Because I didn't see it

Two bats flew out at the same time from the cave to different directions looking for food. After some time one of them flew back first into the cave, and the other one flew back later but with a bleeding head.

"What happened ?
"Uh..Do you really want to know?"
"Yes, of course"
"Come with me"

So they flew out again. And after flying for some distance, the bat with the bleeding head pointed at one electricity pole and said to his friend,

"Do you see that electricity pole?"
"Yes, I do. But why?"
"Why? Because I didn´t see it! That´s why."

Not Knowing C;