Snakes are solitary animals (other than for breeding). When they are near another snake, regardless of species, they feel threatened, either for food sources, hiding places or even against attack from the other snake. It is not uncommon for snakes who would not normally prey on other snakes to cannibalize and eat their cage mates, and many from that unfortunately die (the shock of eating so large a prey or from vomiting the meal afterwards).

In order to give your pet the best possible environment, it's best if you house them seperately, with the exception for breeding. =)