Deer camouflage

Coming back to my car after taking sunset photos the other day, I came around a blind corner and found a beautiful doe standing between me and the car. She was as shocked as I was, but stood there quietly while I took several pictures.

Just minutes before I had been photographing prairie grasses, big blue stem in particular, which reached at least two feet above my head.

Looking at the deer I was struck by how similar their coloration was to those grasses, and wondered whether deer coloration is really camouflage. With a little help from photoshop, here's the result of my experiment: on the left the image of the deer from the top photo layered behind the the prairie grass and, on the right, the image of the deer disappearing into the prairie grass.

Is their natural camouflage in fall vegetation (prime reproductive time) just a coincidence or was their some selection for this coloration during a vulnerable period of their annual cycle? White tailed deer are widespread across the US and well adapted to a variety of habitats, but here in the upper Midwest, they are supposedly forest animals. It seems to me they favor forest edge more than interior forest, and I often see them bounding away through tall thickets toward the woods. In Minnesota the forest edge usually gives way to grassy fields, where the dominant native grasses produce tall, yellow-brown vegetation. Their natural predators, mountain lion (also nicely camouflaged in prairie grass) and wolf, could have hunted both forest and prairie and would have controlled population sizes better in historical times than hunting pressure from humans does today.

Even in mid-winter, deer seem well camouflaged against the tans and browns found in bark of most hardwoods. It could just be the lighting, but they do seem to be a slightly darker brown in winter than in summer and fall.