Short Story: Explorer crash–lands on uncharted planet, is stripped of technology and observed by alien?

Another story I read a few years ago that is likely to be from the 70s or 80s.

This one involves a pilot crashing his ship on an unknown planet. The crash was caused by an alien creature who resides in a metal pyramid on the planet's surface. After the impact, a message is played back to the pilot, constructed from his own audio logs. It tells him that all technology has been taken from him and challenges him to survive.

With each passing day, the once civilized man more closely resembles an animal, driven by instinct. However, he is able to retain his sense of reason and begins formulating a plan to penetrate the force-field surrounding the pyramid and to infiltrate the structure itself.

When he first catches a glimpse of the alien (referred to as "the Other"), he becomes frightened and runs. Later, he conquers his fear and resolves to return to the pyramid to confront the Other. The Other, although physically more powerful, is terrified by the vicious animal that has somehow bypassed the pyramid's defenses. In the end, the pilot is repeatedly smashing the Other's skull in with a rock, long after the alien's demise.