How did Skeet, Buck and Nig all get Thornton's attention?

From the text:

For the most part, however, Buck's love was expressed in adoration. While he went wild with happiness when Thornton touched him or spoke to him, he did not seek these tokens. Unlike Skeet, who was wont to shove her nose under Thornton's hand and nudge and nudge till petted, or Nig, who would stalk up and rest his great head on Thornton's knee, Buck was content to adore at a distance.