How would you expect prey to respond to a predator they have never encountered before (a novel predator)? explain your reasoning?

The prey will be confused by the appearance of a new animal, and it will not be sure if it's a predator or harmless animal. This usually causes the prey animals big problems because that confusion usually leads to their death. Also the defensive system that the prey has developed is made for the predators it knows, but is usually ineffective with the newly introduced predators.