Perhaps I was too hasty in outright saying 'animals can't reason'. Many animals certainly show an ability to reason in a very primal sense.
A better thing to say would be 'animals can't philosophise or theorise about the nature of their existence or their role in the universe or make calculated moral judgements etc.' But, as I have said elsewhere, I think we, as a species, tend to over-anthropomorphise animals. They largely live by nothing but instinct.
But then, the same can be said of us; we have our own weird little instincts.