Jottings on protective colour in animals

I have often been puzzled about the remarkable change of colour in the roedeer, a species that I can watch almost daily from my house. In the winter the greyish brown coat can hardly be distinguished against the dull, brownish shrubby wood, at the border of which they come to feed. The only visible part of the animal is the white patch on their hindquarters. It is known that this patch is a guiding mark for the young to follow their mother. Some years ago a roedeer calf followed a boy on a bicycle with a white mudguard even to the boy's house. We may take it that also adults follow the leader by this mark. In the summer, on the contrary, the bright reddish coat makes the roedeer very conspicuous against the bright green background. I know how dangerous it is to speculate on the meaning of colour in animals, and I agree that in many cases no explanation is possible as the colour, so striking for the human eye, may have no significance for the animal and its environment. However, I dare to suggest a hypothetical explanation of what use the red colour can be to the roedeer, and to many other deer too. Roedeer have no enemies in western Europe, with the exception of dogs and men (especially when driving motorcars!), but formerly here and still in other parts of Europe and Asia lynx and wolf are their predators. Now it is known that Carnivora as well as most other mammals, with the exception of the Primates, are more or less colour blind and hence that for them a bright red object on a bright green background will be much less conspicuous than a dark brown on a bright background. The white patches on the hindquarters of the roedeer are somewhat less developed in the summer coat, but still conspicuous and as we may take it that the deer too