Our 5 year old Border Collie, Loki, has always had a rather pronounced bone right on the top of his head, near where his head meets the top of his neck. I'm not exactly sure what the name of the bone is, but I know all dogs have them; some are just more pronounced than others.
I've noticed over the last few months that that top bone, as well as some other areas on his head are becoming slightly more boney than they were before. His eye sockets are more easily felt than they were before, as well as his jaw bone. It's not visibly noticeable unless you're really looking for it, but since I do rub his head on a daily basis, I've noticed the change. Is this normal with age, or should I be concerned? He has always been a healthy weight, so I'm a little unsure what this could be. Any ideas? Thanks!!