I know other's have asked but could you give us some insight into how you got such close-up photos without losing anything in image quality? It would be very helpful if you could shed some light on what type of equipment you used and just how long you had to wait for setting up the shots. Did you sit in a blind or were you just walking around and happen to come across these?
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CDL.
Equipment was a Canon Rebel XT, and a Canon 100-400 "L" lens. These images did loose some quality with the resize to the web, I should have sharpened them prior to posting but I got lazy. For image quality, I believe it's a couple of things that contribute to it. First is quality lenses, but that said I've gotten some great shots with the "lowly" Canon 75-300 $150.00 lens. Second is to not shoot with the lens wide open. These were set to about f7.1, and not shoot all the way at 400mm. Also, even though the lens is image stabilized, try for the higher shutter speeds (i.e. 1/400 sec @ 400mm). Keeping the ISO as low as possible. With all that in mind I also shoot in RAW so I have more control over things like white ballance and exposure. .JPG can give some good photos, but I've found that I throw more away and can't salvage some of my minor mistakes with them and keep the quality.
Now as to getting that close... well I cheated a little bit, these shots were all taken in Yellowstone, and the animals aren't as skittish as outside the park. That being said, keep a low profile and move slowly & in a non-threatening manner. Only move when the animal is comfortable or not watching. If they get nervous, wait it our, or leave, last thing you want to do is stress them out, and risk injury to them or you. The mule deer in the last shot is getting a bit stressed/P.O.'d at me. You can see this by the wider eyes (whites are starting to show), and the ears flattening out. I was about 10 feet from her. The next shot I took after that she really pinned her ears back, and that was my clue to leave her alone and back off. As soon as I backed off she relaxed and went back to feeding. For the Coyote shots, I never got out of the vehicle. Not pressuring it let it roam along at it's own pace sniffing and mousing it's way along. I also noticed the bison trail it was walking in (easier than walking through the snow itself) and was able to anticipate the shot with the tree by figuring out where the trail went. Once it started in that direction I set up the shot and waited for the coyote to come into the frame.
Sorry this was so long, hope it helped...