He did not know that it was a wolverine, standing outside, all a-trembling with its own daring, and cautiously scenting out the contents of the cave.

The cub knew only that the sniff was strange, a something unclassified, therefore unknown and terrible--for the unknown was one of the chief elements that went into the making of fear.
The hair bristled upon the grey cub's back, but it bristled silently.

How was he to know that this thing that sniffed was a thing at which to bristle?
It was not born of any knowledge of his, yet it was the visible expression of the fear that was in him, and for which, in his own life, there was no accounting.

But fear was accompanied by another instinct--that of concealment.

The cub was in a frenzy of terror, yet he lay without movement or sound, frozen, petrified into immobility, to all appearances dead.