Do species of snakes in the same family ever bite one another and die from the poison? How about between families? Maybe snakes in general don't bite each other.
-- Bob and friends, North Park
Snake biting snake is not unheard of, but it's apparently rare (though the best watched are in captivity, whose behavior may nor mirror that of snakes in the wild.) Occasionally, two snakes are seen heading for the same item of food and taking a chomp at one another, but that's the exception. Though there is a story of one snake eating another when they started at the opposite end of some rodent, met in the middle, and the bigger snake jut ate lunch and lunch partner. Poisonous snakes do have some immunity to venom. The more closely related the species are, the more immunity they have. It would take much more rattlesnake venom to kill another rattlesnake than to kill a mammal of equal weight.
Herpetologists believe the average intersnake squabble is settled by what's called a combat dance. The disputants twine round each other until one is somehow judged to be the top dog. Interestingly, any biting that might occur during a combat dance is likely to be between nonvenemous snakes.