The graybanded kingsnake (Lampropeltis alterna) has been suggested as a possible mimic of the rattlesnakes and copperheads found in the same area. The presumed mimicry supposedly confers advantages to the "harmless" kingsnake, since predators would be less likely to attack a dangerously venomous snake.

Sounds all too logical doesn't it? I have come across a specimen of Crotalus viridis oreganus (Northern Pacific Rattlesnake) that seem to contradict the mimicry hypothesis. This snake was first seen stretched out in the open on the road about 11:30 am, near Sunol, Alameda Co., Calif. The surrounding area is oak savannah type habitat. The snake then slowly crawled into the shade on the shoulder, where it was subsequently photographed.

As one can see, this snake superficially resembles a California kingsnake (Lampropeltis getulus californiae) in having narrow cream colored crossbands on a dark background. The dark colors on this rattler is not black but a dark olive brown.

My question is: Why is a rattlesnake "mimicking" a harmless kingsnake in coloration? If the Batesian mimicry hypothesis is correct, then we should see kingsnakes in this area mimicking rattlesnakes in coloration, instead of the exact reverse.

The answer may lie in the cryptic value of the kingsnake pattern. As one can see from the photo, the dark color of the snake matches quite well with the shade provided by the roadside vegetation, while the light colored area is indistinguishable from the patches of filtered sunlight that has managed to reach the snake.

If I had not seen the snake crawl into the shade, it would be extremely unlikely that I would have seen it. Similarly, a California kingsnake in the same type of microhabitat would be next to impossible to find by sight. In conclusion, one has to be extremely careful about invoking Batesian mimicry when two different species resemble each other in coloration. What may seem to be logical may in fact be completely wrong.

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