The Fruit Bats

Nice addition showing them, it really added to the exotic atmosphere.

Then a bit later, as they're walking through the jungle trying to get to the lone Japanese soldier that got away, you can see their shadows all over the canopy and the actors, and I thought "they probably could rigged up something to create the shadows while filming to make it look like the bats were still flying" (because filming takes hours, and the entire scene could have taken more than a day).

Then you see a character in a scene where the fruit bat shadows are over the river and even on the other side, and I thought "Whoa, they probably couldn't fake THAT".

So what, did the have a person in charge of scaring the bats back into the sky every time they needed to film another shot with their shadows falling to the ground?

I searched the interwebs for production notes but didn't find any.