Sorry for the late reply. I do not do much wildlife photography, but I did do a 4 week safari trip a few years back. Here's some thoughts for you.
In South Africa, where I was, the safari trips were first thing in the morning or last thing in the afternoon. You never went out during the middle of the day because it was too hot (and the animals are all hiding). So, lots of nice diffuse light.
My trips were all in a Land Rover. You are yards away from the animals at best, using a long zoom. Flash wouldn't help in these situations. Often, the best shots come up right when you are hitting a pot hole, so stability is key. Also, the conditions are extremely unpredictable. We had one leopard pose for us for 20 minutes on a perfectly lit branch, but that was rare. The animals (other than cats and waterbuffalo) are often moving constantly, so think of this as shooting a sporting event.
Rangers are very picky about what they allow you to use.I really doubt any would allow a flash of any sort -- the sudden bright light could scare the animals, which could then be dangerous. They don't even want you to wear white shirts, because they are so unnatural and distracting. For example, we once happened apon some elelphants after dark. The ranger used his spot light, and gradually moved it along the ground towards the animals, so as not to startle them, briefly shined it on them (2 or 3 seconds) and moved it off. They are very careful about respecting the animals. (If they are not, don't go out with them.)
I also brought along a video camera with a IR light. Some of my best images are on the video, e.g. quick glimpses of a cheetah ducking into the brush that I would never have been fast enough to get on film. Especially since the most amazing part of seeing these animals is seeing them MOVE. The loping gait of a giraffe herd. The slow lumber of an elephant, turning into a quick charge. The spooky grace of the cats. My photos, though nice, are rather dull in comparison, and my wife and i often turn to the video for memories.
Hope this helps. Have fun!