. That's the most discouraging point I read.

[NNadir]

6. It is indeed a tragic circumstance. Your point about genetic diversity

is an important one.

It can have long term bearing on species survival.

I have understood that cheetahs are at more risk from their current approach to extinction because of an earlier near extinction event.

One thing is certain. For wild animals being near large human populations is a very bad thing.

[nealmhughes]

4. We had not seen wild water fowl in the Tennessee Valley for many years.

Now there are heron and cranes of every variety on our ponds and lakes. Truly magnificent to watch them so in for a landing. Some cranes are so large that they cast a shadow when overhead! I guess DDT damage has been mitigated...
There are now quite a few alligator also, when they were presumed to have all moved much further south.
I hope that China can do that.
Now let's take care of the manatee.

[Dead_Parrot]

7. There may be exceptions...

A theory kicking around about the Chatham Island Robin (the entire population is descended from one bird) is that they've been near the brink so many times they've now got a sort genetic immunity to inbreeding problems. If the dolphins have had a similar past (quite possible, since they've also been restricted to one environment) They may be able to bounce back also.

Worth a go, I reckon. :)

[Xithras]

8. Yes and no.

Because of random DNA recombination when two animals mate, it's unlikely that you'd ever have a 100% mutated generation. Even if inbreeding creates negative genetic mutations in half of one generation, the other half is still producing viable offspring. So long as that half is producing offspring at a rate exceeding the death rate of the species, it has a chance to recover.

You DO lose genetic variation, and the founder effect may create a rebounded species with some differences from the original population, but the species may survive.

It's theoretically possible to resurrect a population from only two individuals. It would be a messy process with lots of deaths and deformities, but if darwinian evolutionary processes were followed (i.e. prevent the deformed individuals from breeding) you could easily end up with a viable population.