Wednesday, September 1, 2010

If You’ve Seen One Cheetah, You’ve Seen Them All

No, I’m not trying to denigrate large cats again; I’m being, regrettably, accurate. It’s a sad truth that, once you’ve seen one captive cheetah, the next one you see will be the same one—on a genetic level, that is. This is because cheetahs are a quintessential example of a species that has undergone what’s known as a “population bottleneck.” This happens when a species’ numbers are reduced so drastically that even when their populations recover a little and start to increase, they’ve lost their genetic variation: individuals remaining in the population are incredibly similar—with cheetahs, they are genetically identical. So much so that cheetahs can accept skin grafts from one another, something that can only happen in other animals, including humans, with identical twins.

This might seem great from a medical perspective—now anybody can be your organ donor!—but it doesn’t bode well for the survival of the species as a whole. (And there’s the whole problem of inbreeding, a process whose negative results are evidenced by royal families past and present.) In order for a species to adapt to changing conditions, individuals within it have to exhibit heritable variations from one another—so that, in a given situation, the faster one will survive, for example, or the shorter one will produce more young. Or, to give what may be a more relevant example, the ones that are immune to a disease will survive while those that aren’t will die. If a disease comes along that’s a danger to one cheetah, no cheetah has much of a chance against it.

Zoos are doing their best with breeding programs and Species Survival Plans, working with the modicum of genetic variation present and trying to maintain or even increase it, but it’s an uphill battle. It’s hard to say if cheetahs will manage to overcome the devastation wrought by near-extinction or if near-extinction will become true extinction. And, of course, what’s just as worrying is that cheetahs may simply be in the vanguard: how many other endangered species will have their populations reduced to almost nothing before we realize they need to be saved?

On the other hand, there’s always the hope that we can learn from our mistakes and keep a careful watch to make sure that other species don’t end up in the straits cheetahs were and are in. And we can take the time to appreciate the cheetahs we can still see. That is, when they happen to be visible in the exhibit. For such big spotted things, they’re pretty damn elusive…

[A note: I do write all text and take all pictures. Please do not reproduce either without my permission.]


Anca said...

A melancholy account (it ought to hold us accountable) and lovely photos.

Florcita said...

how interesting. I didn't know this about cheetahs. I mean I knew they were on the verge of extinction, etc... but I didn't know that about the genetic part. How sad, especially because they are so beautiful.
Hey. you left a comment on my Flickr... followed you here :)

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