The Question and Answer section for Call of the Wild is a great resource to ask questions, find answers, and discuss the novel.
Mercedes had a number of items packed on the sled that were tossed aside in an attmept to lighten the load. These included dishes, canned goods, blankets, and a tent.
From the text:
He sprang at the foremost man (it was the chief of the Yeehats), ripping the throat wide open till the rent jugular spouted a fountain of blood. He did not pause to worry the victim, but ripped in passing, with the next bound...
Buck heard the "call of the wild." The call symbolizes freedom.