In chapter 3, how did the nine sled dogs get wounded?

Four of five starving huskies have invaded the camp. They pounce on the food, crazed by its smell. The team has never seen such dogs. Gaunt skeletons with eyes and fangs. The strange huskies attack, and Buck finds himself viciously fighting for his life. Just as he kills two of the huskies. Spitz treacherously attacks Buck from the side. Buck shakes him off and concentrates on driving off the strange dogs. The men are forced to concentrate on defending the food. The team takes flight into the forest, where they regroup to return to camp. All are terribly wounded, and the sled harness is a mess, having been chewed in various places. Half of their food is gone.