Relevant portions of the Summa:

Excellent question by Cassini. Excellent response by Hansel.

Relevant portions of the Summa:

https://www.newadvent.org/summa/1078.htm

https://www.newadvent.org/summa/1072.htm

https://www.newadvent.org/summa/1076.htm

https://www.newadvent.org/summa/1079.htm

https://www.newadvent.org/summa/1081.htm

I’m quite sure my 🐩, 🐕, and 🐈 have souls, they’re just not immortal souls because they aren’t made in God’s image and are lower than humans. 
Haven’t readers ever seen their pets look “guilty,” only to discover they’ve done something naughty while nobody was looking?  They can also show compassion, anger, happiness, etc. 

There's a certain kind of small dog, a type of poodle, that eats its own feces. Could it be that God doesn't only allow humans to make perverse choices, but animals as well?

Please someone correct me if this is wrong, but my understanding is as follows:

The offspringing of plants and animals belongs entirely to the order of generation, or providence, as some call it. The souls of animals and plants are entirely material. Hence they are not immortal. Hence their parents possess the entire potency necessary to actuate the substantial form in the offspring. God does not directly infuse their souls into new plants and animals.

Mankind constitutes to a class entirely unique. We most certainly participate the order of generation, our parents possessing the entire potency needed to generate our bodies - material intellective powers and emotions, inclusive. But they have no potency whatsoever to engender the immortal souls of their children; for such are entirely immaterial, spiritual, immortal. Only God can create, ex nihilo, intellectual substances (angels) and immortal human souls.

At every human conception, God creates, out of nothing, the soul of the person conceived, and infuses that soul into the corporeal body. I think that theologians have discussed the exact moment in time when the soul is infused. The operative principle is that the matter is capable of receiving the form when it is properly disposed. St. Thomas, I believe, held that the human soul was infused some time after conception. Many others believe the infusion takes place at conception. What we do know for certain is that, no matter what stage of the pregnancy, it is a most grave mortal sin to try to induce abortion by any known means.

What is most wonderful to my mind, is the consideration that, though the work of Creation formally ended on the Seventh Day, when God rested; and though for all time ensuing the creature participates the order of generation or providence; nevertheless God has not stopped creating, ex nihilo, with regard to men. Each man is properly called a new creation, and participates both the orders of creation and generation. This alone puts the earth at the center of the universe; for the earth was created for man. Man is the center of the creation, and his dwelling the center of the universe.

Such considerations bring home the sheer vileness and malignancy of evolution, including theistic evolution.