Because during Katrina so many people wouldn't evacuate without their pets and there were so very many left-behind pets following Katrina, people evacuating during Isaac were allowed to take their pets. They didn't even have to be in a kennel, just on a leash. A pet shelter now is being made available during hurricane evacuations in central and northern Louisiana.
Don't know what arrangements are made for zoo animals, but there is a Wild Life Reserve off I-12 in Louisiana. Took my grandchildren there the summer after Katrina. When the workers returned they saw no animals at all. They were devastated. A few hours later, the animals started coming out of the distant forest area. This area just happens to be the highest elevation on the reserve. The animals knew instinctively where to go. EVERY ANIMAL survived, including the one that was born while they were in the trees. God's hand was most certainly on those animals. Although I no longer have my Dachshund, I would never have left her behind.