Cause of death?

I found this Brown Long-Eared Bat on a neighbour's wall last night, but I'm still trying to work out how and why it died.  They're widespread and common in South Cumbria, particularly in woodlands, but I've not seen one around here before.  I know that not everyone will admire them, but did you know that in order to retain heat during the day these bats drain the blood from their ears and tuck them under their wings?  And think of all those midges they eat!