Batesian mimicry in water snakes?

While searching for morels with my mycology class today, we ended up finding almost as many herps as mushrooms. On campus, in Four-Mile Creek (near the horse stables) we saw 3 huge softshell turtles on a fallen tree in the water. It was difficult to see because they were far away, but their shells appeared to be spotless, which would make them smooth softshells.

Later we spotted a large (approaching 1m) northern water snake about 10m from water, which quickly evaded capture by slithering under a log pile. While searching for its possible escape to the water, we found and captured a smaller water snake (pictured above). While it isn't doing it in the picture, it displayed a very peculiar behavior. When it was constrained by a large mammalian potential predator (me), it flattened its head and puffed out the area on both sides of the back of its head (where the venom glands of a venomous snake would be). This gave its head the more triangular appearance of a venomous snake. It seems that this could potentially be an example of Batesian mimicry, convincing predators that it is more dangerous than it really is.

-posted by Andrew Henterly