From Catherine Vosper:

Re: Mice show pain in their faces, study finds (May 9): The only surprise here is that anyone should be surprised by this news. Anyone who has loved an animal knows their faces express many things including pain but not exclusively pain. You can read confusion, excitement, fear, anger etc. in an animal’s face whether it be mouse, cat, dog, ferret or whatever. I think reptiles and snakes may be a little difficult.