It doesn't mean they are natural enemies. It is the forest rule only the strongest one can survive in jungle. According to mongoose and snakes. mongoose are Omniverse and snakes are carnivores. Mongoose prfers to eat small animals like birds reptiles, snakes ,fish,***** , fruits. And snakes prefers to eat birds, Rabbits,eggs, , earthworms. So they both can eat each other.which makes them biggest enemies. Sometimes they don't attack each other.