What kind of physical shape dogs in when they arive in skagway?

The dogs were worn out and worn down, they suffered from weight loss, injury, and exhaustion.

They were in a wretched state, worn out and worn down. Buck’s one hundred and forty pounds had dwindled to one hundred and fifteen. The rest of his mates, though lighter dogs, had relatively lost more weight than he. Pike, the malingerer, who, in his lifetime of deceit, had often successfully feigned a hurt leg, was now limping in earnest. Sol-leks was limping, and Dub was suffering from a wrenched shoulder-blade.

They were all terribly footsore. No spring or rebound was left in them. Their feet fell heavily on the trail, jarring their bodies and doubling the fatigue of a day’s travel. There was nothing the matter with them except that they were dead tired.