What is the foundation of human rights, that is not foundation, for animal rights also?

We hear of the “Rights of Man.” I wish we heard more of them than we do—and could see them observed as well as talked of. But who ever thought of an animal’s rights—the rights of a brute. We hear it spoken of as a man’s duty to be kind to the brutes—but never of the brute’s right to just treatment. But why has not a brute rights, as well as men? What is the foundation of human rights, that is not foundation, for animal rights also? A man has rights—and they are important to him because their observance is necessary to his happiness, and their violation hurts him. He has a right to personal liberty. It is pleasant to him—permanently pleasant and good. It is therefore his right. And every creature—or I will call it, rather, every existence, (for whether created or not, they certainly exist, they are) every existence, that is capable of enjoying or suffering, has rights, and just mankind will regard them. And regard them as rights. The horse has rights. The dog. The cat, and the rat even. Real rights. And these rights are sacred[.] They are not to be invaded. Mankind are to study the happiness of all beings, so far as they are connected with them. How far it is to be carried, depends upon how far the most perfect good will can carry it. Farther then it can go—it is under no obligation to go. Does anybody seriously think it right, to trifle with animal happiness and animal suffering? They do trifle with them, and talk about dominion over them being given to man. If this dominion involve ill treatment—it was a bad gift, whoever gave it—in my opinion. They talk of dominion—and found upon it the right of capricious treatment. But that any body thinks it right to injure the brute, I doubt. Whoever will do it—is liable to extend the like injury to mankind. “Dominion” is claimed over portion of mankind as well as brute-kind, and by “divine right” too.
~ Nathaniel P. Rogers (October 31, 1845)