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Sorry I`m no expert but how ironic. I was only commenting to a friend earlier that I have not seen a bat this year. Last year several flitted over the pond.
I have had bats in my garden for 30 years but never found a dead one. Cats would have to be very good to catch one as they are on the wing so much.
I would ask your neighbours if they have seen any dead ones as they could be being poisoned by something. It is illegal to kill them but there is something a bit suspect about finding 2 dead in the same place. It may need to be reported so tell your neighbour about your finds.