Anti-Light Retriever

You know how you have golden retrievers? This is like that except that their fur absorbs ambient light. Eventually this renders the space around the dog dimmer, but it takes a while. Their natural coloring tends to be darker than the average golden retriever, but the resemblance to the breed is obvious.
I'm not entirely sure what the dogs do with the light once absorbed but it doesn't seem to harm them. I currently have none of the breed in my possession, having passed them on to others.