Animals are found susceptible of kindness, both to their own species and to ours
 David Hume, An Enquiry Concerning the Principles of Morals (1751). copy citation

Context

“how can we suppose, that his passionate tenderness arises from some metaphysical regards to a self-interest, which has no foundation or reality? We may as well imagine that minute wheels and springs, like those of a watch, give motion to a loaded waggon, as account for the origin of passion from such abstruse reflections. Animals are found susceptible of kindness, both to their own species and to ours; nor is there, in this case, the least suspicion of disguise or artifice. Shall we account for all THEIR sentiments, too, from refined deductions of self-interest? Or if we admit a disinterested benevolence in the inferior species, by what rule of analogy can we refuse it in the superior?” source