Looking for Different Shots 

Animal & Insect photography is among my favourite subjects. I love going to any of the Zoos to see and practice photographing animals. They give you a great opportunity to take some really wonderful shots if you take the time and have patience.
After you have got all the standard shots, and you are good at getting exposures right, the correct focus and your framing is good, it is time to take the next step - photos with expression.
Equipment 
To get the best chance of getting expressions, a long telephoto or telephoto zoom is desirable. I used a Tamron 150 - 600 mm zoom for these shots. I also used a monopod, braced against my waist or dropped to ground level.
Capturing animals showing behaviour or having interesting expressions takes more time. It is best to plan your day to get there before the crowds. Learn the animals’ behaviour in certain weather conditions. Eg the lemurs all huddle up in the sun or their nests if it is cold.
Come back later if the animals are asleep. They could well be out on your way back.
Watch them while they are eating or interacting with other animals. Wait for interesting expressions. Use different angles. Wait for a bird to flap its wings or dive in the water.
Sunny Days - If you can go on a sunny day after a cold spell, all the animals will be out and active. However, you will have to watch out for mottled light ruining your shot. Go early or late to minimize that.
Be prepared to visit often. Every time you go, you will find something different.