How does Ivan feel about captivity in the zoo?

Initially, Ivan doesn't understand where he has been taken because it is unlike anything he ever saw in regard to a zoo. He is confused.

I have three walls of glass. The fourth wall is a curtain of wooden slats strung together.
This doesn’t look like the zoos on TV. Where are the other animals?
Where are the gorillas?
Is this where Ruby ended up? In a cage just like her old cage, still alone? Is she cold? Hungry? Sad?
Is there anyone to tell her stories when she can’t get to sleep?