Thursday, October 21, 2010

Spotted Cats

Discovery News announced yesterday that the spotted patterns on woodland species of wild cats are tied to the patterns of dappled light in their forest environments.

Cats in open ranges, such as lions, tend to have plain coloration. Tiger stripes, according to the University of Bristol researcher William Allen, are still something of a mystery.

Full article by Jennifer Viegas 
Previous GurneyJourney post on Dappled Light 
Thanks, Libby!


Matthew Scheuerman said...

Tiger stripes are a mystery? Really? I can remember being told in grade school that tiger's have stripes because of the tall grass they tend to hide in.

This is , of course, an assumption on my part that all tigers hide in grass before attacking their victims.

James Gurney said...

Yes, I've always thought so, too, but so says the article. Such things as grass/stripes and dappled light/spots always seemed intuitively obvious to me, but presumably the scientist has to make such observations testable and repeatable.

Nice photo in your link. Really proves the point to me!

Joe Jusko said...

I was always under the same assumption; tall grass, bamboo, banyan trees, etc.

Casey Klahn said...

If I may add coyotes to the mix, I love the description of them as "Prairie Ghosts." It is uncanny how they appear, then disappear, then reappear if you see them in higher angled light, and at some distance. Their hair is sufficiently irregular in depth, and that provides for breakup, and they color-match the grass, of course.

But, in angulated light, they are illuminated like a candle.

Yes, go figure a scientist to put into question the grass over stripes theory of the Tiger's camouflage.

Kessie said...

Aw, and here I thought it was going to be a discussion on that tricky spiral and s-shape they have going on in the pattern of their spots. I forget about it, set out to paint a spotted cat, and get flummoxed every time.

Jobot said...

I am completely amazed at how closely the Clouded Leopards' camoflage resembles densely crossed roots or branches (like those of the banyan).

My Pen Name said...

Physics has had its foundations totally changed in the past 100 years- each new major discovery seem to invalidate the old.
The biological sciences tend to be a little bit more 'sure of themselves' which makes me less sure of them -
i would be careful about accepting current scientific thought as absolute - and always leave room for doubt.
look at the views of dinasaurs 50 years ago - but don't be surprised if, in 50 years, our views look even sillier.
Case in point, recently a book came out with an 'evolutionary' explanation why we like certain types of art - we like landscapes, we are told, because the remind us of the african savannah (really, what about mountain ranges, which seem more popular?) in any event, the much vaunted out of africa theory is now being seriously questioned making the whole exercise of that book rather silly.
The explanation might be totally unrelated- tiger stripes a genetic defect for gene for sharp teeth rather than pure natural selection, which seems a bit reductionist in itself.

just look at all the arguments back and forth about whether butter is good for you :)

My Pen Name said...

@matthew s
Nice picture, but I could put a gray squirrel on the sidewalk by central park, and he'd be a perfect match, but it wouldn't prove that's why he got his grey coat. And if it's so great for tall grass, should the tiger's prey have them too?

Cavematty said...

You're completely right "my pen name", you should never accept scientifc theory as absolute unless it is regarded as such - through repeatable and observable testing. For example the theory of gravity. I've never heard anyone suggest that gravity does not exist, despite it being poorly understood, as we can all observe it at all times.

That is actually the foundation of the scientific method - every theory is criticised and attacked and competed with by every other scientist in order to get the most correct possible theories at all times.

In which context evolution, and the theory of natural selection is the most accurate, elegant, logical and probable explanation we currently have for how extremely complex (and seemingly designed) organisms came to be. Until a better explanation is presented it will generally be accepted as the best explanation we have. But science by it's very nature does not consider any fact incontrovertible, to the contrary science heartily encourages discussion, debate and testing of all ideas.

The general idea of natural selection states that any distinct and remarkable feature of an organism must, or must have at some time, been advantageous to that organism. Or else it must be the side-effect of an advantageous feature / behaviour. Otherwise that particular organism would not have been the one that out-lasted it's competitors. That does not imply that all organimsms must evolve along the same path at all.

Comparing concrete to a squirrel, whose species evolved to be the way it is long before concrete was invented, is not helpful. Evolution generally works extraordinarily slowly compared to the normal human frame of reference.

My Pen Name said...

cavematty - we can observe the condition of gravity - or a tiger's stripes - theorizing about why things are (which involves non-repeatable or non testable events in the past, which by definition, cannot be repeated) is a whole other story.
So, yes, we can safely say, yes, what we call a tiger has stripes (we can get into metaphysical discussions about what stripes (or art!) are but the whys become far more grey.

I did not compare the squirrel 'seriously' rather to point out just because something blends into its background doesn't mean the background is the reason it looks that way - who knows - the tiger can have stripes for an entirely different reason, and acquired them in a total different environment but it just turns out that their habitat changed and the stripes are a great asset but not so much for, say the tigers in greener jungles or siberia.

to the contrary science heartily encourages discussion, debate and testing of all ideas.
oh yeah, like human biodiversity - completely open topic, no pressure there, just as James Watson.

Just a few years ago, naturalist at the AMNH were shocked to learn that Franz Boas fudged his data (and I am being polite) - the impact of his 'research' will take decades to undo.

pure science is a great myth- scientific journals, universities, etc are ran by humans, and humans are corrupt, idealogical, irrational, emotional, illogical - yes even scientists.

My Pen Name said...

Evolution generally works extraordinarily slowly compared to the normal human frame of reference.
maybe, maybe not
The 10,000 Year Explosion:
How Civilization Accelerated Human Evolution

Cavematty said...

I meant in terms of our day to day perceptions, but you've got a good point with that link. I've never heard of that book before, and it sounds very interesting. Thanks for the link :)

A. L. Ryder said...

Well I don't know why scientists have to think about it so hard... I've always just taken Rudyard Kipling's word on the subject as fact.

David Teter said...

I've also heard that the stripes are also on their skin...

What about the chicken and the egg?

Shard said...
This comment has been removed by the author.
Roberto said...

@ NetRaptor
(...tricky spiral and s-shape they have going on in the pattern of their spots.)
This sounds interesting! can you elaborate? Thanx -RQ

James Gurney said...

Interesting points, everybody!

I wonder how the adaptive coloration theory would account for anomalies like the cheetah (savannah environment, but spotted), and the North American whitetail deer (forest environment, but plain brown).