Daily Archives: December 24, 2010

Spot On

A leopard, just trying to blend in (photo by Sally Reeder)

Sometimes scientists struggle to prove the obvious:  There is probably a study in progress right now to explain why you feel wet if a bucket of water is thrown on you.  In that same vein, I did not say “aha!” and slap my forehead in astonishment at the results of research done by William Allen and his colleagues at University of Bristol (UK).

Basically these guys were exploring why some big cats have spots and some don’t.  I’m going to assume that you have not recently conducted extensive research in that area yourself, yet you knew that it had something to do with camouflage, right?  If you’ve seen any nature documentaries, you’ve watched leopards or lions sneak up on their prey and then pounce.  You figured the coat patterns (or lack thereof) helped the big cats blend into their environment.

If that’s what you thought, good for you — Dr. Allen and his team have proven you right!  Yes, most cats (with the notable exception of cheetahs) stalk and ambush from relatively short distance, so the camouflage on their coats allows them to get close to their unsuspecting next meal.

Apparently there had previously been an alternative hypothesis — one that hadn’t occurred to me — that the spot patterns were some sort of signal between cats of the same species.  Nope.  The cat’s coat has no relationship to its sociability.

The research team studied 37 species of non-domestic cats, investigating how coat patterns matched the cats’ habitat.  The results, published a couple of months ago in the Proceedings of the Royal Society, confirm that big cats who spend most of their time in the dappled light of treetops — like leopards, for instance — have more complex patterns than cats who hang out in open areas, like lions.  (As we know, lions don’t have spots.)

OK, so what’s the deal with tigers — why stripes and not spots or blotches?  A Discovery.com reporter asked Dr. Allen about that.  His response was, “There aren’t enough species of stripy cat to reliably make associations between stripes and potential drivers of stripyness.”  In laymen’s terms, that translates to “Hell if I know.”

Another unanswered question is why cheetahs have spots.  I have personally witnessed them hunting gazelles in Tanzania, and I can tell you that cheetahs would blend into their environment a lot better without the spots.  It’s also unknown at this point why coat markings in some species change as the animal matures.  For that matter, do coat patterns evolve over generations, as the animals’ environment changes?

It may be up to other scientists to answer these questions; Dr. Allen has already moved on to a new study about color and pattern on snakes and certain mammals, such as giraffes.  Let me think… do you suppose he’ll eventually learn that it has something to do with the creature’s habitat?  And by the way, has it been conclusively proven that a bear defecates in the woods?