There was no telling.

Something might happen.

The porcupine might unroll.

There might be opportunity for a deft and ripping thrust of paw into the tender, unguarded belly.
But at the end of half an hour he arose, growled wrathfully at the motionless ball, and trotted on.

He had waited too often and futilely in the past for porcupines to unroll, to waste any more time.