When I took this picture at Peter's zoo last week, the mouth of the C. horridus was closed. It reacted on the measurement flash which is some milliseconds before the actual exposition flash and opened the mouth in this little time period.
I tried this out a second time - same result.
Incredible how fast these snakes can react on external disturbance!

http://www.flickr.com/photos/guenterleitenbauer/3781799003/

The timing is pretty good. Some years ago I photographed 3 captive western diammondbacks with a Nikon FM with flash (2 non-agressive and the other completely nut, with a lot of rattling and strike) but none has open their mouth like this.

We don't have to forget that rattlesnakes are among the fastest snakes to strike.......

And your pics still stun me ........

HI!

I remember an article (but dont know where).
There the author means that rattler can reach up to 300 m/sec. on strike.

i think a rattler can strike fast,but check out some bitis and deathadders then
on topic: nice picture Guenter