@MaximumNut
I think the famous soliloquy from
Macbeth explains this very well:
"Life's but a walking shadow, a poor player,
That struts and frets his hour upon the stage,
And then is heard no more. It is a tale
Told by an idiot, full of sound and fury,
Signifying nothing."
The gorilla beats his fist against his chest, he roars, and displays his strength and dominance as an apex predator, yet he, even with a less developed brain than ours, understands that with all his power, he still cannot defeat the slowly creeping beast that is death. His life is abruptly cut short without warning, a metaphor for how little little control we have our lives and surroundings.
Yet, upon deeper inspection, I have come to a more hopeful analysis. While it is true that he beats his chest, it does not seem to be with violence or anger, one of the 5 stages that people go through when accepting death. And although he knows that he will die tomorrow, there is no sign of desperation, shock, or even fear, just acceptance. He knows that he will not make it to the next day, yet he seems almost content with this information, which is strange considering that as a wild animal, their greatest instinct is based on survival. In his final moments of life, it seems like the only thing he felt was peace. Knowing all of this, the conclusion that I've come to is that the theme of this short story is not about the fear and terror we feel in the face of death, but rather the lack thereof. Maybe I'm reading too deep into this, or maybe It's because it's 2 in the morning and I can't think straight, but I think the author is trying to tell us that death is not something that should dread, but something that we should come to terms with, so that it doesn't control us and prevent us from living a life devoid of regret and dissatisfaction.