The Red Pandas are at times very photogenic and can be caught in a very natural background, making for natural looking shots.
The orang utangs, can give some great images, but if they are inside, you will be shooting through glass that has kids (and adults) handprints all over it - unless you get there quick.
Have a look at their website and look at the competition winning photos, may give you some ideas.
CANON EOS 50D 7 PAGE IN-DEPTH TEST
In the EOS 50D, Canon has created its best specified APS-C-format DSLR to date. Barney Britton tests the new 15-million-pixel model and delivers his verdict