One of the trickiest times to photograph wildlife is during a snowstorm. The bright, white snowflakes distract many auto-focus mechanisms on lenses no matter how expensive the glass. Thanks to a bit of modern technology though, there is a more reliable work-around than manually focusing, provided you have an animal that is not moving too quickly.
In the case of this bull moose during a winter storm, I had been attempting to get an auto-focused shot of him, but the snow was so thick, shots were being lost as the snow continued to fall quite heavily. The Canon 7D, along with most newer cameras, have the ability to switch to a live-view mode. By using this feature, I had turned it on showing a preview of the scene, zoomed in by a factor of 10, and was able to get a much more reliable focus of the moose in just a few seconds. With the help of the live-view mode, you can zoom in much more than what you can capture to ensure that the subject you want is in focus and not a snowflake a few inches from it. Once you are able to see that it is in focus, you can switch back to standard camera operation and begin snapping away, as I did with this impressive bull moose in dumping snow. I have used this trick a number of times on a number of subjects, and it could even be used in other environments, if perhaps you have a bird perched nearby, but the only clear shot is through a number of branches, for example.
If you have the time, it is a great tool to get in the habit of using. Peace of mind when getting tricky shots is priceless.