The Zoo
The controlling symbolism of the poem is the zoo. The animals are caged behind bars, of course, because this poem was written before zoos tried to replicate natural habitats. As a result, zoos at the time resembled prisons to a far greater degree. And so, the zoo a symbol of imprisonment.
The Lion
The lion is described as having an untamed heart, an inherent characteristic of its species. This is in contrast with human beings in which “some man” out there is his counterpart. Thus, the lion symbolizes the pure spirit of freedom that no cage can imprison.
The Eagle
Unlike the lion, the eagle symbolizes the segment of humanity which will never be satisfied with imprisonment. The eagle symbolizes that spirit that exists within only some humans that will never stop searching for a way out of their cage.
The Mole
Like the eagle, the mole is pure symbolic imagery. The nature of the mole is to dig downward for the purpose of burrowing rather than escape. Thus, the mole symbolizes that aspect of humanity that does not try to escape from its cage but dig beneath it. It won’t enjoy freedom in this way, but it can create the illusion that its cage is of its own design and be satisfied with its own blindness to the truth.
The Snake
Snakes are traditionally a symbol of evil, but in this case, the evil is more allusive and oblique. The snake’s reptilian nature adapted to deal with its cold-blooded biology is to remain still for extended periods of time. The portrait of eternal stillness situates the snake as that last remaining segment of humanity that is driven neither to escape from its cage nor to dig itself out of it toward a prison of its own making, but rather to do nothing and stoically accept the conditions imposed upon them until death. The choice of a snake as the reptilian symbol implicitly suggests the evil within this preference.
