Glen Johnson , Feb 18, 1997; 08:51 p.m.
I would use Sensia RD 100, Kodak E100S, or E100SW Ektachrome. The Kodak Elite II 100 ought to be OK too. I might even go as fast as ISO 200 to pick up the extra stop for the reasons given below.
You will be able to freeze the motion of the snake acceptably well if you can get your shutter speed up to 1/250th of a second, although faster speeds will be even better. You will be trading off action stopping speed against loss in depth of field, so you will have to decide the best compromise. Depth of field will be less important in the side shot, at least if you can make an accurate prediction of the plane of the snake's strike and set the focus up manually for this plane. The wider angle of the lens you will use for this shot will work in your favor as far as depth of field is concerned too.
From the front, with the tele lens, depth of field will be a problem. This is a place where the modern focus tracking feature could pay off. If you use it, try to lock onto the snake's eyes. The motor drive will provide an interesting sequence here too. An alternative is to prefocus manually on a particular plane and when the snake is just ready to break that plane, fire the shutter.
What are you going to use as the target/bait?