Rigsby would dig and Jack would fill the holes. But something about the holes didn't bother Jack. Rigsby had a curiosity that intrigued Jack. He would find things that Jack didn't know were even in the backyard. He would bring him old pieces of shovel, chewed up dog bones, large stones, and once he even brought him a dying bird that he found on the ground. Rigsby had carried it so gently in his mouth that the bird was not hurt, and Jack was able to nurse it back to health within a week.
They had this relationship, Jack and Rigsby. Jack didn't mind that Rigsby dug holes, and Rigsby didn't mind keep Jack company. Didn't mind encouraging him to run further, didn't mind protecting him from traffic and from the burglar that was trying to break in that warm June night. He didn't mind bringing Jack his newspaper every morning and he never once missed giving Jack a friendly hello when he came home from work. They had a relationship, and even though only one could speak, it never got in the way of their communication.
I guess Rigsby needed a hole to dig and Jack needed a hole to fill. It worked out well.