Hi, This is actually one of my favorite novels! I prefer to work through this question with you-- it'll build your comprehension of the novel and its themes. I want you to consider the arc of their friendship-- how did it start? What was their relationship at first? What initially tied them together? Once we get through that starting point, we can trace how their friendship affected them.
A person can change their opinions/feelings on animals for multiple reasons. For example, they can make friends with an animal or start a relationship that involves no communication (cause animals can't talk) but lots of love. Also, if the animal starts being friendly to the person, there's a high chance that the person may not take their love for granted.