How are zoos and circuses presented in the novel, Memoirs of a Polar Bear?

The circuses and the zoo represent variations on the idea of home for the three central bear characters - more specifically, the only "home" they really know as young bears, a life in which they are exploited, controlled, and treated as objects rather than as individuals with identities and purposes. They are a different sort of cage, but essentially represent the same thing as the physical cages in which the bears are kept - oppression, exploitation, and denial of freedom and/or identity.