Captive gorilla population

[zooman]

Depends on what you mean by viable.

If you mean a self-sustaining population, then the general Rule-of-Thumb would be 250 pairs. Of course, that would presume that all animals were breeding - which we know does not always happen, for a variety of reasons. So many conservation geneticists suggest 500 pairs.

Note that these numbers are for a self-sustaining population to survive ad infinitum. If you want a population to survive for less time, then you don't need as many animals.



Hix

Hi Hix. l had heard of this. Obviously gorillas are not into "pairs". Interesting if this was to be correct. Ignoring the pair concept. We do-not have enough gorillas to have a ongoing geneticly diverse pool.

 

[Hix]

We do-not have enough gorillas to have a ongoing geneticly diverse pool.

For most threatened species maintained in captivity we don't have enough. That's why the idea is to hold them just until we can put them back into the wild.

The sad thing is, some endangered species are doomed because of low numbers: Californian Condors, Spix Parrots, Northern Hairy-nosed Wombats, Javan Rhinos. They will all most likely become extinct within the next few hundred years because of the small gene pool. In reality, extinction could come even sooner if the wild population suffered a catastrophic stochastic event (like a massive bushfire in Ujong Kulong, or a contagious and fatal species-specific disease develops).



Hix

 

[zooman]

So we live in hope! That countries like africa. Who's goverments are among the most corrupt in the world. Will change or that global warming is not happening!

Are we really all doomed. Just as HRH has said "we" are the frogs in the boiling water.

Not trying to be a pessimist here. Just rtemoving the googles of hope.

What is the reality here??????????????

 

[Yassa]

I don`t believe javan rhinos, spix aras and californian condors are doomed and will go extinct because of a too small gene pool. The concept that a species needs a certain amount of genetic variability to survive long-term is a theory, not more! I have no doubt that preserving genetic diversity is a good thing, but there are too many examples about heavily inbred species and populations which are thriving to take this theory as true. Did you know that both the southerrn white rhino and the Kruger elephants were decimated to less then 2 dozends about 100 years ago? Then they were protected, and now both number more then 10.000, growing and no signs of inbreeding damage. Genetic diversity creates itselves through breeding, mixing of the existing genes and mutations. Inbreeding CAN have catastrophic results if the animals carry a damaged gene, but if they are genetically healthy, it`s likely not to have effects. Many island species are the living proof for this, with just very few founders (or even just a pregnant female) being washed on a newly created volcanic island like the Galapagos Islands and founding new species through heavy inbreeding in the first generations.

 

[Pertinax]

The Laysan teal shows no sign of becoming extinct either, despite the most extreme form of population crash and subsequent inbreeding.

 

[Buckeye092]

We do-not have enough gorillas to have a ongoing geneticly diverse pool.

Actually we do. The genetic diversity of gorillas is one of the highest of any captive animal and as long as breeding and transfers occur this species isnt going to disappear from zoos anytime soon. You have to look at the statistics - there are over 700 gorillas in captivity with nearly half that have reproduced and are reproducing. Very few species have this large population and genetic diversity.

 

[zooman]

. You have to look at the statistics - there are over 700 gorillas in captivity with nearly half that have reproduced and are reproducing. Very few species have this large population and genetic diversity.

I have been supplied with the stats from 3 sources. Your quote above sounds good. I would suggest that it is actually missleading.

Not going to debate it just yet. Still corallating, as there are allot of animals at breeding age that are not breeding.

 

[Hix]

I don`t believe javan rhinos, spix aras and californian condors are doomed and will go extinct because of a too small gene pool. The concept that a species needs a certain amount of genetic variability to survive long-term is a theory, not more! I have no doubt that preserving genetic diversity is a good thing, but there are too many examples about heavily inbred species and populations which are thriving to take this theory as true. Did you know that both the southerrn white rhino and the Kruger elephants were decimated to less then 2 dozends about 100 years ago? Then they were protected, and now both number more then 10.000, growing and no signs of inbreeding damage. Genetic diversity creates itselves through breeding, mixing of the existing genes and mutations. Inbreeding CAN have catastrophic results if the animals carry a damaged gene, but if they are genetically healthy, it`s likely not to have effects. Many island species are the living proof for this, with just very few founders (or even just a pregnant female) being washed on a newly created volcanic island like the Galapagos Islands and founding new species through heavy inbreeding in the first generations.

I really didn't want to get into a detailed discussion of conservation genetics, which is why I made the broad statements I did. I deliberately didn't mention exceptions (such as species that are prolific - i.e. produce a lot of young rapidly, and can breed at an early age) because the species I mentioned don't really fall into that category. Stating that inbreeding isn't a problem because you know of examples that don't appear to be affected by inbreeding is a bit blinkered, in my view.

Yes, many island species are founded by a solitary individual that has reproduced rapidly and produced viable self-sustaining populations. And I'm sure you could quote me several examples. But what about the individuals of species that washed ashore, produced small inbred populations and then went extinct in a few generations. There are no record of those species (and I can't quote you any examples) - but that doesn't mean they don't exist.

I was not aware that there was a popolation of Kruger elephants that got down to two dozen or so animals 100 years ago. But, assuming that there were a roughly even ratio of males to females (i.e. 12 females) and the fact they are pregnant for two years and don't have another calf for a few more years, I can't see anyway that population could reach 10,000 in only 100 years.

Furthermore, I said those four species would probably go extinct "within the next few hundred years" - that could be three to five hundred years away. At that time I would expect genetic diversity to be very, very low; infant mortality, stillbirths and miscarriages will be high; and the entire species will be highly susceptible to disease. Having said that, there is a very small chance that a population will thrive and survive (but it is a very small chance).

Finally, if inbreeding is not such a problem, why is it such an important consideration in PVAs?



Hix