Yes, service animals are allowed. Per federal law, they are generally allowed anywhere a person is allowed in a business. Ask the help desk for more information about accessibility.
I've seen service dogs at the zoo. There may be a law that they must allow it. Furthermore, several animals (such as leopards) find the experience mentally enriching!
It depends on the kind of animal. They wouldn't want someone's service crocodile or rhino upstaging the other animals in the zoo.
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