I seem to recall from somewhere that Tolkien likened Aragorn to a type of animal, I think a wolf, but I can't for the life of me remember where he may have said this. Did Tolkien actually make a comparison like this? If so, where did he make this comparison?
This is perhaps stretching, but might you be thinking of "Thorongil"? It's the name Aragorn used during his time in Gondor and Rohan, and means "Eagle of the Star":
Thorongil men called him in Gondor, the Eagle of the Star, for he was swift and keen-eyed, and wore a silver star upon his cloak; but no one knew his true name nor in what land he was born.
Return of the King Appendix A "Annals of the Kings and Rulers" Chapter 1: "The Númenórean Kings" (iv) Gondor and the Heirs of Anárion The Stewards
That Thorongil is Aragorn is revealed in Appendix B:
2957-80 Aragorn undertakes his great journeys and errantries. As Thorongil he serves in disguise both Thengel of Rohan and Ecthelion II of Gondor.
Return of the King Appendix B "The Tale of Years" (ii) The Third Age
It would also be a much more complimentary comparison, since eagles are traditionally associated with Manwë (good) and wolves with Morgoth/Sauron (bad).