Objection 1. It would seem that there is no hope in dumb animals. Because hope is for some future good, as Damascene says (De Fide Orth. ii, 12). But knowledge of the future is not in the competency of dumb animals, whose knowledge is confined to the senses and does not extend to the future. Therefore there is no hope in dumb animals.
Objection 2. Further, the object of hope is a future good, possible of attainment. But possible and impossible are differences of the true and the false, which are only in the mind, as the Philosopher states (Metaph. vi, 4). Therefore there is no hope in dumb animals, since they have no mind.
Objection 3. Further, Augustine says (Gen. ad lit. ix, 14) that "animals are moved by the things that they see." But hope is of things unseen: "for what a man seeth, why doth he hope for?" (Romans 8:24). Therefore there is no hope in dumb animals.
On the contrary, Hope is an irascible passion. But the irascible faculty is in dumb animals. Therefore hope is also.
I answer that, The internal passions of animals can be gathered from their outward movements: from which it is clear that hope is in dumb animals. For if a dog see a hare, or a hawk see a bird, too far off, it makes no movement towards it, as having no hope to catch it: whereas, if it be near, it makes a movement towards it, as being in hopes of catching it. Because as stated above (1, 2; 26, 1; 35, 1), the sensitive appetite of dumb animals, and likewise the natural appetite of insensible things, result from the apprehension of an intellect, just as the appetite of the intellectual nature, which is called the will. But there is a difference, in that the will is moved by an apprehension of the intellect in the same subject; whereas the movement of the natural appetite results from the apprehension of the separate Intellect, Who is the Author of nature; as does also the sensitive appetite of dumb animals, who act from a certain natural instinct. Consequently, in the actions of irrational animals and of other natural things, we observe a procedure which is similar to that which we observe in the actions of art: and in this way hope and despair are in dumb animals.
Reply to Objection 1. Although dumb animals do not know the future, yet an animal is moved by its natural instinct to something future, as though it foresaw the future. Because this instinct is planted in them by the Divine Intellect that foresees the future.
Reply to Objection 2. The object of hope is not the possible as differentiating the true, for thus the possible ensues from the relation of a predicate to a subject. The object of hope is the possible as compared to a power. For such is the division of the possible given in Metaph. v, 12, i.e. into the two kinds we have just mentioned.
Reply to Objection 3. Although the thing which is future does not come under the object of sight; nevertheless through seeing something present, an animal's appetite is moved to seek or avoid something future.
Source: Summa Theologica (New Advent)