It is common to use personal pronouns for pet animals as explained in the following source:
From Writer’s digest.com:
An animal is referred as “it” unless the relationship is personal (like a pet that has a name). Then it’s OK to use “he” or “she” when referring to the animal. This also applies to using “who” and “whom.” If the animal has a personal relationship with the person, then use “who” or “whom.” Otherwise you must exclusively use “which” or “that.” Here’s an example that incorporates both of these rules:
Personal: My horse, whom I call Steve, is my best friend. He comforts me when I ride him.
Generic: The stray dog, which I saw chasing its own tail, was shedding hair.
The “personal” rule also holds true if you’re writing a kids book and the animals can talk—as you’re giving them human traits and making them characters your readers can get to know. Even if the animals don’t have specific names, they are given personalities and this is enough to make them personal.