That's a wonderful conundrum.
Would a Buddhist find it acceptable to use the discomfort of another being in order to stay alive?
Well, the monkey was not killed, nor was it physically damaged.
So we are faced with the dilemma about causing mental suffering or some temporary physical pain.
The captivation was probably a cause of anxiety, but the monkey decided to try to grab the bait and the monkey decided to eat the salt. As was shown, the monkey did not appear to even register awareness of being captive while it ate the salt.
After eating the salt, was it torture to deprive the monkey of water?
I think that this stage is crucial as it exhibits deliberately forcing another being to endure suffering for one's own benefit.
Sitting here, I would like to think that I would never cause suffering to another being. However, f I were dying of thirst I would almost certainly act the same way, if I knew that I was likely to find water without lasting harm to the monkey.
However, does the person in the film need to visit that desert area and hunt to survive? If not, then I place him in a different position from a person who is there through misfortune. Why? Well, if a person knows that he is going there and will use other beings in order to survive, his intention is different. He is then deliberately planning to inflict suffering, whereas someone there through misfortune may be driven to it through desperation.
That's my 'thinking', without delving into Buddhist vows or scripture.