Animals feel, communicate, imitate, take decisions, actions, play, eat, sleep, run from dangers, do all kind of stuff.
But thinking?
Before answering this question seriously, a definition of thinking should be in place. Dualists traditions such a christianity have attributed souls (although not immortal souls) to animals. Having a soul (the article goes the brain-is-the-mind path) clearly involves having mental states, no doubt about that. Being God's creations, animals deserve a good treatment, to touch on the ethical side of complex issue.
The simple fact the animals can see, hear, smell, etc. implies phenomenal experiences (as David Chalmers, among others, calls them). There is no science yet to explain them but there're there, for the simple reason that we experience them and they look familiar to what we do when we experience them.
But thinking? I believe a proper definition of rational thinking involves the ability of having articulate language. I don't know of any animal species capable of that. Sounds? Yes. But sentences with truth value? Anyone?
The danger here is to project our abilities into a small set of faculties animals have and say, look!, we're no better, we're no different.