How did Buck perfrom as the lead dog?

Basically, Buck was an amazingly good lead dog after he
killed Spitz and then forced the men to put him in as the lead
dog.

It was with Buck as the lead dog in the pack that the
men were able to set records for the quickest runs.  Much of that was due to the fact
that Buck was a really great lead dog.

With Buck as lead
dog, the team managed to make forty miles every day for a whole two weeks.  This was
impressive enough to make everyone in Skaguay make a big deal of Perrault and
Francois.