What do you mean by drilled and why would customs do this?
When bats come in small shipments, and for some reason particularly from Pakistan. Customs seem to think they may be hollow and contain drugs, so the drill holes in them to make sure.
They thens end them on to you with little regard that they have just killed the bat.
You will receive no compensation for this either, it's just something you have to accept in the fight against drug smuggling.
There's been a few threads regarding drilled bats recently.