The Zoo is the perfect place to test your photography skills - plus its a lot of fun - with or without your camera. Some of my favorite photos were taken at the zoo of both animals and peoples' reactions to them.
As mentioned in previous blog entries, animal movements are often unpredictable and your camera settings need to be adjusted accordingly. Use your shutter priority mode and set to 1/250th of a second or faster to ensure movements aren't blurred. Normally this might darker a photo, but the natural light of shooting outside will offset the faster shutter speed. As a consequence a tripod or monopod won't be necessary at these shutter speeds. Zoos are often crowded with families - you don't want to be "that guy" taking up space plus you don't want to carry all that extra equipment.
It's also a good idea to bring a zoom lens to close the effective distance to the animals. Note that the maximum aperture of zoom lenses rises with the focal range. For a basic kit zoom lens the maximum aperture at 70mm is F5.6, but when zoomed in close to 300mm the maximum aperture is F6.5 which sharpens the depth of field but also effectively darkens the exposure. This makes planning your shots and picking your position even more important; getting situated where the sun/lighting benefits your subject becomes more critical. Since the animals are often in motion, you'll need to be on the move to keep the lighting in your favor.
Lastly, fight the urge to "overzoom", because going in tight reduces your light, limits your settings, and shrinks your frame. Given the choice, I'd rather have both the content and the extract light and do my zooming virtually in post production cropping tight onto subjects.