The victim of last week's mountain lion attack was sedated and resting after doctors completed a nearly six-hour surgery to repair his scalp on Wednesday at California Pacific Medical Center in San Francisco.
"It went well, it went very well," said hospital spokesman Kevin McCormack.
Doctors will monitor Jim Hamm's condition over the next several days.
The microvascular surgery entailed taking muscle from Hamm's back and skin from his thigh to cover his exposed skull.
Hamm, 70, has also shown recovery signs after contracting an infection from bacteria common in cats' mouths and claws.
A mountain lion ripped into the Fortuna man's head, face, torso and arms as he hiked Brown Creek Trail with his wife in Prairie Creek Redwoods State Park on Jan. 24.
Nell Hamm, 65, fought the cat with a tree branch until it eventually released her husband.
Jim Hamm was taken to Mad River Community Hospital in Arcata. After showing signs of the infection, he was flown to the larger San Francisco facility.