I don’t think fruit bats go in caves. Fruit bats are not even the same suborder of animals the rest of the bats are in. Fruit bats live in the open and fly in the daytime and have big eyes with keen sight. They constitute a separate suborder called Megachiroptera, in the family named Pteropodidae, of the order Chiroptera (bats).
They once belived that fruit bats derived from primates, but DNS studies show they came from bats, although they split a very long time ago (like lemur from monkeys).
Most of the early outbreaks occurred during rainy weather. I am not aware one way or another if fruit bats would seek shelter when the weather was bad (most critters do). Normally, they would hang out in trees.