Do you have a manual mode where you can set all the settings? If so, you want a high shutter speed. To compensate you'll want a low F-stop, and a slightly higher exposure. This will ensure you don't lose any light but you get faster and un-blurry pictures of your animal. Also, though autofocus can be great, the one draw back is that it takes a second or two to calibrate, and you may miss a great shot.
If not...Sport mode all the way!
"The wise man thinks he knows nothing.
The fool thinks he knows everything."