Back in 1941, it was estimated that there were only about 15 left.
Wow, it's a wonder there's any left then. I don't keep up with it but can't imagine many species getting that low and then making a comeback. In my book, if you're at 15, you're all but gone.
15 birds, how will that tiny gene pool affect the future survival? I would think some retardation would be unavoidable, but that's a guess/assumption.
In population genetics, the concept of 'island populations" is an interesting topic to consider with numerous case examples. They are called island populations because they are isolated small populations, as sometimes happens on islands with shiprecks and such. Contrary to misconception, inbreeding does not necessarily cause a loss of intelligence of the group unless one or more of the individuals in the group are particularly low in IQ due to a genetic issue. What happens is that traits tend to show up at a much higher rate because there is less genetic diversity. People rarely consider the benefits of inbreeding because the negatives can be so daunting, Imagine a group of geniuses having a small reproductive group, but the genetic code for heart disease was carried in a couple of people and cancer in a couple more such that after a few generations, lots of people are coming down with heart disease and/or cancer, but are still very smart. Now, if a couple of those geniuses carried a rare and recessive allele for mental retardation, then that certainly could start showing up in much higher than expected numbers (
https://www.jstor.org/stable/68793).
No doubt the whooping cranes will have some sort of genetic issues as result of their genetic code being bottlenecked down to a few individuals, but it would not necessarily be mental retardation.
