Answer:
A lot of things
Step-by-step explanation:
One thing is their experience with a certain animal, for example, a person might love dogs, then one day, a wild dog bites that person and from that point on, they are afraid of dogs and don't want to be close to them.
Other reason can be that they saw a documentary on a certain animal and that changes their perception of said animal, for example, many people think that sharks are wild and vicious animal, but one day they watch a documentary about sharks and realize that, like dogs, sharks have different personalities and some even approach divers because they like to be petted.