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You should always get permission from the owner before photographing, especially if you're taking pictures of big animals. You'll need to be familiar with the geography of the area you're working in, so you can identify the animals you're photographing. If you are willing to test out some different lenses, you may want to buy some tripods or monopods. You also want to think about the type of weather that you will face, such as how often you will need to travel.