"Ese perro tiene orejas muy grandes."
Translation:That dog has very big ears.
You may also hear the word oído for ear---which refers to the whole organ. Oreja is only the outer ear---for both animals and humans---and the only part that can be visualized in terms of size. Therefore one never says oídos grandes.
If in english we must to say: Our, your , their... ears, when in spanish we say: las orejas When we talk about animals is not fulfilled this rule? That is: That dog has its ears very big
That man has very big ears. You don't need a possessive there, and if you include it, it would sound completely unnatural.