What was the "moose" truly idenified as? What did this illistare about Chris's survival skills?

The moose was actually a caribou.

When I’d questioned Gordon Samel and Ken Thompson shortly after they’d discovered McCandless’s body, both men insisted—adamantly and unequivocally— that the big skeleton was the remains of a caribou, and they derided the greenhorns ignorance in mistaking the animal he killed for a moose. “Wolves had scattered the bones some,” Thompson had told me, “but it was obvious that the animal was a caribou. The kid didn’t know what the hell he was doing up here.”