What is the meaning of the title of chapter four The Toil of Trace and Trail

I think you mean chapter 5. This chapter contrasts the readers conceptions of "civilization" and "wildness." When the dogs are sold to Hal and his relatives, their decline is rapid and painful. These people are described as "manifestly out of place." The author writes about them disparagingly (Charles has "weak and watery eyes," Hal is "callow," and Mercedes "flutters") because they have no business intruding upon the domain of the pioneer. Charles, Hal and Mercedes have become so "civilized" that they are unable to adapt to new conditions.