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I just got to wondering about this. What is the evolutionary purpose of having either keeled or unkeeled scales? What benifits do they provide to the snakes, if any? Thanks for the help.

EP
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2.1.8 corns(candy cane, creamsicle, ghost, 4 normal,
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1 w. hognose
1 bearded dragon
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Thats a good question, I don't have an answer but I can offer some speculation. From what I can see there are four possible benefits from keeled scales:

1. Cameoflage, smooth scale have a sheen to them or a reflection of light, keeled do not.
2. Traction? you could look at it as the difference between a smooth tire and one with tred, the smooth will work better on smooth terrain and the treded, on mud and water.
3.Heat absorbtion, since keeled scales produce less reflection then smooth, maybe they also absorb heat better?
4 Breeding, Grahms crayfish snake for example has keeled scales only around the cloaca and on the tail.

Perhaps a bit of all of these reasons, I would favor 1, and 3, because it seems to me that the best movers through whatever medium, are usually the smooth scaled. I think that there is also a larger percentage of basking snakes amoung the keeled scaled snakes, Though I couldn't say that is one behavor, or habitat that excludes keeled scaled snakes or smooth keeled snakes.