The zoo is a nice place to have lots of practice taking pictures in different lighting and situations. Use it as a learning experience and have fun.
Of course animals sleep, don't we?

Especially since some are nocturnal and do their hunting at night, they will be sleeping during the day.
Think of it as a place with many situations, nice scenery and lighting variations. I'd suggest a monopod as a tripod is bulky to carry and set up, especially where people will be walking around.
Many zoos have outdoor and indoor exhibits, birds, insects, fish and reptiles and whatever else. You can learn about how your camera works and have a good time.
By the way, many zoos have the copyrights to sell images taken there, restricted. Keep that in mind. Public zoos you should be OK because it's funded by your taxes. Privately funded like San Diego have been known to claim they own all commercial rights. Check it out when you go in, look at the zoo maps and the back of your ticket.
It's still fine to take pictures for personal use. If you take kids or friends, you can always take pictures of yourself and your family with nice scenic backgrounds.
I can't believe all the negative comments from people who think a walkabout at the zoo is a waste of time. It's fun and a perfect place to learn about your equipment. You have nice scenery and hundreds of subjects. :thumbup: