I had a Canon SLR and several lenses with me that day at the Houston serpentarium. It is relatively dark inside, so all pics had to be taken with a tripod. As I approached the python, it was yawning and I went nuts wanting a picture of it. Breaking the rules, I reached over the rail and wiped the plexiglass clean and waited some 45 minutes, ever fearful I'd never see another yawn. But the 3-quarter hour wait was worth it!