We talk a lot about external threats to wildlife populations, because they are by far the biggest causes for concern.
But in the case of cheetahs, dwindling populations aren’t just the result of land encroachment, poaching, and global warming.
It’s in their genes.
Maybe a better way to put it is that it’s not in their genes.
About 10,000 years ago, at the end of the last ice age, hundreds of species died off in a mass extinction event. Cheetahs manage to survive…but just barely. In the years and millennia following, cheetah populations rebounded, reaching levels of around 100,000 animals in the wild by the turn of the 20th century.
But something was still missing: genetic diversity.
A 5-year study from the early 80’s showed that the cheetah gene-pool resembles that of highly-inbred mice used for scientific research. Essentially, the entire population had been built up from too small a stock; the result was a species in which 70% of the males had abnormal sperm and infant mortality soared to over 29%, even in captivity. In the wild, only about 5% of cheetahs survive to adulthood.
To give you an idea of just how serious the inbreeding problem is in cheetahs, among related animals of most species, you can expect to see 80% gene similarity; related cheetahs have 99% gene similarity. Their genes are so remarkably similar, in fact, that even between unrelated animals, skin grafts aren’t rejected. Any one cheetah is essentially any other’s identical twin.
Scientists are desperately trying to force some diversity back into the gene pool via breeding in captivity, but until they do, cheetahs are an incredibly vulnerable species, not only because of the hunting and environmental threats that have already decimated wild populations (most current estimates put the wild population under 2,000 animals), but because a single illness could essentially wipe out the entire species (genetic diversity helps some members of a population fight infections, even when others succumb).
Beyond captive breeding, better protection for remaining wild cheetahs is absolutely vital. Currently, populations are relatively isolated from one another; the more chance they have of mixing, the better the chance that there will be different genes in the mix.