Saw a post talking about the white Rhino only had 200 animals left but now there are so many more. But how is this done without serious inbreeding. Or is there something I’m missing?
Edit: yes, I know how sexy time works.
In: Biology
The White Rhino has 2 genetically distinct sub-species, the Nothern and Southern. There are only 2 Northern White Rhinos left alive. Both female and both under 24/7 armed guard.
Zoologist here who works with critically endangered/extinct in the wild species. My time to shine! I’m going to try to keep this eli5 so there will be a lot of oversimplification.
So what you are essentially asking about is how to overcome the bottleneck effect. Think of a bottle laying on its side. The fat end that holds the liquid is the whole gene pool of a species or population. Lots of different genes all mixed up in different combinations. Lots of unique combinations of genes in an individual are expressed by various traits/characteristics These traits/characteristics are called phenotypes.
If we are talking about rhinos these traits (phenotypes) would be every characteristic that makes up an individual rhino. Maybe a random rhino we look at has a long tail, short ears, thick skin, a medium sized horn, etc. All these traits are phenotypic expressions of the genes (each option of a trait is called an allele but we won’t get into that). Different combinations of genes express different phenotypes. So the way this rhino looks is due to its unique combination of looooots of genes to produce different phenotypes. Like a jumbled up code that determines how they look which is written in their DNA. The DNA is a blueprint in each and every cell that are instructions on how to build this particular rhino.
Ok so we have this big pool of genes that is essentially a collection of all the genes that exist in all living rhinos. This means we have lots of available combinations. Some combinations are advantageous and work well together and some are not advantageous and are kinda bad combinations that don’t work out so well. Maybe a rhino has genes (given to them by a randomized mix up of its parents genes) that make them very large and heavy but hey also have genes for weak flimsy legs… uh oh that’s a bad combo and most of the rhinos who got similar combinations can’t walk well and end up dying off early. Because these fat rhinos with weak legs don’t live long enough to breed the combination starts to get more rare because it’s not propitiated. The strong legged rhinos have an easier go at things so the live long enough to breed and keep their strong legged genes around. This is natural selection!
Okay now let’s say a big meteor hits rhino-land and wipes out 90% of all rhinos. It’s totally random who survives and has nothing to do with good combinations and bad combinations of genes. Taking this huge gene pool and reducing it drastically is the “bottleneck”.
So now we have two problems. 1) we used to have looooooots of options to chose from but not anymore and 2) maybe a lot of the options we have left are bad combination options. This is called genetic drift.
So things go on in rhino-land as the always have and natural selection continues to happen but it’s a little more tricky now that we have less diversity. There is potential for a lot more inbreeding and bad combinations of genes. Some will still be good combinations though and that will keep the population going! But the rhinos have one more saving grace. Mutation! So mutation is kind of a fluke in the genes that could produce a new phenotype out of the blue. Like the DNA says 1+1=2 but one in a million times the DNA gets mixed up and says 1+1=3. Oops! It wasn’t supposed to happen but it did and now instead of just working with 1’s and 2’s we have some 3’s in the mix. The 3 gene could be a bad mutation like the rhino was born with a messed up heart. in that case the mutation would probably die off with the individual. But maybe that 3 gene could be a good fluke! Like the rhino was born extra strong, now that gene will probably continue to get passed on because it ended up being useful. Even if the 3 gene was just kinda neutral and wasn’t much of an advantage or disadvantage… well this is a win anyway. It increased the genetic diversity and gives us more gene combination option and increases the gene pool!
Now repeat this mutation scenario over and over and over and over again. You will start to end up with a lot of crazy genes that weren’t there from your bottle necked gene pool. Sloooooowly the diversity of the pool keeps going up. More options means a higher chance of good gene combinations and the populations genetics become more stable and eventually makes it past the bottleneck!
Even if there was just 2 there is no 100% guarantee that inbreeding will cause any major affects. The risk is there don’t get me wrong but it is possible. As you
Move further along the tree it gets safer too.
With 200 you have enough to support normal breeding.
Genetic diversity would be horrible with inbreeding and would leave them vulnerable but it’s not a 100% death. With 200 an issue with genetics is not likely to kill them outright. It’s cripple the population but those who have not inbreed will most likely survive.
It should also be noted that any genetic infection issues can be avoided with proper hygiene and viral protection agents. Won’t fix it and there will be purely genetic issues but it helps with virus that hate certain genes.
So when I want to join a religious cult living in isolation, gotta make sure they have at least 200 members.
At least in America, the AZA (Association of Zoos & Aquariums) maintains studbooks for each animal, one of the primary goals being to maintain genetic diversity. They can recommend transfers between zoos to make sure the gene pool stays diverse. I’m assuming this is only at AZA accredited zoos. [https://www.aza.org/studbooks](https://www.aza.org/studbooks)
Not only can inbreeding be avoided, but inbreeding isn’t a genetic death sentence. It’s kind of a secret weapon for species coming back. Unless they get really unlucky, the carriers of defective genes die off without breeding, so after a few generations, the species has relatively broken free of any genetic defects caused by inbreeding.
They lack genetic diversity, and are more likely to have genetic diseases, but they still live on
Not only can inbreeding be avoided, but inbreeding isn’t a genetic death sentence. It’s kind of a secret weapon for species coming back. Unless they get really unlucky, the carriers of defective genes die off without breeding, so after a few generations, the species has relatively broken free of any genetic defects caused by inbreeding.
They lack genetic diversity, and are more likely to have genetic diseases, but they still live on
A very rigorous and extensive planned breeding program. Like others said, as long as they aren’t too genetically similar to start with, 200 is easily a big enough genetic pool to produce offspring without inbreeding effects. You just have to ensure, through relocation or captive breeding, that the various populations intermingle and continue diversifying. So you start by cataloging the existing animals and their genealogies as far as you can. Then you closely monitor the existing animals and ensure different lines are interbreeding. If a population becomes too isolated and begins trying to inbreed, then you move some viable adults from a different population into the stagnating one. It’s a lot of work.
They did this with a type of gigantic vulture in California, they captured the remaining 23 BIRDS left and put them in a breeding program. There are now over 200 in captivity. The trick is to round those fuckers up and do the PewDiePie “now FRICK”
I actually just had this conversation with my professor last week because I was doing a presentation on de-extinction.
In this case, I believe the last male died, so they impregnated the female rhinos using his preserved semen.
The larger the population, the less need there is for inbreeding. It’s when there’s only a few members left that it’s an issue.
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