When you want to touch animals, you should touch it from the side while talking to it, and not from the back, because they will be startled.
"When you want to touch animals"=「動物を触りたいときは」
"you should touch it from the side while talking to it"=「話しかけながら横側から触ります」
"and not from the back"=「後ろからではなく」
"because they will be startled"=「なぜかというと、動物たちは驚くから」