What kind act did Perrault perform for Buck?

He takes care of Buck's feet.

Explanation:

Perrault and Buck are characters in the novel "The Call of the Wild" by author Jack London. Buck is a brave dog that, after being stolen from his home, is sold to be a sled-dog. One of the men who buy Buck is Perrault, the sled-driver who works as a mailman, delivering dispatches in a rough and cold region. Buck's life changes completely. Once a domestic dog, living comfortably and unaware of the harsh world, Buck was now a true survivor. He quickly learns how to defend himself and how to be a leader. However, he is not a husky; he belongs to a domestic breed whose feet are not meant for snow-covered ground. In an act of kindness, Perrault begins to rub Buck's feet every night to make him feel better. Also, to protect his feet until they grow accustomed to the trail, he makes footgear out of his own moccasins for Buck to wear. This information is provided in chapter 3 of the novel:

Buck's feet were not so compact and hard as the feet of the huskies. His had softened during the many generations since the day his last wild ancestor was tamed by a cave dweller or river man. All day long he limped in agony, and camp once made, lay down like a dead dog. Hungry as he was, he would not move to receive his ration of fish, which Francois had to bring to him. Also, the dog-driver rubbed Buck's feet for half an hour each night after supper, and sacrificed the tops of his own moccasins to make four moccasins for Buck. This was a great relief, and Buck caused even the weazened face of Perrault to twist itself into a grin one morning, when Francois forgot the moccasins and Buck lay on his back, his four feet waving appealingly in the air, and refused to budge without them. later his feet grew hard to the trail, and the worn-out footgear was thrown away.