The bush viper lives up in the trees of the tropical forests of Africa, and does most of its hunting at night. They are highly venomous and are found only in tropical sub-Saharan Africa.
Here in the Northern US, a viper is a type of poisonous snake. Snake is a more general word. However, we don't have many snakes around here. It may be interesting to hear what others (who live around more snakes) have to say.