Question: how can you tell the difference between poisonous and nonpoisonous snakes?
Answer: Instead of having round pupils, a venomous snake has slit-like elliptical eyes that resemble cat 's eyes. ... 
Non venomous snakes, on the other hand, have a steadily sloping jaw since they have no venom sacks. ... 
Often, many vipers will have a heat-sensing pit.