Spitz (a dog) Timeline and Summary

Spitz, "a big, snow-white fellow," steals from Buck.
Spitz laughs at Curly’s violent death, precipitating some hatred from Buck.
Spitz fights with both Billee and Joe.
He leads the team, both literally in the traces and otherwise.
He begins a rivalry with Buck, stealing his sleeping spot in the snow and fighting with him.
When the camp is attacked by outside dogs, Spitz takes advantage of the opportunity to attack Buck.
He goes after Buck again when Buck is vulnerable (having just run from a dog-gone-mad).
After a rabbit chase, Spitz and Buck fight. Buck wins.