The Underneath by Kathi Appelt, illustrated by David Small

From chapters.ca:
A calico cat, about to have kittens, hears the lonely howl of a chained- up hound deep in the backwaters of the bayou. She dares to find him in the forest, and the hound dares to befriend this cat, this feline, this creature he is supposed to hate. They are an unlikely pair, about to become an unlikely family. Ranger urges the cat to hide underneath the porch, to raise her kittens there because Gar- Face, the man living inside the house, will surely use them as alligator bait should he find them. But they are safe in the Underneath...as long as they stay in the Underneath.