Bats are nocturnal creatures so it’s natural that a celebration about the end of the light seasons and the beginning of the dark ones would incorporate them. Additionally in the old days big bonfires were lit at Halloween which would draw mosquitoes and moths to them which in turn would draw bats therefore bats were common sight during the early Samhain festivals and later Halloween celebrations. Certain groups thought that bats were able to communicate with the dead however this was never proved as the bats can’t communicate with the said groups. Also once vampire legends found their way into Halloween folklore the position of the bat was guaranteed as it was thought that vampires could transform into bats.