The poem’s clever use of techniques such as similes and metaphors clearly puts an image in the reader’s mind of the actions of animals and their ways of life.
Such is the inactivity of the resigned incarcerated animals.
The word ’empty’ whilst literally untrue, conveys the irony of ‘dead’ or ’empty’ lives.
The dismissal of ‘these’ animals reveals how incarceration has reduced the snakes, the lions and tigers to beings regarded as a mere group of uninteresting objects, deprived of their natural vitality and therefore unjustly now dismissed.
Humans crave sensations and excitement and only the untamed, proud and frustrated jaguar can give the visitors what they believe they have ‘bought’ of paid for.