As to this specific skull, one of the clues was that baby caribou first grow small, spiky antlers during their first three months. Yearlings develop larger spiked antlers, as seen on this Baffin skull.

Caribou/reindeer males and females both grow antlers, whereas other antlered species such as moose, deer, and elk only have males with antlers. Caribou do not grow horns, as do pronghorns, sheep, goats, and a few other animals.