Wildlife photography can be a hard and dangerous profession. Getting close to wildlife can often times be very difficult, especially if it's a prey animal. So how do you get close and remain safe? Well for me it's using my vehicle. Some photogs will use a blind and hunting camo, which may be good for birds and prey animals, but in my opinion, I would not go that route for bear photography. If anything, the bear will get close not knowing you're there, and then you startle him. I would rather have the bear know where I am and what I am doing. So to photograph predators it's best to have the protection of your vehicle and for prey animals, a vehicle is a common thing these days, and they don't perceive it as a threat. In your vehicle you can cover a lot of ground, looking for the animals as opposed to them finding you. Just remember the animals in the wild are most comfortable when it is silent. Meaning shut your vehicle off after you're in position, try to keep equipment inside your vehicle, move slowly, and make little noise. I think you'll find the wildlife will stick around longer, you'll be safe from the aggressive animals, and in the long run it will be safer for the animals as well.
The image below is a field of elk grazing in Rocky Mountain National Park. The animals in the National Parks are especially used to humans and vehicles. None of the lek seemed to mind the photographers snapping pictures.